DRC-2009-006752 - 0901a068801522dd

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GROUND WATER QUALITY DISCHARGE PERMIT UGW370004
Statement of Basis
For a
Uranium Milling Facility
South of Blanding, Utah
Owned and Operated by
Denison Mines (USA) Corp.
Independence Plaza, Suite 950
1050 17th Street
Denver, Colorado 80265
September 2009
PURPOSE
The purpose of this Statement of Basis (hereafter SOB) is to describe the technical and
regulatory basis to proposed modifications to requirements found in a Ground Water Quality
Discharge Permit No. UGW370004, (hereafter Permit) for the Denison Mines (USA) Corp.
(hereafter DUSA) uranium mill facility located about six miles south of Blanding, Utah in
Sections 28, 29, 32» and 33, Township 37 South, Range 22 East, Salt Lake Baseline and
Meridian, San Juan County, Utah.
Major changes associated with thi.s Permit modification include but are not limited to:
• Approval of DUSA Background Ground Water Quality Reports dated October 2007 and
April 30, 2008.
• Calculation of a mean and standard deviation for each Point of Compliance (hereafter
POC) groundwater monitoring well, and the establishment of sampling frequency for al!
POC wells.
• Establishment and revision of Ground Water Compliance Limits (hereafter GWCL).
• Update the status of certain POC wells with parameters in Out-of-Compliance Status.
• Addition of Best Available Technology (hereafter BAT) Standards and Performance
Monitoring for Feedstock Material Stored Outside the Feedstock Storage Area.
• Addition of Performance Monitoring for inspections of Tailing Cell and Pond Liner
Systems.
• Addition of Seeps and Springs and tailings cell water monitoring.
• Resolution of certain previous compliance schedule requirements.
Other minor Permit changes include but are nol limited to: the correction of formatting,
numbering, and other errors, resetting of some compliance schedule items, and the completion of
several compliance schedule items.
BACKGROUND
The White Mesa uranium mill was constructed in 1979 - 1980 and licensed under federal
regulations by the Nuclear Regulatory Commission (hereafter NRC), Source Material License
SUA-1358.
Page 1 of 42
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GROUND WATER QUALITY DISCHARGE PERMIT UGW370004
Statement of Basis
For a
Uranium Milling Facility
South of Bianding, Utah
Owned and Operated by
Denison Mines (USA) Corp,
Independence Plaza, Suite 950
1050 17th Street
Denver, Colorado 80265
September 2009
PURPOSE
The purpose of this Statement of Basis (hereafter SOB) is lo describe the technical and
regulatory basis to proposed modifications to requirements found in a Ground Water Quality
Discharge Permit No. UGW370004, (hereafter Permit) for the Denison Mines (USA) Corp.
(hereafter DUSA) uranium mill facility located about six miles south of Bianding, Utah in
Sections 28, 29, 32, and 33, Township 37 South, Range 22 East, Sait Lake Baseline and
Meridian, San Juan County, Utah.
Major changes associated with this Permit modification include but are not limited to:
• Approval of DUSA Background Ground Water Quality Reports dated October 2007 and
April 30, 2008.
• Calculation of a mean and standard deviation for each Point of Compliance (hereafter
POC) groundwaler monitoring well, and the establishment of sampling frequency for all
POC wells.
• Establishment and revision of Ground Water Compliance Limits (hereafter GWCL).
• Update the status of certain POC wells with parameters in Out-of-Compliance Status.
• Addition of Best Available Technology (hereafter BAT) Standards and Performance
Monitoring tor Feedstock Material Slored Outside the Feedstock Storage Area.
• Addition of Performance Monitoring tor inspections of Tailing Cell and Pond Liner
Systems.
• Addition of Seeps and Springs and tailings cell water monitoring,
• Resolution of certain previous compliance schedule requirements.
Other minor Permit changes include but are not limited to: the correction of formatting,
numbering, and other errors, resetting of some compliance schedule items, and the completion of
several compliance schedule items.
BACKGROUND
The While Mesa uranium mill was constructed in 1979 - 1980 and licensed under federal
regulations by the Nuclear Regulatory Commission (hereafter NRC), Source Material License
SUA-1358.
Page 1 of42
Page 2 of 42

On August 16, 2004, the NRC delegated its uranium mill regulatory program to the State of
Utah, by extending Agreement State status. As a result, the Utah Division of Radiation Control
(hereafter DRC) became the primary regulatory authority for the DUSA White Mesa mill for
both radioactive materials and groundwater protection. Later, DUSA was issued a State Ground
Water Quality Discharge Permit No. UGW370004 on March 8, 2005. Previous to the
modification proposed herein today, the Permit was last modified on March 17, 2008.

Excess Total Uranium Concentrations with Long-Term Increasing Trends in
Downgradient Wells

In the original DRC December 1, 2004 Statement of Basis, three wells (MW-14, MW-15, and
MW-17) located downgradient of the tailings cells were found to have long-term increasing
concentration trends for total uranium. These three wells and downgradient well MW-3, had
total uranium concentrations above the Utah Ground Water Quality Standard (hereafter GWQS),
found in UAC R317-6-2 (see December 1, 2004 DRC SOB, pp. 6-7). These findings were of
concern to the DRC because they appeared to indicate that the tailings cells had possibly
discharged wastewater into the underlying shallow aquifer.

To resolve this concern, the Executive Secretary required DUSA to evaluate groundwater quality
data from the existing wells on site, and submit a Background Ground Water Quality Report for
Executive Secretary approval, in accordance with Part I.H.3 of the Permit. One of the purposes
of this report was to provide a critical evaluation of historic groundwater quality data from the
facility, and determine representative background quality conditions and reliable groundwater
protection levels or compliance limits for the Permit.

The Permit also required several new monitoring wells be installed around Tailings Cells 1 and
2, followed by groundwater sampling and analysis, and later submittal of another Background
Ground Water Quality Report to determine reliable background conditions and groundwater
compliance limits for the new wells.

During the course of discussions with DUSA staff, and further DRC review, the DRC decided to
supplement the analysis provided in the background report for the existing wells. On April 3,
2007 the DRC notified DUSA in a letter that the State would commission the University of Utah
to perform a geochemical and isotopic groundwater study at White Mesa. DUSA did not
contribute financially to the study, but provided the DRC and the University access to perform
the study (see May 19, 2008 DRC Memo, p. 7).

University of Utah Study

The University of Utah conducted a study entitled “Evaluation of Solute Sources at Uranium
Processing Site” (hereafter Study) at the DUSA White Mesa Uranium Mill. The purpose of this
Study was to verify if the increasing and elevated trace metal concentrations (such as uranium)
found in the monitoring wells at the mill were due to leakage from the on-site tailings cells. To
investigate this potential problem, the study examined groundwater flow, chemical composition,
noble gas and isotopic composition, and age of the on-site groundwater. Similar evaluation was
also made on samples of the tailings wastewater and nearby surface water stored in the northern
wildlife ponds at the facility. Fieldwork for the Study was conducted July 17 - 26 of 2007. A
final report was provided to the DRC via email on May 18, 2008. The May, 2008 University of
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Utah Study Final Report (hereafter University Report) has been included as Attachment 1,
below.

With respect to the four downgradient wells in question described above, the University of Utah
Study collected groundwater isotopic and other geochemical samples from three wells, MW-3,
MW-14, and MW-15. No sampling was performed in well MW-17 due in part to its more cross-
gradient hydraulic position, in that the other three wells were more directly downgradient of the
tailings cells. Also, the 10-foot long well screen in well MW-17 prevented depth profile
sampling there. Since the same problem was also found in well MW-3, and funding was limited,
the DRC chose to sample MW-3 and MW-3A instead. Consequently, it was assumed that the
isotopic and geochemical conditions in well MW-17 are similar as those found in the other
downgradient wells.

After review of the May, 2008 University Report, DRC staff agreed with DUSA that
downgradient wells MW-3, MW-14, MW-15, and MW-17 (with excess total uranium
concentrations) are likely the product of artificial recharge from the wildlife ponds mobilizing
natural uranium in the vadose zone, and not from tailings cell leakage. This conclusion is based
on at least 3 lines of isotopic evidence (see University Report, and May 19, 2008 DRC
memorandum):
1. Tritium Signature - wells MW-3, MW-3A, MW-14, and MW-15 had tritium signatures in
groundwater at or below the limit of detection (0.3 Tritium Units). These values are
more than an order of magnitude below the corresponding surface water results found in
either the tailings cells or the wildlife ponds. Consequently, the groundwater in these 4
downgradient wells is much older than water in the tailings cells, and is of a different
origin than the tailings wastewater.
2. Stable Isotopes of Deuterium and Oxygen-18 in Water - the Deuterium and Oxygen-18
content of the groundwater matrix and tailings wastewater matrix was tested in all of the
water sources studied. University results showed that wells MW-3, MW-3A, MW-14,
and MW-15 (all downgradient with the elevated uranium concentrations) had Deuterium
/ Oxygen-18 signatures that were almost twice as negative as any of the surface water
results. Consequently, groundwater in these downgradient wells had a different
geochemical origin than the tailings cell wastewater.
3. Stable Isotopes on Dissolved Sulfate - the University Study evaluated 2 stable isotopes
found on sulfate minerals dissolved in the water samples (Oxygen-18, and Sulfur-34).
These samples showed that the sulfate solutes in groundwater from downgradient wells
MW-3, MW-3A, MW-14, and MW-15 had a different isotopic signature than the sulfate
minerals dissolved in the tailings wastewater. In the case of Oxygen-18 on sulfate, the
downgradient wells showed more negative values than the tailings cells wastewater. For
Sulfur-34, the results were inversed, with groundwater showing more positive values than
the negative values seen in the tailings wastewater. As a result, the sulfate dissolved in
the downgradient wells, with elevated uranium concentrations, has a different origin than
the tailings wastewater.

As a result of these findings, together with the conclusions reached in the DUSA Background
Ground Water Quality Reports, the Executive Secretary has determined that the elevated and
rising total uranium concentrations seen in wells MW-3, MW-14, MW-15, and MW-17 are not
the product of tailings cell leakage. Instead, they are likely the result of changing geochemical
conditions brought on by artificial recharge to the shallow aquifer by mounding from the nearby
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south wildlife ponds. These changes are possibly caused when rising water caused by the
recharge mounds, flows along subterranean paths that were previously un-traveled and
unsaturated, thereby dissolving solutes that were once fixated to the geologic formation.
Changes in redox conditions would no doubt also be related to these rising water levels, and
could contribute to the additional solutes in question. Consequently, the Executive Secretary is
confident that background groundwater concentrations, and GWCLs developed thereon, from
available historic data from these and other DUSA wells located downgradient of the tailings
cells have not been adversely influenced by tailings cell leakage.

Wildlife Ponds

The University Study documented that artificial recharge water from the wildlife ponds has
altered the shallow aquifer geochemistry at the Mill site. The recharge water is from the local
reservoir (Recapture Reservoir). To this day, no lining system has been constructed under any of
the wildlife ponds; therefore, the wildlife ponds provide a nearly constant source of recharge to
the shallow aquifer at the site (see December 1, 2004 DRC SOB, p. 4). The University Study
showed that significant and measurable quantities of tritium are present in wells MW-27 and
MW-19, indicating that recharge to the aquifer from the wildlife ponds is occurring (see
University Report, pp. 26 - 27).

Under the Utah Ground Water Quality Protection Rules (UAC R317-6-1.2), background
concentration is defined as a pollutant concentration that “… has not been affected by that
facility, practice, or activity.” Under a strict interpretation, the proposed changes to GWCLs in
wells MW-19 and MW-27 may not appear consistent with the Ground Water Quality Protection
Rules, in that the wildlife ponds are on the Mill property, and as a result, could possibly be
considered to be an extension of the uranium milling activity and have altered the tritium and
stable deuterium / oxygen-18 signatures there. However, this impact is one of a secondary
nature, and not the direct result of any tailings cell discharge; therefore, the Executive Secretary
has determined that the hydraulic influence of the wildlife ponds will not be considered, for
purposes of monitoring the tailings cells and the setting of GWCLs for downgradient wells.

While the wildlife ponds are related to facility operations, they are not central to tailings
disposal. These ponds provide a habitat for migratory birds, and encourage them to avoid
contact with the acid laden tailings cells. However, if the constant source of artificial recharge
continues at the wildlife ponds, the isotopic signatures seen in the wells near the wildlife ponds
will eventually be propagated to locations that are downgradient of the tailings cells. When this
happens, it is likely that the isotopic tools we have today will be lost or impaired, and therefore it
could be much more difficult in the future for DUSA to prove that a future exceedance of a
GWCL in a downgradient well is not the product of a tailings cell release. In the event that the
DUSA is unable to distinguish natural uranium concentrations from concentrations attributed to
tailings cell leakage, the Executive Secretary would have no other choice, but to require DUSA
to cleanup the aquifer.

However, the loss of these isotopic tools could be prevented if the wildlife ponds were
appropriately lined to minimize seepage losses to groundwater. By denying the artificial
recharge from the wildlife ponds; the underlying groundwater mounds would be reduced in size,
groundwater flow would return to its normal pathways, and the aquifer would eventually return
to equilibrium.
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Therefore, DUSA is proceeding at its own risk. If the GWCLs (set herein this Permit
modification) are exceeded in the future, and DUSA is not successful at showing how the
groundwater in the affected wells have a different geochemical signature than the tailings
wastewater, i.e., groundwater is old vs. young tailings wastewater, or different isotopic
fingerprint (S-34, O-18, etc,) - then it will be DUSA’s burden to implement GW corrective
action, as per UAC R317-6-6.15.

BACKGROUND REPORTS

Existing Wells

On December 29, 2006, DUSA submitted a Background Ground Water Quality Report for the
on-site Existing Wells (Background Report). An Addendum to the Background Report was
submitted to the DRC on April 19, 2007. DUSA claimed the “purpose of the Addendum is to
supplement the Background Report by focusing exclusively on pre-operational site data and all
available regional data to develop the best available set of background data for the site that
could not conceivably have been influenced by mill operations.”

Review of both reports were conducted by the URS Corporation (URS) on behalf of the DRC.
After review of the Background Report, URS concluded that modifications to the Report were
required in order for the analysis in the Report to more specifically comply with certain
Environmental Protection Agency Guidance (hereafter EPA Guidance) for data preparation and
statistical analysis of groundwater quality data, including treatment of non-detectable values,
statistical methods, etc. In an August 9, 2008 DRC e-mail, the DRC provided DUSA with the
following EPA Guidance to be followed:
1. February, 1989, "Statistical Analysis of Ground-Water Monitoring Data at RCRA Facilities
Interim Final Guidance", U.S. Environmental Protection Agency, Office of Solid Waste,
530-SW-89-026, and
2. July, 1992, "Statistical Analysis of Ground-Water Monitoring Data at RCRA Facilities
Addendum to Interim Final Guidance", U.S. Environmental Protection Agency, Office of
Solid Waste.

In an August 10, 2007 Completeness Review, DRC Findings, and Confirmatory Action Letter
(CAL), the DRC documented ways in which the Background Report needed to be revised in
order to conform to the EPA Guidance before the review process could be completed. The CAL
also outlined the DUSA commitment to revise the Background Report in accordance with the
EPA Guidance and submit a Decision Tree/Flowchart for the groundwater data preparation and
statistical analysis process on or before August 16, 2007 (see August 10, 2007 DRC CAL).
On August 16, 2007 DUSA submitted a Decision Tree/Flowchart diagram. The Decision
Tree/Flowchart was conditionally approved by the DRC on August 24, 2007. On October 26,
2007 DUSA submitted a Revised Background Ground Water Quality Report for on-site Existing
Wells (Revised Background Report). A Revised DUSA Addendum was submitted on November
16, 2007.
Review of the October 26 and November 16, 2007 DUSA reports was conducted by URS on
behalf of the DRC, and is documented in a June 16, 2008 URS Completeness Review for the
Revised Background Groundwater Quality Report: Existing Wells (hereafter URS
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Memorandum). The Revised Background Report included new proposed GWCLs for the 38
constituents in each of the 13 existing wells, for a total of 494 individual data sets. As
documented in the URS Memorandum, there were some GWCLs (24 out of a total of 494) where
an unapproved approach (e.g., highest historic value instead of the Poisson Limit) was used by
DUSA to determine the GWCL. DUSA took this unapproved approach as a means to set
GWCLs for contaminants with increasing concentration trends.

While it is true that the Flowchart did allow a modified approach to setting GWCLs for upward
trending constituents, the August 24, 2007 Conditional Approval for the Flowchart plainly states
that “Please be advised that before the DRC considers such a proposal, DUSA will be required
to provide sufficient technical explanation and justification for why the most recent data is both
representative and protective of local groundwater resources.”

Therefore, because there was no discussion with or approval by the DRC about this modified
approach before the Revised Background Report was received by the DRC on October 26, 2007;
DUSA failed to correctly follow the approved Flowchart. Consequently, GWCLs proposed for
upward trending constituents were not approved by the Division.

In addition, there were also some GWCLs (31 out of a total of 494) where there was a
typographical error in the value of the GWCL. These DUSA proposed GWCLs that varied from
the Decision Tree/Flow Chart and the GWCLs that contained typographical errors are listed in
Table 1 of the URS Memorandum, along with the final GWCLs set by the Executive Secretary.
The June 16, 2008 URS Memorandum has been included as Attachment 2. In the end, the URS
Memorandum recommended acceptance of 439 of the 494 DUSA GWCLs proposed.

The June 16, 2008 URS Memorandum, was shared with DUSA by e-mail on June 18, 2008. On
July 2, 2008, INTERA, Inc. on behalf of DUSA submitted a Response to the URS Memorandum
(Response Memo). In the Response Memo, DUSA presented additional information and asked
the Executive Secretary to take this new information into consideration when determining
GWCLs.

After review of the Revised Background Report, Revised Addendum, URS Memorandum,
DUSA Response Memo, and consideration of the University of Utah Study Final Report; the
Executive Secretary has determined the following: 1) The DRC accepts 439 of the 494 GWCLs
values proposed by DUSA in the October 26, 2007 Revised Background Report, and 2) For the
remaining 55 GWCLs, the DRC will adopt the values calculated by URS in Table 1 of the June
16, 2008 URS Memorandum.

New Wells

Compliance schedule item Part I.H.1 required DUSA to install several new monitoring wells,
primarily around the tailings Cells 1 and 2. After at least eight quarters of groundwater quality
data in these new wells, Part I.H.4 required DUSA to also submit a Background Ground Water
Quality Report for the new wells that complied with the information requirements of Part I.H.3.

On December 4, 2007, DUSA submitted a Background Ground Water Quality Report for the
New Wells (New Wells Background Report). Review of the New Wells Background Report,
was conducted by DRC Staff. After review of the New Wells Background Report, it was
apparent that the report was not written in conformity with the EPA Guidance.
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In a February 14, 2008 Completeness Review, DRC Findings, Request for Information, and
Confirmatory Action Letter (CAL), the DRC outlined a number of these issues with the New
Wells Background Report that needed to be resolved before the review process could be
completed. The CAL also summarized the DUSA commitment to revise the New Wells
Background Report to conform to the EPA Guidance provided to them in the August 9, 2008
DRC e-mail, and resubmit the report by April 30, 2008.

On April 30, 2008, DUSA submitted the Revised New Wells Background Report. DRC review
is found in a June 24, 2008 DRC Findings and Recommended Action Memorandum (DRC New
Wells Memorandum). The Revised New Wells Background Report concluded that the sampling
results for the new wells confirm that the groundwater at the Mill site and in the region is highly
variable naturally and has not been impacted by tailings cell operations and that varying
concentrations of constituents at the site are consistent with natural background variation in the
area.

The Revised New Wells Background Report included new proposed GWCLs for the 38
constituents in each of the nine new wells, for a total of 342 individual data sets. As documented
in the DRC New Wells Memorandum, there were several GWCLs (146 out of a total of 342)
where DUSA used the wrong approach to determine the GWCL or where there was a
typographical error in the value of the GWCL. These proposed GWCLs are listed in Table 1
along with the corrected GWCL values set by the Executive Secretary in the DRC New Wells
Memorandum, which is included below as Attachment 3.

In 43 of those instances, DUSA recommended an approach that varied from the Decision
Tree/Flow Chart diagram (e.g., mean plus 20% instead of the mean plus two standard deviations
for data sets with very low variability). In the Revised New Wells Background Report, DUSA
claimed that during the calculation of GWCLs that were determined by the mean plus two
standard deviations, a condition arose that didn’t occur during the same calculation of the
existing wells. Because data from the new wells is limited to around two years and was analyzed
by the same laboratory, the standard deviation could be typically lower than similar values for
the existing wells, in some cases resulting in a GWCL that is very close to the average value of
the data set. Therefore, for the cases where following the flowchart resulted in a GWCL that is
very close to the average value of the data set, DUSA proposed GWCLs that were be based on
the mean plus 20 percent (x +20%) rather than following the flowchart.

The GWCLs proposed by the x +20% method were rejected by the DRC during review of the
New Wells Background Report and during review of the July 2, 2008 Response Memo because
DUSA didn’t follow the Decision Tree/Flow Chart diagram, which was created by DUSA, and
was conditionally approved by the DRC on August 24, 2007. Additionally, this proposed
method was not based on the EPA Guidance given to DUSA in an August 9, 2008 DRC e-mail.
Further, it is not unexpected to see data sets with low variability when using the same analytical
laboratory over a short period of time. However, this problem can be addressed in the future, if
it occurs, in that DUSA has the ability to provide new descriptive statistics for a given well and
contaminant as more data becomes available, and request the Executive Secretary approval
thereof.

Also, DUSA argues that, assuming a normal distribution, setting a value of two standard
deviations above the mean, virtually guarantees that each well will be out of compliance (falsely)
in about two and a half percent of all concentration values measured in groundwater samples
Page 8 of 42

from that well. While it is true that a GWCL that is set at the mean plus the second standard
deviation, which corresponds to the 95% upper confidence limit, has a 2.5% (0.025) probability
of any parameter in any well falsely exceeding its GWCL during any given sampling event.
DUSA would not be considered in out of compliance until two consecutive groundwater quality
samples exceed the respective GWCL (x +2 concentration) for each well and contaminant in
question. On a statistical basis this equates to a 0.062% (0.0252) probability that any given well
and parameter will twice, consecutively, falsely exceed its respective GWCL.

After review of the Revised New Wells Background Report and consideration of the University
of Utah Study Final Report; the Executive Secretary has determined the following: 1) The DRC
accepts 196 of the 342 GWCLs values proposed by DUSA in the April 30, 2008 Revised New
Wells Background Report, and 2) For the remaining 146 GWCLs, the DRC will adopt the values
calculated by DRC staff in Table 1 of the June 24, 2008 DRC New Wells Memorandum. For
details on the wells and parameters affected, see Table 1 in Attachment 3, below.

DRAFT PERMIT AND STATEMENT OF BASIS
The Draft Permit and SOB were shared with DUSA on April 1, 2009. After DUSA review of the
documents, a meeting was held on May 11, 2009 to discuss the Draft Permit and/or SOB.
During the meeting, DUSA voiced a concern about the new compliance schedule item at Part
I.H.4 of the Permit. This new compliance schedule item, required DUSA to conduct an
groundwater study, similar July 2007 University of Utah Study, in the monitoring wells and
surface water sites that were not part of the July 2007 University of Utah Study. DUSA argued
that the study was not repeatable as the July 2007 University of Utah Study was based on new
“cutting edge” or research groundwater analysis technology. DUSA claimed there were other
methods that DUSA could use to determine if the groundwater had been impacted by tailings cell
wastewater. The DRC invited DUSA to submit (in writing) what other methods they might use
in the future. To this date, no other method to determine if groundwater has been impacted by
tailings cell wastewater has been proposed by DUSA; therefore the Supplemental Isotopic
Groundwater and Surface Water Investigation and Report compliance schedule item found at
Part I.H.4 of the Permit stands.
DUSA was also concerned with setting GWCLs for constituents with rising concentration trends.
As discussed above, the Decision Tree/Flowchart does allow a modified approach to setting
GWCLs for upward trending constituents, after consultation and DRC approval. During the May
11, 2009 meeting, DUSA discussed different options on how to deal with these upward trending
constituents. The DRC asked DUSA to put these options in writing. On June 5, 2009, DUSA
submitted a technical memorandum, written by its consultant INTERA, that included a proposal
dealing with upward trending constituents. The proposal was as follows (see July 5, 2009
INTERA Memo, p.16):

• During each GWDP renewal review, each data set will be evaluated for increasing or
decreasing trends.
• Each statistically significant increasing trend (decreasing pH) will be evaluated to
determine if it is attributable to causes related to Mill operations. In performing such an
evaluation, consideration will be given to the behavior in the well of the indicator
constituents: chloride, sulfate, fluoride and uranium, among other things. If there have
been no statistically significant rising trends in any of the indicator constituents, then that
would be considered to be prima facie evidence that the trend is due to natural
influences. If one or more indicator constituents demonstrates a significant upward trend,
Page 9 of 42

then a further analysis would be performed to determine if the trend or trends are due to
natural influences.
• If the trend is determined to be unrelated to Mill operations, evidence for that
determination will be documented in a report attached to the renewal application.
• The report will include a graph of statistically significant trending data and an
extrapolation of that trend to the next renewal date.
• The extrapolated value on the date of the next GWDP renewal will be set as the GWCL
for the period between the two renewals.

The June 5, 2009 DUSA proposal was rejected by the DRC because this “extrapolation method”
was not based on any EPA Guidance. Therefore for the time being, the proposed GWCLs for the
constituents with upward trends will be set as shown in Table 2 of the Permit.

MAJOR PERMIT CHANGES

GROUND WATER CLASSIFICATION
The original Ground Water Quality Discharge Permit was issued by the DRC on March 8, 2005.
As described in the related DRC December 1, 2004 Statement of Basis, groundwater
classification was determined on a well-by-well approach in order to acknowledge the spatial
variability of groundwater quality at the DUSA facility, and afford the most protection to those
portions of the shallow aquifer that exhibited the highest quality groundwater. On an interim
basis, the Executive Secretary decided to base the well-by-well groundwater classification on the
mean total dissolved solids (hereafter TDS) concentration available at the time, and omit any
consideration of concentration variance. Part IV.N.2 allows the Permit, to be re-opened and
modified when a change in background groundwater quality has been determined.

Groundwater quality data documented in DUSA’s background groundwater quality reports dated
October 2007 (existing wells) and April 30, 2008 (new wells), show an updated mean TDS
concentration and standard deviation for each individual POC well. These reports show the
shallow aquifer at White Mesa has highly variable TDS concentrations, ranging from about
1,019 (MW-27) to over 7,365 mg/L (MW-22). Table 1 of the Permit has been updated with
these new mean TDS and standard deviation calculations.

Using the TDS data from the DUSA background reports, and after calculation of average TDS
concentration for all 24 POC wells, the Executive Secretary determined that four wells (MW-1,
MW-5, MW-11, and MW-30) at the facility appear to exhibit Class II or drinking water quality
groundwater. Of these four wells, only MW-1 is located hydraulically upgradient of the tailings
cells. The 20 other wells appear to exhibit Class III or limited use groundwater at the site. For
details, see Table 1 of the modified Permit.

A key element in determination of groundwater classification is the presence of naturally
occurring contaminants in concentrations that exceed their respective GWQS. In such cases, the
Executive Secretary has cause to downgrade aquifer classification from Class II to Class III (see
UAC R317-6-3.6). During the review of the DUSA Background Ground Water Quality Reports,
the wells where this was necessary are show below:

Page 10 of 42

Well Location Parameter GWQS New GWCL Rationale
MW-18 Upgradient of
Cell 1 Uranium 30 µg/L 55.1 µg/L
Well-18 is upgradient of
the tailing cells. In
addition, the U of U Study
showed that well MW-18
had different geochemical
signature than the tailing
cells.
MW-19 Upgradient of
Cell 1 Thallium 2 µg/L 2.1 µg/L
Well-19 is upgradient of
the tailing cells, therefore
it is unlikely groundwater
in this well has been
affected by tailing cell
wastewater.
MW-25 SE corner of
Tailing Cell 3A Manganese 800 µg/L 1,806 µg/L
Manganese concentrations
in MW-25 have been
consistent since GW
sampling began in 2005.
Nearby well MW-11
analyzed by the U of U
Study had a different
geochemical signature than
the tailing cells.
MW-27 Upgradient of
Cell 1 Uranium 30 µg/L 34 µg/L
Well-27 is upgradient of
the tailing cells, therefore
it is unlikely groundwater
in this well has been
affected by tailing cell
wastewater.
MW-31 Downgradient of
Tailing Cell 2 Selenium 50 µg/L 71 µg/L
U of U Study showed that
well MW-31 had different
geochemical signature than
the tailing cells. In
addition, the Background
Ground Water Quality
Reports concluded that
there had been no impacts
from tailings cell disposal.

Revision of Groundwater Compliance Limits, Part I.C and Table 2
During this Permit modification, a new GWCL was calculated for each constituent in each POC
well. For details, see Table 2 of the modified Permit. After review of the October 26, 2007
DUSA Revised Background Report, November 16, 2007 Revised Addendum, June 16, 2008
URS Memorandum, July 2, 2008 DUSA Response Memo, April 30, 2008 Revised New Wells
Background Report, and consideration of the May, 2008 University of Utah Study Final Report;
the Executive Secretary has set GWCLs for each of the 38 constituents in each POC well, as
follows:

Page 11 of 42

Nutrients

Ammonia (as N) - GWCLs for Ammonia (as N) were calculated by either: 1) the fraction of the
GWQS, be it a Class II (6.25 µg/L), or Class III (12.5 µg/L) aquifer, 2) mean plus two standard
deviations (x +2 ), 3) Aitchison’s Mean + two standard deviations (Aitchison x +2 ), or 4)
Cohen’s Mean + two standard deviations (Cohen’s x +2 ). The revised GWCLs for Ammonia
(as N) ranged from 0.21 mg/L (MW-15) to 7.0 mg/L (MW-24). None of the GWCLs for
Ammonia (as N) accepted by the Executive Secretary in this proposed action are above the Utah
GWQS.

Nitrate + Nitrite (as N) - GWCLs for Nitrate + Nitrite (as N) in 15 of the 22 POC wells were
calculated by the fraction of the GWQS, be it a Class II (2.5 µg/L), or Class III (5.0 µg/L)
aquifer. The other 7 wells were calculated by other methods, as shown in the table below:

Nitrate (as N) Exceptions
Well New GWCL Calculated By
MW-2 0.12 µg/L Highest Historical Value
MW-3 0.73 µg/L x +2
MW-3A 1.3 µg/L x +2
MW-15 0.27 µg/L x +2
MW-19 2.83 µg/L x +2
MW-26 0.62 µg/L Cohen’s x +2
MW-27 5.6 µg/L x +2

During review of the New Wells Background Report and other reports, a Nitrate contaminant
plume was identified by DRC staff in five monitoring wells in the mill site area, including wells:
MW-30, MW-31, TW4-22, TW4-24, and TW4-25. Therefore, the GWCL for Nitrate in wells
MW-30 and MW-31 in this Permit modification were set at the fraction of the GWQS, i.e., 2.5
and 5.0 µg/L for the Class II and III aquifers, respectively; rather than the GWCLs proposed by
DUSA in these wells. None of the GWCLs for Nitrate + Nitrite (as N) accepted by the
Executive Secretary in this proposed action are above the Utah GWQS.

The presence of this Nitrate contamination plume was brought to the attention of DUSA in a
September 30, 2008 DRC letter. Shortly thereafter, DUSA agreed to investigate the source and
extent of the contamination and submit a report to the DRC on or before January 4, 2010, for
Executive Secretary review and approval. This agreement was formalized on January 28, 2009
in a Stipulated Consent Agreement signed by both parties. DUSA has identified a number of
potential sources for the contamination, including potential offsite and historic sources. DUSA
has noted that TW4-25 is located nearly one quarter of a mile upgradient of the Mill’s tailings
cells, suggesting that the plume has originated upgradient of the Mill’s tailings cells.

Heavy Metals

Arsenic - the GWCLs for arsenic were calculated in the same way as the original March 8, 2005
Permit in each POC well, with some exceptions (see table below). Therefore, the GWCL for
arsenic in the majority of the wells will remain at the fraction of the GWQS (50 µg/L), be it a
Class II (12.5 µg/L), or Class III (25 µg/L) aquifer.

Page 12 of 42

Arsenic Exceptions
Well New GWCL Calculated By
MW-5 17 µg/L Highest Historical Value
MW-11 15 µg/L Highest Historical Value
MW-24 17 µg/L Aitchison’s x +2
MW-28 21 µg/L x +2

None of the GWCLs for arsenic accepted by the Executive Secretary in this proposed action are
above the Utah GWQS.

Beryllium - the GWCLs for beryllium were calculated in the same way as the original March 8,
2005 Permit in each POC well. Therefore, the GWCL for beryllium in all wells will remain at
the fraction of the GWQS (4 µg/L), be it a Class II (1.0 µg/L), or Class III (2.0 µg/L) aquifer.

Cadmium - the GWCLs for cadmium were calculated in the same way as the original March 8,
2005 Permit in each POC well, with some exceptions (see table below). Therefore, the GWCL
for cadmium in the majority of the wells will remain at the fraction of the GWQS (5 µg/L), be it
a Class II (1.25 µg/L), or Class III (2.5 µg/L) aquifer.

Cadmium Exceptions
Well New GWCL Calculated By
MW-1 4.2 µg/L Highest Historical Value
MW-3 4.67 µg/L Cohen’s x +2
MW-3A 8.3 µg/L Cohen’s x +2
MW-5 2 µg/L Poisson Limit
MW-12 7 µg/L Highest Historical Value
MW-25 1.5 µg/L x +2
MW-28 5.2 µg/L x +2
MW-32 4.72 µg/L Cohen’s x +2
Footnote: bold text = GWCL that is greater than the State GWQS.

The cadmium GWCLs proposed in wells MW-3A, MW-12, and MW-28 are above the Utah
GWQS of 5 µg/L. For the cadmium GWCL in well MW-3A (8.3 µg/L), the Executive Secretary
believes this is acceptable after review of the University of Utah study, which showed that well
MW-3A had a different geochemical signature than the tailing cells (see University Report, pp.
26 - 27). Additionally, well MW-3A is far downgradient of the tailing cells; therefore, it is
highly unlikely that the cadmium concentrations seen in well MW-3A could be attributed to the
tailing cells.

The cadmium GWCL proposed in well MW-12 is likely due to suspect data collected in the past
sampling events, as cadmium concentrations have been non-detect in all sampling events, but
one since 2nd Quarter 2005. However, the statistical methodology agreed to previously, leads the
Executive Secretary to set this GWCL above the GWQS in this well. In the future, if additional
data shows the situation has changed, the GWCL can be adjusted at that time.

Since groundwater sampling began in well MW-28 (2nd Quarter 2005), cadmium concentrations
have been around 4.5 µg/L. Unfortunately, well MW-28 was not part of the University of Utah
Study. However, the Background Ground Water Reports concluded that, the sample results for
Cadmium in MW-28 are within the range established for the site, and the Executive Secretary
Page 13 of 42

believes that the cadmium levels in well MW-28 are not likely caused by tailings cell
wastewater, and is therefore proposing a GWCL that is slightly greater than the GWQS (5.0
µg/L). A new compliance schedule item was added at Part I.H.4 of the Permit that requires
DUSA to perform a geochemical isotopic investigation in the monitoring wells and surface water
sites that were not part of the July 2007 University of Utah Study. If the new groundwater
isotopic study required by Part I.H.4 shows that groundwater quality in this well has been
adversely affected by the mill operations, Division review and appropriate action will be taken.

Chromium - the GWCLs for chromium were calculated in the same way as the original March
8, 2005 Permit in each POC well. Therefore, the GWCL for chromium will remain at the
fraction of the GWQS (100 µg/L), be it a Class II (25 µg/L), or Class III (50 µg/L) aquifer.

Cobalt - the GWCLs for cobalt were calculated in the same way as the original March 8, 2005
Permit in each POC well, with two exceptions (MW-28 and MW-32). Therefore, the GWCL for
cobalt will remain at the fraction of the GWQS (730 µg/L), be it a Class II (182.5 µg/L), or Class
III (365 µg/L) aquifer. The GWCLs proposed for cobalt in wells MW-28 (47 µg/L) and MW-32
(75.21 µg/L) were calculated by the mean plus two standard deviations (x +2 ). None of the
GWCLs for cobalt proposed herein by the Executive Secretary are above the Utah GWQS.

Copper - the GWCLs for copper were calculated in the same way as the original March 8, 2005
Permit in each POC well. Therefore, the GWCL for copper will remain at the fraction of the
GWQS (1,300 µg/L), be it a Class II (325 µg/L), or Class III (650 µg/L) aquifer.

Iron - the GWCLs for iron were calculated in the same way as the original March 8, 2005 Permit
in each POC well, with some exceptions (see table below). Therefore, the GWCL for iron in the
majority of the wells will remain at the fraction of the GWQS (11,000 µg/L), be it a Class II
(2,750 µg/L), or Class III (5,500 µg/L) aquifer. The revised GWCLs for iron ranged from 81.7
µg/L (MW-27) to 14,060 µg/L (MW-32).

Iron Exceptions
Well New GWCL Calculated By
MW-2 151.6 µg/L Cohen’s x +2
MW-3 427.13 µg/L Cohen’s x +2
MW-15 81.7 µg/L Cohen’s x +2
MW-18 414.68 µg/L x +2
MW-24 4,162 µg/L x +2
MW-26 2,675.83 µg/L x +2
MW-28 299 µg/L Cohen’s x +2
MW-29 1,869 µg/L x +2
MW-32 14,060 µg/L x +2

The iron GWCL of 14,060 µg/L in well MW-32 is above the Utah GWQS of 11,000 µg/L. Well
MW-32 has shown high iron concentrations since groundwater sampling began there in the 1st
Quarter of 2005. These iron concentrations are not believed to be related to tailing cell
wastewater, as uranium concentrations found in well MW-32 are among the lowest at the facility
(5.26 µg/L). Additionally, there is a significant downward trend in iron in well MW-32.
Therefore, the Executive Secretary believes that the iron levels in well MW-32 are not likely
caused by tailings cell wastewater, and is therefore proposing a GWCL that is greater than the
Page 14 of 42

GWQS (11,000 µg/L). The Background Ground Water Reports also noted that there is a
statistically significant downward trend in iron in MW-32, and iron is relatively immobile except
at very low pH and would be unlikely to indicate potential tailings cell seepage before other
constituents, such as chloride and uranium. If the new groundwater isotopic study required by
Part I.H.4 shows that groundwater quality in this well has been adversely affected by the mill
operations, Division review and appropriate action will be taken.

Lead - the GWCLs for lead were calculated in the same way as the original March 8, 2005
Permit in each POC well, with two exceptions (MW-1 and MW-5). Therefore, the GWCL for
lead will remain at the fraction of the GWQS (15 µg/L), be it a Class II (3.75 µg/L), or Class III
(7.5 µg/L) aquifer. The GWCL for lead in wells MW-1 (5.59 µg/L) and MW-5 (4.1 µg/L) were
calculated by the Poisson Limit. None of the GWCLs for lead accepted by the Executive
Secretary are above the Utah GWQS.

Manganese - the proposed GWCLs for manganese exceed the Utah GWQS (800 µg/L) in 11 of
22 wells (see table below). For the remaining 11 wells, GWCLs were set at 400 µg/L and below
using the fractions approach. The Background Reports showed the shallow aquifer at White
Mesa has highly variable manganese concentrations, ranging from 61 µg/L (MW-30) to 7,507
µg/L (MW-24).

Manganese Exceptions
Well New GWCL Calculated By
MW-3 4,233 µg/L x +2
MW-3A 6,287 µg/L x +2
MW-12 2,088.80 µg/L x +2
MW-14 2,230.30 µg/L x +2
MW-17 915.4 µg/L x +2
MW-24 7,507 µg/L x +2
MW-25 1,806 µg/L x +2
MW-26 1,610 µg/L Highest Historical Value
MW-28 1,837 µg/L x +2
MW-29 5,624 µg/L x +2
MW-32 5,594.9 µg/L x +2

For the excess manganese GWCLs proposed in wells MW-3, MW-3A, MW-14, and MW-29 that
are above the Utah GWQS of 800 µg/L, the Executive Secretary believes this is appropriate
based on the University of Utah study, which showed that these wells had a different
geochemical signature than the tailing cells wastewater (see University Report, pp. 26 - 27).
Therefore, it is unlikely that the manganese concentrations seen in these wells could be attributed
to the tailing cells.

Unfortunately, wells MW-12, MW-17, MW-24, MW-25, MW-26, MW-28, and MW-32 were
not part of the University of Utah Study. A new compliance schedule item was added at Part
I.H.4 of the Permit that requires DUSA to perform a geochemical isotopic investigation in the
monitoring wells and surface water sites that were not part of the July 2007 University of Utah
Study. In the meantime, the Executive Secretary believes it is unlikely that the concentrations
found in these wells can be linked to tailing cell wastewater. If the new groundwater isotopic
Page 15 of 42

study required by Part I.H.4 shows that groundwater quality at these wells have been adversely
affected by the mill operations, Division review and appropriate action will be taken.

Mercury - the GWCLs for mercury were calculated in the same way as the original March 8,
2005 Permit in each POC well. Therefore, the GWCL for mercury will remain at the fraction of
the GWQS (2.0 µg/L), be it a Class II (0.5 µg/L), or Class III (1.0 µg/L) aquifer.

Molybdenum - the GWCLs for molybdenum were calculated in the same way as the original
March 8, 2005 Permit in each POC well, with two exceptions (MW-14 and MW-15). Therefore,
the GWCL for molybdenum will remain at the fraction of the GWQS (40 µg/L), be it a Class II
(10 µg/L), or Class III (20 µg/L) aquifer. The GWCL for molybdenum in wells MW-14 (25
µg/L) and MW-15 (30 µg/L) were calculated by the Highest Historical Value. None of the
GWCLs for molybdenum proposed herein by the Executive Secretary are above the Utah
GWQS.

Nickel - the GWCLs for nickel were calculated in the same way as the original March 8, 2005
Permit in each POC well, with some exceptions (see table below). Therefore, the GWCL for
nickel in the majority of the wells will remain at the fraction of the GWQS (100 µg/L), be it a
Class II (25 µg/L), or Class III (50 µg/L) aquifer.

Nickel Exceptions
Well New GWCL Calculated By
MW-2 60 µg/L Highest Historical Value
MW-3 100 µg/L Highest Historical Value
MW-3A 105 µg/L Aitchison’s x +2
MW-5 44.1 µg/L Poisson Limit
MW-11 46.2 µg/L Highest Historical Value
MW-12 60 µg/L Highest Historical Value
MW-15 97 µg/L Highest Historical Value
MW-32 94 µg/L Highest Historical Value

The nickel GWCL of 105 µg/L in well MW-3A is above the Utah GWQS of 100 µg/L.
However, the Executive Secretary believes this is appropriate because the University Study
showed that well MW-3A had a different isotopic geochemical signature than the tailing cells
wastewater (see University Report, pp. 26 - 27). Additionally, well MW-3A is far downgradient
of the tailing cells; therefore it is highly unlikely that the nickel concentrations seen in well MW-
3A could be attributed to the tailing cells.

Selenium - the GWCLs for selenium were calculated in the same way as the original March 8,
2005 Permit in each POC well, with some exceptions (see table below). Therefore, the GWCL
for selenium in the majority of the wells will remain at the fraction of the GWQS (50 µg/L), be it
a Class II (12.5 µg/L), or Class III (25 µg/L) aquifer).

Selenium Exceptions
Well New GWCL Calculated By
MW-2 26.6 µg/L Cohen’s x +2
MW-3 37 µg/L Highest Historical Value
MW-3A 89 µg/L x +2
Page 16 of 42

MW-15 128.7 µg/L Cohen’s x +2
MW-19 28.96 µg/L Cohen’s x +2
MW-28 11.1 µg/L Aitchison’s x +2
MW-30 34 µg/L x +2
MW-31 71 µg/L x +2

The selenium GWCLs in wells MW-3A, MW-15, and MW-31 are above the Utah GWQS of 50
µg/L. However, the Executive Secretary believes this is appropriate because the University
Study showed that wells MW-3A, MW-15, and MW-31 had different isotopic geochemical
signatures than the tailing cells wastewater (see University Report, pp. 26 - 27). Therefore, it is
unlikely that the selenium concentrations seen in these wells could be attributed to the tailing
cells.

Silver - the GWCLs for silver were calculated in the same way as the original March 8, 2005
Permit in each POC well. Therefore, the GWCL for silver will remain at the fraction of the
GWQS (100 µg/L), be it a Class II (25 µg/L), or Class III (50 µg/L) aquifer.

Thallium - the GWCLs for thallium were calculated in the same way as the original March 8,
2005 Permit in each POC well, with some exceptions (see table below). Therefore, the GWCL
for thallium in the majority of the wells will remain at the fraction of the GWQS (2 µg/L), be it a
Class II (0.5 µg/L), or Class III (1.0 µg/L) aquifer.

Thallium Exceptions
Well New GWCL Calculated By
MW-3 1.6 µg/L Highest Historical Value
MW-3A 1.4 µg/L Aitchison’s x +2
MW-18 1.95 µg/L Cohen’s x +2
MW-19 2.1 µg/L Cohen’s x +2
MW-25 1.1 µg/L x +2
MW-29 1.2 µg/L Highest Historical Value

The thallium GWCL of 2.1 µg/L in well MW-19 is slightly above the Utah GWQS of 2.0 µg/L.
The Executive Secretary believes this is appropriate because the University Study showed that
there was no isotopic evidence that well MW-19, which is upgradient of the Mill site, had been
exposed to tailing cell wastewater.

Tin - the GWCLs for tin were calculated in the same way as the last Permit modification (March
17, 2008) in each POC well. Therefore, the GWCL for tin will remain at the fraction of the
GWQS (17,000 u/l), be it a Class II (4,250 µg/L), or Class III (8,500 µg/L) aquifer.

Uranium - the proposed GWCLs for uranium exceed the Utah GWQS (30 µg/L) in 9 of 22 wells
(see table below). The remaining 13 wells GWCL are set at 22 µg/L and below. The
Background Reports showed the shallow aquifer at White Mesa has highly variable uranium
concentrations, ranging from 4.9 µg/L (MW-28) to 98 µg/L (MW-14).

Page 17 of 42

Uranium Exceptions
Well New GWCL Calculated By
MW-3 47.32 µg/L x +2
MW-3A 35 µg/L x +2
MW-14 98 µg/L Highest Historical Value
MW-15 65.7 µg/L Highest Historical Value
MW-17 46.66 µg/L x +2
MW-18 55.1 µg/L x +2
MW-23 32 µg/L x +2
MW-26 41.8 µg/L x +2
MW-27 34 µg/L x +2

The uranium GWCLs in wells MW-3, MW-3A, MW-14, MW-15, and MW-18 are above the
Utah GWQS of 30 µg/L. However, the Executive Secretary believes this is appropriate because
the University Study showed that these wells had different isotopic geochemical signatures than
the tailing cells wastewater (see University Report, pp. 26 - 27). Therefore, it is unlikely that the
uranium concentrations seen in these wells could be attributed to the tailing cells.

The uranium GWCL of 34 µg/L in well MW-27 is above the Utah GWQS of 30 µg/L. Although
the University Study showed that significant and measurable quantities of tritium is present in
well MW-27, indicating that recharge to the aquifer from the wildlife ponds is occurring, there
was no isotopic evidence that well MW-27 had been exposed to tailing cell wastewater.

Unfortunately, wells MW-17, MW-23, and MW-26 were not part of the University of Utah
Study. A new compliance schedule item was added at Part I.H.4 of the Permit that requires
DUSA to perform a geochemical isotopic investigation in the monitoring wells and surface water
sites that were not part of the July 2007 University of Utah Study. In the meantime, the
Executive Secretary believes it is unlikely that the concentrations of uranium found in MW-17,
MW-23, and MW-26 can be linked to tailing cell wastewater. If the new groundwater isotopic
study required by Part I.H.4 shows that groundwater quality at these wells have been adversely
affected by the mill operations, Division review and appropriate action will be taken.

Vanadium - the GWCLs for vanadium were calculated in the same way as the original March 8,
2005 Permit in each POC well, with one exception (MW-15). Therefore, the GWCL for
Vanadium will remain at the fraction of the GWQS (60 µg/L), be it a Class II (15 µg/L), or Class
III (30 µg/L) aquifer. The GWCL for vanadium in well MW-15 was calculated by the Highest
Historical Value, or 40 µg/L. None of the GWCLs for vanadium proposed by the Executive
Secretary in this action are above the Utah GWQS.

Zinc - the GWCLs for zinc were calculated by the mean plus two standard deviations (x +2 ),
Cohen’s x +2 , or by the fraction of the GWQS (5,000 µg/L), be it a Class II (1,250 µg/L), or
Class III (2,500 µg/L) aquifer. None of the GWCLs for zinc proposed by the Executive
Secretary in this action are above the Utah GWQS.

Radiologics

Gross Alpha - GWCLs for gross alpha in 12 of the 22 POC wells were calculated by the fraction
of the GWQS (15 pCi/L), be it a Class II (3.75 pCi/L), or Class III (7.5 pCi/L) aquifer. The other
Page 18 of 42

10 wells were calculated by other methods, as shown in the table below:

Gross Alpha Exceptions
Well New GWCL Calculated By
MW-2 3.2 pCi/L Cohen’s x +2
MW-3 1.0 pCi/L Highest Historical Value
MW-17 2.8 pCi/L Highest Historical Value
MW-19 2.36 pCi/L Cohen’s x +2
MW-23 2.86 pCi/L Aitchison’s x +2
MW-26 4.69 pCi/L x +2
MW-27 2.0 pCi/L Aitchison’s x +2
MW-28 2.42 pCi/L Aitchison’s x +2
MW-29 2.0 pCi/L Aitchison’s x +2
MW-32 3.33 pCi/L x +2

None of the GWCLs for gross alpha proposed by the Executive Secretary in this action are above
the Utah GWQS.

Volatile Organic Compounds (VOCs)

Acetone - the GWCLs for acetone were calculated in the same way as the original March 8,
2005 Permit in each POC well. Therefore, the GWCL for acetone will remain at the fraction of
the GWQS (700 µg/L), be it a Class II (175 µg/L), or Class III (350 µg/L) aquifer.

Benzene - the GWCLs for benzene were calculated in the same way as the original March 8,
2005 Permit in each POC well. Therefore, the GWCL for benzene will remain at the fraction of
the GWQS (5 µg/L), be it a Class II (1.25 µg/L), or Class III (2.5 µg/L) aquifer.

2-Butanone (MEK) - the GWCLs for 2-Butanone (MEK) were calculated in the same way as
the original March 8, 2005 Permit in each POC well. Therefore, the GWCL for 2-Butanone
(MEK) will remain at the fraction of the GWQS (4,000 µg/L), be it a Class II (1,000 µg/L), or
Class III (2,000 µg/L) aquifer.

Carbon Tetrachloride - the GWCLs for carbon tetrachloride were calculated in the same way
as the original March 8, 2005 Permit in each POC well. Therefore, the GWCL for carbon
tetrachloride will remain at the fraction of the GWQS (5 µg/L), be it a Class II (1.25 µg/L), or
Class III (2.5 µg/L) aquifer.

Chloroform - the GWCLs for chloroform were calculated in the same way as the original March
8, 2005 Permit in each POC well, with one exception (MW-26). Therefore, the GWCL for
chloroform will remain at the fraction of the GWQS (70 µg/L), be it a Class II (17.5 µg/L), or
Class III (35 µg/L) aquifer.

Well MW-26 is part of the chloroform investigation and cleanup, and is currently operated as a
pumping well for chloroform removal. The Executive Secretary proposes that the well MW-26
chloroform GWCL be set at the State GWQS or 70 µg/L. This is consistent with the on-going
investigation and cleanup process at the facility.

Page 19 of 42

Chloromethane - the GWCLs for chloromethane were calculated in the same way as the
original March 8, 2005 Permit in each POC well, with some exceptions (see table below).
Therefore, the GWCL for chloromethane in the majority of the wells will remain at the fraction
of the GWQS (30 µg/L), be it a Class II (15 µg/L), or Class III (30 µg/L) aquifer.

Chloromethane Exceptions
Well New GWCL Calculated By
MW-23 5.7 µg/L x +2
MW-28 4.6 µg/L x +2
MW-31 6.1 µg/L x +2
MW-3A 9.4 µg/L x +2

None of the GWCLs for chloromethane accepted by the Executive Secretary are above the Utah
GWQS.

Dichloromethane - the GWCL for dichloromethane was calculated in the same way as the
original March 8, 2005 Permit in each POC well, with one exception (MW-26). Therefore, the
GWCL for dichloromethane will remain at the fraction of the GWQS (5 µg/L), be it a Class II
(1.25 µg/L), or Class III (2.5 µg/L) aquifer.

Well MW-26 is part of the chloroform investigation and cleanup, and is currently operated as a
pumping well for chloroform removal. Dichloromethane is a degradation product of chloroform.
In this Permit modification, the Executive Secretary recommends that the well MW-26
dichloromethane GWCL be set at the State GWQS or 5 µg/L. This is consistent with the on-
going aquifer cleanup project.

Naphthalene - the GWCLs for naphthalene were calculated in the same way as the original
March 8, 2005 Permit in each POC well. Therefore, the GWCL for naphthalene will remain at
the fraction of the GWQS (100 µg/L), be it a Class II (25 µg/L), or Class III (50 µg/L) aquifer.

Tetrahydrofuran (THF) - has been seen in five historic monitoring wells, including: MW-1,
MW-2, MW-3, MW-5, and MW-12. In the October 2007 Revised Background Ground Water
Quality Report, DUSA proposed GWCLs for THF in these wells at concentrations above the
Permit GWCL and/or the Utah GWQS. In the Background Ground Water Reports and in
previous submittals by DUSA, DUSA has taken the position that the THF in these wells is due to
glues that were used in the completion of the casings for those wells. The Executive Secretary
has denied this proposal in this action because THF is not a naturally occurring constituent in
groundwater, and DUSA has not, to date, provided corroborating evidence to the Executive
Secretary that the THF is caused by glues used in the completion of the wells. Therefore, the
GWCL in each POC well was set at the fraction of the GWQS (46 µg/L), be it a Class II (11.5
µg/L), or Class III (23µg/L) aquifer.

Toluene - the GWCLs for toluene were calculated in the same way as the original March 8, 2005
Permit in each POC well. Therefore, the GWCL for toluene will remain at the fraction of the
GWQS (1,000 µg/L), be it a Class II (250 µg/L), or Class III (500 µg/L) aquifer.

Xylenes (total) - the GWCLs for xylenes (total) were calculated in the same way as the original
March 8, 2005 Permit in each POC well. Therefore, the GWCL for xylenes (total) will remain at
Page 20 of 42

the fraction of the GWQS (10,000 µg/L), be it a Class II (2,500 µg/L), or Class III (5,000 µg/L)
aquifer.

Others

Field pH - the GWCLs for field pH were calculated using the Permit GWCL (6.5 - 8.5 s.u.) or
the mean minus two standard deviations (x - 2 ). The field pH GWCL in wells MW-28 (6.1 -
8.5 s.u.) and MW-29 (6.46 - 8.5 s.u.) exceed the Utah GWQS at the lower end of the range.

For well MW-29, the Executive Secretary believes this action is appropriate because the
University Study showed that well MW-29 had a different isotopic geochemical signature than
the tailing cells wastewater (see University Report, pp. 26 - 27). Therefore, it is unlikely that the
low pH concentrations seen in well MW-29 could be attributed to the tailing cells.

Unfortunately, well MW-28 was not part of the University of Utah Study. A new compliance
schedule item was added at Part I.H.4 of the Permit that requires DUSA to perform a
geochemical isotopic investigation in the monitoring wells and surface water sites that were not
part of the July 2007 University of Utah Study. The Executive Secretary believes it is unlikely
that the low pH concentrations found in well MW-28 can be linked to tailing cell wastewater. If
the new groundwater isotopic study required by Part I.H.4 shows that groundwater quality in this
well has been adversely affected by the mill operations, Division review and appropriate action
will be taken.

Fluoride - the GWCLs for fluoride were calculated by the mean plus two standard deviations
(x +2 ) or fraction of the GWQS (4 mg/L), be it a Class II (1.0 mg/L), or Class III (2.0 mg/L)
aquifer. None of the GWCLs for fluoride accepted by the Executive Secretary are above the
Utah GWQS.

Chloride - there was no GWQS set for chloride in the original March 8, 2005 Permit, primarily
because the U.S EPA has not determined an appropriate drinking water health standard for this
contaminant. However, as a part of the DUSA’s background groundwater quality reports dated
October 2007 (existing wells) and April 30, 2008 (new wells), DUSA proposed a GWCL be set
at each POC well for chloride. The Executive Secretary believes this is appropriate given the
presence of chloride in the tailings wastewater and its extremely high groundwater mobility. In
the DUSA reports referenced above, the chloride GWCLs were calculated by the Highest
Historical Value or mean plus two standard deviations (x +2 ); ranging from 10 mg/L (MW-23)
to 143 mg/L (MW-31).

During review of the 3rd Quarter, 2008 Chloroform and Tailings Cell Groundwater Reports, it
was identified by DRC Staff that certain wells associated with the nitrate plume also showed
high concentrations of chloride ranging from 113 mg/L (TW4-19) to 1,180 mg/L (TW4-24) in
the southwest part of the mill site. Further, some of the new tailings cell monitoring wells also
shows elevated chloride concentrations, e.g., MW-28 (99 mg/L), MW-30 (121 mg/L), and MW-
31 (124 mg/L). Therefore, it appears there may be a chloride plume that co-exists with the
nitrate plume. However, because there is not a corresponding human health or Ground Water
Quality Standard for chloride, the Executive Secretary is unable to determine if the chloride
concentrations in these tailings cell wells pose any potential for health risk to the public.
Without such a health limit, a determination was made to set the corresponding chloride GWCLs
in these wells based on the mean plus two standard deviation approach proposed in the DUSA
Page 21 of 42

New Well Background Groundwater Quality Report. This resulted in chloride GWCLs of 105
mg/L (MW-28), 128 mg/L (MW-30), and 143 mg/L (MW-31), see Draft Permit, Table 2.

There is a possibility that the co-existence of the chloride and nitrate plumes could cause the
DUSA statistics (upon which the chloride GWCLs in these three wells are based) to be biased
slightly higher than what otherwise may have been calculated. However, it was noted that in the
event that the apparent chloride and nitrate plumes are shown to have a common source, that it is
likely that the chloride concentrations in wells MW-28, MW-30 and MW-31, will increase above
the proposed GWCLs; due to the fact that a much higher concentration exists in upgradient well
TW4-24 (1,180 mg/L). Under such circumstances two things would happen: 1) non-compliance
would be triggered and the Executive Secretary would call for a contaminant investigation report
under UAC R317-6-6.15(D), and 2) because nitrate and chloride are both mobile groundwater
contaminants, it is likely that any corrective action for the nitrate plume can be adjusted to
adequately address the chloride problem. For these reasons, the Executive Secretary decided to
accept the chloride GWCLs proposed for these wells by DUSA.

Sulfate - there was no GWQS set for sulfate in the original March 8, 2005 Permit, for the same
reason as stated above, the lack of an EPA drinking water standard. However, as part of the
DUSA’s background groundwater quality reports dated October 2007 (existing wells) and April
30, 2008 (new wells), DUSA proposed a GWCL be set at each POC well for sulfate. Again, the
Executive Secretary believes this is appropriate given the extremely high sulfate concentrations
in the tailings wastewater and its extremely high groundwater mobility. In the DUSA reports
referenced above, the sulfate GWCLs were calculated by the Highest Historical Value or mean
plus two standard deviations (x +2 ); ranging from 532 mg/L (MW-31) to 3,663 mg/L (MW-3).

TDS - there was no GWQS set for TDS in the original March 8, 2005 Permit. After review of
the DUSA’s background groundwater quality reports dated October 2007 (existing wells) and
April 30, 2008 (new wells) a GWCL was set at each POC well for TDS. The TDS GWCLs were
calculated by the Highest Historical Value or mean plus two standard deviations (x +2 );
ranging from 1,075 mg/L (MW-27) to 6,186 mg/L (MW-3).

Routine Groundwater Compliance Monitoring Frequency - Quarterly Monitoring, Part
I.E.1(b); Routine Groundwater Compliance Monitoring - Semi-annual Monitoring, Part
I.E.1(c)
Routine groundwater quality monitoring is commonly done on a quarterly basis (4-times/year).
However, the Executive Secretary may allow a reduced frequency of routine groundwater
sampling if site specific groundwater conditions warrant [see UAC R317-6-6.16(A)(2)]. For
certain sites where groundwater velocities have been found to be low (e.g., one to two feet per
year), the Executive Secretary has approved a semi-annual sampling frequency (2-times/year) in
order to avoid statistical problems such as auto-correlation, and allow a better measure of natural
groundwater quality variations.

As described in the DUSA Ground Water Quality Discharge Permit - December 1, 2004
Statement of Basis, there are two different frequencies of routine groundwater monitoring at the
White Mesa Mill, as follows:
• Semi-annual (2-times/year) where groundwater velocity is less than 10 feet/year, and
• Quarterly (4-times/year) where groundwater velocity is equal to or greater than 10
feet/year.
Page 22 of 42

Part I.H.2 of the Permit required DUSA to submit a Revised Hydrogeologic Report after the
installation of the eight new compliance monitoring wells (MW-23, MW-24, MW-25, MW-27,
MW-28, MW-29, MW-30, and MW-31), as required by Part I.H.1. The new wells were installed
during May 2005 and DUSA submitted the Revised Hydrogeologic Report on August 23, 2005.
The Revised Hydrogeologic Report was to include: 1) hydrogeologic data from each of the eight
new wells installed, 2) aquifer test results to determine local hydraulic conductivity at these eight
wells, and existing well MW-32 (formerly TW4-17), and 3) the calculation of linear groundwater
velocity for all nine wells.

After review of the Revised Hydrogeologic Report, DRC staff found that DUSA provided
aquifer permeability data and average linear velocity calculations for six of the eight new wells.
Of these six, three were shown to have average linear velocities of greater than 10 feet/year,
including: MW-25 (14.5 feet/year), MW-30 (12.9 feet/year), and MW-31 (10.6 feet /year). As a
result, the Executive Secretary has decided that these three wells should be sampled on a
quarterly basis (see November 16, 2007 DRC Memorandum, Table 1), as set forth in Part
I.E.1(b).

The Revised Hydrogeologic Report did not include any DUSA calculation of average linear
groundwater velocities for wells MW-24 and MW-3A. In the report, DUSA explained that: 1)
limited water in well MW-24 prevented the determination of aquifer permeability data needed,
and 2) no average linear groundwater velocity for well MW-3A was calculated due to its close
proximity to well MW-3 (within 10 feet); which DUSA determined previously to be 3.6
feet/year.

In the case of well MW-24, where DUSA failed to provide aquifer permeability and velocity
information, the Executive Secretary has decided to assign a quarterly sampling frequency in
Part I.E.1(a). This approach is conservative, in that it provides more protection of groundwater
thru added sample frequency. In the event that DUSA provides the necessary information, the
Executive Secretary may reconsider this decision and modify the Permit as needed.

For well MW-3A, the Executive Secretary agrees that its close proximity to well MW-3 can be
used as a guide, and semi-annual monitoring frequency has been assigned at Part I.E.1(c).

All other existing new DUSA tailings cell monitoring wells were found with local groundwater
velocities of less than 10 feet/year and will be sampled on a semi-annual basis, see Part I.E.1(c).
Average linear groundwater velocity for well MW-32 had previously been estimated by DRC
staff at 19 feet/year (see November 23, 2004 DRC Memorandum, Table 1); based on aquifer
testing in two nearby wells. Therefore, well MW-32 was required to be sampled on a quarterly
basis in the original Permit. The August 23, 2005 DUSA Revised Hydrogeologic Report tested
aquifer permeability in well MW-32 and calculated a liner velocity of 3.3 feet/year (see
November 16, 2007 DRC Memorandum, Table 1). Therefore, the Executive Secretary has re-
assigned a semi-annual sampling frequency to well MW-32 in Parts I.E.1(b) and I.E.1(c) of the
Permit.

Wells with Parameters in Out-of-Compliance Status
Accelerated groundwater monitoring begins when any contaminant in any monitoring well
exceeds its respective GWCL (see Part I.G.1). As defined in Part I.G.2 of the Permit, out-of-
compliance status exists when two consecutive samples from a well exceeds the GWCL in Table
2 of the Permit.
Page 23 of 42

After review of the October 26, 2007 and April 30, 2008 DUSA background groundwater quality
reports and Executive Secretary approval of background concentrations, discussed above, there
appear to be a few wells with parameters that will continue to exceed the new GWCLs;
therefore, theses wells will remain in accelerated sampling and out-of-compliance status and are
explained below:

Tetrahydrofuran in MW-1
The original Permit provided DUSA the opportunity to develop a plan and complete a study to
explain the occurrence of THF, a man-made chemical, in five historic monitoring wells,
including: MW-1, MW-2, MW-3, MW-5, and MW-12. To this end, DUSA submitted plans
dated April 7 and December 15, 2005 for Executive Secretary review. Said study set out to
demonstrate that the THF contamination was caused by PVC solvents and glues used in the
original well construction. After completion of the study, which included a series of THF
sampling and analysis at well MW-2 during a well purging event, the June 26, 2007 DUSA
report concluded that the sample results were inconclusive, because no THF was found in MW-2
and the basis for the study in that well was not satisfied. Hence, the DUSA report provided no
cause for the THF contamination. In a letter dated December12, 2007, the Executive Secretary
agreed with DUSA and advised the company that, in the absence of meaningful study results,
that routine compliance monitoring for THF would be required for the foreseeable future at all
POC wells at the facility. Later, the Executive Secretary removed the Part I.H.18 study
requirement from the Permit.

Because THF is a man-made chemical, the GWCL in all the POC wells in Table 2 of the Permit
was set at the fraction of the GWQS, be it a Class II (11.5 µg/L), or Class III (23 µg/L) aquifer.
At well MW-1, the THF GWCL has been exceeded in every groundwater sampling event from
2nd Qtr 2005 to 4th Qtr 2007. Therefore, well MW-1 will remain in out-of-compliance status for
THF and is required to be sampled on a quarterly basis until the Executive Secretary determines
otherwise.

Chloroform in MW-26
Well MW-26 is part of the chloroform investigation and cleanup, and is currently operated as a
pumping well for chloroform removal. The Executive Secretary proposes that the well MW-26
chloroform GWCL be set at the State GWQS or 70 µg/L. This is consistent with the on-going
investigation and cleanup process at the facility. Because of the existing contamination, this
GWCL has been exceeded in every DUSA groundwater sampling event since sampling began in
the 2nd Qtr 2005. Therefore, well MW-26 will remain in out-of-compliance status for chloroform
and is required to be sampled on a monthly basis until the groundwater concentrations fall below
the GWQS. 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.

Dichloromethane in MW-26
Well MW-26 is part of the chloroform investigation and cleanup, see discussion above.
Dichloromethane is a degradation product of chloroform. In this Permit modification, the
Executive Secretary recommends that the well MW-26 dichloromethane GWCL be set at the
State GWQS or 5 µg/L. Again, this is consistent with the on-going aquifer cleanup project. This
GWCL has been exceeded in every ground water sampling event since sampling began in the 2nd
Qtr 2005. Therefore, well MW-26 will remain in out-of-compliance status for dichloromethane
Page 24 of 42

and is required to be sampled on a monthly basis until the groundwater concentrations fall below
the GWQS.

Nitrate + Nitrite (as N) in Wells MW-30 and MW-31
As part of the April 30, 2008 Revised Background Ground Water Quality Report, DUSA
proposed a GWCL for Nitrate + Nitrite (as Nitrogen) [hereafter Nitrate] in wells MW-30 and
MW-31 that was above the State GWQS (10 mg/L) [ibid., Table 10]. During review of the New
Wells Background Report and other reports, a Nitrate contaminant plume was identified by DRC
staff in five monitoring wells in the mill site area, including wells: MW-30, MW-31, TW4-22,
TW4-24, and TW4-25. Chloroform well TW4-25 is located upgradient of the Mill’s tailings
cells.

On September 30, 2008, the Executive Secretary issued a request for a voluntary plan and
schedule for DUSA to investigate and remediate this Nitrate contamination. On November 19,
2008 DUSA submitted a plan and schedule prepared by INTERA, Inc., which identified a
number of potential sources for the contamination, including several potential historic and offsite
sources. On January 27, 2009, the Executive Secretary and DUSA signed a Stipulated Consent
Agreement by which DUSA agreed to conduct an investigation of the Nitrate contamination,
determine the sources of pollution, and submit a report by January 4, 2010. After review and
approval of this report, the Executive Secretary will determine if a groundwater corrective action
plan is required. Until completion of this report and Executive Secretary approval, it would be
premature to set any Nitrate GWCL in excess of the GWQS.

Therefore, the GWCL for Nitrate in wells MW-30 and MW-31 in this Permit modification were
set at the fraction of the GWQS, i.e., 2.5 and 5.0 µg/L for the Class II and III aquifers,
respectively. Historically, the Nitrate concentrations in both of these wells have exceeded the
GWCL in every groundwater sampling event since sampling began in the 2nd Qtr 2005.
Therefore, the Executive Secretary expects that wells MW-30 and MW-31 will remain in
accelerated sampling and out-of-compliance status for Nitrate for the foreseeable future.

Uranium in MW-26
In the October 26, 2007 Background Report, DUSA calculated the uranium background
concentration in well MW-26 on the mean plus two standard deviations (x +2 ), as 41.8 µg/L,
which is above the State GWQS (30 µg/L). This DUSA proposal was based on groundwater
quality data collected through August 2007. However, there have been recent groundwater
sampling events where consecutive uranium exceedances have been seen in well MW-26; 59.2
µg/L in February 2008 and 46.3 µg/L in March 2008. Therefore, it is possible that MW-26 will
be in accelerated monitoring and out-of compliance status shortly after execution of the Permit.
Because well MW-26 was not included in the recent University of Utah study, it is unclear if the
uranium concentrations seen in well MW-26 are the product of the same processes responsible
for the long-term increasing trends seen existing wells MW-3, MW-14, and MW-15, as
discussed above. A new Compliance Schedule Item has been added at Part I.H.4 of the Permit
and requires DUSA to conduct a groundwater study similar to the July 2007 University of Utah
Study for the monitoring wells and surface water sites that were not part of the University of
Utah Study. After DRC review of the associated report, the Executive Secretary will determine
the source/origin of the uranium concentrations in well MW-26. For more information on the
groundwater investigation, see discussion on Part I.H.4, below.

Page 25 of 42

Manganese in MW-14
In the October 26, 2007 DUSA Background Report, the manganese background concentration in
well MW-14 was calculated by the mean plus two standard deviations (x +2 ), as 2,230.30
µg/L, which is in excess of the GWQS (800 µg/L). This proposed GWCL was based on
groundwater data collected through August 2007. However, in every groundwater sampling
event after August 2007, well MW-14 has had manganese concentrations that exceed the
proposed GWCL. Therefore, the Executive Secretary anticipates that future sampling could
place well MW-14 in accelerated sampling and out-of compliance status, as per Part I.G.2.

However, the recent University of Utah Study indicates that groundwater in well MW-14 is older
in age (lower tritium signature) and more indicative of upgradient groundwater found in well
MW-18 rather than the younger water from the wildlife ponds (higher tritium signature). This is
substantiated by tritium and stable deuterium / oxygen-18 geochemical evidence from the recent
University of Utah Study, as presented below:
Summary of Selected University of Utah Groundwater Isotopic Results (1)
Water Source Tritium [TU(3)] Deuterium
(‰) (4)
Oxygen-18
(‰) (5)
North Wildlife
Ponds
WP2(2) 5.98 -45 -1.3
South Wildlife
Ponds
WP3 5.94 -60 -5.3 Surface
Water
Tailings Cell 3 TC3 6.01 (7.24) (6) -12 4.9
MW-18 (shallow) <0.3 -103 -13.7 Upgradient of
Tailings Cells MW-18 (deep) 0.05 -107 -13.9
MW-14 (shallow) 0.36 -110 -13.8
Ground
Water Downgradient
of Tailings Cells MW-14 (deep) <0.3 -112 -13.9
Footnotes:
1) From May, 2008 University of Utah isotopic groundwater geochemistry study received via email from Dr. Kip Solomon on
May 18, 2008, Tables 4 (tritium) and 10.
2) WP2 = the DUSA northern wildlife pond located near the northeast corner of the White Mesa mill site area, see University
of Utah report, Figure 1. WP3 = south wildlife ponds.
3) TU = a standard tritium unit, or 1 tritiated molecule of water (3H1HO) in 1E+18 molecules of H2O.
4) Deuterium is a stable heavy isotope of hydrogen, 2H. The delta or value represents the amount of deviation in the ratio of
2H/1H in the sample, as compared to a global reference sample of water.
5) Oxygen-18 is a stable heavy isotope of oxygen, 18O. The value represents the amount of deviation in the ratio of 18O/16O
in the sample, as compared to a global reference sample of water.
6) A second or repeat analysis of tailings cell sample TC3 had a tritium concentration of 7.24 +/- 0.55 TU.

As a result of this isotopic evidence, the Executive Secretary has determined that the manganese
concentrations in well MW-14 are most likely natural, and not caused by tailings cell leakage. It
is therefore appropriate to set a GWCL at a concentration that is in excess of the 800 µg/L
GWQS.

However, as per Part I.G.2 of the Permit, accelerated sampling for manganese in well MW-14
could be required after two consecutive samples are discovered in excess of the GWCL. If this
were the case, the Executive Secretary would expect DUSA to provide definitive evidence to
confirm and verify how the current geochemical conditions are equivalent to those found in 2007
by the University of Utah.

Page 26 of 42

MINOR PERMIT CHANGES

Groundwater Monitoring: Monitoring Well MW-3A, Part I.C, Table 2
After reviewing the DUSA Monitor Well MW-3 Verification, Retrofit or Re-construction Report
that DUSA submitted on August 8, 2005, the DRC concluded in an April 25. 2007 DRC
Findings and Request for Information Letter (RFI), that concentration comparison between wells
MW-3 and MW-3A appeared inconsistent and made it difficult to come to any conclusions
concerning the data that would help determine which well has the best screen placement for
groundwater monitoring purposes. Therefore, quarterly sampling must continue in both wells
until sufficient data is available and the DRC can make a conclusion regarding the effects of
partial well penetration and screen length.

DUSA failed to sample well MW-3A for all constituents during the 1st and 3rd quarters of 2008.
Therefore, well MW-3A has been added as a POC well and will be sampled on a semi-annual
sampling frequency (2-times/year).

Tailings Cells 2 and 3 Slimes Drain Requirements: Performance Standards [Part I.D.3(b)],
Monitoring Requirements [Part I.E.7(b)], and Reporting [Part I.F.11] - in May 2007, the
DRC approved a DUSA DMT Monitoring Plan that outlined monthly slimes drain recovery head
testing that would be conducted for at least 90-hours and achieve a stable water level condition.
This monitoring program formed the basis for the annual average head calculations (Equation 1)
that were added to the Permit in March, 2008. The first DUSA report related to this matter was
submitted by email on March 2, 2009 (4th Quarter 2008 DMT Performance Standard Monitoring
Report).

DRC review of this and other previous DUSA quarterly DMT reports have found significant
problems in the monthly slimes drain recovery tests, including many tests failed to run for at
least 90-hours, and achieve steady or stable water level conditions at the end of the tests. From
this review, the DRC concluded that none of the monthly recovery data collected in 2007, and
only two monthly tests collected in 2008 met the 90-hour duration and the stable water level
criteria. As a result, it is clear that any averaging of annual recovery head would be significantly
biased by the large amount of unreliable data from both these years. Calculation errors were also
found in the 4th Quarter, 2008 DUSA DMT Monitoring Report suggesting that inattention was
apparent in its preparation. Details on these agency findings are found in a March 30, 2009 DRC
Memorandum.

As a result of these findings, the Executive Secretary has decided to clarify the Permit and add
new requirements in order to improve the monthly recovery test data collection process and
reporting. These changes include:
• Specific wording to mandate that each monthly test be run for at least 90-hours, and
achieve a stable water level condition [Part I.D.3(b)],
• Minor reference changes in the monitoring requirements in Part I.E.7(b) to mandate that
at least 12 monthly tests be conducted each year that meet the test performance standards
in Part I.D.3, and
• Additional reporting requirements, including a quality assurance evaluation and data
validation for both the data collected, and the related calculations (Part I.F.11).

Page 27 of 42

Mill Site Chemical Reagent Storage, Part I.D.3(g); Completion of Compliance Item 16,
Revised Stormwater Best Management Practices (SBMP) Plan, Part I.H.16
The SBMP Plan (dated May 15, 2008) required under the compliance schedule at Part I.H.16
was approved by the Executive Secretary on July 1, 2008. Therefore, DUSA has satisfied the
requirements of compliance schedule item 16 and the Executive Secretary has struck this
compliance schedule item from the Permit. Reference to compliance schedule item I.H.16 in the
Permit at Part I.D.3(g) has been modified to reference the currently approved plan.

Cell 4A Design Modification - Approval of the Overflow Spillway from Tailings Cell 3, Part
I.D.5, Table 5
This table has been updated to include a revised engineering drawing for the modified overflow
spillway from Tailings Cell 3 to Tailings Cell 4A, which was approved by the DRC on August
19, 2008.

BAT Performance Standards for Tailings Cell 4A, Part I.D.6; Cell 4A BAT Performance
Standards Monitoring, Part I.E.8; Routine Cell 4A BAT Performance Standards
Monitoring Reports, Part I.F.3; Completion of Compliance Item 19, Cell 4A BAT
Monitoring, Operations and Maintenance Plan, Part I.H.19
Part I.H.19 of the Permit, required DUSA to submit a Cell 4A BAT Operations and Maintenance
Plan (hereafter O&M Plan) for Executive Secretary review and approval, before use of Cell 4A
for tailings disposal. The BAT Monitoring Operations and Maintenance Plan (dated September
16, 2008) was approved by the Executive Secretary on September 17, 2008. To ensure that the
approved plan was enforceable under the Permit, Parts I.D.6, I.E.8, and I.F.3 were modified to
reference the currently approved plan. Therefore, DUSA has satisfied the requirements of
compliance schedule item 19 and the Executive Secretary has struck this compliance schedule
item from the Permit.

Leak Detection System (LDS) Maximum Allowable Daily Head, Part I.D.6(a); Cell 4A BAT
Performance Standards Monitoring - Weekly LDS Monitoring for Maximum Allowable
Head, Part I.E.8(a)(2)
Part I.H.19 of the Permit, required DUSA to submit a Cell 4A BAT Operations and Maintenance
Plan (hereafter O&M Plan) for Cell 4A for Executive Secretary review and approval. On
September 16, 2008, DUSA submitted a Revised O&M Plan (Revision 1.3). In the O&M Plan,
DUSA asked that the datum for the LDS maximum allowable daily head measurement be moved
from the lowest point of the LDS sump to the lowest point on the Cell 4A floor, i.e., to a point
where the LDS sump meets the Cell 4A floor, as measured on the lower FML. DUSA consultant
Geosyntec argued that this approach is allowed under the RCRA rules and guidance. After
consultation with URS, the DRC agreed with this change and approved the O&M Plan on
September 17, 2008. DRC staff looked at the LDS sump pump, transducer, and related
geometries and determined that transducer reading of 2.28 feet would be deemed a failure of
BAT. For more information, on how the 2.28 feet value was calculated, see DRC memorandum
of January 6, 2009. This new compliance requirement was also added at Part I.E.8(a)(2).

Slimes Drain Monthly and Annual Average Recovery Head Criteria, Part I.D.6(c)
Before Cell 4A could be placed into service, a monthly and annual average recovery head criteria
needed to be established. As a part of Cell 4A design approval, DUSA demonstrated that the
Cell 4A tailings could be de-watered in a period of 6.4 years, leaving a final head of 1.0 foot
above the upper Flexible Membrane Liner. To ensure that the cell performs as per these
predictions, these criteria have been added to Part I.D.6(c) of the Permit.
Page 28 of 42

BAT Requirements for Feedstock Material Stored Outside the Feedstock Storage Area,
Part I.D.11; Completion of Compliance Item 21, Feedstock Material Stored Outside the
Feedstock Storage Area Management Plan, Part I.H.21
On May 9, 2007, DRC and NRC staff performed an inspection at the Mill site. During the
inspection DRC staff found several hundred 55-gallon drums containing alternate feedstock
material; many of which were bent, dented, and rusting at the perimeter of the drum pile. While
none were found to be leaking, the DRC staff observed that the drums were triple stacked at least
ten deep, with less than a 3-inch spacing between rows of drums, which made it impossible to
physically enter and visually inspect the condition of each of the drums.

Therefore, in the previous DUSA Permit modification (dated March 17, 2008) the Executive
Secretary added a new DMT requirement for feedstock materials stored outside the ore feedstock
storage area in Part I.D.11 of the Permit. This new DMT requirement required DUSA to submit
a management plan for Executive Secretary approval to manage feedstock materials stored
outside the ore feedstock storage area.

On June 20, 2008, DUSA submitted a White Mesa Mill-Containerized Alternate Feedstock
Material Storage Procedure. After reviewing the submittal, the DRC found that the procedure
again failed to address all of the DRC concerns listed in the April 29, 2008 DRC Request for
Additional Information Letter. In order to expedite resolution of these concerns, the DRC has
modified Part I.D.11 with new performance requirements for storing feedstock material outside
of the ore storage area, with an eye to the following goals: 1) containers are maintained in a
water tight condition to prevent soil and groundwater pollution, and 2) aisleways are provided
between containers to allow physical entry and visual inspection, early detection, and timely
remediation of leakage. In the event that DUSA cannot meet goals 1 and 2, options are provided
in Part I.D.11 for DUSA to seek out DRC approval and perform said storage over an engineered
surface of concrete or asphalt with certain other performance criteria. Related BAT monitoring
requirements were also added at Part.I.E.7(d) and (e).

As a result of the Executive Secretary’s actions described above, the original purpose of Part
I.H.21 has been satisfied. Therefore, the Executive Secretary has struck this compliance
schedule item from the Permit. Reference to compliance schedule item I.H.21 in the Permit at
Part I.D.11 has also been removed.

GROUND WATER COMPLIANCE AND TECHNOLOGY PERFORMANCE MONITORING, Part I.E
Part I.E was modified to include the sampling of tailing cell waste waters, seeps and springs in
addition to the sampling of groundwater monitoring wells.

Compliance Monitoring Parameters - Field Parameters, Part I.E.1(d)(1)
As part of its routine groundwater monitoring program, the Permittee is required to collect field
parameters. To be consistent with the currently approved DUSA Quality Assurance Plan
(hereafter QAP), redox potential (Eh) has been added as a required field parameter. This will
provide useful information to document the potential for reductive de-chlorination of the
chloroform groundwater contamination plume.

Groundwater Monitoring: Monitoring Wells MW-20 and MW-22, Part I.E.2
Monitoring wells MW-20 and MW-22 were installed in 1994 and are located at a distance of
more than 3,000 feet south of the tailings cells. Because DUSA had not provided any monitoring
data for these wells, the DRC added a new requirement at Part I.E.2 of the Permit during the last
Page 29 of 42

Permit modification (March 17, 2008). This new requirement required DUSA to begin quarterly
monitoring in both wells. After eight consecutive quarters of sampling, DUSA will submit a
report determining background groundwater quality and a calculation of groundwater velocities
in the vicinity of wells MW-20 and MW-22.

During this Permit modification additional requirements have been added at Part I.E.2. The
report that DUSA is required to submit after eight quarters of sampling will be a Background
Report that will include: data preparation and statistical analysis of groundwater data following
the same Decision Tree/Flowchart used for the previous background reports; aquifer test results
to determine local hydraulic conductivity and other aquifer properties; and a calculation of
average liner groundwater velocity based on well specific hydraulic conductivity, hydraulic
gradient, and effective aquifer porosity.

The Background Report is required to be submitted by March 1, 2010. After review of
Background Report the Executive Secretary will evaluate if wells MW-20 and MW-22 should be
added as POC wells, and adjust the sampling frequency in accordance with criteria found in Part
I.E.1(b) or (c). If it is determined that wells MW-20 and MW-22 should be added as POC wells,
the Executive Secretary will re-open this Permit and establish Groundwater Compliance Limits
in Table 2 for wells MW-20 and MW-22.

White Mesa Seeps and Springs Monitoring, Part I.E.6; White Mesa Seeps and Springs
Monitoring Reports, Part I.F.7; Completion of Compliance Item 8, White Mesa Seeps and
Springs Sampling Work Plan and Report, (WPR) Part I.H.8
Part I.H.8 of the Permit, required DUSA to submit a plan of groundwater sampling and analysis
of all seeps and springs found downgradient or lateral gradient from the tailings cells for
Executive Secretary review and approval. The original compliance date to submit the WPR was
180 days of the issuance of the original Permit, or September 8, 2005. The WPR (dated
November 20, 2008) was conditionally approved by the Executive Secretary on March 3, 2009.
Therefore, DUSA has satisfied the requirements of Part I.H.8, and the Executive Secretary has
struck this item from the Permit. To ensure that the approved plan was enforceable under the
Permit, Parts I.E.6 and I.F.7 were modified to reference the currently approved plan and outline
critical items and requirements. Reference to former compliance schedule item I.H.8 at Parts
I.E.6 and I.F.7 has also been removed.

Weekly Feedstock Storage Area Inspection, Part I.E.7(d)
Part I.E.7(d) was modified to require weekly inspections of all feedstock storage, as to
demonstrate compliance with the performance standards found in Part I.D.11.

Feedstock Material Stored Outside the Feedstock Storage Area Inspections, Part I.E.7(e)
Certain monitoring requirements have been added to Part I.E.7(e) for Feedstock Material Stored
Outside the Feedstock Storage Area. These changes include weekly inspections and prior
Executive Secretary approval should DUSA construct a storage area with a hardened surface.

Inspections of Tailing Cell and Pond Liner Systems, Part I.E.7(f)
In the DUSA 2006 Annual Technical Evaluation Report, the entry for March 24, 2006 refers to
tears found in the Tailing Cell 1 liner that were repaired and covered. After review of this
DUSA report, a Request for Information was made by the DRC dated May 4, 2007. DUSA
provided a response dated July 13, 2007, wherein the method of discovery and repair were
Page 30 of 42

described. In their response, DUSA advised that these "tears" were several dime-sized defects
on a small section of the liner that were above the solution level in the cell.

However, since there was no DRC approved liner maintenance provision plan in use by DUSA, a
new compliance schedule was added at Part I.H.12 in the previous DUSA Permit modification
(dated March 17, 2008). The purpose of the provision was for the equipment, material, training,
and procedures to be used for the timely detection of any openings in the polymer liners, and the
reliable repair and quality assurance testing of any such repairs to the polymer liners for Cells 1,
2, 3, and the Roberts Pond.

On September 29, 2008, DUSA submitted a Revised Liner Maintenance Provisions for Tailings
Cells 1, 2, 3, and Roberts Pond. The DRC approved this plan on October 9, 2008. The new
requirements at Part I.E.7(f) were taken from said plan.

Tailings Cell Wastewater Quality Monitoring, Part I.E.10; Tailings Cell Wastewater
Quality Reports, Part I.F.9; Completion of Compliance Item 5, Tailings Cells Wastewater
Quality Sampling Plan, Part I.H.5
Part I.H.5 of the Permit required DUSA to submit a Tailings Cells Wastewater Quality Sampling
Plan (WQSP) for Executive Secretary review and approval within 150 days of the issuance of the
original Permit, or August 8, 2005. The WQSP (dated November 21, 2008) was approved by the
Executive Secretary on March 3, 2009. Therefore, DUSA has satisfied the requirements of
compliance schedule item 8 and the Executive Secretary has struck this compliance schedule
item from the Permit.

To ensure that the approved plan was enforceable under the Permit, Part I.E.10 was modified to
reference the currently approved plan and outline certain key requirements, including:
• Identification of seven specific sampling locations required to be sampled. However,
provisions were provided to allow DUSA to forgo sampling of the slimes drains until
such time as de-watering operations begin at Tailing Cells 3 and 4A.
• Listing of specific field and laboratory parameters required to be measured, sampled, and
analyzed,
• Provisions for collection and analysis of quality control samples,
• Prior notification, to allow the Executive Secretary to observe and collect split samples,
and
• Prohibition on omission of any sampling location required, without prior written
permission from the Executive Secretary.

Part I.F.9 was also modified to clarify when and where a depth to wastewater measurement
should be taken during slimes drain sampling. Reference to the former compliance schedule
item I.H.8 in the Permit at Part I.E.10 has been removed.

REPORTING REQUIREMENTS - Routine Groundwater Monitoring Reports, Part I.F.1
Part I.F.1 requires that the Permittee submit quarterly monitoring reports of field and laboratory
analyses of all well monitoring and samples described in Parts I.E.1, I.E.2, I.E.3, I.E.5, and I.E.7
of this Permit; however the reference to Part I.E.7 is incorrect. Part I.E.7 refers to DMT
Performance Standards Monitoring, not Groundwater Monitoring. Therefore, the reference to
Part I.E.7 has been removed from Part I.F.1.

Page 31 of 42

Routine Groundwater Monitoring Reports - Time Concentration Plots, Part I.F.1(g)
Part I.F.1(g) was added to the Permit, which requires DUSA to submit time concentrations plots
for four constituents (chloride, fluoride, sulfate, and uranium) with each quarterly groundwater
monitoring report. These constituents are the best indicators of potential seepage impacts from
the tailings impoundments. Increasing trends could provide early indication of seepage even
before GWCLs are exceeded.

Aquifer Permeability Data, Part I.F.6(c)
Part I.F.6(c) was modified to ensure that aquifer permeability data submitted for the
Groundwater Monitoring Well As-Built Reports will include field data, data analysis, and
interpretation of slug tests, aquifer pump tests, or other hydraulic analyses to determine local
aquifer hydraulic conductivity in each well.

OUT OF COMPLIANCE STATUS - Violation of Permit Limits, Part I.G.2(a)(2)
This section has been simplified because many of the revised GWCLs in Table 2 already reflect
the mean plus two standard deviation concentrations. Therefore, Part I.G.2(a)(2) is no longer
needed to determine Out of Compliance Status and has been removed from the Permit.

Compliance Schedule Items Reset for: On-site Chemicals Inventory Report, former Part
I.H.9 - new Part I.H.1; Infiltration and Contaminant Transport Modeling Work Plan and
Report, former Part I.H.10 - new Part I.H.2; Plan for Evaluation of Deep Supply Well
WW-2 [PDW], former Part I.H.11 - new Part I.H.3
Changes in these sections were limited to re-numbering and minor typographical corrections.
Reference to Part I.H.9 of the Permit elsewhere in the Permit (Part I.F.8) has been updated.

New Compliance Schedule Item for Supplemental Isotopic Groundwater and Surface
Water Investigation and Report (new Part I.H.4)
In July 2007, the University of Utah performed a groundwater study to characterize groundwater
flow, chemical composition, noble gas composition, and age at White Mesa. This study
established groundwater age and an isotopic benchmark for each monitoring well, wildlife pond,
and tailings cell sampled during the study. Due to limited funding, the study did not include
sampling and analysis of every POC well or surface water site at White Mesa. Therefore, the
Executive Secretary has determined that the Permittee shall perform an investigation in the
monitoring wells and surface water sites that were not part of the July 2007 University of Utah
Study. The purpose of this supplemental investigation and associated report shall be to establish
isotopic benchmarks and a ground/surface water age at these locations. The Permittee must
conclusively demonstrate that the supplemental investigation conducted is similar to the one
performed by the University of Utah in July 2007.

New Compliance Schedule Item for the New Decontamination Pad (new Part I.H.5)
During a DRC inspection on November 17, 2008, it was discovered that DUSA had constructed
a New Decontamination Pad (hereafter NDP), without prior Executive Secretary approval, as
required by Part I.D.4 of the Permit. In a December 2, 2009 DRC e-mail, the DRC explained
that prior authorization for design, construction, or operation of the NDP is not required, so long
as wash water in the sediment basin of either facility does NOT exceed the State GWQS, as
outlined in Table 2 of the Groundwater Permit. DUSA did not consider this to be a practical
solution, and agreed that it would not use the NDP until the Executive Secretary had approved
the design and construction of the NDP. The NDP has not yet been placed into service;
Page 32 of 42

therefore, Part I.H.5 of the Permit was added requiring DUSA to provide information and secure
Executive Secretary approval before the NDP can be placed into service.

New Compliance Schedule Item for the Existing Decontamination Pad (new Part I.H.6)
The Existing Decontamination Pad (hereafter EDP), was constructed prior to the DRC becoming
the primary regulator for the White Mesa Mill in August, 2004. Shortly thereafter, when DUSA
was issued the first State Ground Water Quality Discharge Permit on March 8, 2005, the EDP
was inadvertently omitted. To rectify this situation, Part I.H.6 of the Permit was added requiring
DUSA to submit As-Built drawings, update the DMT Monitoring Plan for the EDP, and perform
an annual inspection of the facility.

RESOLVED COMPLIANCE SCHEDULE ITEMS

Completion of Compliance Item 1, Installation of New Groundwater Monitoring Wells,
Part I.H.1
Part I.H.1 of the Permit required DUSA to install eight new groundwater monitoring wells within
30 days of Permit issuance, and is a requirement that dates back to the original March 8, 2005
Permit. DUSA compliance is summarized below:
• During May 2005, DUSA installed the new wells required, including: MW-23, MW-24,
MW-25, MW-27, MW-28, MW-29, MW-30, and MW-31. Later, on August 23, 2005,
DUSA submitted a report (see Revised Hydrogeological Report discussed below), that
documented how the new wells had been installed in accordance with requirements of
Part I.H.1 of the Permit.

As described above, DUSA has satisfied the requirements of Permit compliance schedule item
I.H.1 of the Permit. Therefore, the Executive Secretary has struck this compliance schedule item
from the Permit.

Completion of Compliance Item 2, Revised Hydrogeologic Report, Part I.H.2
Part I.H.2 of the Permit required DUSA to submit a Revised Hydrogeologic Report 60 days after
the installation of the new compliance monitoring wells, or before July 1, 2005. DUSA
compliance is summarized below:
• On August 23, 2005, DUSA submitted a Perched Monitoring Well Installation and
Testing at the White Mesa Uranium Mill April through June 2005 Report (hereafter
Revised Hydrogeologic Report).
• After review of the Revised Hydrogeologic Report, the DRC concluded in a November
19, 2007 Closeout and Notice of Enforcement Discretion Letter that the report did not
include a permeability contour or saturated thickness maps, as specified in the December
1, 2004 Statement of Basis. Additionally, the report was not certified by a Utah Licensed
Professional Geologist, as required by Utah Administrative Code R317-6-6.7; however,
the Executive Secretary decided to use enforcement discretion and accept the August 23,
2005 report on the basis that the report will be revised and resubmitted again as a part of
the Permit renewal application due on September 9, 2009 and will include the missing
items described above.

As described above, DUSA has satisfied the requirements of Permit compliance schedule item
I.H.2 of the Permit. Therefore, the Executive Secretary has struck this compliance schedule item
from the Permit.
Page 33 of 42

Completion of Compliance Item 3, Background Ground Water Quality Report: Existing
Wells, Part I.H.3
Part I.H.3 of the Permit required DUSA to submit a Background Ground Water Quality Report
of the existing POC wells listed in Part I.E.1, within 90 days after the issuance of the Permit, or
June 8, 2005. DUSA compliance with Part I.H.3 is summarized below:
• On June 23, 2005, DUSA asked the DRC to extend the deadline for filing the
Background Ground Water Quality Report for Existing Wells to August 31, 2005. The
DRC did not respond to the DUSA request.
• DUSA was unable to meet the August 31, 2005 date. In an October 27, 2006 Final
Consent Agreement DUSA agreed to stipulated penalties in the event they did not submit
the Background Ground Water Quality Report for Existing Wells for Executive Secretary
review and approval, on or before January 2, 2007.
• DUSA submitted the Background Ground Water Quality Report: Existing Wells on
December 29, 2006.
• On April 19, 2007 DUSA submitted an addendum to the December 29, 2006 submittal.
• Review of both of these reports was conducted by URS Corporation on behalf of the
DRC. URS completed the review and presented their findings in an August 9, 2007
Completeness Review for the Background Groundwater Quality Report: Existing Wells
Memo.
• After the report and addendum were reviewed, the DRC sent DUSA an August 10, 2007
Completeness Review, Findings, and Confirmatory Action Letter. This letter required
that DUSA: 1) Submit a Decision Tree/Flowchart that describes groundwater data
preparation and the statistical analysis process on or before August 16, 2007, and 2)
Submit a Revised Background Ground Water Quality Report For Existing Wells that
conforms with the EPA Guidance, within 60 days after Executive Secretary approval of
the Decision Tree/Flowchart.
• On August 16, 2007 DUSA submitted a Decision Tree/Flowchart diagram which was
submitted in compliance with the August 10, 2007 DRC Confirmatory Action Letter.
• The DRC responded in an August 24, 2007 Conditional Approval Letter that approved
the Decision Tree/Flowchart based on several conditions. As a result the revised
background report was then due by October 23, 2007.
• On October 26, 2007 DUSA submitted a Revised Background Ground Water Quality
Report for Existing Wells.
• On November 16, 2007 DUSA submitted a revised addendum to said report.
• Review of both of the October 26 and November 16, 2007 DUSA reports was conducted
by URS Corporation on behalf of the DRC. URS completed the review and presented
their final findings to the DRC in a June 16, 2008 memorandum where several questions
were identified with respect to the DUSA proposed GWCLs. The majority of these
questions were determined to have been caused by DUSA’s application of the Decision
Tree / Flowchart.

Based on the June 16, 2008 URS work, the DRC accepted 439 of the 494 GWCLs values
proposed by DUSA in the October 26, 2007 Revised Background Ground Water Quality Report
for Existing Wells. These revised GWCLs were made in Table 2 of the Permit. For the
remaining 55 GWCLs, the DRC has determined to use the revised values calculated by URS.
For additional details, see the June 16, 2008 URS memorandum, in Attachment 1, below.
As described above, DUSA has satisfied the requirements of Permit compliance schedule item
I.H.3 of the Permit, and appropriate GWCLs have been established in Table 2 of the Permit.
Page 34 of 42

Therefore, the Executive Secretary has struck this compliance schedule item from the Permit.
Reference to compliance schedule item I.H.3 in the Permit at Part I.B has also been removed.

Completion of Compliance Item 4, Background Ground Water Quality Report: New
Monitoring Wells, Part I.H.4
Part I.H.4 of the Permit required DUSA to submit a Background Ground Water Quality Report
for the new wells required to be installed under Part I.H.1. Installations of the new wells were
completed between April and June, 2005. Within 60 days after completion of eight consecutive
quarters of groundwater sampling and analysis of the new wells, the original Part I.H.1 required
DUSA to submit a report for Executive Secretary approval to establish background groundwater
quality for these new wells. Said report deadline would therefore have been June 1, 2007.
DUSA compliance is summarized below:
• DUSA submitted the Background Ground Water Quality Report for New Wells on June
4, 2007.
• After reviewing the report, the DRC responded in a February 14, 2008 Completeness
Review, DRC Findings, Request for Information, and Confirmatory Action Letter. The
letter required DUSA to: 1) submit a Revised Background Ground Water Quality Report
for New Wells that conforms with the EPA Guidance provided to DUSA on August 9,
2007 and 2) resubmit the revised report by April 30, 2008.
• DUSA submitted the Revised Background Ground Water Quality Report for New Wells
on April 30, 2008. DRC review of the April 30, 2008 report is documented in the June
24, 2008 DRC Findings and Recommended Action Memorandum, see Attachment 3,
below.

The DRC accepts 196 of the 342 GWCLs values proposed by DUSA in the April 30, 2008
Revised Background Ground Water Quality Report for Existing Wells. For the remaining 146
GWCLs proposed, the DRC will adopt the other values calculated by DRC staff. For details, see
Attachment 3, below.

As described above, DUSA has satisfied the requirements of Permit compliance schedule item
I.H.4 of the Permit. Therefore, the Executive Secretary has struck this compliance schedule item
from the Permit. Reference to compliance schedule item I.H.4 in the Permit at Part I.B has also
been removed.

Completion of Compliance Item 6, Monitoring Well Remedial Action and Report, Part
I.H.6
Part I.H.6(a) of the Permit required DUSA to develop seven wells at the facility so that they
produce clear groundwater and comply with the requirements of Part I.E.4(c), including wells:
MW-5, MW-11, MW-18, MW-19, MW-20, MW-22, and TW4-16. Part I.H.6(b) required DUSA
to complete monitoring well MW-3A with a permanent surface well completion according to
EPA RCRA TEGD. Said work was to be documented in a report required to be submitted to the
DRC by June 5, 2005. DUSA compliance with these requirements is outlined below:
• DUSA submitted a report dated August 1, 2005. Later DRC determined the August 1,
2005 DUSA submittal to be inadequate, and issued an April 26, 2007 Notice of Non-
Compliance.
• DUSA submitted, a May 1, 2008 Monitor Well Remedial Action Report that documented
proper development of wells: MW-11, MW-18, MW-19, MW-20, MW-22, and TW4-16;
and completion of the protective steel casing at well MW-3A.
Page 35 of 42

• On June 17, 2008, the DRC sent DUSA a Confirmatory Action Letter documenting the
DUSA commitment to provide written plan and deadlines by June 20, 2008 for other
outstanding information, including turbidity issues for wells MW-5, MW-20, and MW-
22.
• On June 20, 2008, DUSA submitted additional data that showed turbidity values below
the 5 NTU standard for wells MW-5, MW-20, and MW-22. After reviewing the June 20,
2008 letter, it was apparent that DUSA had fulfilled the requirement of Part I.H.6(a),
therefore on August 5, 2008 the DRC sent DUSA a Closeout Letter.

As described above, DUSA has satisfied the requirements of Permit compliance schedule item
I.H.6 of the Permit. Therefore, the Executive Secretary has struck this compliance schedule item
from the Permit.

Completion of Compliance Item 7, Monitoring Well MW-3 Verification, Retrofit, or
Reconstruction Report, Parts I.H.7(1) and I.H.7(2)
Part I.H.7(1) of the Permit required DUSA to complete monitoring well MW-3A, as follows: 1)
with a permanent surface well completion according to EPA RCRA TEGD, and Part I.H.6(b) of
this Permit, and 2) provide an elevation survey certified by a state of Utah licensed engineer or
land surveyor by August 4, 2005. DUSA compliance with these requirements is outlined below:
• DUSA submitted a report dated August 8, 2005.
• On April 25, 2007, the DRC issued a Request for Information which summarized a
DUSA commitment to provide the required information by September 11, 2007.
• On May 1, 2008, DUSA submitted, by e-mail, a Monitor Well Remedial Action Report
that documented that monitoring well MW-3A had been retrofitted with a protective steel
casing during the 2nd Quarter of 2007. However, no elevation survey data was included
as required.
• On June 17, 2008, the DRC sent DUSA a Confirmatory Action Letter documenting a
DUSA commitment to provide a written plan and deadline by June 20, 2008 for several
activities, including submittal of the missing elevation survey for well MW-3A.
• On June 20, 2008, DUSA submitted written commitment to supply the well MW-3A
certified elevation survey data by July 7, 2008.
• On July 10, 2008, DUSA submitted, by e-mail, the well MW-3A elevation survey data
performed by Fisher & Sons Surveying, a Utah Licensed Professional Land Surveyor.
After reviewing the elevation survey data, it was apparent that DUSA had fulfilled the
requirement of Part I.H.7(2), therefore on August 5, 2008 the DRC sent DUSA a
Closeout Letter.

As described above, DUSA has satisfied the requirements of Permit compliance schedule item
I.H.7 of the Permit. Therefore, the Executive Secretary has struck this compliance schedule item
from the Permit.

Completion of Compliance Item 12, Liner Maintenance Provisions, Part I.H.12
Part I.H.12 of the Permit required DUSA to submit Liner Maintenance Provisions to be
incorporated into the existing DMT Monitoring Plan for Executive Secretary review and
approval within 90 days of Permit issuance, i.e., by June 15, 2008. DUSA compliance with this
requirement is summarized below:
• On June 12, 2008, DUSA submitted by email Liner Maintenance Provisions for Tailings
Cells 1, 2, 3, and Roberts Pond as Appendix D of the White Mesa Mill Tailings
Page 36 of 42

Management System and Discharge Minimization Technology (hereafter DMT)
Monitoring Plan.
• After review of the June 12, 2008 submittal, the DRC sent DUSA a Request for
Information, Plan Revision, and Confirmatory Action Letter dated August 1, 2008, which
summarized the DUSA commitment to provide a revised plan on or before September 1,
2008.
• On September 29, 2008, DUSA submitted, by e-mail, a Revised Liner Maintenance
Provisions for Tailings Cells 1, 2, 3, and Roberts Pond - Appendix D of the White Mesa
Mill DMT Plan.
• After review of the revised plan, the DRC sent DUSA a Conditional Approval Letter on
the condition that DUSA submit a final version of the Liner Maintenance Provisions for
DRC records by November 1, 2008.
• DUSA submitted a final copy of the Liner Maintenance Provisions by a letter dated
October 22, 2008. The DRC accepted the submittal and issued a Closeout Letter dated
October 30, 2008.

The performance monitoring standards for liner inspections and repair were added to Part
I.E.7(f) of the Permit. As described above, DUSA has satisfied the requirements of Permit
compliance schedule item I.H.12 of the Permit. Therefore, the Executive Secretary has struck
this compliance schedule item from the Permit.

Completion of Compliance Item 15, Contingency Plan, Part I.H.15
Part I.H.15 of the Permit required DUSA to submit a Contingency Plan for Executive Secretary
approval that provides a detailed list of actions DUSA will take to regain compliance with Permit
limits and DMT or BAT requirements, as defined in Parts I.C and I.D of the Permit within 180
days of issuance or by September 8, 2005. DUSA compliance is summarized below:
• DUSA submitted a Draft Contingency Plan, dated April 14, 2006 for Executive Secretary
review.
• After review of the plan, the DRC sent DUSA a Request for Additional Information
Letter on September 5, 2007.
• On October 12, 2007, DUSA sent the DRC a Revised Draft Contingency Plan.
• After review of the revised plan, the DRC sent DUSA a May 2, 2008 Conditional
Approval Letter that required DUSA to provide an update Plan prior to placing Cell 4A
into operation.
• DUSA submitted a revised Contingency Plan dated August 8, 2008, which is currently
under DRC review.

As described above, DUSA has satisfied the requirements of Permit compliance schedule item
I.H.15 of the Permit. Therefore, the Executive Secretary has struck this compliance schedule
item from the Permit. Reference to compliance schedule item I.H.15 in the Permit at Part
I.G.4(d) has also been removed.

Completion of Compliance Item 18, Repair of Monitor Well MW-5, Part I.H.18
Part I.H.18 of the Permit required DUSA to submit an As-Built report for the repairs of
monitoring well MW-5 on or before May 1, 2008. DUSA compliance is summarized below:
• DUSA submitted an April 29, 2008 Repair of Monitor Well MW-5 report. DRC review
found there was no evidence that the elevation survey was performed by a Utah licensed
Page 37 of 42

Professional Engineer or Land Surveyor. Additionally, the elevation given in the report
was unclear whether it was the ground surface or the groundwater monitoring point.
• On June 17, 2008, the DRC sent DUSA a Confirmatory Action Letter documenting
DUSA’s commitment to provide by June 20, 2008 a written deadline for completing the
elevation survey.
• In a June 20, 2008 letter, DUSA committed that the well MW-5 elevation survey data
would be completed and transmitted to the DRC by July 7, 2008.
• On July 10, 2008, DUSA submitted, by e-mail, the MW-5 survey data performed by
Fisher & Sons Surveying (Utah Licensed Professional Land Surveyor). After reviewing
the survey data and the June 20, 2008 letter, it was apparent that DUSA had fulfilled the
requirement of Part I.H.18, therefore on August 5, 2008 the DRC sent DUSA a Closeout
Letter.

As described above, DUSA has satisfied the requirements of Permit compliance schedule item
I.H.18 of the Permit. Therefore, the Executive Secretary has struck this compliance schedule
item from the Permit.

Completion of Compliance Item 22, Quality Assurance Plan (QAP) Revision, Part I.H.22
DUSA was required to submit a revised version of the DUSA groundwater Quality Assurance
Plan (QAP) on or before April 30, 2008 for Executive Secretary review and approval, that would
mandate DUSA to resolve all non-conformance with QAP requirements on or before submittal
of the next quarterly groundwater monitoring report. DUSA compliance is summarized below:
• On March 14, 2008 DUSA submitted, by e-mail, Revision 1 of the QAP.
• After review of the document, DRC staff determined that additional modifications to the
QAP were needed. A conference call was held with DRC and DUSA representatives on
May 5, 2008 where potential QAP modifications were discussed and agreed on. This
resulted in a May 8, 2008 DRC Request for Additional Information and Confirmatory
Action Letter that documented the DUSA commitment to make certain changes and re-
submit the revised QAP on or before June 6, 2008.
• On June 5, 2008 DUSA submitted, by e-mail, Revision 2 of the QAP.
• During the review of Revision 2 of the QAP, the DRC identified additional changes that
needed to be made. These additional changes were outlined in an e-mail sent to DUSA
on June 13, 2008.
• One June 18, 2008 DUSA submitted, by e-mail, Revision 3 of the QAP.
• After reviewing Revision 3 of the QAP, the DRC sent DUSA a QAP Revision 3
Approval Letter on June 20, 2008.

As described above, DUSA has satisfied the requirements of Permit compliance schedule item
I.H.22 of the Permit. Therefore, the Executive Secretary has struck this compliance schedule
item from the Permit.

Compliance Items Removed From the Permit
The Compliance items from Parts I.H.13, I.H.14, I.H.17, and I.H.20 of the Permit have been
removed. All of these items in Part I.H of the Permit are listed as <Reserved>. These
“<Reserved>” items are former placeholders of compliance items whose requirements have been
satisfied and were removed during the March 17, 2008 Permit modification.

Page 38 of 42

Correction of Formatting and Other Changes
During this Permit modification, a number of formatting inconsistencies were identified;
therefore, the following items were corrected and/or changed:
• Various Font types and sizes were used as the Normal text in paragraphs in the Permit;
therefore, to be consistent throughout the Permit, paragraphs were changed to one Font
type and size (Times 12 pt).
• To be consistent, all paragraph alignment throughout the Permit has been changed to
Justified.
• Incorrect numbering was found at Parts I.E.7(b) and I.E.7(d), the numbering at these
locations were corrected. Additionally, numbering at several locations in the Permit were
out of alignment with the correct indentation; therefore, they were moved into the correct
position.
• Different hyphens (– or -) were used throughout the Permit. To be consistent, the (-)
hyphen was chosen as one to be used, the other hyphen was changed, accordingly.
• Inadvertent Extra spaces, periods, commas, etc… have been removed, accordingly.
• Missing spaces, periods, commas, etc… have been added, accordingly.
• At several locations in the Permit, the first letter of a word was either incorrectly
capitalized or was not capitalized as needed; therefore, these instances have been
corrected appropriately.
• In the previous DUSA Permit modification (dated March 17, 2008), as result of a merger
IUC changed its name to Denison Mines (USA) Corp. (DUSA). This name change was
made throughout the Permit. However, a few IUC references were identified in this
Permit modification and have been changed to DUSA, accordingly.
• References to deadlines - throughout the Permit the Permittee is required to
report/submit/complete something by XX days, wherever this is mentioned, the qualifier
“calendar” has been inserted. This protocol has been used throughout the document.
• Reference to an approved plan - throughout the Permit, where an approved plan is
mentioned, the qualifier “currently approved” has been inserted. This protocol was
already in use at some locations in the Permit, now it is throughout.

Page 39 of 42

References

Denison Mines (DUSA) Corp., September 2008, “White Mesa Mill Tailings Management
System and Discharge Minimization Technology (DMT) Monitoring Plan,” 17 pp, 5
appendices.
Denison Mines (DUSA) Corp., June 5, 2009, “Re: White Mesa Uranium Mill; Groundwater
Discharge Permit No. UGW370004 - New Decontamination Pad,” letter from David
Frydenlund to Loren Morton, 2 pp.
Denison Mines (DUSA) Corp., June 5, 2009, “Re: White Mesa Uranium Mill; Groundwater
Discharge Permit No. UGW370004 - Seeps and Springs Monitoring,” letter from David
Frydenlund to Loren Morton, 2 pp.
EPA (U.S. Environmental Protection Agency), 1989, “Statistical analysis of ground-water
monitoring data at RCRA facilities: Interim final guidance,” 530-SW-89-026, Office of
Solid Waste, Permits and State Programs Division, U.S. Environmental Protection
Agency, 401 M Street, S.W. Washington, D.C. 20460.
EPA (U.S. Environmental Protection Agency), 1992, “Statistical analysis of ground-water
monitoring data at RCRA facilities: Addendum to Interim final guidance,” Office of
Solid Waste, Permits and State Programs Division, U.S. Environmental Protection
Agency, 401M Street, S.W. Washington, D.C. 20460.
Hurst, T.G. and D.K. Solomon, May, 2008, “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,” unpublished report by the
University of Utah Department of Geology and Geophysics, 62 pp. [transmitted via
5/18/08 email from Kip Solomon to Loren Morton (DRC)].
INTERA, Inc., Prepared for Denison Mines (USA) Corp., April19, 2007, “Addendum:
Evaluation of Pre-Operational and Regional Background Data, Background Groundwater
Quality Report: Existing Wells for Denison Mines (USA) Corp.’s White Mesa Mill Site,
San Juan County, Utah.”
INTERA, Inc., Prepared for Denison Mines (USA) Corp., October 2007, “Revised Background
Groundwater Quality Report: Existing Wells. For Denison Mines (USA) Corp.’s White
Mesa Mill Site, San Juan County, Utah.”
INTERA, Inc., Prepared for Denison Mines (USA) Corp., November 16, 2007, “Revised
Addendum: Evaluation of Pre-Operational and Regional Background Data, Background
Groundwater Quality Report: Existing Wells for Denison Mines (USA) Corp.’s White
Mesa Mill Site, San Juan County, Utah.”
INTERA, Inc., Prepared for Denison Mines (USA) Corp., April 30, 2008. “Revised Background
Groundwater Quality Report: New Wells. For Denison Mines (USA) Corp.’s White Mesa
Mill Site, San Juan County, Utah.”
INTERA, Inc., Prepared for Denison Mines (USA) Corp., July 2, 2008. “Re: State of Utah
Ground Water Discharge Permit No. UGW37004 (the “GWDP”) White Mesa Mill -
Response to URS Memorandum: Completeness Review for the Revised Background
Groundwater Quality Report: Existing Wells for Denison Mines (USA) Corporation’s
White Mesa Mill Site, San Juan County, Utah.”
Page 40 of 42

INTERA, Inc., Prepared for Denison Mines (DUSA) Corp., July 5, 2009. “Denison Mines
(DUSA) Corp. -- Determination of Ground Water Compliance Limits (GWCLS),”
unpublished consultants memorandum from Daniel W. Erskine Ph.D. (INTERA) to
Loren Morton (UDEQ DRC) and Phillip Goble (UDEQ DRC), 20 pp., 1 figure.
URS Corporation, April 30, 2008, “Completeness Review for the Revised Background
Groundwater Quality Report: Existing Wells for Denison Mines (USA) Corporation’s
White Mesa Mill Site, San Juan County, Utah,” unpublished consultants memorandum, 4
pp., 1 figure, 3 tables [transmitted via 5/6/08 email from Bob Sobocinski (URS) to Loren
Morton (DRC)].
URS Corporation, June 16, 2008, “Completeness Review for the Revised Background
Groundwater Quality Report: Existing Wells for Denison Mines (USA) Corporation’s
White Mesa Mill Site, San Juan County, Utah,” unpublished consultants memorandum, 4
pp., 1 figure, 3 tables [transmitted via 6/16/08 email from Bob Sobocinski (URS) to
Loren Morton (DRC)].
Utah Division of Radiation Control, November 23, 2004, “Review of Hydro Geo Chem, Inc.
Report - Report on Perched Zone Water Movement, White Mesa Mill Site, near
Blanding, Utah, October 20, 2004,” unpublished regulatory document from Dean
Henderson to Loren Morton 3 pp., 2 tables, and 4 figures.
Utah Division of Radiation Control, December 1, 2004, “Statement of Basis for a Uranium
Milling Facility at White Mesa, South of Blanding, Utah,” unpublished regulatory
document, 57 pp., and 12 attachments.
Utah Division of Radiation Control, August 10, 2007, “December, 2006 Background
Groundwater Quality Report: Existing Wells for Denison Mines (USA) Corp.’s White
Mesa Mill Site, San Juan County, Utah; and October 27, 2006 Utah Water Quality Board
Final Consent Agreement (Docket No. UGW06-03): Completeness Review, DRC
Findings, and Confirmatory Action Letter,” from Dane Finerfrock to David
Frydenlund 3 pp., 1 attachment.
Utah Division of Radiation Control, August 24, 2007, “August 16, 2007 DUSA Decision Tree /
Flow Chart for Statistical Analysis for Background Groundwater Quality: Conditional
Approval,” letter from Dane Finerfrock to David Frydenlund 3 pp, 2 attachments.
Utah Division of Radiation Control, November 16, 2007, “Revised Hydrogeologic Report -
Groundwater Discharge Permit (Permit), Part I.H.2, Denison Mines (USA) White Mesa
Mill, near Blanding, Utah,” unpublished regulatory document from Dean Henderson to
Loren Morton 5 pp., 1 figure, 3 tables.
Utah Division of Radiation Control, February 14, 2008, “May 31, 2007 Background
Groundwater Quality Report For New Wells at the Denison Mines (USA) Corp.’s White
Mesa Mill Site, San Juan County, Utah. State of Utah Ground Water Discharge Permit
No. UW370004): Completeness Review, DRC Findings, and Confirmatory Action
Letter,” from Dane Finerfrock to David Frydenlund 4 pp.
Utah Division of Radiation Control, February 22, 2008, “As-Built Report for New Tailings
Monitoring Wells - Groundwater Discharge Permit (Permit), Part I.H.1, Denison Mines
(USA) White Mesa Mill, near Blanding, Utah,” unpublished regulatory document from
Dean Henderson to Loren Morton, 1 pp.
Utah Division of Radiation Control, March 14, 2008, Public Participation Summary, Ground
Water Discharge Permit, DUSA, Permit No. UGW370004.
Page 41 of 42

Utah Division of Radiation Control, April 29, 2008, “April 14, 2008 DUSA Drummed Feedstock
Management Procedure: Groundwater Discharge Permit UGW37004 Part I.H.21:
Request for Additional Information,” letter from Dane Finerfrock to David Frydenlund
2 pp.
Utah Division of Radiation Control, May 2, 2008, “October 12. 2007 Draft Contingency Plan for
Denison Mines Corporation (DMC), as Required Under Part I.H.16 of the State of Utah
GWDP #UGW37004: Conditional Approval,” letter from Dane Finerfrock to David
Frydenlund 1 pp.
Utah Division of Radiation Control, May 19, 2008, “Denison Mines Corporation (USA) and
Proposed Background Groundwater Quality for Existing Wells (October, 2007 Intera
Report); April 28, 2008 URS Finding and DRC Recommended Action,” unpublished
regulatory document from Loren Morton to Dane Finerfrock, 9 pp.
Utah Division of Radiation Control, June 18, 2008, “Denison URS Findings on 10/07 Intera
Background Groundwater Quality Report - Existing Wells,” e-mail from Loren Morton to
David Frydenlund 1 pp.
Utah Division of Radiation Control, June 20, 2008, “June 18, 2008 White Mesa Uranium Mill
Ground Water Monitoring Quality Assurance Plan (QAP) Proposed Revision 3.0, Ground
Water Discharge Permit No. UGW370004 (Permit): Approval,” letter from Dane
Finerfrock to Steven Landau 2 pp.
Utah Division of Radiation Control, July 1, 2008, “June 13, 2008 DUSA Letter; June 2008
White Mesa Mill Revised Storm Water Best Management Practices Plan (SWBMPP);
March 17, 2008 Utah Groundwater Discharge Permit No. UGW37004; February 2007
DUSA Storm Water Best Management Practices Plan: Approval of Revised Plan,” letter
from Dane Finerfrock to Steven Landau 1 pp.
Utah Division of Radiation Control, July 2, 2008, “RE: DUSA Cell 4A Construction: Two Items
noted,” e-mail from Greg Corcoran (Geosyntec) to David Rupp (DRC) 1 pp.
Utah Division of Radiation Control, August 5, 2008, “Part I.H.6, Monitoring Well Remedial
Action and Report; Part I.H.7 Monitor Well MW-3 Verification, Retrofit, or
Reconstruction Report; and Part I.H.18 Repair of Monitor Well MW-5 for the White
Mesa Mill, Ground Water Discharge Permit No. UGW370004 (Permit): Closeout
Letter,” from Dane Finerfrock to Steven Landau 1 pp.
Utah Division of Radiation Control, August 19, 2008, “White Mesa Uranium Mill Cell 4A
Overflow Spillway from Cell 3 to 4A: Design Modification Approval,” from Dane
Finerfrock to Harold Roberts 2 pp., 1 attachment.
Utah Division of Radiation Control, September 17, 2008, “September 16, 2008 DUSA E-mail
Conveying Proposed Revisions to the Cell 4A BAT Monitoring, Operations, and
Maintenance Plan (O&M Plan); September 16, 2008 DRC E-mail with Comments on the
O&M Plan; September 12, 2008 DUSA E-mail Conveying Proposed Revisions to the
White Mesa Mill Tailings Management System; and Discharge Minimization
Technology (DMT) Monitoring Plant (DMT Plan) and the O&M Plan: O&M and DMT
Plan Approval, and Authorization to Operated Tailings Cell 4A,” letter from Dane
Finerfrock to Ron Hochstein 1 pp.
Utah Division of Radiation Control, October 9, 2008, “White Mesa - June 12, 2008 DUSA Liner
Maintenance Provisions - Cells 1, 2, 3, and Roberts Pond, Groundwater Discharge Permit
Page 42 of 42

(No. UGW370004): Conditional Approval,” letter from Dane Finerfrock to Steven
Landau 2 pp.
Utah Division of Radiation Control, December 2, 2008, “Denison Mines Decontamination Pad -
Reply After Conference Call,” e-mail from Loren Morton to David Frydenlund 1 pp.
Utah Division of Radiation Control, January 6, 2009, “Engineering Module 75E - Tailings Cells
1 - 3 and Roberts Pond DMT and Cell 4A BAT Performance Standards and Monitoring
Inspection,” unpublished regulatory document from Dave Rupp to Loren Morton 7 pp., 1
photo.
Utah Division of Radiation Control, February 26, 2009, “November 20, 2008 Work Plan for
Tailings and Slimes Drain Sampling Program, Groundwater Discharge Permit (Part
I.H.5) - Denison Mines (USA) White Mesa Uranium Mill, near Blanding, Utah,”
unpublished regulatory document (Memorandum to File) by Dean Henderson 7 pp.
Utah Division of Radiation Control, March 2, 2009, “Seeps and Springs Sampling Plan,
Groundwater Discharge Permit (Part I.H.8) - Denison Mines (USA) White Mesa
Uranium Mill, near Blanding, Utah,” unpublished regulatory document from Dean
Henderson to Loren Morton 6 pp.
Utah Division of Radiation Control, March 30, 2009, “Technical Memorandum on Changes
Proposed to the Ground Water Discharge Permit for Slimes Drain Head Recovery Testing,”
unpublished regulatory document from Dave Rupp to Loren Morton.
Utah Division of Water Quality, January 19, 2007, Administrative Rules for Ground Water
Quality Protection, R316-6, Utah Administrative Code.
Utah Division of Water Quality, March 8, 2005, Ground Water Discharge Permit, DUSA, Permit
No. UGW370004.
Utah Division of Water Quality, June 13, 2006, Ground Water Discharge Permit, DUSA, Permit
No. UGW370004.
Utah Division of Water Quality, March 17, 2008, Ground Water Discharge Permit, DUSA,
Permit No. UGW370004.

PRG:prg
ATTACHMENT 1
University ofUtah Final Report
May 2008

Utah Division of Radiation Control

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

Prepared by T. Grant Hurst and D. Kip Solomon
Department of Geology and Geophysics
University of Utah
Submitted
May 2008

ii

EXECUTIVE SUMMARY
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 flow, chemical composition, noble gas composition, and age.
The White Mesa Uranium Mill, operated by Denison Mines Co., USA (DUSA), is
located near the western edge of the Blanding Basin. The stratigraphy underlying
surficial aeolian deposits is composed of alternating sandstones and shales of varying
thicknesses. The principle formation in which groundwater is found is the Burro Canyon
Formation of Early Cretaceous age (100 Ma). This formation is composed of sandstone
interbedded with shale, and is generally considered to be of low to moderate
permeability.
Temperature and salinity profiles taken in each of the wells indicate that
stratification of the water column is present. This is supported by dissolved noble gas
compositions determined by collecting passive diffusion samples at two depths in most
wells. Dissolved noble gases had distinct compositions at two depths in all wells
sampled at different depths. Low-flow sampling was employed to attempt to isolate flow
paths within the water column, and samples were collected for tritium, sulfur and oxygen
isotopes of sulfate, hydrogen and oxygen isotopes of water, nitrate and sulfate, and
trace metal concentrations in groundwater. Based on temperature and salinity profiles
and dissolved gas compositions, stratification of the water column is evident. However,
stratification is not delineated in low-flow sampling results of trace metal concentrations
or isotopic fingerprinting.
iii

Measurable levels of tritium were found in several wells in the northeast portion
of the site. Because these wells also indicated stable isotope fingerprints similar to
those of surface water sites, it is likely that they are being influenced by hydrologic
loading from the wildlife ponds in the northeast corner of the Mill. Isotopic similarities
between wildlife ponds and tailings cells suggest some interaction among surface water
sites. Tritium concentrations of less than 0.5 TU in a number of monitoring wells
suggest water infiltrated the land surface more than 50 years ago, while small but
measurable amounts of chlorofluorocarbons indicates recharge to the saturated zone is
occurring. Trace metal concentrations observed in monitoring wells are similar to
concentrations measured recently in routine groundwater sampling at the Mill.
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. While analysis of trace metal concentrations, age-dating methods, and
stable isotope fingerprinting do not indicate significant leakage from the tailing cells,
active vertical and horizontal groundwater flow is clearly evident. The fact that active
groundwater flow occurs at the site confirms the need for on-going monitoring in order
to evaluate the future performance of the tailing cells..
iv

TABLE OF CONTENTS
Executive Summary ii
I. Introduction 1
II. Methods 6
A. Deployment and collection of Diffusion Samplers 6
B. Temperature-Salinity Profiles 7
C. Low-Flow Sampling 8
D. Sampling of Surface Water Sites 11
E. Decontamination Procedures 11
F. Equipment Blank Samples 12
III. Field Results 13
A. Temperature and Salinity Profiles 13
B. Low-Flow Sampling: Well-Pumping Field Notes and Observations 17
IV. Analytical Results 19
A. Chlorofluorocarbon Age Dating 19
B. Tritium/Helium-3 and Noble Gas Analysis 24
C. Anions 36
D. Trace Metals 37
E. δ D and δ18O Isotope Ratios in Water 39
F. δ34S and δ18O Isotope Ratios in Sulfate 42
V. Discussion 48
VI. Conclusions and Recommendations 52
VII. References 57
1

I. INTRODUCTION
The White Mesa Uranium Mill, operated by Denison Mines Co., USA, is located 6
miles south of the town of Blanding in southeastern Utah. It sits on White Mesa near
the western edge of the Blanding Basin within the Canyonlands section of the Colorado
Plateau physiographic province. Elevations range from approximately 3,000 feet at the
bottom of deep canyons in the southwest portion of the region to more than 11,000 feet
in the Henry, Abajo, and La Sal Mountains. The average elevation at the Mill is 5,600
feet above mean sea level (Titan, 1994).
The stratigraphy of White Mesa is composed of the following units, in descending
order: aeolian silts and fine-grained aeolian sands of variable thickness (several feet to
25 or more feet); the Dakota Sandstone and the Burro Canyon Formation (total
thickness ranging from 100 to 140 feet); the Morrison Formation; the Summerville
Formation; the Entrada Sandstone; and the Navajo Sandstone. The Morrison
Formation is composed of the Brushy Basin Member (shale), the Westwater Canyon
Member (sandstone), the Recapture Member (shale), and the Salt Wash Member
(sandstone). The Summerville Formation is primarily sandstone with interbedded shale
layers. Approximately 1,000 to 1,100 feet of material with low average vertical
permeability separates the Entrada and Navajo Sandstones from the Brushy Basin
Member (HGC, 2003).
Titan Environmental’s 1994 report on the hydrogeology of the Mill, and supported
by Hydro Geo Chem, Inc.’s, 2005 site hydrogeology study, identified the primary
formations in which groundwater is found beneath the Mill site as the Dakota Sandstone
and the Burro Canyon Formation (sandstone interbedded with shale). HGC (2003)
2

reports the geometrically averaged permeability of the Dakota Sandstone based on field
tests as 3.89 x 10-5 cm/sec. Titan (1994) reported the geometrically average hydraulic
conductivity of the Burro Canyon Formation as 1.1 x 10-5 cm/sec. The Brushy Basin
Member of the Morrison Formation has generally been considered as impermeable
(Intera, 2007), leading to the conclusion that groundwater within the Mill site is perched
(Titan, 1994; HGC, 2003; HGC, 2005; Intera, 2007; and others). Water level data
collected in June 2007 indicate that groundwater flow is generally from the northeast to
the southwest of the site (Intera, 2007).
The White Mesa Uranium Mill became operational in 1980. To date, 4 million
tons of conventionally-mined and alternate feed uranium ores have been processed,
recovering more than 25 million pounds of U3O8 and 34 million pounds of Vanadium.
The Mill was in standby status from November 1999 to April 2002 during which alternate
feed materials were received and stockpiled. After processing these alternate feed
materials, from April 2002 to May 2003, the Mill returned to standby status, where
alternate feed materials were again received and stockpiled. The Mill resumed
processing of alternate feed materials in March 2005. Processing of conventionally-
mined ores is expected to resume in 2008.
In order to evaluate sources of solute concentrations at the Denison Mines Co.,
USA, White Mesa Uranium Mill, low-flow groundwater sampling was implemented in 15
monitoring wells. Furthermore, surface water samples were collected from three tailings
cells and two wildlife ponds. Passive diffusion samplers were also deployed and
collected in order to characterize the dissolved gas composition of groundwater at
different depths within the wells. Samples were collected and analyzed for the
3

following: tritium, nitrate, sulfate, deuterium and oxygen-18 of water, sulfur-34 and
oxygen-18 of sulfate, trace metals (uranium, manganese, and selenium), and
chlorofluorocarbons.
Depth profiles of temperature and salinity measurements were taken in the wells
to determine the extent of stratification of different formation waters. Differences in
temperature and salinity throughout the water column can indicate flow-paths of
differing travel times, as well as potential differences in recharge location. Furthermore,
these profiles provided insight regarding the water quality conditions existing in the wells
before purging and sampling was conducted.
Our approach for evaluating solute sources is as follows. Indicators of
groundwater age have been correlated to solute concentrations of the trace metals
uranium, manganese, and selenium. Young groundwater found down-gradient of the
Mill, that is associated with high levels of solute concentrations, would suggest a solute
source at or near the mill. High solute concentrations in waters both up- and down-
gradient of the Mill would indicate an aquifer source (i.e. background) for solute
concentrations. Old groundwater found up- or down-gradient of the Mill, associated with
high solute concentrations, would also indicate an aquifer source for solute
concentrations.
Chlorfluorocarbons (CFCs) are anthropogenic gases that have been released to
the atmosphere since the early 1940’s. CFC’s in the vadose zone are likely to be
similar to the current atmospheric CFC concentrations, and dissolve in groundwater to
provide an apparent age of when water recharged the saturated zone. Tritium, the
radioactive isotope of hydrogen containing one proton and two neutrons, was released
4

to the global hydrosphere during above-ground nuclear weapons testing in the 1950’s
and 1960’s. As part of the water molecule, tritium provides an estimate of the time at
which water infiltrated ground surface. The presence of tritium in a water sample, or the
presence of tritiogenic helium-3, indicates that water recharged the saturated zone
within the last 50 years. These methods are used to determine apparent recharge
dates for groundwater within the Mill site.
Analytical results for sulfur-34 and oxygen-18 isotopes of sulfate, and deuterium
and oxygen-18 isotopes of water provide a possible fingerprint of water originating from
the Mill tailings cells. Down-gradient waters with a similar isotopic fingerprint as the
tailings cells, in addition to a significantly different isotopic fingerprint up-gradient of the
tailings cells, may imply the tailings cells as contamination point-sources.
5

Figure 1: Aerial View of White Mesa Mill displaying sample points
6

II. METHODS
A. Deployment and Collection of Diffusion Samplers
Passive diffusion samplers designed to collect dissolved gases were deployed at
two different depths in Monitoring Wells (MW) 1, 2, 3A, 5, 11, 14, 15, 18, 19, 22, 27, 29,
30, and 31. One diffusion sampler was deployed in MW-3 in the center of the saturated
portion of the screened interval. Upon arrival at each well, a water level measurement
was made, and appropriate depths for sampler placement were determined. Samplers
were deployed approximately 1m above the bottom of the screened interval and 1m
below the top of the screened interval. In wells that did not have a fully saturated
screened interval (MW-2, 3, 3A, 5, 14, 15, 27, 29, 30, 31), the top diffusion sampler was
placed approximately 1m below the top of the water level.
A cluster of 6 stainless steel 3/8” nuts were attached to the bottom of the
diffusion sampler line in order to counter any buoyant effect from the volume of air
inside the samplers at depth. Samplers were attached to nylon line, which was used to
avoid twisting of the line while being lowered into the well. Samplers were attached
using nylon zip-ties at either end of the sampler. The samplers were attached in such a
way to allow stretching in the sampler line, thereby preventing potential separation of
the gas-permeable membrane from the copper tubing. Sampler line was secured to the
outer well casing, which was then locked and wrapped in security tamper-evident tape.
Diffusion samplers were allowed to equilibrate inside the wells for at least 48
hours. This was to ensure that the dissolved gases in groundwater were at equilibrium
with the gaseous volume inside the diffusion samplers. Samplers were removed from
the wells prior to taking temperature-salinity profiles and prior to low-flow sampling.
7

Approximately two-minutes elapsed between commencing removal of the samplers
from the well and the time by which all four sample volumes (two sample volumes for
one sampler, and one sampler at two different depths for each well) were sealed. This
was to minimize any re-equilibration between the sample volume and atmosphere from
taking place, preserving the dissolved gas signature of the well water. This time-frame
was monitored and all samplers were removed within the two-minute window. The
diffusion samplers were sealed using a crimping tool that seals the copper tubes such
that they are impermeable to gas leakage, creating a representative sample of the
dissolved gases in the groundwater.
Each sample volume was labeled according to the order in which it was sealed,
and electrical tape was wrapped around the exposed ends to protect the sealed ends.
Samplers were then sealed in zip-lock plastic bags and stored for transport to the
laboratory.
B. Temperature-Salinity Profiles
Profiles of temperature and salinity with depth were measured using a Hydrolab
MiniSonde 4A and Surveyor 4A handheld unit. Dedicated bladder pumps installed
previously by DUSA were left in the well to prevent disturbance of any temperature or
salinity gradient that may have been present within the water column. Pump head-caps
were secured to the side of the well casing to allow for insertion of the Hydrolab probe
into the well.
Measurements of temperature (oC) and specific conductance (µS cm-1) were
made at one-foot intervals throughout the saturated interval in the well. Total dissolved
gases (mm Hg) and dissolved oxygen (mg L-1) were made at the depths at which the
8

passive diffusion samplers were deployed. The probe was allowed to equilibrate until
the total dissolved gas measurement did not fluctuate by more than 0.1% over a period
of 5 minutes (generally 0.1% equaled approximately 1 mmHG). This equilibration
process lasted from 15 minutes to more than one hour at some wells. Profiles were
taken until the Hydrolab probe reached the bottom of the well, or until it could not be
lowered below the DUSA dedicated bladder pumps.
Upon completion of temperature and salinity profile measurements, the
dedicated bladder pump was removed from the well by DUSA employees and stored in
plastic bags for the duration of sampling.
C. Low-Flow Sampling
A Grundfos Redi-Flo 2 submersible pump was used for low-flow groundwater
sampling in the aforementioned wells. The pump was controlled using the Grundfos
Variable Frequency Drive (VFD) control unit, powered by a generator. Generally, the
pump was lowered to approximately 1.5 m below the top of the screened interval, or 1.5
m below the top of the water level in wells that did not have fully saturated screened
intervals. In several wells (MW-14, MW-18, MW-19, and MW-22), the pump was then
lowered to a second sampling depth approximately 1.5 m above the bottom of the
screened interval. A pressure transducer was lowered to a depth determined at each
well individually in order to monitor the head present above the pump, allowing for
drawdown to be monitored while pumping. This was done to ensure low-flow conditions
were maintained during the well sampling process.
The discharge tube from the pump was connected to a flow-through cell on the
Hydrolab probe. This was used to monitor temperature (oC), dissolved oxygen (mg L-1),
9

total dissolved gases (mm Hg), and specific conductance (µS cm-1). Discharge from the
flow-through cell was monitored periodically using a 1000 mL beaker and a stopwatch.
After turning on the pump, the frequency on the VFD unit was increased slowly
until water began flowing from the discharge tubing. Head was monitored constantly
while increasing the frequency, and upon filling the flow-through cell on the Hydrolab
probe, water quality parameters were then monitored. Parameters were considered
stable when their change was less than 5% over a period of 5 minutes. Furthermore, a
minimum purge volume of 2 pump tubing volumes (1 pump tubing volume is
approximately 3 gallons for the length of tubing installed onto the pump) was removed
before sampling occurred. With the exception of MW-18 the field parameters were
stable prior to sampling. After 1 hour of purging the field parameters in MW-18 were not
stable. Nevertheless, samples were collected in accord with the sampling plan that
called for a maximum purge time of 1 hour.
When the field water quality parameters were considered stable, and when the
minimum purge volume of two tubing volumes had been pumped, sampling began.
Samples were generally taken in the following order: tritium (1 L sample), nitrate (125
mL sample), sulfate (125 mL sample), δD/δ18O (15 mL sample), δ34S/δ18O (1 L sample),
trace metals (1x250 mL sample; 2x125 mL samples), CFC’s (5x125 mL samples).
Bottles containing samples for tritium, δD/δ18O, and δ34S/δ18O, were rinsed three times
to eliminate contamination from atmospheric or other sources. Nitrate, sulfate, and
trace metal sample bottles were not rinsed because bottles were pre-acidified by the
analyzing laboratory.
Trace metals collected as 1x250 mL sample were unfiltered, while one 125 mL
10

sample was filtered and the second was left unfiltered. 125 mL trace metal samples
were collected using a field collection hood made of a sterile garbage bag clipped to a
PVC frame. Pump discharge tubing was run through the top of the garbage bag, and
samples were collected within the bag to decrease the possibility for contamination of
the samples by the atmosphere. Dust particles or other atmospheric input to the
sample could contaminate the sample and create interference in analyzing for trace
amounts of metals. Filtered samples were obtained using a Waterra FHT-45 micron
inline disposable filter, attached directly to the end of the discharge tubing, and
disposed of after each use.
Upon finishing trace metal sample collection, discharge tubing was disconnected
from the pump reel connection and a length of 3/8” diameter copper tube was attached
to the pump reel. This was used to collect CFC samples in order to eliminate as much
plastic from the pump line as possible, and also to allow for the discharge tubing to be
inserted directly into the sample bottles. CFC sampling procedures were followed as
specified by the United States Geological Survey Reston CFC Laboratory (USGS,
2007). A 3 gallon glass desiccator was used as the sample collection vessel, and was
filled with purge water after the minimum purge volume had been removed from the
well. Bottles were submerged and the copper discharge tube was inserted into the
bottles, which were then positively purged for approximately 10 bottle volumes (1250
mL). Bottles were filled underwater in order to eliminate any contact with the
atmosphere, and caps were also submerged and placed securely on bottle mouths
underwater. After checking for bubbles within the sample bottle, the cap was wrapped
tightly with electrical tape to protect the cap from any dislodgement during transport.
11

After collecting all of the samples, the pump was disengaged. In the four wells
that sampling was to occur at multiple depths, the water was allowed to discharge from
the pump tubing into the well, and then the pump was lowered to the next depth.
Purging was then only completed for 2 tubing volumes before sampling began again,
which was completed in the same fashion as for the previous depth.
D. Sampling of Surface Water Sites
To sample the wildlife ponds, a 5-foot long, 4-inch diameter section of perforated
PVC pipe (well-screen pipe) was lowered onto the sloping bank of each pond and
completely submerged. The Grundfos pump was then lowered into the tubing, and
connected to the control unit and Hydrolab flow-through cell. Pumping and sampling
was then conducted as previously described. Purging was conducted for two pump
tubing volumes before sampling commenced.
For sampling the tailings cells, a Global Water Instrumentation, Inc., super
submersible pump (part number GP9216B) was used to collect water samples.
Because these pumps are inexpensive, replaceable, and easily disposed of, it was used
in place of the Grundfos submersible. For tailings cells 1 and 3, the pump tubing was
draped over and secured to the railing of platforms on top of the pond. The pump was
lowered to several feet below the water surface, and was then purged for approximately
two tubing volumes. Purge water was collected and returned back to the tailings cells.
For sampling the Tailings Cell 2 slimes drain, the pump was simply lowered down the
vertical drain access pipe and lowered several feet below the observed water surface.
Purge water was collected and disposed of in what was previously Tailings Cell 2.
During sampling of the tailings cells, heavy rubber gloves were worn because of the
12

acidity of the solution.
E. Decontamination Procedures
Decontamination procedures of the pump and pump tubing were conducted in
order to eliminate the possibility of well-to-well cross contamination. Upon removal of
the pump from the well, it was lowered into a 5 foot long, 4 inch diameter vertical PVC
column that was capped and sealed on the bottom end. De-ionized (DI) water was then
poured into the column, and the pump was turned on. Approximately 5 gallons of DI
water was then purged through the system to eliminate residual well water in the pump
tubing. This water was collected and containerized in the same fashion as well purge
water.
After purging the pump and pump tubing with DI water, the pump was
disconnected from the pump tubing and connected to a tank of compressed Nitrogen
gas. N2 gas was allowed to flow through the pump tubing for approximately 60 seconds
in order to flush residual DI water from the pump tubing. In order to more effectively
purge DI water from the pump tubing, the pump reel was placed on its side while
purging with N2 gas. This purged DI water was also containerized in the same fashion
as the well purge water.
F. Equipment Blank Samples
Equipment blank samples were collected at the conclusion of the sampling event.
These samples were collected for the following constituents: nitrate (125 mL sample),
sulfate (125 mL sample), and trace metals (1x125 mL sample, 1x250 mL sample).
Blanks were collected after sampling the final well and immediately after purging the
pump and pump tubing with 5 gallons DI water. Equipment blank samples were
13

collected using DI water directly from the pump discharge tubing.

III. FIELD RESULTS
A. Temperature and Salinity Profiles
Temperature and salinity profiles with depth are presented below for the 15 wells
sampled. Salinity is presented as specific conductance in units of µS cm-1, which is
nominally about 1.5 times the level of total dissolved solids in mg L-1. Vertical
stratification of specific conductance and temperature are apparent in all of the wells,
with a general increasing trend in specific conductance with depth in the saturated
interval and a general decreasing trend in temperature with depth in the saturated
interval. Dashed lines represent the top of the well screens, while dotted lines represent
the bottom of the well screens. Figures marked with an asterisk (*) are profiles taken
entirely within the screen and saturated interval; therefore neither the top or bottom of
the well screen is indicated. These wells are MW-2 and MW-5 (Figures 3 and 6,
respectively). Figures marked with a dagger (†) are sites at which the static water level
was below the top of the well screen and do not include a dashed line. These wells are
MW-3, MW-3A, MW-14, MW-15, MW-27, MW-29, MW-30, and MW-31 (Figures 4, 5, 8,
9, 13, 14, 15, and 16, respectively).
14

Temperature and Salinity vs. Depth (MW-1)
0
5
10
15
20
25
30
35
40
45
1760 1770 1780 1790 1800 1810 1820 1830 1840 1850
Specific Conductance (µS/cm)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(f
t
)
0
5
10
15
20
25
30
35
40
45
13.60 13.80 14.00 14.20 14.40 14.60 14.80 15.00
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(ft
)
Well Screen Top Well Screen Bottom Specific Conductance Temperature
Figure 2: MW-1

Temperature and Specific Conductance vs. Depth
0
2
4
6
8
10
12
14
3460 3480 3500 3520 3540 3560 3580 3600 3620 3640
Specific Conductance (µS cm-1)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
0
2
4
6
8
10
12
14
13.6 13.7 13.8 13.9 14 14.1 14.2 14.3 14.4 14.5 14.6
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
Specific Conductance Temperature Figure 3: MW-2 *

Temperature and Specific Conductance vs. Depth
0
1
2
3
4
5
6
7
8
5500 5550 5600 5650 5700 5750 5800
Specific Conductance (S cm-1)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
0
1
2
3
4
5
6
7
8
14.47 14.48 14.49 14.5 14.51 14.52 14.53 14.54 14.55 14.56
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
Well Screen Bottom Specific Conductance Temperature Figure 4: MW-3 †

Temperature and Specific Conductance vs. Depth
0
2
4
6
8
10
12
5750 5800 5850 5900 5950 6000 6050 6100
Specific Conductance (µS cm-1)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
0
2
4
6
8
10
12
14.40 14.60 14.80 15.00 15.20 15.40 15.60
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
Well Screen Bottom Specific Conductance Temperature Figure 5: MW-3A †

Temperature and Specific Conductance vs. Depth (MW-5)
0
5
10
15
20
25
2724 2726 2728 2730 2732 2734 2736 2738 2740 2742 2744
Specific Conductance (µS/cm)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
0
5
10
15
20
25
14.1 14.2 14.3 14.4 14.5 14.6 14.7 14.8 14.9 15
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(f
t
)
Specific Conductance Temperature
Figure 6: MW-5 *
Temperature and Specific Conductance vs. Depth
0
5
10
15
20
25
30
35
40
2500 2550 2600 2650 2700 2750 2800 2850 2900 2950 3000
Specific Conductance (µS cm-1)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(f
t
)
0
5
10
15
20
25
30
35
40
13 13.5 14 14.5 15 15.5 16 16.5 17 17.5 18
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
Well Screen Top Well Screen Bottom Specific Conductance Temperature Figure 7: MW-11
15

Temperature and Specific Conductance vs. Depth
0
5
10
15
20
3740 3760 3780 3800 3820 3840 3860 3880 3900
Specific Conductance (µS cm-1)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
0
5
10
15
20
14.20 14.40 14.60 14.80 15.00 15.20 15.40 15.60 15.80
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
Well Screen Bottom Specific Conductance Temperature Figure 8: MW-14 †

Temperature and Specific Conductance vs. Depth
0
5
10
15
20
25
30
4000 4050 4100 4150 4200 4250 4300 4350
Specific Conductance (µS cm-1)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
0
5
10
15
20
25
30
14.20 14.30 14.40 14.50 14.60 14.70 14.80 14.90 15.00
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
Well Screen Bottom Specific Conductance Temperature Figure 9: MW-15 †

Temperature and Specific Conductance vs. Depth
0
10
20
30
40
50
60
70
2000 2200 2400 2600 2800 3000 3200 3400
Specific Conductance (µS cm-1)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
0
10
20
30
40
50
60
70
13.60 13.80 14.00 14.20 14.40 14.60 14.80 15.00
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
Well Screen Top Well Screen Bottom Specific Conductance Temperature
`
Figure 10: MW-18

Temperature and Specific Conductance vs. Depth
0
10
20
30
40
50
60
70
80
90
1100 1300 1500 1700 1900 2100 2300 2500
Specific Conductance (µS cm-1)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
0
10
20
30
40
50
60
70
80
90
13.00 13.50 14.00 14.50 15.00 15.50 16.00 16.50 17.00 17.50 18.00
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
Well Screen Top Well Screen Bottom Specific Conductance Temperature Figure 11: MW-19

Temperature and Specific Conductance vs. Depth
0
10
20
30
40
50
6000 6200 6400 6600 6800 7000
Specific Conductance (µS cm-1)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
0
5
10
15
20
25
30
35
40
45
14.20 14.40 14.60 14.80 15.00 15.20 15.40 15.60
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
Well Screen Top Well Screen Bottom Specific Conductance Temperature Figure 12: MW-22

Temperature and Specific Conductance vs. Depth
0
5
10
15
20
25
30
35
40
45
950 1050 1150 1250 1350 1450 1550
Specific Conductance (µS cm-1)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
0
5
10
15
20
25
30
35
40
45
14.30 14.35 14.40 14.45 14.50 14.55 14.60 14.65 14.70 14.75
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
Well Screen Bottom Specific Conductance Temperature Figure 13: MW-27 †

16

Temperature and Specific Conductance vs. Depth
0
5
10
15
20
4525 4535 4545 4555 4565 4575
Specific Conductance (µS cm-1)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
0
5
10
15
20
14.2 14.3 14.4 14.5 14.6 14.7 14.8
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
Well Screen Bottom Specific Conductance Temperature Figure 14: MW-29 †

Temperature and Specific Conductance vs. Depth
0
5
10
15
20
25
1500 2000 2500 3000 3500
Specific Conductance (µS cm-1)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
0
5
10
15
20
25
13.00 13.50 14.00 14.50 15.00 15.50 16.00 16.50 17.00 17.50 18.00
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
Well Screen Bottom Specific Conductance Temperature Figure 15: MW-30 †

Temperature and Specific Conductance vs. Depth
0
10
20
30
40
50
60
1695 1700 1705 1710 1715 1720 1725 1730
Specific Conductance (µS cm-1)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
0
10
20
30
40
50
14.00 14.20 14.40 14.60 14.80 15.00 15.20
Temperature (oC)
De
p
t
h

B
e
l
o
w

W
a
t
e
r

S
u
r
f
a
c
e

(
f
t
)
Well Screen Bottom Specific Conductance Temperature Figure 16: MW-31 †
Note: * Indicates the profile was taken entirely within the screened and saturated interval; neither well
screen bottom or top are displayed in the figure.
† Indicates the static water level was below the top of the well screen, therefore well screen
bottom is not displayed in the figure.
17

B. Low-Flow Sampling: Well-Pumping Field Notes and Observations
Low-flow sampling techniques were implemented for collecting groundwater
samples from the Mill. Theoretically, this technique allows for sampling a specific depth
in the water column, ostensibly isolating the groundwater flow path at that depth. From
this specific sample depth, stratification within the water column, if present, with respect
to groundwater ages and solute concentrations can be determined. Solute
concentrations can then be correlated to groundwater ages, information that can
ultimately be used in identifying potential sources of solute concentrations.
While very dependent on the hydrogeology of individual sites, flow rates used in
low-flow sampling are often on the order of 0.1-0.5 L min-1 (100-500 ml min-1), but can
be as high as 1 L min-1 (1000 mL min-1). This is the rate at which the pump is extracting
water from the formation at the depth at which the pump is placed, assuming the
formation is able to produce water at that rate. If the formation is unable to produce
water at the rate demanded by the pump, drawdown occurs in the water column. Thus,
the term “Low-flow” sampling is often referred to as “Minimal Drawdown” sampling.
Minimal drawdown is considered less than 0.1 m (10 cm) during purging (Puls and
Barcelona, 1995).
Pumping was conducted at the Mill so as to produce minimal drawdown within
each well (i.e., <0.1 m) during purging. Water levels in the wells were monitored during
pumping using a pressure transducer that converted the pressure head of the water
column into a reading in feet of hydrostatic head above the instrument. The transducer
was generally placed approximately 15-20 feet below the measured surface of the
water, or immediately above the pump unit when the pump was within 15 to 20 feet of
18

the surface of the water.
In some instances where wells were extremely low-yielding, drawdown was
occurring even when the pump was being operated at or near 0.1 L/min (100 mL/min).
This was the case for wells MW-1, MW-3, and MW-3A. For this type of situation, the
pump was lowered to the bottom of the well, at which time the wells were pumped to a
water level near the bottom of the screened interval. MW-1 was pumped to only 1
meter below the top of the screened interval because purging had been taking place for
almost 60 minutes. MW-1 was allowed to recover for approximately 12 hours
(overnight). Well MW-3A was pumped to approximately 1 m above the bottom of the
well screen. MW-3 was pumped to approximately 0.25 m above the bottom of the well
screen. Wells MW-3 and MW-3A were allowed to recover for a period of 3 days due to
both exhibiting extremely low-yielding properties during previous pumping events.
Water levels were monitored periodically during this recovery period in MW-3 and MW-
3A. MW-1 was sampled using the Grundfos pump, while MW-3 and MW-3A were
sampled with DUSA’s dedicated bladder pumps. A full suite of samples was taken from
MW-1 during well pump-down, and also after recovery. Samples taken after recovery
are hereafter denoted as MW-1B.
The passive sampler initially placed at the lower depth in MW-22 is suspected to
have been resting on sediment at the bottom of the well. A second passive diffusion
sampler was installed following removal of the first set, and is denoted as “MW-22(b)
deep” in tables where noble gas data are presented.
19

IV. ANALYTICAL RESULTS
A. Chlorofluorocarbon Age Dating
Chlorofluorocarbons in the atmosphere can be used to provide an estimate of
groundwater recharge date due to their changing concentration over time and their
solubility in water. Samples were collected from all 15 wells, including 4 wells sampled
at two depths, 2 wildlife ponds, tailings cells 1 and 3, and cell 2 slimes drain. Analyses
were conducted on most sites, analyzing a minimum of three bottles per site, with
analysis of the fourth and fifth sample bottles if necessary. This was needed when
outliers were found during the analysis of the first three bottles at a site (MW-2, MW-18
Deep, and MW-27). Tailings cells 1 and 3, and the cell 2 slimes drain, have not been
analyzed because of potential damage that extremely high levels of organics could
inflict on the analytical equipment. Both sampling depths in MW-22, and MW-30 have
not yet been analyzed because of strong signal interference with the CFC-12 signal,
potentially attributable to dissolved CO2 or N2O gases. This interference could
potentially damage the laboratory instruments; therefore, these samples were not
analyzed. CFC concentrations are presented in Table 1.
20

Table 1: Mean CFC concentrations in White Mesa water samples
SAMPLE ID Mean CFC-11
(pmoles/kg)
Mean CFC-12
(pmoles/kg)
Mean CFC-113
(pmoles/kg)
MW-1 2.594 1.896 0.092
MW-1B 2.750 1.683 0.093
MW-2 2.157 1.272 0.154
MW-3 1.285 0.826 0.130
MW-3A 2.759 1.885 0.223
MW-5 0.693 0.284 0.000
MW-11 0.179 0.090 0.000
MW-14 shallow 0.305 0.118 0.000
MW-14 deep 0.262 0.129 0.000
MW-15 0.686 0.678 0.014
MW-18 shallow 0.510 0.000 0.000
MW-18 deep 1.428 0.140 0.026
MW-19 shallow 1.503 0.974 0.028
MW-19 deep 1.622 1.110 0.087
MW-22 shallow n/a n/a n/a
MW-22 deep n/a n/a n/a
MW-27 0.809 3.709 0.016
MW-29 0.511 0.244 0.000
MW-30 n/a n/a n/a
MW-31 0.846 0.982 0.000
WP2 0.000 0.849 0.010
WP3 1.675 0.961 0.056
Tailings Cell 1 n/a n/a n/a
Tailings Cell 2 n/a n/a n/a
Tailings Cell 2
Slimes Drain n/a n/a n/a
note: n/a indicates samples were not analyzed because of potential damage to analytical equipment from
sample composition.

Results are reported in units of pico-moles per kilogram, or 10-12 moles of CFC
per kilogram of water sample. Samples MW-1, MW-1B, MW -2, and MW -3A show a
moderate amount of CFC-11, with MW -3, MW -18 deep, and both depths for MW -19
show slightly lower amounts of CFC-11. The remaining samples have very little
dissolved CFC-11. CFC-12 concentrations range from below detection to 3.7 pmoles
kg-1. Only small amounts of CFC-113, if any, were detected in the samples. CFC
concentration in the atmosphere since introduction of CFC’s in the 1940’s and 1950’s
have been monitored, and a historical record of CFC concentrations over the last 60
years allow groundwater ages to be estimated. These concentrations are plotted in
21

Figure 17. Measured CFC concentrations in a groundwater sample are compared with
corresponding atmospheric concentrations, and a groundwater recharge date is
obtained. These ages should be considered as apparent ages as a given sample may
contain a range of ages, and there are numerous processes such as degradation that
can affect CFC concentrations. The ranges are represented by the different calculated
recharge date for each CFC and are presented in Table 2. Samples collected near the
water table are always higher in concentration than deeper samplers. Because higher
concentrations are associated with younger water, this indicates that some recharge is
occurring at the site (i.e. placing younger water on top of older water.)
Atmospheric CFC Concentrations since 1940
0
100
200
300
400
500
600
1930 1940 1950 1960 1970 1980 1990 2000 2010
Year
At
m
o
s
p
h
e
r
i
c

C
F
C

(
p
p
t
)
CFC-11 CFC-12 CFC-113 Figure 17: CFC's in the atmosphere since 1940

22

Table 2: Calculated CFC recharge date ranges
Site CFC-11 Recharge Year CFC-12 Recharge Year CFC-113 Recharge Year
MW-1 1984 2001.5 1980
MW-1B 1985 1991 1980
MW-2 1979.5 1983 1984
MW-3 1971 1972.5 1980
MW-3A 1981.5 1989.5 1985.5
MW-5 1969.5 1966.5 1943
MW-11 1961.5 1958 1943
MW-14 Shallow 1962 1957 1943
MW-14 Deep 1961.5 1958 1943
MW-15 1967 1971 1963.5
MW-18 Shallow 1967.5 -- 1943
MW-18 Deep 1974.5 1961.5 1971
MW-19 Shallow 1975 1978.5 1971.5
MW-19 Deep 1975.5 1981.5 1979.5
MW-22 Shallow n/a n/a n/a
MW-22 Deep n/a n/a n/a
MW-27 1967.5 2001.5 1963.5
MW-29 1967 1965 1943
MW-30 n/a n/a n/a
MW-31 1970.5 1978.5 1943
WP2 -- 1973.5 1962
WP3 1973.5 1975 1974.5
note: n/a indicates samples were not analyzed because of potential damage to analytical equipment
from sample composition

Table 2 cells in which no data values are reported (--) represent situations in
which either no CFC’s were detected, giving a recharge date of pre-modern (before
1950’s), or CFC contamination occurred (i.e. values greater than equilibrium with the
modern atmospheric concentration). No recharge date is presented for wildlife pond 2
(CFC-11 and 113) or MW-18 shallow (CFC-12 and 113) because analytical errors
occurred for two of the three CFC compounds. Samples from wildlife pond 2 and MW-
18 shallow can be considered to have age ranges of ±5 years from the presented
recharge year.
Recharge elevations and temperatures are presented in Table 3. The recharge
temperature for most samples was obtained from noble gas analyses presented in
Section IV B. Samples for which noble-gas recharge temperatures were unavailable
23

were assumed to recharge at 15oC. All samples were assumed to have recharged at
1830 m elevation, or 6000 ft. This is based on the assumption that recharge occurs at
an elevation that is intermediate between the elevation of the study site (1700 m) and
the adjacent topographic highlands (i.e. the Abajo Mountains north of Blanding at about
3000 m.) The uncertainty in apparent age due to uncertainty in the recharge elevation
is about 1 year/1000 m for water that recharged in 1975. The uncertainty in the CFC
recharge year that results from uncertainty in recharge temperature is approximately 1
year/oC (Solomon and Cook, 2000).
Most sites exhibited CFC recharge date ranges of 1960’s and 1970’s, with
several sites in the early and mid 1980’s. Only MW-1 (B sample) and MW-3A had
CFC’s representative of the late 1980’s or early 1990’s. In both cases, wells were
pumped dry (according to Section IV) because of low-yielding characteristics, and well
MW-3A was subsequently sampled using DUSA dedicated bladder pumps. Potential
CFC contamination could have occurred in these wells, as well as MW-3, because of
exposure to atmosphere after pumping the boreholes dry. Furthermore, MW-3 and
MW-3A could have been contaminated because of the plastic tubing in the DUSA
dedicated bladder pumps. Plastics are often a source of contamination in CFC
analysis, and while the Grundfos pump and tubing had been tested for CFC
contamination prior to the sampling event, no such tests had been conducted on the
DUSA bladder pumps.

24

Table 3: Approximate Recharge Elevation and Temperature of Sampled Sites
Site Recharge Elevation (m) Recharge Temperature (oC)
MW-1 1830 15.00
MW-1B 1830 15.00
MW-2 1830 13.96
MW-3 1830 7.95
MW-3A 1830 11.04
MW-5 1830 15.00
MW-11 1830 15.00
MW-14 Shallow 1830 6.93
MW-14 Deep 1830 7.60
MW-15 1830 7.79
MW-18 Shallow 1830 15.00
MW-18 Deep 1830 15.00
MW-19 Shallow 1830 15.00
MW-19 Deep 1830 15.00
MW-22 Shallow n/a n/a
MW-22 Deep n/a n/a
MW-27 1830 6.50
MW-29 1830 13.10
MW-30 n/a n/a
MW-31 1830 15.00
WP2 1830 10.25
WP3 1830 10.25

B. Tritium/Helium-3 and Noble Gas Analysis
Water samples from all 15 wells, including 4 wells sampled at two depths, 2
wildlife ponds, and tailings cell 3 and cell 2 slimes drain, were analyzed for tritium (3H),
the only radioactive isotope of hydrogen, and a suite of dissolved noble gases. Tailings
cell 1 was not analyzed for tritium due to complications that arose during the helium-3
in-growth period (the acid water corroded the metal holding flask). Using the ratio of
tritium and 3He, the daughter product of decayed tritium, in water, an approximate age
of the water sample can be calculated. This age is representative of the time at which
the water parcel was last in equilibrium with the atmosphere in the last 40 to 50 years,
as the tritium incorporated into water molecules has been steadily changing since a
wide-scale atmospheric injection of tritium during above-ground thermonuclear weapons
25

testing in the 1950s and 1960s. As such, tritium concentrations in water samples give a
good idea of when groundwater recharged to the saturated zone. Tritium
concentrations for each site are presented in Table 4.
26

Table 4: Tritium concentrations in White Mesa water samples
Site Tritium Tritium - repeat
(TU) (error ±) (TU) (error ±)
MW-1 0.02 0.34 <0.3
MW-1B 0.03 0.11 n/a
MW-2 0.24 0.73 n/a
MW-3 <0.3 n/a
MW-3A <0.3 n/a
MW-5 <0.3 n/a
MW-11 <0.3 0.16 0.05
MW-14 Shallow 0.36 1.05 0.04 0.05
MW-14 Deep <0.3 n/a
MW-15 <0.3 <0.3
MW-18 Shallow <0.3 <0.3
MW-18 Deep 0.05 0.40 <0.3
MW-19 Shallow 3.11 0.31 n/a
MW-19 Deep 3.96 0.37 n/a
MW-22 Shallow <0.3 n/a
MW-22 Deep 0.87 0.31 <0.3
MW-27 8.67 0.92 n/a
MW-29 <0.3 0.07 0.16
MW-30 <0.3 n/a
MW-31 <0.3 n/a
TC1 n/a† n/a
TC2 Slimes Drain 0.93 0.68 1.04 0.13
TC3 6.01 1.37 7.24 0.55
WP2 5.98 0.39 n/a
WP3 5.94 0.40 n/a
Note: n/a indicates no analysis conducted, † indicates corrosion of metal holding flask preventd analysis.

Error reported is 1σ. Concentration units are reported as tritium units (TU), which
represents a single molecule of 3H1HO in 1018 molecules of 1H2O, or 6.686x107 tritium
atoms kg-1 (Solomon and Cook, 2000). Analyses were repeated on samples that were
not completely degassed during sample preparation. These analyses provided better
resolution in the final concentration and are presented in the “Tritium – Repeat” column.
Most sites exhibited very low to no tritium levels, with a few exceptions. Wildlife
ponds 2 and 3 had about 6 TU in both, in concert with the nature of a surface water site
receiving modern water from the atmosphere. MW-19 had tritium levels of 3.1 and
nearly 4.0 TU for the shallow and deep sampling points, respectively. MW-27 also
27

exhibited elevated tritium levels (8.67 TU). Small amounts of tritium were observed in
the deep sampling point at MW-22 (0.87 TU).
MW-19 (shallow and deep) and MW-27 are close to the northern wildlife ponds and are
likely to be influenced by recharge from the ponds. Recharge occurring due to the
wildlife ponds would contain some amount of tritium due to pond water interacting with
the atmosphere. This means groundwater flow near the wildlife ponds is being
influenced by artificial recharge and the tritium seen in MW-19 and MW-27 is evidence
of water derived from the wildlife ponds. Tritium in MW-22 deep indicates a small
amount of recharge taking place near the well. The southern margin of artificial
recharge is likely to be between MW-27 and MW-31 while the northern margin appears
to be between MW-18 and MW-19.
That MW-27 has the highest tritium levels of all sites, including surface water
sites, does not necessarily mean that it is the youngest water. Atmospheric tritium
concentrations have varied over time, therefore tritium concentrations alone do not
provide an absolute age-date for a given sample. Heilwell et. al (2006) plotted Tritium
concentrations in the atmosphere for the western United States, shown in Figure 18.
The fact that significant and measurable quantities of tritium are present in MW-27, MW-
19, and the wildlife ponds, indicates recharge to the aquifer from the wildlife ponds is
occurring. Tritium in MW-22 deep suggests that an extremely localized area of
recharge is occurring near that well.
28

Figure 18: Atmospheric tritium concentrations in the southwest United States (Heilwell et. al, 2006)

Ten of the wells have small but measurable amounts of CFCs (excluding
samples where contamination during sampling may have occurred), but contain
essentially no tritium. This is likely the result of differences between where the CFC and
tritium “clocks” start. Tritium is part of the water molecule and the travel time associated
with this tracer starts at the land surface. In contrast, CFCs are gases that can dissolve
into water and the clock associated with this tracer is set near the water table. In the
unsaturated zone, CFCs from the atmosphere may be transported as a gas phase by
way of either diffusion or advection. Since transport in the gas phase is typically much
more rapid than transport in the aqueous phase, CFCs can be transported to the water
table in much less time than tritium. In other words, the observation of small amounts of
CFCs with no tritium is interpreted to mean that aqueous phase transport through the
29

unsaturated zone requires more than 50 years, whereas gas phase transport of CFCs
requires much less time. Nevertheless, the mere presence of CFCs below the water
table does suggest that recharge is occurring (if there were no downward water
movement across the water table CFCs from the unsaturated zone would not be
transported to depth.)
Passive diffusion samplers were used to measure dissolved gas composition of
groundwater. These analyses provide insight to the temperature at which a parcel of
groundwater recharged to the saturated zone, and also information about the origin of
water using the ratios of helium-3 to helium-4, and helium-4 to neon-20, along with the
theoretical solubility of noble gases in water. Of the two sample volumes sealed on-site
(two sample volumes for each sampler at each depth), the first volume was initially
analyzed to get the best possible result for dissolved gas concentrations. The first
volume sealed had less time to equilibrate with the atmosphere after being removed
from the well and will therefore be more representative of the in situ dissolved gases.
Concentrations of dissolved gases are presented in Table 5.
An unusually high amount of helium-4 was present in the cell 2 slimes drain
sample (sample TC2 SD). While some amount of helium-4 would be present due to
uranium-thorium decay since construction of the cells, it is highly unlikely that the
majority of helium-4 seen in the sample (9x10-6 ccSTP/g) is due to recent uranium-
thorium decay because of the extremely long half-life of the major isotopes of uranium.
Instead, it is likely that the milling process has accelerated the release of helium that
accumulated within the sediment over geologic time.
Table 6 presents concentrations of measured total helium-4 and R/Ra, along with
30

calculated concentrations of terrigenic helium-4. R is the measured 3He/4He ratio in a
sample and Ra is the 3He/4He ratio of a global air standard (1.384 X 10–6.) Thus, R/Ra
represents the 3He content of the sample and is the customary manner used to report
helium isotope measurements. To obtain the absolute concentration of 3He, the R/Ra
value can be multiplied by Ra (1.384 X 10–6) and the measured concentration of 4He.
Total helium-4 (4Hetot) is the total measured amount of helium-4 in the sample and is
representative of the amount of helium-4 dissolved in water. Terrigenic helium-4
(4Heterr) is calculated by subtracting the amount of helium-4 expected to be present in
water due to interaction with the atmosphere at the time of recharge from the measured
total helium-4 in water, assuming all other sources of helium-4 are negligible. The
helium-4 derived from atmospheric solubility is determined by combining estimates of
recharge temperature and elevation with laboratory measurements of the solubility. The
amount of atmospheric helium in excess of solubility (known as excess air) was
determined using neon measurements. Terrigenic helium-4 is helium-4 that is derived
from Uranium-Thorium series decay in the aquifer material and subsequently escapes
from the rock structure into the water via diffusion.
31

Table 5: In situ Dissolved Gas Concentrations
Site N2 40Ar 84Kr 20Ne 4He 129Xe
(ccSTP/g) (ccSTP/g) (ccSTP/g) (ccSTP/g) (ccSTP/g) (ccSTP/g)
MW-1 Shallow 1.69E-02 5.05E-04 6.37E-08 2.25E-07 6.12E-08 3.89E-09
MW-1 Deep 1.96E-02 5.66E-04 7.17E-08 2.53E-07 7.08E-08 4.57E-09
MW-2 Shallow 9.56E-03 2.64E-04 3.40E-08 1.28E-07 3.26E-08 2.25E-09
MW-2 Deep 1.19E-02 3.19E-04 4.20E-08 1.52E-07 4.15E-08 2.78E-09
MW-3 1.25E-02 3.35E-04 4.24E-08 1.56E-07 3.98E-08 3.10E-09
MW-3A Shallow 1.26E-02 3.48E-04 4.45E-08 1.66E-07 4.31E-08 2.71E-09
MW-3A Deep 1.38E-02 3.31E-04 3.88E-08 1.88E-07 4.96E-08 2.65E-09
MW-5 Shallow 1.68E-02 4.12E-04 5.27E-08 1.72E-07 4.80E-08 3.67E-09
MW-5 Deep 1.75E-02 3.99E-04 5.14E-08 1.81E-07 5.20E-08 3.43E-09
MW-11 Shallow 1.79E-02 4.67E-04 5.96E-08 2.27E-07 8.69E-08 3.63E-09
MW-11 Deep 2.05E-02 4.86E-04 6.05E-08 2.66E-07 1.05E-07 3.84E-09
MW-14 Shallow 1.41E-02 3.90E-04 4.93E-08 1.78E-07 4.34E-08 3.12E-09
MW-14 Deep 1.66E-02 4.40E-04 5.38E-08 2.18E-07 5.48E-08 3.36E-09
MW-15 Shallow 1.52E-02 4.06E-04 4.88E-08 1.92E-07 4.87E-08 2.86E-09
MW-15 Deep 1.63E-02 3.79E-04 4.40E-08 2.21E-07 6.58E-08 2.74E-09
MW-18 Shallow 1.81E-02 4.85E-04 5.92E-08 2.34E-07 6.96E-08 3.64E-09
MW-18 Deep 1.81E-02 5.32E-04 6.67E-08 2.28E-07 7.18E-08 3.95E-09
MW-19 Shallow 2.63E-02 7.16E-04 8.60E-08 3.56E-07 9.62E-08 4.70E-09
MW-19 Deep 2.72E-02 7.08E-04 8.42E-08 3.63E-07 9.44E-08 4.80E-09
MW-22 Shallow 1.20E-02 3.24E-04 4.01E-08 1.71E-07 4.89E-08 2.47E-09
MW-22b Deep 1.19E-02 3.24E-04 4.02E-08 1.66E-07 4.91E-08 2.52E-09
MW-22 Deep 1.22E-02 3.26E-04 4.14E-08 1.84E-07 5.68E-08 2.41E-09
MW-27 Shallow 1.04E-02 3.58E-04 5.32E-08 1.30E-07 3.33E-08 3.39E-09
MW-27 Deep 1.10E-02 3.69E-04 5.38E-08 1.37E-07 3.42E-08 3.36E-09
MW-29 Shallow 1.75E-02 3.49E-04 4.20E-08 2.52E-07 6.34E-08 2.76E-09
MW-29 Deep 2.01E-02 3.93E-04 4.52E-08 3.02E-07 8.37E-08 2.84E-09
MW-30 Shallow 1.24E-02 3.62E-04 4.69E-08 1.55E-07 3.96E-08 2.94E-09
MW-30 Deep 1.35E-02 3.85E-04 4.94E-08 1.64E-07 4.11E-08 3.35E-09
MW-31 Shallow 1.48E-02 4.19E-04 5.60E-08 1.95E-07 6.16E-08 3.52E-09
MW-31 Deep 1.62E-02 4.48E-04 5.84E-08 2.12E-07 6.53E-08 3.85E-09
TC1 1.66E-02 4.19E-04 9.49E-08 6.70E-08 2.73E-08 8.31E-09
TC2 SD 1.31E-02 7.32E-04 1.57E-07 7.85E-08 9.00E-06 2.80E-09
TC3 4.72E-03 2.84E-04 5.13E-08 5.86E-08 1.85E-08 6.35E-09
WP2 1.45E-02 7.39E-04 1.50E-07 1.49E-07 3.46E-08 3.53E-08
WP3 7.50E-03 3.76E-04 7.05E-08 7.74E-08 1.70E-08 3.18E-08

32

Table 6: Summary of Helium Concentrations
Site 3Hetot 4Heterr 4Hetot R/Ra
(ccSTP/g) (ccSTP/g) (ccSTP/g)
MW-1shallow 7.65E-14 4.85E-09 6.12E-08 0.903
MW-1deep 8.55E-14 <1.0E-10 7.08E-08 0.872
MW-2shallow 4.46E-14 2.87E-09 3.26E-08 0.987
MW-2deep 5.42E-14 2.87E-09 4.15E-08 0.944
MW-3 5.46E-14 2.25E-10 3.98E-08 0.992
MW-3Ashallow 5.95E-14 4.03E-10 4.31E-08 0.999
MW-3Adeep 6.77E-14 <1.0E-10 4.96E-08 0.986
MW-5shallow 5.34E-14 5.64E-09 4.80E-08 0.805
MW-5deep 5.44E-14 6.91E-09 5.20E-08 0.757
MW-11shallow 7.14E-14 2.99E-08 8.69E-08 0.594
MW-11deep 8.49E-14 3.76E-08 1.05E-07 0.584
MW-14shallow 5.87E-14 <1.0E-10 4.34E-08 0.979
MW-14deep 7.18E-14 <1.0E-10 5.48E-08 0.946
MW-15shallow 6.32E-14 <1.0E-10 4.87E-08 0.938
MW-15deep 7.60E-14 7.05E-09 6.58E-08 0.835
MW-18shallow 7.91E-14 1.07E-08 6.96E-08 0.821
MW-18deep 8.19E-14 1.64E-08 7.18E-08 0.824
MW-19shallow 1.31E-13 7.44E-09 9.62E-08 0.989
MW-19deep 1.24E-13 4.07E-09 9.44E-08 0.952
MW-22shallow 6.82E-14 4.01E-09 4.89E-08 1.007
MW-22(b)deep 6.81E-14 5.95E-09 5.68E-08 0.965
MW-22deep 7.58E-14 5.25E-09 4.91E-08 1.003
MW-27shallow 4.74E-14 1.32E-09 3.33E-08 1.029
MW-27deep 4.76E-14 1.32E-09 3.42E-08 1.006
MW-29shallow 8.58E-14 <1.0E-10 6.34E-08 0.978
MW-29deep 1.14E-13 <1.0E-10 8.37E-08 0.991
MW-30shallow 5.55E-14 5.26E-10 4.11E-08 1.013
MW-30deep 5.37E-14 3.37E-10 3.96E-08 0.944
MW-31shallow 6.58E-14 1.30E-08 6.16E-08 0.773
MW-31deep 7.59E-14 1.24E-08 6.53E-08 0.840
TC1 3.35E-14 1.26E-08 2.73E-08 0.887
TC2 Slimes Drain 1.96E-14 8.96E-06 9.00E-06 0.002
TC3 2.17E-14 6.42E-09 1.85E-08 0.853
WP2 4.72E-14 <1.0E-10 3.46E-08 0.987
WP3 2.26E-14 2.99E-09 1.7E-08 0.963

In general, higher concentrations of helium-4 indicate older water relative to
waters with lower concentrations of helium-4. High terrigenic helium-4 values are
expected in waters that have been in contact with aquifer material for longer periods of
time as these waters will have had more time to accumulate helium-4 derived from
sediment and rocks thru the in-growth of progeny from the Uranium and Thorium decay
series. R/Ra values greater than one may be an indication of tritiogenic helium-3 in the
33

water. Because helium-3 is the daughter product of tritium decay, water that contained
tritium at one point in time will exhibit relatively higher concentrations of helium-3 than
water that did not contain tritium. R/Ra of less than one may be indicative of an
accumulation of terrigenic helium-4 in the water being sampled.
Measurable amounts of tritium in MW-19 shallow and deep, MW-22 deep, and
MW-27 suggest the presence of younger water mixing with older groundwater (see
Table 4, above). Additionally, the proximity of MW-19 and MW-27 to the northern
wildlife ponds supports the possibility of young water mixing with older groundwater in
those wells. Tritium would be expected in water that is recharging from ponds that were
constructed within the last 15 years, and this tritium is now observable in MW-19 and
MW-27.
MW-30 shallow exhibited an R/Ra value greater than one, suggesting a small
amount of tritiogenic 3He near the top of the water column (see Tables 4 and 6). MW-
19 deep had a tritium concentration of nearly 4 TU, but exhibited an R/RaA value less
than one (compare Tables 4 and 6). This is likely the result of a small amount of
tritiogenic 3He with a larger amount of terrigenic 4He. Excluding MW-19 shallow, which
also had an R/Ra less than one, other samples that contained tritium exhibited R/Ra
values greater than one. This is expected from the decay of tritium to helium-3,
increasing the ratio of helium-3 to helium-4 to a value greater than that of the
atmosphere. Thus, some samples near the wildlife ponds have helium isotope values
that are consistent with transport of young water being recharged at the ponds [e.g.,
MW-27 (shallow and deep) and MW-30 (shallow)]. With the exception of MW-22, the
remainder of samples exhibited R/Ra values less than one, indicating helium-3 was
34

proportionally lower, or helium-4 was proportionally higher to that of the atmosphere.
Evaluating the contribution of various sources for helium-3 and helium-4 inputs
can be accomplished by plotting the following:
EAtot
sol
EAtot
EAtot
HeHe
HevsHeHe
HeHe
44
4
44
33
.−−
−
where 3Hetot is the measured total helium-3 in the sample, 3HeEA is the excess air
component of helium-3 in the sample, 4Hetot is the measured total helium-4 in the
sample, 4Hesol is the equilibrium solubility of helium-4 in the sample, and 4HeEA is the
excess air component of helium-4 in the sample (Solomon, 2000). Excess air results
when the water table rises and traps small amounts of the soil atmosphere as bubbles
that are now below the water table. Due to the increased fluid pressure that now exists
on these bubbles, they partially or completely dissolve thereby imparting extra gas
above thermodynamic equilibrium. The solubility component of helium is determined by
using estimates of the temperature and elevation at which the water sample recharged
combined with laboratory measurements of solubility. If there was no helium-4 input
from excess air or from alpha-decay in the subsurface (i.e. decay from uranium-238,
thorium-230, radium-226, radon-222, etc.), the left-hand side of the equation would
simply be the helium-3/helium-4 ratio observed in the atmosphere, or 1.384 x 10-6. The
right-hand side of the equation, or the fraction of atmospheric helium-4, in this case
would be 1.
35

Table 7: Excess air-corrected helium isotope ratios
Site 3Hetot 3HeEA 4HeEA 4Hesol 4Hetot (3Hetot-3HeEA)/
(4Hetot-4HeEA)
4Hesol/
(4Hetot-4HeEA)
(ccSTP/g) (ccSTP/g) (ccSTP/g) (ccSTP/g) (ccSTP/g)
MW-1shallow 8.55E-14 3.90E-14 2.82E-08 3.94E-08 7.08E-08 1.09E-06 9.24E-01
MW-1deep 7.65E-14 2.66E-14 1.92E-08 3.94E-08 6.12E-08 1.19E-06 9.38E-01
MW-2shallow 5.42E-14 1.93E-15 1.39E-09 3.73E-08 4.15E-08 1.30E-06 9.29E-01
MW-2deep 4.46E-14 0.00E+00 0.00E+00 3.60E-08 3.26E-08 1.37E-06 1.00E+00
MW-3 5.46E-14 2.87E-15 2.07E-09 3.76E-08 3.98E-08 1.37E-06 9.98E-01
MW-3Ashallow 6.77E-14 2.01E-14 1.45E-08 3.67E-08 4.96E-08 1.36E-06 1.00E+00
MW-3Adeep 5.96E-14 7.64E-15 5.52E-09 3.75E-08 4.31E-08 1.38E-06 9.97E-01
MW-5shallow 5.45E-14 9.63E-15 6.96E-09 3.87E-08 5.20E-08 9.95E-07 8.60E-01
MW-5deep 5.35E-14 4.66E-15 3.37E-09 3.91E-08 4.80E-08 1.09E-06 8.76E-01
MW-11shallow 8.50E-14 4.48E-14 3.24E-08 3.93E-08 1.05E-07 5.52E-07 5.41E-01
MW-11deep 7.14E-14 2.80E-14 2.03E-08 3.92E-08 8.69E-08 6.51E-07 5.89E-01
MW-14shallow 7.18E-14 2.96E-14 2.14E-08 3.77E-08 5.48E-08 1.26E-06 1.00E+00
MW-14deep 5.88E-14 1.16E-14 8.41E-09 3.78E-08 4.34E-08 1.35E-06 1.00E+00
MW-15shallow 7.61E-14 3.23E-14 2.33E-08 3.73E-08 6.58E-08 1.03E-06 8.78E-01
MW-15deep 6.32E-14 1.72E-14 1.24E-08 3.80E-08 4.87E-08 1.27E-06 1.00E+00
MW-18shallow 8.19E-14 2.80E-14 2.03E-08 3.94E-08 7.18E-08 1.05E-06 7.64E-01
MW-18deep 7.91E-14 3.08E-14 2.22E-08 3.93E-08 6.96E-08 1.02E-06 8.29E-01
MW-19shallow 1.24E-13 8.74E-14 6.32E-08 3.92E-08 9.44E-08 1.18E-06 1.00E+00
MW-19deep 1.32E-13 8.56E-14 6.19E-08 3.89E-08 9.62E-08 1.34E-06 1.00E+00
MW-22shallow 7.58E-14 1.79E-14 1.29E-08 3.68E-08 5.68E-08 1.32E-06 8.39E-01
MW-22deep 6.82E-14 9.33E-15 6.74E-09 3.69E-08 4.91E-08 1.39E-06 8.72E-01
MW-22deep(b) 6.82E-14 1.40E-14 1.01E-08 3.64E-08 4.89E-08 1.40E-06 9.36E-01
MW-27shallow 4.76E-14 0.00E+00 0.00E+00 3.80E-08 3.42E-08 1.39E-06 1.00E+00
MW-27deep 4.74E-14 0.00E+00 0.00E+00 3.77E-08 3.33E-08 1.42E-06 1.00E+00
MW-29shallow 1.15E-13 6.97E-14 5.04E-08 3.68E-08 8.37E-08 1.35E-06 1.00E+00
MW-29deep 8.58E-14 4.76E-14 3.44E-08 3.67E-08 6.34E-08 1.32E-06 1.00E+00
MW-30shallow 5.38E-14 3.26E-15 2.36E-09 3.85E-08 4.11E-08 1.30E-06 9.91E-01
MW-30deep 5.55E-14 1.09E-15 7.88E-10 3.79E-08 3.96E-08 1.40E-06 9.77E-01
MW-31shallow 7.59E-14 2.13E-14 1.54E-08 3.93E-08 6.53E-08 1.09E-06 7.88E-01
MW-31deep 6.58E-14 1.55E-14 1.12E-08 3.89E-08 6.16E-08 1.00E-06 7.72E-01
Tailings Cell 1 3.35E-14 0.00E+00 0.00E+00 4.11E-08 2.73E-08 1.23E-06 1.00E+00
Tailings Cell 2
Slimes Drain 1.97E-14 0.00E+00 0.00E+00 4.11E-08 9.00E-06 2.19E-09 4.57E-03
Tailings Cell 3 2.18E-14 0.00E+00 0.00E+00 4.11E-08 1.85E-08 1.18E-06 1.00E+00
Wildlife Pond 2 4.73E-14 0.00E+00 0.00E+00 4.33E-08 3.46E-08 1.37E-06 1.00E+00
Wildlife Pond 3 2.26E-14 0.00E+00 0.00E+00 4.33E-08 1.70E-08 1.33E-06 1.00E+00
Atmospheric Helium 1.37E-06 1
Note: Bold-faced type indicates samples with excess air-corrected helium-3/helium-4 ratios greater than
that of atmospheric. Excess air corrections are not needed for the surface water sites (see
previous discussion regarding the formation of excess air.)

The amount of helium-3 in the sample due to excess air input (3HeEA) was
calculated using the ratio in the sample of helium-3 to neon-20 multiplied by the
difference of the measured neon-20 in the sample and the theoretical solubility of neon-
36

20. The calculation was conducted as follows:
()EAsolmeas
NeHe HeNeNeR32020*
20
3 =−
where R(3He/20Ne) is determined as the ratio of helium-3 to neon-20 in the atmosphere,
20Nemeas is the measured amount of 20Ne in the sample, and 20Nesol is the expected
solubility of neon in the water. Neon is useful in this calculation because the ratio of
neon-20 to helium-3 in the atmosphere is constant. Furthermore, the expected solubility
of neon is only a weak function of the temperature and salinity of the water.
Helium-4 dissolved in the sample due to excess air input was calculated in much
the same way as helium-3 due to excess air, but with the ratio of helium-4 to neon-20 in
the atmosphere only. It was conducted as follows:
()EAsolmeas
NeHe HeNeNeR42020*
20
4 =−
where R(4He/20Ne) is the ratio of helium-4 to neon-20 in the atmosphere, 20Nemeas is the
measured amount of 20Ne in the sample, and 20Nesol is the expected solubility of neon in
the water.
The expected solubility of helium-4 in the sample, 4Hesol, is calculated based on
the salinity and temperature of the well water at the time of the sample. Lastly, the total
amount of helium-4 in the sample, 4Hetot, is the total amount of helium-4 in the sample
measured in the laboratory.
The helium-3/helium-4 ratio of He produced in Earth’s crust is lower than the ratio in
the atmosphere (Solomon, 2000.) Therefore, as a parcel of water moves through the
aquifer and acquires helium generated within the aquifer, both the helium-3/helium-4
ratio and the fraction of helium-4 derived from atmospheric equilibration will decline.
Figure 19 plots the above helium isotope relationships for monitoring wells at the Mill.
37

Samples from MW-11 plot at one end of the graph as they contain the largest amounts
of terrigenic helium and thus contain the largest components of old water. Figure 20
plots the above helium isotope relationships for surface water sites (tailings cells and
wildlife ponds) at the Mill.
Figure 19: Helium isotope ratios, corrected for input due to excess air; monitoring wells only

Isotope Ratios of Helium - Monitoring Wells
0.0E+00
2.0E-07
4.0E-07
6.0E-07
8.0E-07
1.0E-06
1.2E-06
1.4E-06
1.6E-06
0.2 0.4 0.6 0.8 1.0 1.2
4Hesol/(4Hetot-4HeEA)
(
3He
to
t
-3He
EA
)/
(
4He
to
t
-4He
EA
)
Monitoring Wells Atmospheric Helium
Atmospheric
helium
MW-11 shallow
MW-11 deep
38

Figure 20: Helium isotope ratios, corrected for input due to excess air; surface water sites only

C. Anions
Nitrate and Nitrite levels as nitrogen, and sulfate levels in water samples were
analyzed by the Utah State Department of Health, Division of Laboratory Services. The
Utah groundwater quality standard (GWQS) of 10 mg L-1 was exceeded by wells MW-30
and MW-31 (UAC R317-6-2).
Sulfate concentrations can be compared with the National Secondary Drinking
Water Regulation, as set by the United States Environmental Protection Agency
(USEPA, 2003), at 250 mg L-1 sulfate in a community water system. This concentration
was exceeded by all monitoring wells except MW-27. This value was also greatly
exceeded by the tailings cells and Cell 2 slimes drain. No GWQS or site-specific
groundwater protection limit (GWPL) is currently in effect for sulfate concentrations.
Isotope Ratios of Helium - Surface Water Sites
0.0E+00
2.0E-07
4.0E-07
6.0E-07
8.0E-07
1.0E-06
1.2E-06
1.4E-06
1.6E-06
0.0 0.2 0.4 0.6 0.8 1.0 1.2
4Hesol/(4Hetot-4HeEA)
(3He
to
t
-3He
EA
)/
(
4He
to
t
-4He
EA
)
Tailings Cells Wildlife Ponds Atmospheric Helium
Atmospheric helium
TC 2 Slimes Drain
39

Table 8 presents the concentrations of inorganic constituents in monitoring wells and
surface water sites.
Table 8: Concentrations of Anions
Site NO2+NO3, N Sulfate
(mg/L) (mg/L)
MW-01 0.35 644
MW-01B 0.25 708
MW-02 <0.1 1,780
MW-03 0.19 2,960
MW-03A 1.07 3,070
MW-05 <0.1 980
MW-11 <0.1 947
MW-14 Shallow <0.1 2,120
MW-14 Deep <0.1 2,050
MW-15 0.13 2,200
MW-18 Shallow 0.36 1,690
MW-18 Deep <0.1 1,810
MW-19 Shallow 2.62 556
MW-19 Deep 2.69 581
MW-22 Shallow 3.36 5,060
MW-22 Deep 3.24 5,100
MW-27 5.46 52.1
MW-29 0.79 2,830
MW-30 15.5 859
MW-31 24.6 598
TC1 113 2,500,000
TC2 Slimes Drain 5.19 666,000
TC3 19.6 107,000
WP2 <0.1 39.9
WP3 <0.1 33.1
Equipment Blank <0.1 <20.0
Note: Bold-faced type indicates samples that exceeded the state GWQS

D. Trace Metals
Concentrations of manganese, selenium, and uranium in groundwater samples
and surface water samples were analyzed by the Utah State Department of Health,
Division of Laboratory Services. Uranium concentrations exceeded the Utah State
GWQS of 30 µg L-1 in 8 of the monitoring wells, and in all three tailings cells (UAC
R317-6-2). MW-3, both depths sampled at MW-14, MW-15, both depths sampled at
MW-18, and both depths sampled at MW-22 had uranium concentrations greater than
40

30 µg L-1.
Concentrations of manganese exceeded the ad-hoc groundwater quality
standard of 800 µg L-1 as put forth in the Groundwater Discharge Permit for
International Uranium (USA) Corporation, now Denison Mines, Co., in 7 monitoring well
samples (Utah Water Quality Board). Wells MW-3, MW-3A, both depths sampled at
MW-14, both depths sampled at MW-18, both depths sampled at MW-22, and MW-29
had concentrations greater than 800 µg L-1. The equipment blank likely exhibits a
presence of manganese because it was taken after decontamination of the pump
following sampling MW-22, the well with highest manganese concentrations. Residual
manganese in the pump tubing following MW-22 sampling thus may have been present
in the equipment blank sample.
Only MW-3A, MW-15, and MW-31 had concentrations of selenium that exceeded
the State GWQS of 50 µg L-1 set forth by the Utah Division of Water Quality (UAC
R317-6-2). Tailings cell 3 was reported to have a selenium concentration of 1550 µg L-
1, while the sample from cell 2 Slimes Drain was reported only as having a
concentration of selenium less than 400 µg L-1. Trace metal concentrations are
presented in Table 9.
41

Table 9: Trace Metal Concentrations
Site Selenium (µg/L) Manganese (µg/L) 238U (µg/L)
MW-01 <2.0 78.8 <1.0
MW-01B <2.0 115 <1.0
MW-02 8.7 <10.0 10.5
MW-03 10.2 2,460 35.9
MW-03A 74.2 1,360 19.9
MW-05 2.42 190 <1.0
MW-11 <2.0 64.7 <1.0
MW-14 Shallow <2.0 2,080 59.4
MW-14 Deep <2.0 2,020 59.4
MW-15 96.4 <10.0 42.9
MW-18 Shallow 2.5 84 41.2
MW-18 Deep 2.3 202 33.3
MW-19 Shallow 10.4 <10 6.94
MW-19 Deep 10.4 <10.0 7.68
MW-22 Shallow 15.2 32,900 38.8
MW-22 Deep 15.3 35,500 39.7
MW-27 10.1 <10.0 29.5
MW-29 3.35 5,100 10.2
MW-30 32.6 <10.0 6.31
MW-31 58.7 <10.0 7.01
TC1 16,200 869,000 581,000
TC2 Slimes Drain <400.0 139,000 23,700
TC3 1,550 248,000 68,100
WP2 <2.0 17 9.92
WP3 <2.0 16.2 <1.0
Equipment Blank <2.0 31.5 <1.0
Note: bold-faced type indicates samples that exceeded the state Groundwater Quality Standard (GWQS)
or, in the case of manganese, the ad-hoc GWQS

E. D and 18O Isotope Ratios in Water
Deuterium and oxygen-18 can be used as environmental tracers of groundwater
because they are part of the water molecule and have a conservative nature.
Enrichment of deuterium and oxygen-18 (i.e. isotopically heavier) may indicate
significant evaporation is occurring at the recharge point, while depletion of deuterium
and oxygen-18 (i.e. isotopically lighter) may indicate groundwater recharge is occurring
at higher elevations and lower temperatures. Enriched values are less negative and
represent a relatively heavier isotopic composition, while depleted values are more
negative and represent a relatively lighter isotopic composition. Groundwater and
42

surface water samples were analyzed for deuterium and oxygen-18 isotope ratios, the
results of which are presented in Table 10 below.
Table 10: δD and δ18O Isotope ratios in water
Site Depth δD (‰) δD σ (±‰) δ18O (‰) δ18O σ (±‰)
MW-01 -113 1.6 -14.8 0.13
MW-01B -113 0.3 -14.3 0.02
MW-02 -113 0.5 -14.2 0.01
MW-03 -106 1.0 -13.2 0.16
MW-03A -107 1.4 -13.3 0.19
MW-05 -112 2.3 -14.1 0.03
MW-11 -115 0.3 -15.6 0.04
MW-14 shallow -110 0.0 -13.8 0.05
MW-14 deep -112 0.5 -13.9 0.03
MW-15 -111 0.5 -14.0 0.09
MW-22 shallow -110 1.7 -13.5 0.23
MW-22 deep -107 0.2 -13.2 0.05
MW-27 -83 0.5 -9.8 0.07
MW-29 -107 2.0 -13.3 0.00
MW-30 -95 0.3 -11.7 0.09
MW-31 -95 1.1 -11.9 0.22
MW-18 shallow -103 1.7 -13.7 0.05
MW-18 deep -107 2.1 -13.9 0.18
MW-19 shallow -81 1.5 -9.6 0.05
MW-19 deep -81 2.0 -9.5 0.04
WP2 -45 1.9 -1.3 0.15
WP3 -60 0.3 -5.3 0.14
TC1 -- -- -- --
TC2 Slimes
Drain -- -- -- --
TC3 -12 7.9 4.9 0.92
Note: isotope ratios are calculated as ()()‰1000*1/
/
1618
1618
18 ⎟⎟
⎠
⎞
⎜⎜
⎝
⎛−=∂
reference
sample
sample OO
OOO VSMOW, where
VSMOW is the name of the reference.

Isotope ratios for deuterium relative to the standard VSMOW for monitoring wells
ranged from -115‰ to -81‰. The highest values of -81‰ and -83‰ were found in
wells MW-19 at both depths and MW-27, respectively. Wildlife ponds 2 and 3 showed
deuterium isotope ratios of -45‰ and -60‰, respectively. Tailings cell 3 had a
deuterium isotope ratio of -12‰.
Isotope ratios for oxygen-18 relative to the standard VSMOW for monitoring wells
43

ranged from -15.6‰ to -9.5‰. The highest values of -9.6‰, -9.5‰, and -9.8‰ were
found in MW-19 shallow, MW-19 deep, and MW-27, respectively. Wildlife ponds 2 and
3 had oxygen-18 isotope ratios of -1.3‰ and -5.3‰, respectively. Tailings cell 3 had an
oxygen-18 isotope ratio of 4.9‰.
Tailings cell 1 and cell 2 slimes drain were not analyzed by the contract laboratory
because of damage that could have been incurred upon the laboratory equipment due
to the low-pH of the wastewater collected.
Figure 21 plots the deuterium and oxygen-18 isotope ratios for each sample site.
Figure 22 plots the regressed isotope ratio data along with the Global Meteoric Water
Line after Craig (1961) and the Utah Meteoric Water Line after Kendal and Coplen
(2001).
δD & δ18O isotope ratios of water
-140
-120
-100
-80
-60
-40
-20
0
20
-20.0 -15.0 -10.0 -5.0 0.0 5.0 10.0
δ18O
δD
Monitoring Wells Surface Sites Figure 21: δD and δ18O isotope ratios of water

WP3 WP2
TC3
MW-19 (deep & shallow), MW-27
MW-30
MW-31
MW-11
44

Figure 22: and δ18O isotope ratios of water, regressed δ-Deuterium vs. δ18O data with Global Meteoric
Water Line and Utah Meteoric Water Line

The monitoring wells plot along a line of similar slope to the Utah (local) meteoric
water line, but offset slightly. The surface water sites plot along a line with a slope one
might expect to see in evaporated waters. Wells MW-19 (shallow and deep), MW-27,
MW-30, and MW-31 have enriched (more positive) values for δ18O and plot along the
evaporation line suggesting that these wells have been influenced by evaporated
surface water from the wildlife ponds. Nevertheless, the δD values for evaporated
versus meteoric water for these wells is small suggesting the presence of non-
evaporated background water (i.e. a mixture of pond and background water.) Well MW-
11 does not show an evaporated signal suggesting that neither pond water or leakage
from tailing cells is present at this well today.
Monitoring wells MW-3, MW-3A, MW-14 (shallow and deep), MW-15, MW-18
(shallow and deep), and MW-22 (shallow and deep) have more depleted δ18O. These
wells have elevated uranium concentrations, but as they do not bear an evaporated
18O isotope ratios of water
-140
-120
-100
-80
-60
-40
-20
0
20
-20 -15 -10 -5 0 5 10
18
GMWL UMWL Monitoring Wells (Regressed)
Surface Sites (Regressed)Monitoring Wells Surface Sites
WP2
WP3
TC3
45

stable isotope signal it does not appear that the elevated uranium values are the result
of leakage from tailing cells (or wildlife ponds.)

F. 34S and 18O Isotope Ratios in Sulfate
Sampled wells and surface water sites were analyzed for isotope ratios of 34S/32S
and 18O/16O as sulfur-34 and oxygen-18 in the dissolved sulfate molecule. These
isotope ratios can be used in fingerprinting waters of a common source, i.e. if leakage
from tailings cells were occurring, wells impacted by leakage might have similar isotopic
fingerprints of 34S and 18O as the tailings cells wastewater. Conversely, if no leakage
from tailings cells were occurring, wells might have significantly different isotopic
fingerprints of 34S and 18O as compared to the tailings cells. This is because of
fractionation processes occurring in the ore refining process, and the use of sulfuric acid
from an outside source in ore refinement. Furthermore, evaporation from the surface
water sites would preferentially fractionate for oxygen-18 over oxygen-16, meaning the
residual solution would become enriched in oxygen-18. This means that if isotopic
ratios are different between wells and surface water sites, it is expected that surface
water sites would have enriched (e.g. isotopically heavier) isotopic ratios of oxygen-18
relative to well waters. Table 11 shows analytical results for 34S and 18O isotope ratios
as they pertain to the sulfate ions in solution.
46

Table 11: 34S and 18O isotope ratios of sulfate
Site δ18O - SO4 (‰) δ34S - SO4 (‰)
MW-1 -2.36 9.17
MW-1B -2.22 9.88
MW-2 -8.59 12.13
MW-3 -7.03 13.69
MW-3A -6.69 12.66
MW-5 -3.93 9.55
MW-11 -5.08 9.34
MW-14 -2.69 9.63
MW-14 -1.81 9.86
MW-15 -4.61 9.07
MW-18 -4.03 5.05
MW-18 -3.63 5.23
MW-19 -4.08 7.40
MW-19 -4.88 7.27
MW-22 -9.99 -2.44
MW-22 -10.27 -3.07
MW-27 2.02 -0.20
MW-29 -5.58 9.73
MW-30 -3.31 11.04
MW-31 -2.18 6.39
TC1 3.97 -0.89
TC2 Slimes
Drain 4.58 -0.93
TC3 4.34 -1.04
WP2 4.52 0.90
WP3 3.15 0.19
Note: isotope ratios are calculated as ()()‰1000*1/
/
3434
3434
34 ⎟⎟
⎠
⎞
⎜⎜
⎝
⎛−=∂
reference
sample
sample SS
SSS . The reference
standard is Canyon Diablo Troilite having a 34S/32S ratio of 0.04500451.

Isotope ratios for 18O of sulfate ranged from -10.3‰ to -1.8‰ in monitoring wells.
Wildlife ponds 2 and 3 had positive 18O isotope ratios of 4.5‰ and 3.1‰, respectively.
Ratios in tailings cell 1, Cell 2 slimes drain, and tailings cell 3 were also positive at
3.9‰, 4.5‰, and 4.3‰, respectively. 34S isotope ratios ranged from -3.0‰ to 13.6‰ in
monitoring wells. Wildlife ponds 2 and 3 had 34S isotope ratios of 0.9‰ and 0.19‰,
respectively. 34S isotope ratios in tailings cell 1, Cell 2 slimes drain, and tailings cell 3
were -0.89‰, -0.92‰, and -1.04‰, respectively.
47

δ34S & δ18O Isotope ratios of Sulfate
-4.00
-2.00
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
-12.00 -10.00 -8.00 -6.00 -4.00 -2.00 0.00 2.00 4.00 6.00
δ18O (‰)
δ34
S
(
‰
)

Monitoring Wells Wildlife Ponds Tailings Cells Figure 23: 34S and 18O isotope ratios as sulfur-34 and oxygen-18 in sulfate
Figure 23 shows the results of analyses done at the University of Waterloo
Environmental Isotope Laboratory for 34S and 18O isotope ratios in sulfate. Several
distinct relationships are apparent. The surface water sites (wildlife ponds and tailings
cells) are heavily enriched in 18O, and yet depleted in 34S relative to monitoring wells.
This is likely due to evaporative fractionation of lighter water molecules, causing
enrichment of heavier water molecules in the ponds, and subsequent enrichment of
oxygen-18. MW-27 is also similar in isotopic composition to the surface water sites.
This suggests groundwater there has been influenced by the wildlife ponds found
directly upgradient.
Most monitoring well sites exhibit a slight depletion of oxygen-18 with significant
enrichment of sulfur-34. Both sampling depths for MW-22 exhibited 34S isotope ratios
similar to surface water sites, but 18O-SO4 is distinct from the surface water sites. This
MW-22 shallow and deep
MW-27
MW-3 MW-14 shallow
MW-14 deep
MW-15
MW-18 shallow and deep
48

may be explained by a recharge of surface water that isn’t evaporated. Wells MW-3,
MW-14 shallow and deep, MW-15, and MW-18 all exhibited elevated concentrations of
uranium, but are isotopically distinct from the surface water sites.

δ34S vs. SO4 Concentration
-5.00
-3.00
-1.00
1.00
3.00
5.00
7.00
9.00
11.00
13.00
15.00
0 1000 2000 3000 4000 5000 6000
SO4 Concentration (mg L-1)
δ34
S
(
‰
)
Monitoring Wells Wildlife Ponds Figure 24: 34S isotope ratios of Sulfate vs. dissolved SO4 Concentration
Figure 24 presents sulfate concentration versus the 34S isotopic ratios for each
site. Because of extremely high sulfate levels in the tailings cells and Cell 2 slimes
drain, those points are not included in Figure 24. Figure 25 below presents the log of
sulfate concentration versus the 34S isotopic ratios on the sulfate ions for each site.
MW-27
MW-22 shallow and deep
MW-15
MW-14 shallow and deep
MW-18 shallow and deep
MW-3
49

δ34S vs. log of SO4 Concentration
-4.00
-2.00
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
1 10 100 1000 10000 100000 1000000 10000000
log[SO4 (mg/L)]
δ34
S
(
‰
)
Monitoring Wells Tailings Cells Wildlife Ponds Figure 25: 34S isotope ratios of Sulfate vs. log dissolved SO4 concentration

δ18O vs. SO4 Concentration
-12.00
-10.00
-8.00
-6.00
-4.00
-2.00
0.00
2.00
4.00
6.00
0 1000 2000 3000 4000 5000 6000
SO4 Concentration (mg L-1)
δ18
O
(
‰
)
Monitoring Wells Wildlife Ponds Figure 26: 18O isotope ratios of Sulfate vs. dissolved SO4 concentration
Figure 26 relates the oxygen-18 isotope ratios to the dissolved sulfate
MW-27
MW-22 shallow and deep
MW-3
MW-14 shallow and deep; MW-15
MW-27
MW-22 shallow and deep
50

concentration for each of the sample sites. A very general inverse correlation between
increasing sulfate concentrations and oxygen-18 depletion is seen. MW-27 exhibits an
isotopic fingerprint very similar to that of the wildlife ponds, as well as similar sulfate
concentrations. MW-22 is anomalous in that it exhibits a significantly more depleted
δ34S value but has elevated sulfate. However, because of its location it is unlikely MW-
22 is being influenced by similar aspects of the groundwater system as the other
monitoring wells.

δ18O vs. log of SO4 concentration
-12.00
-10.00
-8.00
-6.00
-4.00
-2.00
0.00
2.00
4.00
6.00
1 10 100 1000 10000 100000 1000000 10000000
log[SO4 (mg/L)]
δ18
O
(
‰
)
Monitoring Wells Tailings cells Wildlife Ponds Figure 27: 18O-SO4 isotope ratios of sulfate vs. log of dissolved sulfate concentration

Figure 27 plots oxygen-18 isotope ratios of sulfate to the log of sulfate
concentrations for each of the sample sites in order to include tailings cells. In this case
the tailings cell wastewater is seen to exhibit both an enriched 18O signature and
extremely high sulfate content.
MW-27
MW-22 shallow and deep
MW-14 shallow and deep
MW-3
MW-15
MW-18 shallow and deep
51

V. DISCUSSION
Most groundwater samples from the Mill contain significant amounts of terrigenic
helium-4, indicative of older waters. Several samples have tritiogenic helium-3,
indicative of young water, however these are only found in areas influenced by the
wildlife ponds (MW-19, and MW-27). Tritiated water is introduced into the system by
recharge from the wildlife ponds and appears in wells around the wildlife ponds. As
recharge water from the wildlife ponds propagates through the system, evidence of
tritiated water will appear in successive monitoring wells further from the ponds.
Wells MW-19 (both sample depths) and MW-27 exhibited the most enriched
(heaviest) δD/δ18O isotopic signatures of all the monitoring well samples. This can likely
be attributed to the water table mounding that is occurring because of the nearby wildlife
ponds. Water that is isotopically enriched due to evaporation, the wildlife ponds, when
mixed with water that is isotopically depleted, groundwater, would produce an isotopic
fingerprint that is isotopically heavier than that of groundwater but isotopically lighter
than that of surface water. That the isotopic signatures of MW-19 and MW-27 are being
influenced by recharge from the wildlife ponds is also supported by the elevated tritium
concentrations in both wells. Significant amounts of tritium in MW-19 and MW-27
suggest younger water, and because of only modest amounts of precipitation, recharge
is likely to mostly be occurring from the nearby wildlife ponds.
The influence of evaporated isotopic signatures is most prominent in MW-19 and
MW-27, but is not evident in wells immediately down-gradient from MW-19 and MW-27,
such as MW-30 and MW-31. This suggests the southern margin of artificial recharge
due to the wildlife ponds, and the southernmost extent of the water table mound, is
52

likely between MW-27, and MW-30 and MW-31. Furthermore, mixing of the evaporated
isotopic signatures with groundwater in MW-18 is not apparent, suggesting that the
northern extent of the water table mound is likely between MW-19 and MW-18.
Because of the consistent similarities seen in δ34S values, δ18O values, and
sulfate concentrations between MW-27 and the wildlife ponds, it is likely that water in
MW-27 has its origin in the wildlife ponds. Furthermore, young water as evidenced by
the presence of tritium in MW-27 indicates a tritiated recharge source, whereas tritium-
free waters in the majority of the other monitoring wells indicates a recharge source
composed of older water. Tritiated waters from the wildlife ponds that are likely
recharging the aquifer system would show similar isotopic signatures between the
monitoring wells and the wildlife ponds, as is seen in analytical data. This strongly
suggests the influence of recharge from the wildlife ponds is propagating through the
aquifer and has, to date, reached downgradient at least as far as MW-27.
Potential causes of similarities in sulfur isotope ratios between the wildlife ponds
and tailings cells include: eolian transport of aerosols from the tailings cells, surface
runoff from the Mill facility, and/or rainout of sulfuric acid released to the atmosphere
from the Mill. When compared with isotope fingerprints observed in the tailings cells,
fingerprints of monitoring wells exhibit strong differences, with the exception of MW-27.
This suggests that elevated concentrations of trace metals seen in wells down-gradient
of the facility are not being caused by tailings cell leakage.
The uniqueness of the stable isotope fingerprints of the tailings cells provide a
valuable tool in monitoring groundwater wells for evidence of leakage from the tailings
cells. Because of the extremely high concentrations of sulfate in the tailings cells, even
53

small amounts leakage could dramatically alter the isotopic signature of the monitoring
wells, evidence that would appear much earlier than elevated trace metal
concentrations. For example, consider a mixture of 2 mL of water from a tailing cell
having a δ34S value of -1.0 ‰ and a SO4 concentration of 1,000,000 mg/L with 998 mL
of background water having a δ34S value of 8.0 ‰ and a SO4 concentration of 1,800
mg/L. The mixture would have a SO4 concentration of 3,800 mg/L and δ34S value of 3.3
‰. The change in SO4 concentration from 1,800 to 3,800 mg/L would be difficult to
attribute to leakage from tailings cells as the SO4 concentrations in background water
varies from less than 1,000 mg/L to more than 5,000 mg/L. However, a change in δ34S
value from 8.0 ‰ to 3.3 ‰ could identify the tailings as the source of contamination.
However, the stable isotope fingerprints of the tailings cells are very similar to that
of the wildlife ponds. This may pose a problem for using stable isotopes of sulfate in the
future. As the wildlife ponds continue to recharge the groundwater system, the isotopic
fingerprint they bear will also be introduced into the aquifer. It is likely that eventually
the entire groundwater system will bear an isotopic fingerprint similar to that of both the
tailings cells and wildlife ponds, rendering δ34S and δ18O on sulfate irrelevant for
detecting tailings cell leakage.
In a letter dated 31 January 2008 from Denison Mines (USA) Corp. to the
Executive Secretary of the Utah Radiation Control Board, Mr. David Frydenlund, the
Vice President of Regulatory Affairs Counsel, stated that several areas of low ground on
the Mill site may have had an effect on the isotopic signature of sulfur-34 from sulfate in
MW-27. He states that while the site is graded such that surface water runoff drains
toward Tailings Cell 1, two areas up-gradient of MW-27 have historically experienced
54

water pooling to six inches deep after heavy rains. This water is a combination of direct
precipitation and runoff from the northern portion of the mill area. This area of the Mill
site has since been re-graded to remedy this issue. Although, it is possible that such
water may have infiltrated through the vadose zone and recharged the saturated zone,
this is a relatively small area and it seems unlikely that such an ephemeral head source
could produce the isotopic signature observed in MW-27. More investigation is needed
to better understand the occurrence of young water in the vicinity of MW-27.
Mr. Frydenlund also suggested that historical stock watering ponds up-gradient
of MW-22 may have influenced the isotopic signature of sulfur-34 of sulfate and the
presence of tritium in that well. Reportedly, these stock watering ponds were used
during spring and fall from the early 1980s to 2001, but water was not maintained in the
ponds for the entire year. The ponds were not utilized between 2001 and 2005, and
were filled once between 2005 and 2006. Because the water used to fill the ponds from
the 1980s to 2001 was pumped from the deep Entrada/Navajo aquifer, it is unlikely
these waters were tritiated, though some tritium input may have occurred due to
precipitation. Additionally, water used to fill the ponds in 2005-2006 originated in
Recapture Reservoir (north of Blanding). While this water would possibly have been
tritiated and, depending on the regional isotopic signature of sulfur-34 on sulfate, may
have had a similar isotope fingerprint as the wildlife ponds and tailings cells, it is unlikely
for that water to have recharged before the July 2007 sample event. While it seems
unlikely that several years of tritiated water versus nearly 20 years of nontritiated water
could produce the young isotopic signature in well MW-22, more investigation is needed
and the cause the isotopic signatures is currently unknown.
55

VII. CONCLUSIONS AND RECOMMENDATIONS
A number of important conclusions can be made about the groundwater system
at Denison Mine, Co.’s White Mesa Mill based on the presented information.
Temperature and salinity profiles suggest that the water column in the aquifer is
stratified with respect to chemical composition, as salinity systematically increased with
depth. Furthermore, some wells (e.g. MW-1, MW-3, MW-5, MW-15) exhibited markedly
different levels of salinity at different depths, differentiated by a drastic change in salinity
across a very small depth. Also, noble gas compositions, particularly with respect to
helium-4, suggest the water column is stratified with respect to age. Helium-4
concentrations determined from diffusion samplers were in every case greater at depth
than samples taken near the water table (with the exception of well MW-19); suggesting
longer subsurface residence time or age. Although not delineated by low-flow sampling
at multiple depths, the systematic changes in temperature and salinity with depth, as
well as helium-4 concentrations at depth, suggest the water column is stratified.
Furthermore, this suggests that the existing monitoring wells sample a range of flow
paths and groundwater ages. Passive samples from near the top of the well screens
are more likely to detect leakage from the tailing cells than samples collected from the
bottom of screens. While conventional low-flow sampling at this site does not appear to
be practical or effective, passive sampling for dissolved ions (e.g. using dialysis
membranes) might be effective.
Helium ratios corrected for inputs from excess air suggest older water farther
away from the wildlife ponds. 3He/4He ratios closer to atmospheric values suggest
water that is younger than 50 years. Most samples exhibiting this characteristic were
56

located close to the wildlife ponds, while samples farther away from the ponds had
ratios less than atmospheric.
Low-flow sampling methods employed in monitoring wells were unable to
distinguish stratification in the water column when a monitoring well was sampled at two
depths. No significant differences were seen in concentrations of metals or anions, or in
isotopic fingerprints, between samples taken at two depths. Additionally, age dating
techniques that required active pumping for sample collection did not indicate marked
differences in groundwater age between shallow and deep samples. However, this is
likely the result of the inability of active pumping to collect depth-specific samples, rather
than the lack of an age gradient.
Small but measurable quantities of chlorofluorocarbons were found in 10 wells
(MW-1, MW-2, MW-5, MW-11, MW-14 shallow and deep, MW-15, MW-18 deep, MW-
29, and MW-31) that did not contain tritium. CFCs are present in the unsaturated zone
as gases at near-modern atmospheric concentrations. That CFCs are present in some
samples near the water table indicates that water does propagate downward through
the vadose zone and ultimately recharge the aquifer, again suggesting stratification in
the aquifer. However, the absence of tritium in those waters suggests it takes infiltration
water longer than 50 years to travel through the vadose zone. Because some amount
of recharge to the aquifer is taking place, as evidenced by the recharge mound near the
wildlife ponds, the system elsewhere can therefore be considered recharge-limited and
not permeability-limited. Active groundwater flow clearly occurs vertically and
horizontally, and if leakage from tailing cells occurs in the future a contaminated plume
is likely to result at the water table.
57

Tritium measured in monitoring wells near the wildlife ponds suggests young
water is recharging to those wells (MW-19 and MW-27). Surface water sites also
contained significant amounts of tritium. The wildlife ponds contained atmospheric
concentrations of tritium. The presence of tritium in the wildlife ponds and nearby
monitoring wells strongly suggests recharge is occurring from the wildlife ponds to the
aquifer. Because the wildlife ponds were constructed in the mid-1990’s, water
recharging from the ponds would bear a tritium concentration indicative of the
atmospheric tritium in the last 10 to 15 years. Recharge from the wildlife ponds can
potentially shift the flow dynamics of the system significantly, as is evidenced by
mounding of the water table around the ponds. Such a shift in flow paths could result in
temporal variations in groundwater chemistry.
Nitrate concentrations in two wells (MW-30 and MW-31) exceeded the Utah
State Groundwater Quality Standard (GWQS) of 10 mg/L. All wells except for one
(MW-27) exceeded the National Secondary Drinking Water Standard for sulfate set by
the United States Environmental Protection Agency (250 mg/L). Five wells exceeded
the GWQS for uranium (30 µg/L), including: MW-3, MW-14, MW-15, MW-18, and MW-
22. Five wells exceeded the ad-hoc standard for manganese (800 µg/L), including:
MW-3, MW-3A, MW-14, MW-22, and MW-29. Three wells exceeded the GWQS for
selenium of 50 µg/L (MW-03, MW-15, and MW-31). The majority of wells that exceeded
water quality standards were tritium-free, contained very small amounts of CFCs, and
did not bear isotopic signatures similar to those of either the tailings cells or the wildlife
ponds. This suggests natural, background values of trace metal contamination in the
groundwater system.
58

Evaporative enrichment of δD and δ18O is seen in surface water samples.
Values in monitoring wells fall along a line similar to the Utah Meteoric Water Line, but
offset slightly. Some apparent enrichment of both δD and δ18O is seen in wells MW-27
and MW-19 shallow and deep. This suggests mixing that is occurring between enriched
water recharging from the wildlife ponds and older, depleted groundwater. There are no
other indications enriched water in any of the other monitoring wells. Even though
several wells down-gradient of the tailings cells exhibited elevated levels of uranium
concentrations, the stable isotope data does not indicate any amount of mixing between
evaporated, enriched surface water and isotopically lighter groundwater. Therefore, it is
unlikely that elevated and increasing uranium concentrations in MW-3, MW-14, MW-15,
MW-18, and MW-22 can be attributed to leakage from the tailings cells. However, the
stable isotope value of groundwater is insensitive to additions of trace amounts of
enriched (surface) water.
δ34S and δ18O isotopic signatures on dissolved sulfate provide distinction
between surface water sites and monitoring wells. The tailings cells and wildlife ponds
exhibit significantly enriched δ18O-SO4 values relative to monitoring wells, and depleted
δ34S-SO4 values relative to monitoring wells. MW-27 is the only monitoring well to bear
an isotopic fingerprint closely related to that of the surface water sites, suggesting
recharge from the wildlife ponds has reached MW-27 and further evidence that the
wildlife ponds are providing recharge to the aquifer. Sites with high concentrations of
metals (MW-3, MW-14 shallow and deep, MW-15, MW-18, and MW-22) bear very
different isotopic fingerprints than those of the surface water sites.
In general, the data collected in this study do not provide evidence that tailings
59

cell leakage is leading to contamination of groundwater in the area around the White
Mesa Mill. Evidence of old water in the majority of wells, and significantly different
isotopic fingerprints between wells with the highest concentrations of trace metals and
surface water sites, supports this conclusion. The only evidence linking surface waters
to recharging groundwater is seen in MW-27 and MW-19. Measurable tritium and CFC
concentrations indicate relatively young water, with low concentrations of selenium,
manganese, and uranium. Furthermore, stable isotope fingerprints of δD and δ18O
suggest mixing between wildlife pond recharge and older groundwater in MW-19 and
MW-27. δ34S-SO4 and δ18O-SO4 fingerprints closely relate MW-27 to wildlife pond
water, while the exceptionally low concentration of sulfate in MW-27, the only
groundwater site to exhibit sulfate levels below 100 mg/L, suggest no leachate from the
tailings cells has reached the well.
CFC concentrations in tritium-free sites suggest a recharge-limited aquifer. This
means that if a contaminated fluid was introduced to the system, it would likely be
transported by the vertical flow of groundwater and would propagate through the
system. This site is, therefore, susceptible to contamination due to tailings cell leakage,
and must therefore be carefully monitored for such contamination. Sulfur-34 and
oxygen-18 isotopes of sulfate will be useful until the isotopic fingerprint of the surface
water sites has propagated through the entire system.
Sulfur isotopes that begin indicating input of water with a similar fingerprint as
that of tailings cells may be an early indication that a leak in the tailings cell liner has
developed. This signal would appear much earlier than elevated metal concentrations
because mixing of isotope ratios, with sulfate concentrations as drastically different as
60

between tailings cells and wildlife ponds, is observable after only a very small amount of
water has infiltrated (approximately 1% tailings cell water to 99% groundwater). Trace
metal concentrations as well as inorganic anions should also be monitored on a regular
basis.
61

VII. Sources Cited
Craig H. 1961. Isotopic variation in meteoric waters. Science. 133, 1702-1703.
Denison Mines, 2008. Letter from Mr. David Frydenlund, Vice President of Regulatory
Affairs and Counsel, to Mr. Dane Finerfrock, Executive Secretary of the Utah
Radiation Control Board. Re: White Mesa Uranium Mill, Background
Groundwater Quality Report for Existing Wells—Additional Information Relating
to MW-27 and MW-22. 31 January 2008.
Hydro Geo Chem Inc. Site Hydrogeology and Estimation of Groundwater Travel Times
in the Perched Zone; White Mesa Uranium Mill Site Near Blanding, Utah. 30
January 2003.
Heilwell, V. M., D. K. Solomon, and P. M. Gardner. 2006. Borehole Environmental
Tracers for Evaluating Net Infiltration and Recharge Through Desert Bedrock.
Vadose Zone Journal. 5, 98-120.
Intera. 2007. Revised Background Groundwater Quality Report: Existing Wells For
Denison Mines (USA) Corp.’s White Mesa Uranium Mill Site, San Juan County,
UT. October 2007.
Kendall C. and T.B. Coplen. 2001. Distribution of oxygen-18 and deuterium in river
waters across the United States. Hydrological Processes. 15, 1363-1393.
Puls, Robert W. and Michael J. Barcelona. 1995. Low-Flow (Minimal Drawdown)
Ground-water Sampling Procedures. U.S. Environmental Protection Agency
Ground Water Issue, EPA/540/S-95/504.
Solomon D.K. 2000. 4He in Groundwater. Environmental Tracers in Subsurface
Hydrology.
62

Solomon D.K. and P.G. Cook. 2000. 3H and 3He. Environmental Tracers in Subsurface
Hydrology.
Titan Environmental Corporation. 1994. Hydrogeologic Evaluation of White Mesa
Uranium Mill. July 1994.
United States Environmental Protection Agency. 2003. National Primary Drinking Water
Regulations. EPA 816-F-03-016.
United States Geological Survey. 2007. CFC Sampling Method – Bottles.
http://water.usgs.gov/lab/chlorofluorocarbons/sampling/bottles/ . Accessed 12
October 2007.
Utah Administrative Code Rule R317-6. December 2007.
Utah Department of Environmental Quality. 2005. Monitoring and Water Quality:
Drinking Water Standards. R309-200.
Utah Water Quality Board. Ground Water Discharge Permit. Permit No. UGW370004.
ATTACHMENT 2
URS Existing Wells Memorandum
June 16,2008
Denison Mines Corp. White Mesa Mill Site
URS 39400260.10100; Summary of Calculated GWCLs
June 16, 2008

Page 1 of 4
To: Loren Morton, UDRC File: 39400260.10200
From: Robert Sobocinski and Brian Harper
Date: June 16, 2008
Re: Completeness Review for the Revised Background Groundwater Quality Report:
Existing Wells for Denison Mines (USA) Corporation’s White Mesa Mill Site, San Juan
County, Utah
Based on comments provided by the Utah Division of Radiation Control (the Division) in letters
dated August 10 and August 24, 2007, Denison Mines (USA) Corporation (DUSA) submitted
the Revised Background Groundwater Quality Report: Existing Wells for DUSA’s White Mesa
Mill Site, San Juan County, Utah (the Revised Background Report) to the Division in October
2007. URS has performed a completeness review of the Revised Background Report. This is a
revised version of the completeness review issued on April 30, 2008. Findings and observations
from the review are as follows.
1. DUSA performed the data evaluation and statistical analysis in accordance with the
statistical process flowchart (attached Figure 191) conditionally approved by the Division
on August 24, 2007. The statistical analysis was performed in accordance with U.S.
Environmental Protection Agency (EPA) guidance and adequately addressed the presence
and variable percentage of non-detect values in the background water quality data sets.
2. There are 13 wells with 38 constituents for each well, resulting in 494 individual data sets,
each of which has a corresponding Groundwater Compliance Limit (GWCL) proposed by
DUSA in Table 16 of the Revised Background Report. Each data set represents a single
constituent at a single well (e.g., uranium at MW-05). For the most part, the proposed
GWCLs appear to have been calculated correctly following the flow chart process.
However, there are some GWCLs (24 out of a total of 494) where the wrong approach
(e.g., highest historic value instead of the Poisson limit) was used to determine the GWCL.
These incorrect GWCLs are listed in attached Table 1 along with the correct GWCL. The
incorrect GWCLs appear to be the result of inadvertent errors and not due to a
misunderstanding or deliberate misrepresentation. Attached Table 1 also contains
corrections that appear to be simple errors (see items 7 and 8 below).
3. Attached Table 2 categorizes the GWCLs based on the percentage of non-detects and the
statistical approach. Table 2 assumes the 24 flowchart errors have been corrected and that
the issues listed in items 5, 6, 7, and 8 below have been addressed (see attached Table 1).
The following observations are made from Table 2:
• Most of the data sets consist of a majority of non-detects. Slightly more than half of
the 494 data sets consist of greater than 90% non-detects.
1 Intera Figure 19 included herein has been updated to reflect the requirements of the August 24, 2007 DRC
Conditional Approval.
Denison Mines Corp. White Mesa Mill Site
URS 39400260.10100; Summary of Calculated GWCLs
June 16, 2008

Page 2 of 4
• Largely because most data sets consist of a majority of non-detects, only 16.4% of
the 494 proposed GWCLs were established as a mean plus two standard deviations.
These GWCLs were calculated following the first two paths shown on the attached
Figure 19 flowchart.
• 28.9% of the 494 proposed GWCLs were established following the “Non-
Parametric Statistics” approach (third path on the attached Figure 19 flowchart):
10.1% were the highest historical result in the data set (based on the non-parametric
statistical method), and 18.8% were established as a fraction of the Groundwater
Quality Standard (GWQS) as allowed by the process shown on the flowchart. The
conditionally approved process allows the option of using the greater of the highest
historical result or the fraction of the GWQS to represent the GWCL.
• 53.8% of the 494 proposed GWCLs were established following the fourth path of
the attached flowchart (non-detects > 90%): 2.0% of the GWCLs were calculated as
the Poisson prediction limit, and 51.8% were established as a fraction of the GWQS
as allowed by the process shown on the Figure 19 flowchart. The fact that over half
of the GWCLs were established as a fraction of the GWQS following the fourth
path on the flowchart illustrates that for many constituents, the data sets consist of
primarily non-detected results.
4. Attached Table 3 shows that 16 of the proposed GWCLs (about 3.2% of the total) are
higher than the respective GWQSs. Refer to attached Table 2 for the breakdown by
approach of these GWCLs that exceed the GWQS.
5. For cadmium in wells MW-1, MW-2, MW-3, and MW-5, it appears that the proposed
GWCL exceeds the GWQS because of the extreme concentration range observed in the
early data (pre-March 1982). For this reason, URS removed the pre-March 1982 data from
the cadmium data sets for the four wells and revised the GWCL. The revised GWCLs,
which are less than the GWQS, are listed in attached Table 1.
6. The proposed GWCLs for tetrahydrofuran in wells MW-1 and MW-3 exceed the GWQS,
and in wells MW-5 and MW-12, the proposed GWCLs exceed the fraction of the GWQS.
Because tetrahydrofuran is a man-made chemical, and the purpose of the groundwater
monitoring is detection monitoring, the GWCL should be set at the fraction of the GWQS
(see attached Table 1). In general, based on the assumption that background levels of man-
made organic chemicals (with the possible exception of chlorofluorocarbons) are not
present in detectable concentrations in groundwater at the White Mesa Mill Site, the
GWCLs for all organic chemicals should be set at the fraction of the GWQS. This would
include the organic chemicals in well MW-26 not associated with the chloroform plume
remediation. In accordance with Utah Administrative Code R317-6-6.15.F, the GWCL for
chloroform, chloromethane (degradation product), dichloromethane (degradation product),
and carbon tetrachloride (trace co-contaminant) in well MW-26 should be set at the
GWQS. Well MW-26 is discussed further in item 10 below.
Denison Mines Corp. White Mesa Mill Site
URS 39400260.10100; Summary of Calculated GWCLs
June 16, 2008

Page 3 of 4
7. For cobalt, the correct approach for establishing the compliance limit (fraction of the
GWQS) is identified in wells MW-2, MW-3, MW-12, MW-14, MW-15, MW-17, and
MW-26; however, there is a typographical error in the value of the GWCL. The fraction of
the standard for cobalt for these wells should be 365 micrograms per liter (μg/L) instead of
362 μg/L (see attached Table 1).
8. For xylenes, the correct approach for establishing the compliance limit (fraction of the
GWQS) is identified for all the wells; however, there is a typographical error in the value
of the GWCL for each of the wells. For Class II groundwater (MW-1, MW-5, and MW-
11), the fraction of the GWQS should be 2,500 μg/L instead of 2.5 μg/L, and for Class III
groundwater (MW-2, MW-3, MW-12, MW-14, MW-15, MW-17, MW-18, MW-19, MW-
26, and MW-32), the fraction of the GWQS should be 5,000 μg/L instead of 5 μg/L (see
attached Table 1).
9. In Section 9.3 of the Revised Background Report, DUSA states that seepage from the
tailings impoundments would be indicated by rising concentrations of chloride, sulfate,
fluoride, and uranium. URS agrees with this because: 1) these constituents are abundant in
tailings wastewater (see Table 15 of the Revised Background Report), and 2) these
constituents are relatively mobile and conservative in the groundwater environment. In
contrast, many other constituents are either not present in relatively high concentrations in
tailings wastewater and/or are reactive in the subsurface environment. URS recommends
that for the four conservative constituents listed above, DUSA considers preparing and
including time-concentration plots in the groundwater monitoring reports. Increasing
trends could provide early indication of seepage even before GWCLs are exceeded. Also,
to provide confirmation that seepage has or has not occurred, DUSA might consider
analyzing groundwater, tailings wastewater, and wildlife pond water for isotopic uranium.
If significant differences exist in the ratio of U-234 to U-238 between these waters, isotopic
uranium analyses may provide another tool for determining whether GWCL exceedances
are related to impacts from the impoundments.
10. With regards to special consideration for well MW-26 (Section 13.3.4 of the Revised
Background Report), URS believes that given the location of MW-26, along the eastern
edge of Tailings Cell 2, it should be retained as an impoundment monitoring well. GWCLs
were established and presented in the “Flow Sheet GWCL” column of Table 16 of the
Revised Background Report; these values should be used as the groundwater discharge
permit GWCLs for well MW-26 (with the error shown in attached Table 1 corrected and
the exceptions discussed in item 6 above). However, URS agrees with DUSA, that
exceedences of GWCLs at MW-26 should be interpreted in the context of its use as a
pumping well for the chloroform plume remediation.
11. DUSA proposes that the groundwater at wells MW-18 and MW-19 be reclassified as Class
III water (Section 13.3.1 of the Revised Background Report). The GWCLs proposed in
Table 16 of the Revised Background Report assume that this reclassification has occurred.
If the Division does not approve reclassification of groundwater at wells MW-18 and MW-
Denison Mines Corp. White Mesa Mill Site
URS 39400260.10100; Summary of Calculated GWCLs
June 16, 2008

Page 4 of 4
19, defers reclassification, or reclassifies groundwater at other wells, then the proposed
GWCLs based on the fraction of the GWQS for these wells need to be revised in Table 16.
12. In Section 13.3.1 of the Revised Background Report, DUSA also notes that consideration
should be given to reclassifying groundwater at wells MW-1 and MW-5 because the
proposed GWCLs for cadmium and lead in MW-1 and cadmium in MW-5 exceed the
GWQS. However, when the GWCLs are corrected as shown in Table 1, none of the
proposed GWCLs for wells MW-1 and MW-5 exceeds respective GWQSs. Therefore,
reclassification is not necessary.
In summary, with the exception of the errors that will require correction, DUSA established
GWCLs in accordance with the methodology given in the conditionally approved flowchart.
This methodology was developed in accordance with EPA guidance, and it takes into account
that much, if not the majority, of background data consists of non-detected results. After
correcting errors and revising the GWCLs for cadmium and tetrahydrofuran, 16 proposed
GWCLs still exceed the corresponding GWQSs (Table 3). Despite exceeding GWQSs, it
appears that these proposed GWCLs were established in accordance with the conditionally
approved flowchart (with a few exceptions). As such, URS recommends that the Division
approves these 16 proposed GWCLs (with exceptions corrected), because there is no physical or
chemical basis for a background concentration to be limited to the GWQS. Even in approving
these proposed GWCLs, several upward-trending data sets may require additional attention
during future monitoring events.

REFERENCES
Utah Department of Environmental Quality (UDEQ), Division of Radiation Control (DRC)
2007a. Completeness Review, DRC Findings, and Confirmatory Action Letter. Letter from D.L.
Finerfrock (DRC) to D. Frydenlund (DUSA). August 10, 2007.

Utah Department of Environmental Quality (UDEQ), Division of Radiation Control (DRC)
2007b. DUSA Decision Tree/Flow Chart for Statistical Analysis for Background Groundwater
Quality: Conditional Approval. Letter from D.L. Finerfrock (DRC) to D. Frydenlund (DUSA).
August 24, 2007.

Denison Mines (DUSA) Corporation 2007. Revised Background Groundwater Quality Report:
Existing Wells. Prepared for Denison Mines (USA) Corporation, Denver, CO. October, 2007.

Database of Wells and Analytes Listed in the Statement of Basis
Negative Value?
Zero Value?
Truncated Value?
Duplicate Value?
Units Consistant?
Non-detects Exceeding Criteria Specified by URS Memo*
Analysis Internally Consistent?(TDS and Charge Balance Check)
YesNo
No
Yes
No
No
No
Yes
Yes
No
Yes
Yes
Yes
Radionuclide?
Yes
Remove from DatasetDetection Limit and U-Flag Data Qualifier NoNo
Review for Units
Remove from Dataset
Remove from Dataset (chloride, sulfate, or TDS ONLY)
Correct Value Confirmed?
Remove from Dataset
Remove from Dataset
Determine Percentage Non-Detects in Remaining Data
Plot Data Sets as Box Plots to Identify Extreme Values As Specified in Background Report. Extreme Value?
No
Remove from Dataset
Yes
At Least 8 Data Points Remaining?
Defer Analysis Until Eight Data Points Avalible
0-15 Percent Non-Detects >15-50 Percent Non-Detects >90 Percent Non-Detects
No
Yes
No
Substitute One Half of Detection Limit
Log Transform Data
Use Probability Plots to Determine if Cohen’s or Aitchison’s Method
Calculate Descriptive Statistics (Redo Tables In Background Report)
Screen for Trends Using Least Squares Regression.
Calculate GWCL (Mean +2Sigma)
Calculate Descriptive Statistics (Redo Tables In Background Report)
Yes
No
Calculate GWCL (Mean +2Sigma)
Calculate GWCL Using Greater of Fraction Approach under UAC R317-6-4-4.5(B)(2) or 4.6(B)(2) or Poisson Prediction Limit
Yes
No
>50-90 Percent Non-Detects
Calculate Upper Prediction Limit (Highest Historical Value)
Calculate GWCL Using Greater of Fraction Approach under UAC R317-6-4-4.5(B)(2) or 4.6(B)(2) or the Highest Historic Value
Estimate Mean and Standard Deviation
Screen for Trends Using Mann-Kendall Screen for Trends Using Mann-Kendall
Yes
Use Non-Parametric StatisticsNo
Screen for Trends Using Least Squares Regression
Wednesday, April 16, 2008
Groundwater Data Preparation and Statistical Process Flow for Calculating Groundwater Protection Standards, White Mesa Mill Site, San Juan County, Utah
Upward Trend?Upward Trend?
No No
Yes
Consider Modified Approch to GWCL
Upward Trend?Upward Trend?
No No
Yes
Consider Modified Approch to GWCL
Log Transform Data
Log-Normal or Normal?Shapiro WilkProbability PlotsHistograms
Log-Normal or Normal?Shapiro WilkProbability PlotsHistograms
*A non-detect considered “insensitive” will be the maximum reporting limit in a dataset and will exceed other non-detects by, for example, an order of magnitude (e.g., <10 versus <1.0 µg/L). In some cases, insensitive non-detects may also exceed detectable values in a dataset (e.g., <10 versus 3.5 µg/L). All insensitive non-detectable values will be removed regardless of relation to GWQS.
Figure 19Groundwater Data Preparation and Statistical Process Flow for Calculating Ground Water Compliance Limits, White Mesa Mill Site, San Juan County, Utah.
Table 1 - Revisions to Proposed GWCLs
Well Parameter GWQS
Percentage
Detects
DUSA Proposed
GWCL
DRC Revised
GWCL Comment
MW-1 Cadmium 5 ug/L 31.6% 13 ug/L 4.2 ug/L*
The proposed GWCL included early data that is suspect because of the
extreme concentration range observed within a short time period. All data prior
to March 1982 was removed from the data set. Of the remaining data, 10.6%
are detects; therefore, the GWCL should be the highest historical value or the
fraction of the GWQS, whichever is greater. The GWCL should be 4.2 ug/L
(highest historical value).
MW-1 Lead 15 ug/L 4.2% 20 ug/L 5.59 ug/L
This GWCL is proposed based on the highest historical value. According to the
flowchart, it should be the greater of the Poisson limit or the fraction of the
standard, which is 5.59 ug/L (Poisson limit).
MW-1 Tetrahydrofuran 46 ug/L 81.8% 94.41 ug/L 11.5 ug/L
This GWCL is proposed based on the Cohen's mean plus 2 σ. However,
because tetrahydrofuran is not a naturally occurring constituent, background
should be set at the fraction of the GWQS.
MW-1 Xylenes 10,000 ug/L 0.0% 2.5 ug/L 2,500 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 2,500 ug/L instead of 2.5 ug/L.
MW-2 Cadmium 5 ug/L 40.5% 17 ug/L 2.5 ug/L*
The proposed GWCL included early data that is suspect because of the
extreme concentration range observed within a short time period. All data prior
to March 1982 was removed from the data set. Of the remaining data, 10.6%
are detects; therefore, the GWCL should be the highest historical value or the
fraction of the GWQS, whichever is greater. The GWCL should be 2.5 ug/L
(fraction of GWQS).
MW-2 Cobalt 730 ug/L 0.0% 362 ug/L 365 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 365 ug/L instead of 362 ug/L.
MW-2 Lead 15 ug/L 9.5% 20 ug/L 7.5 ug/L
This GWCL is proposed based on the highest historical value. According to the
flowchart, it should be the greater of the Poisson limit or the fraction of the
standard, which is 7.5 ug/L (fraction of standard).
MW-2 Selenium 50 ug/L 66.7% 25 ug/L 26.6 ug/L
This GWCL is proposed based on the fraction of the groundwater standard.
According to the flowchart, it should be Cohen's mean plus two standard
deviations - 26.6 ug/L.
MW-2 Xylenes 10,000 ug/L 0.0% 5 ug/L 5,000 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 5,000 ug/L instead of 5 ug/L.
MW-3 Cadmium 5 ug/L 66.7% 20 ug/L 4.67 ug/L*
The proposed GWCL included early data that is suspect because of the
extreme concentration range observed within a short time period. All data prior
to March 1982 was removed from the data set. Of the remaining data, 52.4%
are detects; therefore, the data set was tested for normality, and normality
could not be rejected and the GWCL should be Cohen's mean plus 2 σ. The
GWCL should be 4.67 ug/L.
MW-3 Cobalt 730 ug/L 0.0% 362 ug/L 365 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 365 ug/L instead of 362 ug/L.
MW-3 Lead 15 ug/L 8.7% 20 ug/L 7.5 ug/L
This GWCL is proposed based on the highest historical value. According to the
flowchart, it should be the greater of the Poisson limit or the fraction of the
standard, which is 7.5 ug/L (fraction of standard).
MW-3 Tetrahydrofuran 46 ug/L 85.7% 123.55 ug/L 23 ug/L
This GWCL is proposed based on the mean plus 2 σ. However, because
tetrahydrofuran is not a naturally occurring constituent, background should be
set at the fraction of the GWQS.
MW-3 Uranium 30 ug/L 98.7% 67.16 ug/L 47.32 ug/L This GWCL is proposed based on the highest historical value. According to the
flowchart, it should be the mean plus two standard deviations - 47.32 ug/L.
MW-3 Xylenes 10,000 ug/L 0.0% 5 ug/L 5,000 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 5,000 ug/L instead of 5 ug/L.
MW-5 Cadmium 5 ug/L 40.0% 20 ug/L 2.0 ug/L*
The proposed GWCL included early data that is suspect because of the
extreme concentration range observed within a short time period. All data prior
to March 1982 was removed from the data set. Of the remaining data, 4.2%
are detects; therefore, the GWCL should be the Poisson limit or the fraction of
the GWQS, whichever is greater. The GWCL should be 2.0 ug/L (Poisson
limit).
MW-5 Nitrate/ite 10 mg/L 50.0% 0.3 mg/L 2.5 mg/L
This GWCL is proposed based on the highest historical value, but according to
the flowchart, the fraction of the groundwater standard can be used because it
is higher - 2.5 mg/L.
MW-5 Lead 15 ug/L 5.3% 10 ug/L 4.1 ug/L
This GWCL is proposed based on the highest historical value. According to the
flowchart, it should be the greater of the Poisson limit or the fraction of the
standard, which is 4.1 ug/L (Poisson limit).
MW-5 Mercury 2 ug/L 3.1% 0.5 ug/L 1 ug/L
This GWCL is proposed based on the fraction of the groundwater standard, but
according to the flowchart, the Poisson limit can be used because it is higher -
1 ug/L.
MW-5 Fluoride 4 mg/L 100.0% 1.68 mg/L 1.42 mg/L This GWCL is proposed based on the highest historical value. According to the
flowchart, it should be the mean plus two standard deviations - 1.42 ug/L.
1 of 6 6/16/2008
Table 1 - Revisions to Proposed GWCLs
Well Parameter GWQS
Percentage
Detects
DUSA Proposed
GWCL
DRC Revised
GWCL Comment
MW-5 Tetrahydrofuran 46 ug/L 57.1% 22.03 ug/L 11.5 ug/L
This GWCL is proposed based on the Cohen's mean plus 2 σ and correctly
follows the flowchart. However, because tetrahydrofuran is not a naturally
occurring constituent, the GWCL should be set at the fraction of the GWQS.
MW-5 Xylenes 10,000 ug/L 0.0% 2.5 ug/L 2,500 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 2,500 ug/L instead of 2.5 ug/L.
MW-11 Beryllium 4 ug/L 5.3% 2 ug/L 1 ug/L
This GWCL is proposed based on the highest historical value. According to the
flowchart, it should be the greater of the Poisson limit or the fraction of the
standard, both of which are 1 ug/L.
MW-11 Manganese 800 ug/L 100.0% 200 ug/L 131.29 ug/L
This GWCL is proposed based on the fraction of the groundwater standard.
According to the flowchart, it should be the mean plus two standard deviations -
131.29 ug/L.
MW-11 Nickel 100 ug/L 4.4% 50 ug/L 46.2 ug/L
This GWCL is proposed based on the highest historical value. According to the
flowchart, it should be the greater of the Poisson limit or the fraction of the
standard, which is 46.2 ug/L (Poisson limit).
MW-11 Xylenes 10,000 ug/L 0.0% 2.5 ug/L 2,500 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 2,500 ug/L instead of 2.5 ug/L.
MW-12 Cobalt 730 ug/L 0.0% 362 ug/L 365 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 365 ug/L instead of 362 ug/L.
MW-12 Nitrate/ite 10 mg/L 14.3% 0.12 mg/L 5 mg/L
Use the fraction of the groundwater standard (5 mg/L) until there are at least 8
data points for analysis.
MW-12 Mercury 2 ug/L 7.1% 3 ug/L 1 ug/L
This GWCL is proposed based on the highest historical value. According to the
flowchart, it should be the greater of the Poisson limit or the fraction of the
standard, which is 1 ug/L (fraction of standard).
MW-12 Tetrahydrofuran 46 ug/L 75.0% 42.18 ug/L 23 ug/L
This GWCL is proposed based on the Cohen's mean plus 2 σ and correctly
follows the flowchart. However, because tetrahydrofuran is not a naturally
occurring constituent, the GWCL should be set at the fraction of the GWQS.
MW-12 Xylenes 10,000 ug/L 0.0% 5 ug/L 5,000 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 5,000 ug/L instead of 5 ug/L.
MW-14 Cobalt 730 ug/L 0.0% 362 ug/L 365 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 365 ug/L instead of 362 ug/L.
MW-14 Zinc 5000 ug/L 71.4% 2500 ug/L 35.04 ug/L
This GWCL is proposed based on the fraction of the groundwater standard, but
according to the flowchart, it should be Cohen's mean plus two standard
deviations - 35.04 ug/L.
MW-14 Xylenes 10,000 ug/L 0.0% 5 ug/L 5,000 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 5,000 ug/L instead of 5 ug/L.
MW-15 Ammonia 25 mg/L 76.9% 12.5 mg/L 0.21 mg/L
This GWCL is proposed based on the fraction of the groundwater standard, but
according to the flowchart, it should be Cohen's mean plus two standard
deviations - 0.21 mg/L.
MW-15 Cobalt 730 ug/L 0.0% 362 ug/L 365 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 365 ug/L instead of 362 ug/L.
MW-15 Iron 11000 ug/L 50.0% 5500 ug/L 81.7 ug/L
This GWCL is proposed based on the fraction of the groundwater standard, but
according to the flowchart, it should be Cohen's mean plus two standard
deviations - 81.7 ug/L.
MW-15 Xylenes 10,000 ug/L 0.0% 5 ug/L 5,000 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 5,000 ug/L instead of 5 ug/L.
MW-17 Cobalt 730 ug/L 0.0% 362 ug/L 365 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 365 ug/L instead of 362 ug/L.
MW-17 Nitrate/ite 10 mg/L 14.3% 0.1 mg/L 5 mg/L
Use the fraction of the groundwater standard (5 mg/L) until there are at least 8
data points for analysis.
MW-17 Uranium 30 ug/L 100.0% 46.8 ug/L 46.66 ug/L This GWCL is proposed based on the highest historical value. According to the
flowchart, it should be the mean plus two standard deviations - 46.66 ug/L.
MW-17 Xylenes 10,000 ug/L 0.0% 5 ug/L 5,000 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 5,000 ug/L instead of 5 ug/L.
MW-18 Sulfate NA 100.0% 1940 mg/L 1938.9 mg/L This GWCL is proposed based on the highest historical value. According to the
flowchart, it should be the mean plus two standard deviations - 1938.9 mg/L.
2 of 6 6/16/2008
Table 1 - Revisions to Proposed GWCLs
Well Parameter GWQS
Percentage
Detects
DUSA Proposed
GWCL
DRC Revised
GWCL Comment
MW-18 Xylenes 10,000 ug/L 0.0% 5 ug/L 5,000 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 5,000 ug/L instead of 5 ug/L.
MW-19 Ammonia 25 mg/L 60.0% 12.5 mg/L 0.31 mg/L
This GWCL is proposed based on the fraction of the groundwater standard, but
according to the flowchart, it should be Cohen's mean plus two standard
deviations - 0.31 mg/L.
MW-19 Fluoride 4 mg/L 100.0% 1.4 mg/L 1.39 mg/L This GWCL is proposed based on the highest historical value. According to the
flowchart, it should be the mean plus two standard deviations - 1.39 mg/L.
MW-19 Xylenes 10,000 ug/L 0.0% 5 ug/L 5,000 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 5,000 ug/L instead of 5 ug/L.
MW-26 Benzene 5 ug/L 3.8% 4.75 ug/L ** 2.5 ug/L
The "flow sheet" GWCL is based on the Poisson Limit and correctly follows the
flowchart. However, because benzene is not a naturally occurring constituent,
the compliance limit should be set at the fraction of the GWQS.
MW-26 Carbon
Tetrachloride 5 ug/L 3.8% 4.75 ug/L ** 5 ug/L
The "flow sheet" GWCL is based on the Poisson Limit and correctly follows the
flowchart. However, because carbon tetrachloride is a trace co-contaminant of
the chloroform plume, in accordance with UAC R317-6-6.15.F, the compliance
limit should be set at the GWQS.
MW-26 Chloromethane 30 ug/L 30.8% 6.6 ug/L ** 30 ug/L
The "flow sheet" GWCL is the highest historical value and correctly follows the
flowchart. However, because chloromethane is a degradation product of
chloroform, in accordance with UAC R317-6-6.15.F, the compliance limit should
be set at the GWQS.
MW-26 Cobalt 730 ug/L 0.0% 362 ug/L ** 365 ug/L
The "flow sheet" GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 365 ug/L instead of 362 ug/L.
MW-26 Nitrate/ite 10 mg/L 70.0% 0.623 mg/L ** 0.623 mg/L
The "flow sheet" GWCL is the correct value; however, the comment in
incorrect. The comment states that the proposed GWCL is the fraction of the
GWQS, but the proposed GWCL is actually Cohen's mean plus two standard
deviations - 0.623 mg/L.
MW-26 Xylenes 10,000 ug/L 0.0% 5 ug/L ** 5,000 ug/L
The "flow sheet" GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the GWCL contains a typographical error. The
fraction of the GWQS should be 5,000 ug/L instead of 5 ug/L.
MW-32 Nitrate/ite 10 mg/L 10.0% 0.1 mg/L 5 mg/L
This GWCL is proposed based on the highest historical value, but according to
the flowchart, the fraction of the groundwater standard can be used because it
is higher - 5 mg/L.
MW-32 Xylenes 10,000 ug/L 0.0% 5 ug/L 5,000 ug/L
The proposed GWCL is based on the fraction of the GWQS and follows the
flowchart correctly; however, the proposed GWCL contains a typographical
error. The fraction of the GWQS should be 5,000 ug/L instead of 5 ug/L.
* These revised GWCLs were calculated by URS and should be verified by DUSA.
** For MW-26, DUSA does not propose GWCLs. The GWCL is from the "Flow Sheet GWCL" column of Table 16 of the Revised Background Report (see item 10
of the URS Completeness Review).
3 of 6 6/16/2008
Table 2 - Groundwater Compliance Limits Categorized According to Statistical Flow Process
Mean + 2
Sigma*
Fraction of
GWQS**
Highest Historic
Value
Fraction of
GWQS Poisson Limit Fraction of
GWQS
Number of GWCLs
Established by Approach 81 4 50 93 10 256 494
Percentage of GWCLs
Established by Approach 16.4% 0.8% 10.1% 18.8% 2.0% 51.8% 100%
Number of GWCLs
Exceeding GWQS by
Approach
12 NA 4 NA 0 NA 16
Percentage of GWCLs
Exceeding GWQS by
Approach
2.4% NA 0.8% NA 0.0% NA 3.2%
Breakdown of GWCLs by approach assumes that the proposed GWCLs that deviate from the approved flowchart have been corrected and that GWCLs
for Cadmium in MW-1, MW-2, MW-3, and MW-5 and for THF in MW-1, MW-3, MW-5, and MW-12 have been revised to the DRC recommended GWCL
* Mean + 2 Sigma includes the arithmetic mean for data sets with 15% or less non-detects and the Cohen's mean for data sets with >15% to
50% non-detects
** The GWCL for THF in MW-1, MW-3, MW-5, and MW-12 has been revised to the fraction of the GWQS because THF is not a naturally
occurring constituent.
NA = not applicable
Parameter Categorized
>50% to 90% Non-Detects or Non-
Parametric Data Sets >90% Non-Detects TotalLess Than 50% Non-Detects
4 of 6 6/16/2008
Table 3 - Proposed GWCLs That Exceed GWQSs
Well Parameter
DUSA
Proposed
GWCL
(ug/L)
Proposed GWCL
Based on
GWQS
(ug/L)
Error in DUSA Proposed
GWCL? (from Table 1)
DRC
Proposed
GWCL
(ug/l)
MW-1 None ---- ---- ---- ---- ----
MW-2 None ---- ---- ---- ---- ----
MW-3 Manganese 4,233.03
Normal
Mean + 2σ 800 No 4,233.0
MW-3 Uranium 67.16
Non-parametric
Highest Historical
Value*
30
This GWCL is proposed
based on the highest
historical value. According
to the flowchart, it should be
the mean plus two standard
deviations - 47.32 ug/L.
47.32
MW-5 None ---- ---- ---- ---- ----
MW-11 None ---- ---- ---- ---- ----
MW-12 Cadmium 7
Non-parametric
Highest Historical
Value
5No7
MW-12 Manganese 2,088.80
Log Normal
Mean + 2σ 800 No 2,088.8
MW-14 Manganese 2,230.30
Normal
Mean + 2σ 800 No 2,230.3
MW-14 Uranium 98
Non-parametric
Highest Historical
Value
ug/L No 98.0
MW-15 Selenium 128.72
Normal
Cohen's Mean + 2σ 50 No 128.7
MW-15 Uranium 65.67
Non-parametric
Highest Historical
Value
30 No 65.7
MW-17 Manganese 915.39
Log Normal
Mean + 2σ 800 No 915.4
MW-17 Uranium 46.8
Non-parametric
Highest Historical
Value*
30
This GWCL is proposed
based on the highest
historical value. According
to the flowchart, it should be
the mean plus two standard
deviations - 46.66 ug/L.
46.66
MW-18 Uranium 55.1
Normal
Mean + 2σ 30 No 55.1
5 of 6 6/16/2008
Table 3 - Proposed GWCLs That Exceed GWQSs
Well Parameter
DUSA
Proposed
GWCL
(ug/L)
Proposed GWCL
Based on
GWQS
(ug/L)
Error in DUSA Proposed
GWCL? (from Table 1)
DRC
Proposed
GWCL
(ug/l)
MW-19 Thallium 2.15
Normal
Cohen's Mean + 2σ 2 No 2.1
MW-26 Manganese 1,610
Non-parametric
Highest Historical
Value
800 No 1,610.0
MW-26 Uranium 41.85
Log Normal
Mean + 2σ 30 No 41.8
MW-32 Iron 14,060
Normal
Mean + 2σ 11,000 No 14,060
MW-32 Manganese 5,594.95
Normal
Mean + 2σ 800 No 5,594.9
* Method is not correct according to Figure 19 flowchart. DRC proposed GWCL assumes correct method is used.
6 of 6 6/16/2008
ATTACHMENTS
DRC New Wells Memorandum
June 24, 2008
J'NM.ffi*,r*.
GARY HERBERT
Lieutenant Governor
State of Utah
Department of
Environmental Quality
Richard W. Sproft
Executive Director
DIVISION OF RADIATION
CONTROL
Dane L. Finerfrock
Director
THRU:
FROM:
DATE:
MEMORANDUM
Loren Morton
Phil Goble
June 24,2AA8
't'6wr
f,@
SLIBJECT: Denison Mines Corporation (USA) and Proposed Background Ground Water
Quality for New Wells (April 30, 2008 Intera Report); DRC Findings and
Recommended Action.
The purpose of this memorandum is to summarize DRC findings regarding the April 30, 2008
Background Ground Water Quality Report for the New Wells (hereafter New Wells Background
Report), to propose a DRC course of action for setting Ground Water Compliance Levels
(GWCLs) for the Denison Mines Corporation (USA) [hereafter DUSA] uranium milling facility
near Blanding, Utah.
The DRC has performed a completeness review of the Background Ground Water Quality for
New Wells (MW-23, MW-24, MW-25,NNV-27, MW-28, MW-29, MW30, MW-31, and MW-
3A). Finding and observations from the review are as follows:
DUSA performed the data evaluation and statistical analysis in accordance with the
statistical process flowchart (attached Figure 17) conditionally approved by the DRC on
August 24,2007. The statistical analysis was performed in accordance with the U.S.
Environmental Protection Agency (EPA) guidance and adequately addressed the presence
and variable percentage of non-detect values in the background water quality data sets.
There are 9 wells with 38 constituents for each well, resulting inS4lindividual data sets,
each of which has a coffesponding GWCL proposed by DUSA in Table 10 of Revised
Background Report for New Wells. Each dataset represents a single constituent at a single
well (e.9., arsenic at MW-23). Most of the proposed GWCLs appear to have been
calculated correctly following the flowchart process. However, there are several GWCLs
(146 out of a total of 342) where the wrong approach was used to determine the GWCL or
where there was a typographical error in the value of the GWCL.
168 North 1e50 west'Po Box '*-';;r:lilr;:xH:'::T::;"':::;'(80r) s36-4250'rax (801) s33-40e7
Printed on 100% recycled paper
1.
2.
Page 2
Of the 146 GWCLs needing correction, ST represented an increase over those proposed by
DUSA. 82 of the 87 GWCLs increased were caused by the change in classification from
Class tr to Class III for three wells (MW-25,NNV-27, and MW-31) which changed the
fraction value used in setting GWCLs under the approved flowchart approach (see Section 5
below). 50 of the 146 GWCLs needing correction resulted in a decrease; while in 9 other
cases, DUSA failed to propose a GWCL for Tin in each of the new wells (see Section 6
below). These incorrect GWCLs are listed in attached Table 1 along with the corrected
GWCL. For the remainin g 196 cases, the DRC agrees with the GWCLs proposed by
DUSA.
In 43 of these instances, DUSA recommended an approach that varied from the Flow Chart
diagram for data sets with very low variability. In the Revised New Wells Background
Report, DUSA claimed that during the calculation of GWCLs that were determined by the
mean plus two standard deviations, a condition arose that didn't occur during the same
calculation of the existing wells. Because data from the new wells is limited to around two
years and was analyzed by the same laboratory, the standard deviation could be typically
lower than similar values for the existing wells, in some cases resulting in a GWCL that is
very close to the average value of the data set. Therefore, for the cases where following the
flowchart resulted in a GWCL that is very close to the average value of the data set, DUSA
proposed GWCLs that were be based on the mean plus 20 percent ( x- +ZOVo) rather than
following the flowchart
This 7 +20Vo method used by DUSA is not based on the EPA Guidance given to DUSA in
an August 9, 2008 DRC e-mail. Additionally, DUSA has failed to follow the Decision
Tree/Flow Chart diagram, which was created by DUSA, and was conditionally approved by
the DRC on Augu st 24,2007 . It is not unexpected to see data sets with low variability
when using the same analytical laboratory over a short period of time. However, this
problem can be addressed in the future, if it occurs, in that DUSA has the ability to provide
new descriptive statistics for a given well and contaminant as more data becomes available,
and request the Executive Secretary approval thereof. Therefore, the DRC rejects the
proposed 7 +20Vo method. These incorrect GWCLs are listed in attached Table 1 along
with the corrected GWCL.
DUSA also argues in the Revised New Wells Background Rep ort: "that assuming a normal
distribution, setting the GWCL at a value of nuo standard deviations above the mean,
virtually guarantees that each well will be out of compliance (falsely) in about two and a
half percent of all concentration values measured in groundwater samples from that well."
While it is true that a GWCL that is set at the mean plus the second standard deviation,
which corresponds to the 957o upper confidence limit, has 2.5%o (0.025) probability of any
parameter in any well falsely exceeding its GWCL during any given sampling event.
DUSA would not be considered in out of compliance status until two consecutive
groundwater quality samples exceed the respective GWCL (7 +2o concentration) for each
well and contaminant in question. On a statistical basis this equates to a 0.062Vo (0.025)
probability that any given well and parameter will twice, consecutively, falsely exceed its
respective GWCL.
Page 3
3.
4.
5.
Attached Table 2 categonzes the GWCLs based on the percentage of non-detects and
statistical approach. Table 2 assumes the 146 flowchart effors have been corrected and the
issues listed in items 5 and 6 below have been addressed (see attached Table 1). The
following observations are made from Table 2:
o Most of the datasets consist of a majority of non-detects. 59.9Vo of the 342 data sets
consist of greater than 90Vo non-detects.
Largely because most data sets consist of a majority of non-detects, only 23Vo of the
342 proposed GWCLs were established as a mean plus two standard deviations. These
GWCLs were calculated following the first two paths shown on the attached flowchart.
16.67o of the 342 proposed GWCLs were established following the "Non-Parametric
Statistics" approach (third path on the attached flowchart): 2.6Vo were the highest
historical result in the data set (based on the non-parametric statistical method), and
I4.O%o were established as a fraction of the Groundwater Quality Standard (GWQS) as
allowed by the process shown on the flowchart. Note that the conditionally approved
process gives DUSA the option of using the greater of the highest historical result or the
fraction of the GWQS to represent the GWCL.
59.9Vo of the 342 praposed GWCLs were established following the fourth path of the
attached flowchart: IVo of the GWCLs were calculated as the Poisson prediction limit,
and 59.97o were established as a fraction of the GWQS as allowed by the process
shown on the flowchart (DUSA has the option of using the greater of the Poisson limit
or the fraction of the standard). The fact that over half of the GWCLs were established
as a fraction of the GWQS following the fourth path on the flow chart illustrates that for
many constituents, the data sets consist of primarily non-detected results.
Attached Table 3 shows that 15 of the proposed GWCLs (about 4.4Vo of the total) are
higher than the respective GWQS. Refer to Table 2for the breakdown of these GWCLs
exceeding the GWQS.
Groundwater Classification Utah Administrative Code R317-6-3.6 states: "Class III ground
water has one or both of the following characteristics: A. Total dissolved solids greater
than 3,000 m/L and less than 10,000 mglL, or; B. One or more contaminants that exceed
the ground water quality standards." So it is not unreasonable to have GWCLs, based on
background groundwater quality data, for Class III groundwater that are higher than the
GWQS, since by definition Class III groundwater can have contaminant concentrations that
exceed the corresponding standard. Most of the monitoring wells (seven of eight) are
classified as having Class III groundwater; while the other well (MW-30) is classified as
having Class II groundwater. Change in classification for three wells (MW-25 ,NNV-27,
and MW-31) will change the fraction value used in setting GWCLs under the approved
flowchart approach. As a result, under the fractions approach; the GWCL values will now
be set at 50Vo of the GWQS instead of 25Vo. This calculation was not incorporated into the
New Wells Background Report for these wells; therefore they have been updated on the
attached Table 1. See below for the groundwater classification rationale for each new well:
Page 4
Monitor Well Groundwater Classification Comment
MW-23 Class III TDS GWCL - 3,670 pslL
IvIW-24 Class III TDS GWCL - 4,450 pslL
MW-25 Class III*TDS GWCL - 2,976 lt gtL: The
proposed GWCL for manganese
(1,806 pglL) is above the GWQS in
MW-25 and changes the
Groundwater Protection Level to
Class III in this well.
IvIW-27 Class III*TDS GWCL - t,075 lrgtL: The
proposed GWCL for uranium (34
pgL) is above the GWQS in MW-27
and changes the Groundwater
Protection Level to Class III in this
well.
MW-28 Class III TDS GWCL - 4,852 uslL
MW-29 Class III TDS GWCL - 4,400 pslL
MW-30 Class II TDS GWCL - 1,918 pelL
MW-31 Class III*TDS GWCL - 1,320 1tg[L: The
proposed GWCL from selenium (71
pdL) is above the GWQS in MW-31
and changes the Groundwater
Protection Level to Class III in this
well.
MW-3A Class III TDS GWCL - 5,805 uslL
6.In the April 30, 2008 New Wells Background Report, DUSA failed to propose a GWCL for
Tin in all new wells. However, according to the Flowchart, if there is not at least eight data
points remaining, DUSA should defer analysis until eight data points available. DUSA was
required to start analysis for Tin in on-site wells when the White Mesa Uranium Mill began
to receive and process alternate feed material from Fansteel Inc. Analysis for Tin began in
June, 20A6 and there have been seven monitoring events where Tin has been analyzed.
With the help of EPA Region 8 toxicology staff the DRC adopted an ad hoc groundwater
quality standard for tin of 17,000 udl- (See 10127lO5 EPA memorandum). Since the Tin
concentrations in all new wells have been tOIVo non-detect, the GWCL will be set at the
fraction GWQS for Class III water - 8,500 pglL and 4,250 lldL for Class II water.
In the Intera Report, DUSA proposes a GWCL of 36 pgLfor uranium in well MW-24.
Before calculating this GWCL, DUSA correctly removed the uranium outliers (223 and
78.9 pgL). However, DUSA should have also removed the uranium outlrer,46 pdL.
After removing the uranium 46 pglL outlier, the GWCL(x+2o) calculates at 11.90 pgL.
The corrected G\ryCL is shown in the attached Table 1.
In the Intera Report, DUSA proposes GWCLs for pH in all news wells based on the mean
minus 20 percent (- -207o). This 7 -20Vo method used by DUSA is not based on the EPA
Guidance given to DUSA in an August 9, 2008 DRC e-mail. Additionally,DUSA has
failed to follow the Decision Tree/Flow Chart diagram. Therefore, the DRC rejects the
proposed 7 - 207o method for pH GWCLs. These incorrect GWCLs are listed in attached
Table 1 along with the corrected GWCL.
7.
Page 5
In summary, with the exception of some effors that will require correction, DUSA established
GWCLs in accordance with methodology given in the conditionally approved flowchart. This
methodology was developed in accordance with EPA guidance, and it takes into account that
much, if not the majority, of background data consists of non-detected results. In 15 instances, the
established GWCLs exceed corresponding GWQS's. Of these 15, it appears that only 1 may be
an issue in future monitoring (may cause noncompliance) if the GWCL is established as the
GWQS. The DRC agrees with all 15 instances where the proposed GWCL exceeds the GWQS,
determined by DUSA (after correcting all errors), because there is no physical or chemical basis
for a background concentration to be limited to the GWQS. Even in approving these proposed
GWCLs, several upward-trending data sets may require additional attention during future
monitoring events.
After review of the Revised New Wells Background Report and consideration of the University of
Utah StudyFinal Report; DRC staff recommends the following: 1) The DRC should accept 196 of
the 342 GWCLs values proposed by DUSA in the April 30, 2008 Revised New Wells Background
Report, 2) For the remaining 146 GWCLs, the DRC will adopt the values calculated by DRC staff
which can be found in the attached Table 1, and 3) It is recommend this be done with a major
Permit modification, in conjunction with a public comment period and Statement of Basis.
Page 6
References
Hurst, T.G. and D.K. Solomon, May, 2008, "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" unpublished report by the
University of Utah Department of Geology and Geophysics, 62 pp.[transmitted via
5/18/08 email from Kip Solomon to Loren Morton (DRC)1.
INTERA, Inc., Prepared for Denison Mines (USA) Corp., April 30, 2008. "Revised Background
Groundwater Quality Report: New Wells. For Denison Mines (USA) Corp.'s White Mesa
Mill Site, San Juan County, IJtah."
Utah Division of Radiation Control, December 1, 2004, "Statement of Basis for a Uranium
Milling Facility at White Mesa, South of Blanding, Utah," unpublished regulatory
document,5T pp., and 12 attachments.
Utah Division of Radiation Control, May 19, 2008, "Denison Mines Corporation (USA) and
Proposed Background Groundwater Quality for Existing Wells (October,2007 Intera
Report); April 28, 2008 URS Finding and DRC Recommended Action," unpublished
regulatory document from Loren Morton to Dane Finerfrock, 9 pp.
URS Corporation, June 16, 2008, "Completeness Review for the Revised Background
Groundwater Quality Report: Existing Wells for Denison Mines (USA) Corporation's
White Mesa Mill Site, San Juan County, lJtah," unpublished consultants memorandum, 4
pp., 1 figure,3 tables [transmitted via 6116108 email fromBob Sobocinski (URS) to Loren
Morton (DRC)1.
PRG:prg
F/.../DUSA New Wells Memo.doc
File: DUSA Background GWQ Report - New Wells
Groundwater Data Preparation and Statistica! lrocess Flow for
Calculating Groundwater Protection Standards, White Mesa MillSite, San Juan Gounty, Utah
*A non-detect considered 'insensitive" will be the maximum reporting limit in a dataset and will exceed other non-detecis by, for example,
an order of magnitude (e.9., .tO versus <1 .0 pg/L). In some cases, insensitive non-detects may also exceed detectable values in a
Wednesday, April 09, 2008
*r-c;*ffil$ffiINEEAJIr*-L#:q$ffiffiHRtiiHll
Figure 17
Groundwater Data Preparation and Statistical Process Flow for Calculating Ground Water Compliance Limits, \A/hite Mesa Mill Site, San
Juan County, Utah.
dataset (e.9., .t O versus 3.5 pg/L).
Table 1 - Revisions to Proposed GWCLs
Well
Protection
Level Parameter GWQS
Percentage
Detects
DUSA Proposed
GWCL
DRC Revised
GWCL Comment
MW-23 Class III Tin 17,000 µg/L 100% None 8,500 µg/L
DUSA failed to provide a GWCL for Tin in MW-23. Since the Tin
concentrations in MW-23 has been 100% non-detect, the GWCL
will be set at the fraction GWQS for Class III water - 8,500 µg/L.
MW-23 Class III Chloromethane 30 µg/L 50% 15 µg/L 5.7 µg/L
The GWCL proposed is based on the Permit GWCL for Class III
water. According to the flowchart, it should be the mean plus two
standard deviations - 5.7 µg/L.
MW-23 Class III Fluoride 4 mg/L 90.9% 0.7 mg/L 2 mg/L
The GWCL proposed is based on the mean plus two standard
deviations. According to the flowchart, it should be the greater of
the fraction of the standard or the highest historic value. The
GWCL should be 2 mg/L (fraction of the GWQS).
MW-23 Class III pH (s.u.) 6.5 - 8.5 100% 5.8 - 8.5 6.5 - 8.5
The GWCL proposed is based on the mean minus 20%. With
the lowest observed value (6.9) being within the range of the
GWQS, the GWCL should be set at as the GWQS - 6.5 - 8.5.
MW-23 Class III Sulfate TBD 100% 2,669 mg/L 2,524 mg/L
The GWCL proposed is based on the mean plus 20%.
According to the flowchart, DUSA should consider a modified
approach to set a GWCL. However, setting the GWCL at the
mean plus 20% is not protective of human health and the
environmental. It would be more appropriate to set the GWCL as
the mean plus two standard deviations - 2,524 mg/L.
MW-24 Class III Tin 17,000 µg/L 100% None 8,500 µg/L
DUSA failed to provide a GWCL for Tin in MW-24. Since the Tin
concentrations in MW-24 has been 100% non-detect, the GWCL
will be set at the fraction GWQS for Class III water - 8,500 µg/L.
MW-24 Class III Uranium 30 µg/L 100% 36 µg/L 11.9 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the mean plus two standard deviations. However, DUSA failed
to remove an outlier (46 µg/L) before calculating the GWCL.
After removing the outlier, the GWCL is 11.9 µg/L.
MW-24 Class III Fluoride 4 mg/L 100% 0.3 mg/L 0.36 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 0.36 mg/L.
MW-24 Class III pH (s.u.) 6.5 - 8.5 100% 5.7 - 8.5 6.5 - 8.5
The GWCL proposed is based on the mean minus 20%. With
the lowest observed value (6.9) being within the range of the
GWQS, the GWCL should be set at as the GWQS - 6.5 - 8.5.
MW-24 Class III Sulfate TBD 100% 3,113 mg/L 2,903 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 2,903 mg/L.
MW-24 Class III TDS TBD 100% 4,932 mg/L 4,450 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 4,450 mg/L.
MW-25 Class III* Ammonia 25 mg/L 100% 0.8 mg/L 0.77 mg/L
DUSA correctly based the proposed GWCL on the mean plus
two standard deviations. However, the GWCL was calulated
incorrectly, the GWCL should be 0.77 mg/L.
MW-25 Class III*
Nitrate + Nitrite
(as N)10 mg/L 0% 2.5 mg/L 5 mg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water - 5
mg/L.
MW-25 Class III* Arsenic 50 µg/L 0% 12.5 µg/L 25 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
25 µg/L.
MW-25 Class III* Beryllium 4 µg/L 0% 1 µg/L 2 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water - 2
µg/L.
MW-25 Class III* Cadmium 5 µg/L 100% 1.7 µg/L 1.5 µg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 1.5 µg/L.
MW-25 Class III* Chromium 100 µg/L 0% 25 µg/L 50 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
50 µg/L.
MW-25 Class III* Cobalt 730 µg/L 72.7% 182.5 µg/L 365 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
365 µg/L.
Table 1 - Revisions to Proposed GWCLs
Well
Protection
Level Parameter GWQS
Percentage
Detects
DUSA Proposed
GWCL
DRC Revised
GWCL Comment
MW-25 Class III* Copper 1,300 µg/L 0% 325 µg/L 650 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
650 µg/L.
MW-25 Class III* Iron 11,000 µg/L 0% 2,750 µg/L 5,500 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
5,500 µg/L.
MW-25 Class III* Lead 15 µg/L 0% 3.75 µg/L 7.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
7.5 µg/L.
MW-25 Class III* Manganese 800 µg/L 100% 2,037 µg/L 1,806 µg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 1,806 µg/L. With manganese being above the
GWQS in MW-25, it changes the Groundwater Protection Level
to Class III in this well.
MW-25 Class III* Mercury 2 µg/L 0% 0.5 µg/L 1 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water - 1
µg/L.
MW-25 Class III* Molybdenum 40 µg/L 100% 12 µg/L 20 µg/L
The GWCL proposed is based on the highest historical value.
According to the flowchart, it should be the greater of the fraction
of the standard or the highest historic value. The GWCL should
be 20 µg/L (fraction of the GWQS).
MW-25 Class III* Nickel 100 µg/L 0% 25 µg/L 50 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
50 µg/L.
MW-25 Class III* Selenium 50 µg/L 0% 12.5 µg/L 25 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
25 µg/L.
MW-25 Class III* Silver 100 µg/L 0% 25 µg/L 50 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
50 µg/L.
MW-25 Class III* Thallium 2 µg/L 100% 1.2 µg/L 1.1 µg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 1.1 µg/L.
MW-25 Class III* Tin 17,000 µg/L 100% None 8,500 µg/L
DUSA failed to provide a GWCL for Tin in MW-25. Since the Tin
concentrations in MW-25 has been 100% non-detect, the GWCL
will be set at the fraction GWQS for Class III water - 8,500 µg/L.
MW-25 Class III* Uranium 30 µg/L 100% 7.1 µg/L 6.5 µg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 6.5 µg/L.
MW-25 Class III* Vanadium 60 µg/L 0% 15 µg/L 30 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
30 µg/L.
MW-25 Class III* Zinc 5,000 µg/L 10% 1,250 µg/L 2,500 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2,500 µg/L.
MW-25 Class III* Gross Alpha 15 pCi/L 20% 3.75 pCi/L 7.5 pCi/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
7.5 pCi/L.
Table 1 - Revisions to Proposed GWCLs
Well
Protection
Level Parameter GWQS
Percentage
Detects
DUSA Proposed
GWCL
DRC Revised
GWCL Comment
MW-25 Class III* Acetone 700 µg/L 0% 175 µg/L 350 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
350 µg/L.
MW-25 Class III* Benzene 5 µg/L 0% 1.25 µg/L 2.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2.5 µg/L.
MW-25 Class III*
2-Butanone
(MEK)4,000 µg/L 0% 1,000 µg/L 2,000 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2,000 µg/L.
MW-25 Class III*
Carbon
Tetrachloride 5 µg/L 0% 1.25 µg/L 2.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2.5 µg/L.
MW-25 Class III* Chloroform 70 µg/L 0% 17.5 µg/L 35 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
35 µg/L.
MW-25 Class III* Chloromethane 30 µg/L 40% 7.5 µg/L 15 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
15 µg/L.
MW-25 Class III* Dichloromethane 5 µg/L 0% 1.25 µg/L 2.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2.5 µg/L.
MW-25 Class III* Naphthalene 100 µg/L 0% 25 µg/L 50 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II waterwater.
However, since manganese is above the GWQS in MW-25, it
changes the Groundwater Protection Level to Class III in this
well. Therefore, the GWCL will be set at 50% of the GWQS for
Class III water - 50 µg/L.
MW-25 Class III*
Tetrahydrofuran
(THF)46 µg/L 0% 11.5 µg/L 23 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
23 µg/L.
MW-25 Class III* Toluene 1,000 µg/L 0% 250 µg/L 500 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
500 µg/L.
MW-25 Class III* Xylenes (Total) 10,000 µg/L 0% 2,500 µg/L 5,000 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
5,000 µg/L.
MW-25 Class III* Chloride TBD 100% 38.8 mg/L 35 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 35 mg/L.
MW-25 Class III* Fluoride 4 mg/L 100% 1 mg/L 0.42 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 0.42 mg/L.
MW-25 Class III* pH (s.u.) 6.5 - 8.5 100% 5.8 - 8.5 6.5 - 8.5
The GWCL proposed is based on the mean minus 20%. With
the lowest observed value (6.9) being within the range of the
GWQS, the GWCL should be set at as the GWQS - 6.5 - 8.5.
MW-25 Class III* Sulfate TBD 100% 2,075 mg/L 1,933 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 1,933 mg/L.
Table 1 - Revisions to Proposed GWCLs
Well
Protection
Level Parameter GWQS
Percentage
Detects
DUSA Proposed
GWCL
DRC Revised
GWCL Comment
MW-25 Class III* TDS TBD 100% 3,411 mg/L 2,976 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 2,976 mg/L.
MW-27 Class III* Ammonia 25 mg/L 14% 6.25 mg/L 12.5 mg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
12.5 mg/L.
MW-27 Class III*
Nitrate + Nitrite
(as N)10 mg/L 100% 6.1 mg/L 5.6 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 5.6 mg/L.
MW-27 Class III* Arsenic 50 µg/L 0% 12.5 µg/L 25 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
25 µg/L.
MW-27 Class III* Beryllium 4 µg/L 0% 1 µg/L 2 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water - 2
µg/L.
MW-27 Class III* Cadmium 5 µg/L 0% 1.25 µg/L 2.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2.5 µg/L.
MW-27 Class III* Chromium 100 µg/L 0% 25 µg/L 50 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
50 µg/L.
MW-27 Class III* Cobalt 730 µg/L 0.0% 182.5 µg/L 365 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
365 µg/L.
MW-27 Class III* Copper 1,300 µg/L 0% 325 µg/L 650 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
650 µg/L.
MW-27 Class III* Iron 11,000 µg/L 0% 2,750 µg/L 5,500 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
5,500 µg/L.
MW-27 Class III* Lead 15 µg/L 0% 3.75 µg/L 7.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
7.5 µg/L.
MW-27 Class III* Manganese 800 µg/L 0% 200 µg/L 400 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
400 µg/L.
MW-27 Class III* Mercury 2 µg/L 0% 0.5 µg/L 1 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water - 1
µg/L.
MW-27 Class III* Molybdenum 40 µg/L 0% 10 µg/L 20 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
20 µg/L.
Table 1 - Revisions to Proposed GWCLs
Well
Protection
Level Parameter GWQS
Percentage
Detects
DUSA Proposed
GWCL
DRC Revised
GWCL Comment
MW-27 Class III* Nickel 100 µg/L 0% 25 µg/L 50 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
50 µg/L.
MW-27 Class III* Selenium 50 µg/L 100% 12.5 µg/L 25 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
25 µg/L.
MW-27 Class III* Silver 100 µg/L 0% 25 µg/L 50 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
50 µg/L.
MW-27 Class III* Thallium 2 µg/L 0% 0.5 µg/L 1 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water - 1
µg/L.
MW-27 Class III* Tin 17,000 µg/L 100% None 8,500 µg/L
DUSA failed to provide a GWCL for Tin in MW-27. Since the Tin
concentrations in MW-27 has been 100% non-detect, the GWCL
will be set at the fraction GWQS for Class III water - 8,500 µg/L.
MW-27 Class III* Uranium 30 µg/L 100% 37.7 µg/L 34 µg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 34 µg/L. With uranium being above the GWQS in
MW-27, it changes the Groundwater Protection Level to Class III
in this well.
MW-27 Class III* Vanadium 60 µg/L 0% 15 µg/L 30 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
30 µg/L.
MW-27 Class III* Zinc 5,000 µg/L 0% 1,250 µg/L 2,500 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2,500 µg/L.
MW-27 Class III* Acetone 700 µg/L 0% 175 µg/L 350 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
350 µg/L.
MW-27 Class III* Benzene 5 µg/L 0% 1.25 µg/L 2.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2.5 µg/L.
MW-27 Class III*
2-Butanone
(MEK)4,000 µg/L 0% 1,000 µg/L 2,000 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2,000 µg/L.
MW-27 Class III*
Carbon
Tetrachloride 5 µg/L 0% 1.25 µg/L 2.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2.5 µg/L.
MW-27 Class III* Chloroform 70 µg/L 0% 17.5 µg/L 35 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
35 µg/L.
Table 1 - Revisions to Proposed GWCLs
Well
Protection
Level Parameter GWQS
Percentage
Detects
DUSA Proposed
GWCL
DRC Revised
GWCL Comment
MW-27 Class III* Chloromethane 30 µg/L 44.4% 7.5 µg/L 15 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
15 µg/L.
MW-27 Class III* Dichloromethane 5 µg/L 0% 1.25 µg/L 2.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2.5 µg/L.
MW-27 Class III* Naphthalene 100 µg/L 0% 25 µg/L 50 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since manganese is above the GWQS in MW-25, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
50 µg/L.
MW-27 Class III*
Tetrahydrofuran
(THF)46 µg/L 0% 11.5 µg/L 23 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
23 µg/L.
MW-27 Class III* Toluene 1,000 µg/L 0% 250 µg/L 500 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
500 µg/L.
MW-27 Class III* Xylenes (Total) 10,000 µg/L 0% 2,500 µg/L 5,000 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since uranium is above the GWQS in MW-27, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
5,000 µg/L.
MW-27 Class III* Chloride TBD 100% 41.6 mg/L 38 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 38 mg/L.
MW-27 Class III* Fluoride 4 mg/L 100% 1 mg/L 0.85 mg/L
The GWCL proposed is based on the Permit GWCL for Class III
water. According to the flowchart, it should be the mean plus two
standard deviations - 0.85 mg/L.
MW-27 Class III* pH (s.u.) 6.5 - 8.5 100% 6.1 - 8.5 6.5 - 8.5
The GWCL proposed is based on the mean minus 20%. With
the lowest observed value (7.4) being within the range of the
GWQS, the GWCL should be set at as the GWQS - 6.5 - 8.5.
MW-27 Class III* Sulfate TBD 100% 486 mg/L 462 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 462 mg/L.
MW-27 Class III* TDS TBD 100% 1,223 mg/L 1,075 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 1,075 mg/L.
MW-28 Class III Tin 17,000 µg/L 100% None 8,500 µg/L
DUSA failed to provide a GWCL for Tin in MW-28. Since the Tin
concentrations in MW-28 has been 100% non-detect, the GWCL
will be set at the fraction GWQS for Class III water - 8,500 µg/L.
MW-28 Class III Chloromethane 30 µg/L 54.5% 15 µg/L 4.6 µg/L
The GWCL proposed is based on the Permit GWCL for Class III
water. According to the flowchart, it should be the mean plus two
standard deviations - 4.6 µg/L.
MW-28 Class III Chloride TBD 100% 107 mg/L 105 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 105 mg/L.
MW-28 Class III Fluoride 4 mg/L 100% 2 mg/L 0.73 mg/L
The GWCL proposed is based on the Permit GWCL for Class III
water. According to the flowchart, it should be the mean plus two
standard deviations - 0.73 mg/L.
MW-28 Class III pH (s.u.) 6.5 - 8.5 100% 5.4 - 8.5 6.1 - 8.5
The GWCL proposed is based on the mean minus 20%. With
the lowest observed value (6.3) being below the range of the
GWQS, the GWCL should be set on the basis of the mean minus
two standard deviations - 6.1 - 8.5.
MW-28 Class III Sulfate TBD 100% 2,833 mg/L 2,533 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 2,533 mg/L.
MW-28 Class III TDS TBD 100% 4,413 mg/L 3,852 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 3,852 mg/L.
MW-29 Class III Tin 17,000 µg/L 100% None 8,500 µg/L
DUSA failed to provide a GWCL for Tin in MW-29. Since the Tin
concentrations in MW-29 has been 100% non-detect, the GWCL
will be set at the fraction GWQS for Class III water - 8,500 µg/L.
Table 1 - Revisions to Proposed GWCLs
Well
Protection
Level Parameter GWQS
Percentage
Detects
DUSA Proposed
GWCL
DRC Revised
GWCL Comment
MW-29 Class III Manganese 800 µg/L 100% 6,033 µg/L 5,624 µg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 5,624 µg/L.
MW-29 Class III Chloride TBD 100% 46 mg/L 41 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 41mg/L.
MW-29 Class III pH (s.u.) 6.5 - 8.5 100% 5.6 - 8.5 6.46 - 8.5
The GWCL proposed is based on the mean minus 20%. With
the lowest observed value (6.5) being at the lower range of the
GWQS, the GWCL should be set on the basis of the mean minus
two standard deviations - 6.46 - 8.5.
MW-29 Class III Sulfate TBD 100% 3,342 mg/L 2,946 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 2,946 mg/L.
MW-30 Class II
Nitrate + Nitrite
(as N)10 mg/L 100% 16.7 mg/L 2.5 mg/L
The GWCL proposed is based on the mean plus 20%. However,
Intera concludes in Section 2.54 of the Background Report that
the Nitrate + Nitrte (as N) found in MW-30 is associated with the
on-site chloroform contamination. Since this Nitrate + Nitrte (as
N) contamination is associated with the on-site chloroform
contamination, it is a man-made contaminant; therefore,
background should not be set above the fraction of the GWQS -
2.5 mg/L.
MW-30 Class II Tin 17,000 µg/L 100% None 4,250 µg/L
DUSA failed to provide a GWCL for Tin in MW-30. Since the Tin
concentrations in MW-30 has been 100% non-detect, the GWCL
will be set at the fraction GWQS for Class III water - 4,250 µg/L.
MW-30 Class II Uranium 30 µg/L 100% 8.5 µg/L 8.32 µg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 8.32 µg/L.
MW-30 Class II Chloride TBD 100% 150 mg/L 128 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 128 µg/L
MW-30 Class II Fluoride 4 mg/L 100% 1 mg/L 0.51 mg/L
The GWCL proposed is based on the Permit GWCL for Class III
water. According to the flowchart, it should be the mean plus two
standard deviations - 0.51 mg/L.
MW-30 Class II pH (s.u.) 6.5 - 8.5 100% 5.9 - 8.5 6.5 - 8.5
The GWCL proposed is based on the mean minus 20%. With
the lowest observed value (6.9) being within the range of the
GWQS, the GWCL should be set at as the GWQS - 6.5 - 8.5.
MW-30 Class II Sulfate TBD 100% 1,060 mg/L 972 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 972 mg/L.
MW-30 Class II TDS TBD 100% 2,094 mg/L 1,918 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 1,918 mg/L.
MW-31 Class III* Ammonia 25 mg/L 14.3% 6.25 mg/L 12.5 mg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
12.5 µg/L.
MW-31 Class III*
Nitrate + Nitrite
(as N)10 mg/L 100% 28.7 mg/L 5 mg/L
The GWCL proposed is based on the mean plus 20%. However,
Intera concludes in Section 2.54 of the Background Report that
the Nitrate + Nitrte (as N) found in MW-31 is associated with the
on-site chloroform contamination. Since this Nitrate + Nitrte (as
N) contamination is associated with the on-site chloroform
contamination, it is a man-made contaminant; therefore,
background should not be set above the fraction of the GWQS -
5 mg/L.
MW-31 Class III* Arsenic 50 µg/L 0% 12.5 µg/L 25 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
25 µg/L.
MW-31 Class III* Beryllium 4 µg/L 0% 1 µg/L 2 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water - 2
µg/L.
MW-31 Class III* Cadmium 5 µg/L 0% 1.25 µg/L 2.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2.5 µg/L.
Table 1 - Revisions to Proposed GWCLs
Well
Protection
Level Parameter GWQS
Percentage
Detects
DUSA Proposed
GWCL
DRC Revised
GWCL Comment
MW-31 Class III* Chromium 100 µg/L 0% 25 µg/L 50 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
50 µg/L.
MW-31 Class III* Cobalt 730 µg/L 0% 182.5 µg/L 365 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
365 µg/L.
MW-31 Class III* Copper 1,300 µg/L 0% 325 µg/L 650 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
650 µg/L.
MW-31 Class III* Iron 11,000 µg/L 0% 2,750 µg/L 5,500 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
5,500 µg/L.
MW-31 Class III* Lead 15 µg/L 0% 3.75 µg/L 7.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
7.5 µg/L.
MW-31 Class III* Manganese 800 µg/L 0% 200 µg/L 400 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
400 µg/L.
MW-31 Class III* Mercury 2 µg/L 0% 0.5 µg/L 1 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water - 1
µg/L.
MW-31 Class III* Molybdenum 40 µg/L 0% 10 µg/L 20 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
20 µg/L.
MW-31 Class III* Nickel 100 µg/L 0% 25 µg/L 50 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
50 µg/L.
MW-31 Class III* Silver 100 µg/L 0% 25 µg/L 50 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
50 µg/L.
MW-31 Class III* Thallium 2 µg/L 0% 0.5 µg/L 1 µg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 1 µg/L.
MW-31 Class III* Tin 17,000 µg/L 100% None 8,500 µg/L
DUSA failed to provide a GWCL for Tin in MW-31. Since the Tin
concentrations in MW-31 has been 100% non-detect, the GWCL
will be set at the fraction GWQS for Class III water - 8,500 µg/L.
MW-31 Class III* Vanadium 60 µg/L 0% 15 µg/L 30 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
30 µg/L.
MW-31 Class III* Zinc 5,000 µg/L 0% 1,250 µg/L 2,500 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2,500 µg/L.
Table 1 - Revisions to Proposed GWCLs
Well
Protection
Level Parameter GWQS
Percentage
Detects
DUSA Proposed
GWCL
DRC Revised
GWCL Comment
MW-31 Class III* Gross Alpha 15 pCi/L 0% 3.75 pCi/L 7.5 pCi/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
7.5 pCi/L.
MW-31 Class III* Acetone 700 µg/L 0% 175 µg/L 350 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
350 µg/L.
MW-31 Class III* Benzene 5 µg/L 0% 1.25 µg/L 2.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2.5 µg/L.
MW-31 Class III*
2-Butanone
(MEK)4,000 µg/L 0% 1,000 µg/L 2,000 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2,000 µg/L.
MW-31 Class III*
Carbon
Tetrachloride 5 µg/L 0% 1.25 µg/L 2.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2.5 µg/L.
MW-31 Class III* Chloroform 70 µg/L 0% 17.5 µg/L 35 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
35 µg/L.
MW-31 Class III* Chloromethane 30 µg/L 55.6% 7.5 µg/L 6.1 µg/L
The GWCL proposed is based on the Permit GWCL for Class III
water. According to the flowchart, it should be the mean plus two
standard deviations - 6.1 µg/L.
MW-31 Class III* Dichloromethane 5 µg/L 0% 1.25 µg/L 2.5 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
2.5 µg/L.
MW-31 Class III* Naphthalene 100 µg/L 0% 25 µg/L 50 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
50 µg/L.
MW-31 Class III*
Tetrahydrofuran
(THF)46 µg/L 0% 11.5 µg/L 23 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
23 µg/L.
MW-31 Class III* Toluene 1,000 µg/L 0% 250 µg/L 500 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
500 µg/L.
MW-31 Class III* Xylenes (Total) 10,000 µg/L 0% 2,500 µg/L 5,000 µg/L
DUSA followed the flowchart correctly by setting the GWCL at
the fraction of the GWQS (25%) for Class II water. However,
since selenium is above the GWQS in MW-31, it changes the
Groundwater Protection Level to Class III in this well. Therefore,
the GWCL will be set at 50% of the GWQS for Class III water -
5,000 µg/L.
MW-31 Class III* Chloride TBD 100% 159 mg/L 143 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 143 mg/L.
MW-31 Class III* Fluoride 4 mg/L 100% 1.2 mg/L 2 mg/L
The GWCL proposed is based on the highest historical value.
According to the flowchart, it should be the greater of the fraction
of the standard or the highest historic value. The GWCL should
be 2 mg/L (fraction of the GWQS).
MW-31 Class III* pH (s.u.) 6.5 - 8.5 100% 6.0 - 8.5 6.5 - 8.5
The GWCL proposed is based on the mean minus 20%. With
the lowest observed value (6.8) being within the range of the
GWQS, the GWCL should be set at as the GWQS - 6.5 - 8.5.
Table 1 - Revisions to Proposed GWCLs
Well
Protection
Level Parameter GWQS
Percentage
Detects
DUSA Proposed
GWCL
DRC Revised
GWCL Comment
MW-3A Class III Tin 17,000 µg/L 100% None 8,500 µg/L
DUSA failed to provide a GWCL for Tin in MW-3A. Since the Tin
concentrations in MW-3A has been 100% non-detect, the GWCL
will be set at the fraction GWQS for Class III water - 8,500 µg/L.
MW-3A Class III Chloromethane 30 µg/L 75% 15 µg/L 9.4 µg/L
The GWCL proposed is based on the Permit GWCL for Class III
water. According to the flowchart, it should be the mean plus two
standard deviations - 9.4 µg/L.
MW-3A Class III Chloride TBD 100% 73.7 mg/L 70 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 70 mg/L.
MW-3A Class III pH (s.u.) 6.5 - 8.5 100% 5.8 - 8.5 6.5 - 8.5
The GWCL proposed is based on the mean minus 20%. With
the lowest observed value (6.9) being within the range of the
GWQS, the GWCL should be set at as the GWQS - 6.5 - 8.5.
MW-3A Class III Sulfate TBD 100% 4,143 mg/L 3,640 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 3,640 mg/L.
MW-3A Class III TDS TBD 100% 6,657 mg/L 5,805 mg/L
The GWCL proposed is based on the mean plus 20%. According
to the flowchart, it should be the mean plus two standard
deviations - 5,805 mg/L.
Table 2 - Groundwater Compliance Limits Categorized According to Statistical Flow Process
Mean + 2 Sigma**Highest Historic
Value Fraction of GWQS Highest Historic
Value
Fraction of
GWQS Poisson Limit Fraction of
GWQS ***
Number of GWCLs
Established by Approach 80 7 22 2 26 0 205 342
Percentage of GWCLs
Established by Approach 23% 2.0% 6.4% 0.6% 7.6% 0.0% 59.9% 100%
Number of GWCLs
Exceeding GWQS by
Approach
15 0 NA 0 NA 0 NA 15
Percentage of GWCLs
Exceeding GWQS by
Approach
4.4% 0.0% NA 0.0% NA 0.0% NA 4.4%
* Breakdown of GWCLs by approach assumes that the proposed GWCLs that deviate from the approved flowchart have been corrected.
** Mean + 2 Sigma includes the arithmetic mean for data sets with 15% or less non-detects and the Cohen's mean and Aitchison's mean for data sets with >15% to 50% non-detects
*** Includes nine proposed GWCLs for Tin
NA = not applicable
TotalParameter Categorized*
>50% to 90% Non-Detects or Non-
Parametric Data SetsLess Than 50% Non-Detects or Non Parametric Data Sets >90% Non-Detects
Table 3 - Proposed GWCLs That Exceed the GWQS
Well Parameter
Proposed
GWCL
(µg/L)
Proposed GWCL
Based on
No. of Detects/
No. of Samples
used in statistical
analysis
Percent
Detects
GWQS
(µg/L) Trend
Will you have problems if
you make the GWCL equal
to the GWQS?
Why? Error in Selected GWCL? (from Table 1)
DRC Proposed
GWCL
(µg/L)
MW-23 Uranium 32
Normal
Mean + 2 10/11 100% 30 None Probably not
Highs occurred at beginning of
sampling, recent sampling results have
been below GWQS
No 32
MW-24 Manganese 7,507
Normal
Mean + 2 12/12 100% 800 None Yes Results clearly exceed GWQS No 7,507
MW-25 Manganese 2,037 Normal Mean + 20% 11/11 100% 800 None Yes Results clearly exceed GWQS The GWCL proposed is based on the mean plus 20%. According to the
flowchart, it should be the mean plus two standard deviations - 1,806 µg/L.
1,806
MW-27 Uranium 37.7 Normal Mean + 20% 10/10 100% 30 None Yes Results clearly exceed GWQS The GWCL proposed is based on the mean plus 20%. According to the
flowchart, it should be the mean plus two standard deviations - 34 µg/L.
34
MW-28 Cadmium 5.2
Normal
Mean + 2 11/11 100% 5 None Probably not
Even though proposed GWCL
exceeds GWQS, the actual results do
not
No 5.2
MW-28 Manganese 1837
Normal
Mean + 2 11/11 100% 800 None Yes Results clearly exceed GWQS No 1,837
MW-28 pH (s.u.) 5.4 - 8.5 Normal Mean - 20% 11/11 100% 6.5 - 8.5 Down Yes Two results already exceed GWQS
The GWCL proposed is based on the mean minus 20%. With the lowest
observed value (6.3) being below the range of the GWQS, the GWCL
should be set on the basis of the mean minus two standard deviations - 6.1 -
8.5.
6.1 - 8.5
MW-29 Manganese 6033 Normal Mean + 20% 9/10 100% 800 None Yes Results clearly exceed GWQS The GWCL proposed is based on the mean plus 20%. According to the
flowchart, it should be the mean plus two standard deviations - 5,624 µg/L.
5,624
MW-29 pH (s.u.) 5.6 - 8.5 Normal Mean - 20% 9/10 100% 6.5 - 8.5 None Maybe
Although none of the results have
exceed the GWQS, there was one
result near the lower range of the
GWQS
The GWCL proposed is based on the mean minus 20%. With the lowest
observed value (6.5) being at the lower range of the GWQS, the GWCL
should be set on the basis of the mean minus two standard deviations -
6.46 - 8.5.
6.46 - 8.5
MW-31 Selenium 71
Normal
Mean + 2 10/10 100% 50 None Yes Results clearly exceed GWQS No 71
MW-3A Cadmium 8.3
Normal
Cohen's Mean + 2 9/9 66.7% 5 None Probably not
Highs occurred at beginning of
sampling and are the reason for high
proposed GWCL. After more
monitoring events the GWCL should
be re-evalutated
No 8.3
MW-3A Manganese 6,287
Normal
Mean + 2 9/9 100% 800 Down Probably not
Highs occurred at beginning of
sampling and are the reason for high
proposed GWCL. After more
monitoring events the GWCL should
be re-evalutated
No 6,287
MW-3A Nickel 105
Normal
Aitchison's Mean + 2 9/9 55.6% 100 Down Probably not
Highs occurred at beginning of
sampling and are the reason for high
proposed GWCL. After more
monitoring events the GWCL should
be re-evalutated
No 105
MW-3A Selenium 89
Normal
Mean + 2 8/9 100% 50 None Yes Results clearly exceed GWQS No 89
MW-3A Uranium 35
Normal
Mean + 2 8/9 100.0% 30 None Probably not
The first monitoring event results
exceeded the GWQS, the following
monitoring event results do not
No 35
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