DRC-2019-011412 - 0901a06880b1bd2d

Energy Fuels Resources (USA) Inc.
225 Union Blvd. Suite 600
Lakewood, CO, US, 80228 303 974 2140
www.energyfuels.com ENERGY FUELS
September 23, 2019
Sent VIA E-MAIL AND OVERNIGHT DELIVERY
Mr. Ty L. Howard
Director
Division of Waste Management and Radiation Control
Utah Department of Environmental Quality
195 North 1950 West
P.O. Box 144880
Salt Lake City, UT 84114-4880
ay of Waste Monagernent ard Radiation Cortrol
SEP 2 4 2019
17R-C-209-01
Re: Transmittal of Source Assessment Report for MW-25 White Mesa Mill Groundwater Discharge
Permit UGW370004
Dear Mr. Howard:
Enclosed are two copies of Energy Fuels Resource (USA) Inc.'s ("EFRI's") Source Assessment Report
("SAR") for MW-25 at the White Mesa Mill. This SAR addresses the constituent that was identified as
exceeding the GWCL in the 1st Quarter 2019 as described in the Division of Waste Management and Radiation
Control ("DWMRC")-approved Q1 2019 Plan and Time Schedule. EFRI submitted the Plan and Time Schedule
for MW-25 on May 13, 2019. DWMRC approval of the Plan and Time Schedule was received by EFRI on
June 26, 2019. Pursuant to the Plan and Time Schedule EFRI has prepared this SAR.
This transmittal also includes two CDs each containing a word searchable electronic copy of the report.
If you should have any questions regarding this report please contact me.
Yours very truly,
ENERGY FUELS RESOURCES (USA) INC.
Kathy Weinel
Quality Assurance Manager
CC: David C. Frydenlund Paul Goranson Terry Slade Logan Shumway
Scott Bakken
SOURCE ASSESSMENT REPORT
FOR CADMIUM IN MW-25
WHITE MESA URANIUM MILL
Blanding, Utah

Prepared for:
Energy Fuels Resources (USA) Inc.
225 Union Boulevard, Suite 600 Lakewood, Colorado 80228
Prepared by:

6000 Uptown Boulevard NE, Suite 220 Albuquerque, New Mexico 87110
September 23, 2019

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill ES-i Blanding, Utah September 23, 2019
EXECUTIVE SUMMARY
This Source Assessment Report (“SAR”) is an assessment of the sources, extent, and potential
dispersion of cadmium in monitoring well MW-25 at the White Mesa Mill (“the Mill”) as required
under State of Utah Groundwater Discharge Permit UGW370004 (the “GWDP”), Part I.G.4
relating to violations of Part I.G.2 of the GWDP. Cadmium in MW-25 has exhibited exceedances
of the applicable Groundwater Compliance Limits (“GWCLs”).
Groundwater at the Mill site has been evaluated in multiple recent investigations and reports,
including the Revised Background Groundwater Quality Report (INTERA, 2007a), the New Wells
Background Report (INTERA, 2008), the pH Report (INTERA, 2012b), an isotopic investigation
(Hurst and Solomon, 2008), a Pyrite Report (HGC, 2012), and multiple SARs.
Since the time of the New Wells Background Report (INTERA, 2008), the behavior of constituents
in MW-25 have not changed significantly. Cadmium concentrations continue to increase
gradually. Uranium concentrations are significantly increasing; however, an increasing trend was
observed at the time of the New Wells Background Report. There is no trend in chloride
concentrations, and fluoride and sulfate are significantly decreasing , indicating that potential
tailings seepage is not the source of exceedances of the cadmium GWCL. The exceedances of
cadmium in MW-25 are likely due to both geochemical processes and analytical effects. Increased
site-wide pyrite oxidation and an associated decrease in pH may be increasing the mobility of
naturally occurring cadmium within the Burro Canyon Formation. In addition, the current GWCL
for cadmium in MW-25 was based on the 10 data points available when it was originally
calculated. This original GWCL now seems unrepresentative when considering the natural
variability in cadmium concentrations apparent in the larger dataset that now exceeds 100
observations.
As the results of this analysis demonstrate, the behavior of cadmium concentrations in MW-25
have not changed significantly since the time of the New Wells Background Report. Cadmium
concentrations exhibit a gradual, but statistically significant increasing trend. An increasing trend
was also observed at the time of the New Wells Background Report, however the trend was not
significant. The slope of the increasing cadmium trend for MW-25 is not as steep as that observed
for MW-24 (INTERA, 2019), but in both cases, increasing cadmium concentrations most likely
result from natural and site-wide influences. In accordance with the State of Utah Division of
Waste Management and Radiation Control (“DWMRC”)-approved Flowsheet (from INTERA,
2007a, included in this report as Appendix E), increasing trends may necessitate a modified
approach for calculation of GWCLs. A modified approach for calculating a revised GWCL has
been proposed and included in this analysis. The modified approach includes using the fraction of
the groundwater quality standards under the Utah Administrative Code R317-6-4-4.6(B)(2) to

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill ES-ii Blanding, Utah September 23, 2019
determine representative and appropriate GWCLs for trending constituents. Regular revisions to
GWCLs for constituents in wells with significantly increasing trends over time due to background
is consistent with the United States Environmental Protection Agency Unified Guidance (USEPA,
2009). Such revisions account for variability in larger datasets and minimize unwarranted out-of-
compliance status.

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page i Blanding, Utah September 23, 2019
TABLE OF CONTENTS
TABLE OF CONTENTS .............................................................................................................. i
LIST OF TABLES ........................................................................................................................ ii
LIST OF FIGURES ...................................................................................................................... ii
LIST OF APPENDICES ............................................................................................................. iii
ABBREVIATIONS AND ACRONYMS .................................................................................... iv
1.0 INTRODUCTION............................................................................................................. 1
1.1 Source Assessment Report Organization ................................................................ 3 1.2 Limitations Statement ............................................................................................. 3
2.0 CATEGORIES AND APPROACH FOR ANALYSIS .................................................. 4
2.1 Approach for Analysis ............................................................................................ 4
2.2 Approach for Setting Revised GWCLs ................................................................... 5 2.3 University of Utah Study ........................................................................................ 5
3.0 RESULTS OF ANALYSIS............................................................................................... 7
3.1 Data Variability ....................................................................................................... 7
3.2 Decreasing pH ......................................................................................................... 7
3.3 Sorption ................................................................................................................... 8 3.4 Indicator Parameter Evaluation............................................................................... 8 3.5 Groundwater Elevation ........................................................................................... 9 3.6 Cadmium ................................................................................................................. 9
4.0 CALCULATION OF GROUNDWATER COMPLIANCE LIMITS ........................ 11
5.0 CONCLUSIONS AND RECOMMENDATIONS ........................................................ 12
6.0 REFERENCES ................................................................................................................ 13

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page ii Blanding, Utah September 23, 2019
LIST OF TABLES
Table 1. White Mesa Uranium Mill SARs...................................................................................... 2
Table 2. Proposed Revised GWCL. .............................................................................................. 11

LIST OF FIGURES
Figure 1. Location of White Mesa Mill Site and Groundwater Monitoring Wells
Figure 2. MW-25 Groundwater Elevation over Time

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page iii Blanding, Utah September 23, 2019
LIST OF APPENDICES
Appendix A. GWCL Exceedances in Second Quarter 2019 Under the March 19, 2019 GWDP
Appendix B. Geochemical Analysis for Cadmium in MW-25 B-1 Summary of Geochemical Analysis for Cadmium in MW-25 B-2 Comparison of Calculated and Measured TDS in MW-25
B-3 Charge Balance Calculations for Major Cations and Anions in MW-25
B-4 Descriptive Statistics for Cadmium in MW-25 B-5 MW-25 Data Used for Statistical Analysis B-6 Data Removed from Analysis B-7 Box Plot of Cadmium in MW-25
B-8 Box Plot of Cadmium in All Groundwater Monitoring Wells
B-9 Histograms of Cadmium in MW-25 B-10 Time Concentration Plots of Cadmium in MW-25
Appendix C. Geochemical Analysis for pH and Indicator Parameters in MW-25 C-1 Summary of Geochemical Analysis for pH and Indicator Parameters
C-2 Descriptive Statistics for pH and Indicator Parameters in MW-25
C-3 Data Used for Statistical Analysis C-4 Indicator Parameter Data Removed from Analysis C-5 Box Plots for pH and Indicator Parameters in MW-25 C-6 Histograms for pH and Indicator Parameters in MW-25
C-7 Time Series Plots and Linear Regressions for pH and Indicator Parameters in
MW-25
Appendix D. Time Concentration Plots Compared to Background Report Plots
Appendix E. Flowsheet (Groundwater Data Preparation and Statistical Process Flow for Calculating Groundwater Protection Standards, White Mesa Mill Site
[INTERA, 2007a])
Appendix F. Input and Output Files (Electronic Only)

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page iv Blanding, Utah September 23, 2019
ABBREVIATIONS AND ACRONYMS
µg/L micrograms per liter CFCs chlorofluorocarbons CIR Contaminant Investigation Report

Director Director of the Division of Waste Management and Radiation Control DWMRC State of Utah Division of Waste Management and Radiation Control EFRI Energy Fuels Resources (USA) Incorporated

GWCL Groundwater Compliance Limit GWDP State of Utah Ground Water Discharge Permit UGW370004 GWQS Groundwater Quality Standard
INTERA INTERA Incorporated
the Mill White Mesa Uranium Mill, Blanding, Utah OOC out-of-compliance

SAR Source Assessment Report TDS total dissolved solids
USEPA United States Environmental Protection Agency

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page 1 Blanding, Utah September 23, 2019
1.0 INTRODUCTION
Energy Fuels Resources (USA) Inc. (“EFRI”) operates the White Mesa Uranium Mill (the “Mill”),
located near Blanding, Utah (Figure 1). Groundwater at the Mill is regulated under the State of
Utah Groundwater Discharge Permit UGW370004 (the “GWDP”). This is the Source Assessment
Report (“SAR”) required under Part I.G.4 of the GWDP relating to Part I.G.2 of the GWDP with
respect to the cadmium in MW-25.
Part I.G.2 of the GWDP provides that an out-of-compliance (“OOC”) status exists when the
concentration of a constituent exceeds a groundwater compliance limit (“GWCL”) in Table 2 of
the GWDP in two consecutive samples from a compliance monitoring point. The GWDP was
originally issued in March 2005, at which time GWCLs were set on an interim basis, based on
fractions of State of Utah Ground Water Quality Standards (“GWQSs”) or the equivalent, without
reference to natural background at the Mill. The GWDP also required that EFRI prepare a
background groundwater quality report to evaluate all historical data for the purposes of
establishing background groundwater quality at the Mill and developing GWCLs under the
GWDP. As required by then Part I.H.3 of the GWDP, EFRI submitted the following documents to
the Director (the “Director”)1 of the State of Utah Division of Waste Management and Radiation
Control (“DWMRC”)2 :
• A revised background groundwater quality report: the Existing Wells Background
Report (INTERA, 2007a)
• A revised addendum: the Regional Background Report (INTERA, 2007b)
• A revised addendum: the New Wells Background Report (INTERA, 2008)
Based on a review of the Background Reports (the Existing Wells Background Report, the
Regional Background Report, and the New Wells Background Reports [INTERA 2007a; 2007b;
and 2008 respectively]) and other information and analyses, the Director re-opened the GWDP
and modified the GWCLs to be equal to the mean concentration + 2 standard deviations or the
equivalent. The modified GWCLs became effective on January 20, 2010. On January 19, 2018,
and March 19, 2019, revised GWDPs were issued, which set the revised GWCLs as approved by
the Director through SARs. The SARs for White Mesa Uranium Mill are summarized in Table 1.

1 the Director was formerly the Executive Secretary of the Utah Radiation Control Board and the Co-Executive
Secretary of the Utah Water Quality Board. 2 Formerly referred to as the State of Utah Division of Radiation Control.

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page 2 Blanding, Utah September 23, 2019
Table 1. White Mesa Uranium Mill SARs.
Plan and Time Schedule Date
Monitoring Periods Covered
DWMRC Plan and Time Schedule Approval Date
SAR Date SAR Approval Date Constituents
6/13/2011 Q1, Q2, Q3, Q4 of 2010, Q1 of 2011 7/12/2012 10/10/2012 4/25/2013 Multiple
9/7/2011 Q2 2011 7/12/2012 10/10/2012 4/25/2013 Multiple
4/13/2012 Multiple 7/12/2012 pH Report – 11/9/12; Pyrite Report – 12/7/12 4/25/2013 pH – multiple wells
12/13/2012 Q3 2012 2/4/2013 5/8/2013 7/23/2013 TDS – MW-29
3/15/2013 Q4 2012 5/30/2013 8/30/2013 9/17/2013 Selenium – MW-31
8/28/2013 Q1 2013 9/17/2013 12/17/2013 1/7/2014 Tetrahydrofuran – MW-01
9/20/2013 Q2 2013 10/16/2013 1/13/2014 3/10/2014 Gross Alpha – MW-32
12/5/2013 Q3 2013 12/18/2013 3/19/2014 6/5/2014 Sulfate – MW-01; TDS – MW-03A
12/4/2014 Q3 2014 1/8/2015 No SAR – OOC due to well damage
No SAR – OOC due to well damage Uranium – MW-28
5/19/2015 Q1 2015 8/11/2015 12/9/15 2/19/2016 Selenium, Sulfate, TDS, pH – MW-31
9/10/2015 Q2 2015 11/10/2015 No SAR – install packer
No SAR – install packer
Cadmium, Zinc, Beryllium, Nickel – MW-03
12/3/2015 Q4 2015 4/4/2016 6/28/2016 12/20/2016 Sulfate – MW18, Fluoride, pH, Cadmium and Thallium – MW-24
3/10/2017 Q4 2016 5/23/2017 8/21/2017 3/20/2018 Selenium, Sulfate, TDS, and Uranium in MW-31
3/2/2018 Q4 2017 3/30/2018 6/28/2018 7/25/2018 Fluoride – MW-14
8/28/2018 Q2 2018 10/18/2018 1/19/2019 7/9/2019 Uranium, Selenium, pH – MW-30
12/5/2018 Q3 2018 3/5/2019 7/3/2019 -- Cadmium, Thallium, pH, Nickel, Beryllium – MW-24*
2/21/2019 Q4 2018 3/5/2019 7/3/2019 9/5/2019 Manganese – MW-11
5/19/2019 Q1 2019 6/26/2019 9/24/2019 Cadmium – MW-25
Notes:
* = Additional assessments required as stated in letter dated 9/5/19 TDS = total dissolved solids

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page 3 Blanding, Utah September 23, 2019
On April 17, 2019, EFRI submitted an exceedance notice for the first quarter of 2019 to the
Director under Part I.G.1(a) of the GWDP providing notice that the concentrations of specific
constituents in the monitoring wells at the Mill exceeded their respective GWCLs for first quarter
of 2019 and indicating which of those constituents had two consecutive exceedances. A plan and
time schedule for cadmium in MW-25 was submitted on May 19, 2019. The plan and time schedule
was approved by the DWMRC on June 26, 2019.
1.1 Source Assessment Report Organization
On behalf of EFRI, INTERA Incorporated (“INTERA”) performed analyses of cadmium and
indicator parameters in MW-25. A description of the approach used for analysis is provided in
Section 2.0, and the results of the analysis are presented in Section 3.0. The calculation of a GWCL
is discussed in Section 4.0, and conclusions and recommendations are reviewed in Section 5.0.
Section 6.0 provides a list of references cited in this SAR.
The appendices comprise the analyses performed for this SAR and are organized in the following
manner: Appendix A contains a table showing exceedances. Appendix B contains the statistical
analysis performed on cadmium in MW-25. Appendix C contains the pH and indicator parameter
analysis performed on MW-25. Appendix D contains a data plot for cadmium and indicator
parameters in MW-25 using all available data to date compared to the data plot from the
Background Reports (INTERA, 2007a, 2007b, 2008). Appendix E contains the Flowsheet that
was developed based on the United States Environmental Protection Agency’s (“USEPA”)
Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities, Unified Guidance
(USEPA, 2009), which was approved by DWMRC prior to completion of the Background Reports
(INTERA, 2007a, 2007b, 2008). Appendix F is included on the compact disc that accompanies
this SAR and contains the electronic input and output files used for statistical analysis.
Statistical analysis was performed using the R software package (v. 3.5.0). Input and output files
included in Appendix F can be imported into either R or Statistica to recreate the results presented
in this SAR.
1.2 Limitations Statement
This SAR presents the findings and interpretations of INTERA based on, and limited to, the
conditions existing at the time of this SAR and the scope of services agreed upon between INTERA
and EFRI. The calculations presented herein were completed using industry standard practices and
were performed on data received from others. INTERA relies in good faith on information
provided for this SAR, including analytical data, measurements, and previous investigations
performed at the Mill site, but does not make any warranty, expressed or implied, that the
information is accurate and complete.

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page 4 Blanding, Utah September 23, 2019
2.0 CATEGORIES AND APPROACH FOR ANALYSIS
Generally, OOC constituents and wells can be grouped into five categories:
Constituents Potentially Impacted by Decreasing pH Trends Across the Site
Newly Installed Wells with Interim GWCLs
Constituents in Wells with Previously Identified Rising Trends
Pumping Wells
Other Constituents
This SAR addresses cadmium in MW-25, which falls into category one. Due to the limited number
of data points available when the initial GWCL was calculated, cadmium also falls within the fifth
category: Other Constituents.
2.1 Approach for Analysis
The first step in the analysis is to perform an assessment of the potential sources for the
exceedances to determine whether they are due to background influences or Mill activities. If the
exceedances are determined to be within natural variability or site-wide influences, then it is not
necessary to perform any further evaluations on the extent and potential dispersion of the
contamination or to perform an evaluation of potential remedial actions. Monitoring will continue
and where appropriate revised GWCLs will be proposed to reflect changes in background
conditions at the Mill site.
The analysis performed in this SAR considers all available data to evaluate the behavior of the
constituent in the well. Analysis will help to determine if there have been any changes in the
behavior of potential tailings system seepage indicator parameters (e.g., chloride, sulfate, fluoride,
and uranium) since the date of the Background Reports (INTERA, 2007a, 2007b, 2008) that may
suggest a change in the behavior of the groundwater in that well.
As discussed in the Background Reports (INTERA, 2007a, 2007b, 2008), indicator parameters of
potential tailings system seepage include chloride, sulfate, fluoride, and uranium. Chloride is the
best indicator of potential tailings system seepage; however, chloride is problematic as an indicator
parameter for certain groundwater monitoring wells at the Mill site given the presence of the
chloride plume (HGC, 2018). Sulfate and fluoride are useful indicator parameters when the
geochemical conditions allow these constituents to behave conservatively (i.e., are non-reactive).
Uranium can be a mobile metal; behavior ranges from conservative to non-conservative,
depending on the geochemical conditions. Any potential seepage from the tailings system would
be expected to exhibit increasing concentrations of chloride, sulfate, fluoride, and uranium, among
other constituents. While uranium can be the most mobile of trace metals under certain conditions,

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page 5 Blanding, Utah September 23, 2019
it is typically retarded behind chloride, fluoride, and sulfate due to possible sorption (see Section
3.3) and precipitation and would likely not show increasing concentrations in groundwater until
sometime after chloride, fluoride, and sulfate concentrations had begun to increase
(INTERA, 2007a). It is important to note, however, that while the absence of a rising trend in
chloride concentration would indicate that there has been no impact from the tailings system, a
rising trend in chloride concentration as well as in other indicator parameters could also be due to
natural influences (see Section 12.0 of INTERA, 2007a).
The evaluation of SAR parameters and indicator parameters in MW-25 was supported by a
statistical analysis that followed the process outlined in the Flowsheet (included in INTERA,
2007a), a copy of which is attached as Appendix E. The Flowsheet was designed based on
USEPA’s Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities, Unified
Guidance (USEPA, 2009), and was approved by DWMRC prior to completion of the Background
Reports (INTERA, 2007a, 2007b, 2008).
2.2 Approach for Setting Revised GWCLs
If the preceding approach results in the conclusion that the analysis in the Background Reports
(INTERA, 2007a, 2007b, 2008) has not changed, or that the increasing concentrations of SAR
parameters are due to natural variability in groundwater, or site-wide influences such as the
oxidation of pyrite resulting in the site-wide decrease of pH, then a new GWCL may be proposed.
In proposing revised GWCLs, INTERA has adopted the approach in the DWMRC-approved
Flowsheet (Appendix E), including the last decision of the process that directs the analyst to
consider a modified approach to determining a GWCL if an increasing trend is present.
2.3 University of Utah Study
At the request of the DWMRC, T. Grant Hurst and D. Kip Solomon of the Department of Geology
and Geophysics of the University of Utah performed a groundwater study (the “University of Utah
Study”) at the Mill site in July 2007 (Hurst and Solomon, 2008). The purpose of this study was to
characterize groundwater flow, chemical composition, noble gas composition, and water age to
evaluate whether the increasing and elevated trace metal concentrations in monitoring wells at the
Mill, all of which were identified in the Background Reports (INTERA, 2007a, 2007b, 2008), may
indicate that potential seepage from the tailings system is occurring.
To evaluate sources of solute concentrations at the Mill, low-flow groundwater sampling was used
as a method for collecting groundwater quality samples from 15 monitoring wells. In addition,
surface water samples were collected from tailings cells 1, 3, and 4A, and two wildlife ponds.
Passive diffusion samplers were also deployed and collected to characterize the dissolved gas
composition of groundwater at different depths within the wells. Samples were collected and
analyzed for the following constituents: tritium, nitrate, sulfate, deuterium and oxygen-18 of water,

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page 6 Blanding, Utah September 23, 2019
sulfur-34 and oxygen-18 of sulfate, trace metals (uranium, manganese, and selenium), and
chlorofluorocarbons (“CFCs”).
Hurst and Solomon (2008, page iii) concluded generally that,
[t]he 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 observations.
Hurst and Solomon (2008) also concluded that,
[i]n general, the data collected in this study do not provide evidence that tailings
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.
It should be further noted that subsequent to the University of Utah Study EFRI submitted the
Contaminant Investigation Report [“CIR”], White Mesa Uranium Mill Site, Blanding Utah, dated
December 30, 2009 (INTERA, 2009), in connection with the nitrate/chloride plume at the Mill
site.

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page 7 Blanding, Utah September 23, 2019
3.0 RESULTS OF ANALYSIS
This section describes the potential geochemical influences on groundwater in MW-25 and results of
the analyses, summaries of which are provided in Appendix B-1, Appendix C-1, and Appendix D.
Analyses of cadmium in MW-25 were performed as part of the flowsheet (see Appendix B). The
analyses included a box plot to identify and omit extreme outliers, Shapiro-Wilk test for
distribution, and Mann-Kendall trend tests (see Appendices B-1, and B-7 through B-10).
3.1 Data Variability
The current GWCL for cadmium in MW-25 was calculated using only 10 data points that were
available at the time of the New Wells Background Report. Since that time, over 100 data points
for cadmium in MW-25 have become available. Although the mean of the initial data set and the
complete data set are very similar (1.39 and 1.38 micrograms per liter [µg/L], respectively) a
laboratory change in the fourth quarter of 2012 coincides with the appearance of greater variability
in cadmium concentrations (Appendix B-10). This observed variation likely results from
increased sampling frequency and more precise analytical methods and instrumentation.
As noted by DWMRC in a letter dated June 26, 2019, data collected after the laboratory change in
fourth quarter of 2012 should be analyzed in accordance with EPA Unified Guidance to represent
current conditions. Two datasets were analyzed in this SAR: the complete data set and a data subset
starting in the fourth quarter of 2012. Although variation is observed beginning in 2012 (Appendix
B-10), the two data sets are very similar. A summary of this analysis is presented in Appendix B-
1 and Appendix B-4.
3.2 Decreasing pH
Decreasing pH is one of the most important contributors to increasing concentrations of metals at
the Mill site. A decreasing trend in pH is observed in MW-25, although the trend is not significant
(Appendix C-1). A decreasing trend in pH has been observed in many groundwater monitoring
wells across the Mill site, including upgradient and far downgradient monitoring wells (INTERA,
2012b). The Pyrite Report (HGC, 2012) attributes the decline in pH across the Mill site to the site-
wide existence and oxidation of pyrite in the perched zone of the Burro Canyon aquifer. This report
showed that pyrite is present in the Burro Canyon Formation based on boring logs, X-ray
diffraction results, and concentrations of iron and total sulfur in bedrock samples from the Mill
site (HGC, 2012).
Pyrite may oxidize according to the following reaction (Williamson and Rimstidt, 1994):
FeS2(s) + 7/2O2(g) + H2O  Fe2+(aq) + 2SO42-(aq) + 2H+ (reaction 1)

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page 8 Blanding, Utah September 23, 2019
Reaction 1 will increase hydrogen ion concentrations, which results in decreasing pH.
The likely causes for site-wide oxidation of pyrite include the following: (1) infiltration of oxidized
water from the wildlife ponds upgradient of the Mill site; (2) rising water levels and incorporation
of oxygen in air-filled pore spaces; (3) the introduction of oxygen during pumping related to
treatment of the chloride and nitrate plumes; and (4) the introduction of oxygen during increased
sampling of monitoring wells (INTERA, 2012b). Oxidation of pyrite and the resulting decrease in
pH tends to cause subsequent pH-dependent reactions, some of which are described in more detail
below.
3.3 Sorption
Another process that is likely to impact dissolved cadmium and other metals is sorption. Dissolved
metals may be naturally attenuated by sorption, which refers to the processes by which solutes
attach to solid surfaces (adsorption) and become incorporated into the bulk of a solid (absorption).
The solid host is the sorbent, and the solute that sorbs is the sorbate. In most groundwater systems,
minerals make up most of the sorbents. The sorption process can be reversed by a process known
as desorption. Desorption remobilizes sorbates. In general, at lower pH (when dissolved hydrogen
ion concentrations are high) mineral surfaces tend to have a slightly positive charge. With
decreasing pH, positively charged dissolved metals are less attracted to mineral surfaces, and
therefore are less attenuated by sorption. Different dissolved metals have variable affinities for
sorption to different minerals.
As described in more detail in the SAR for MW-24 (INTERA, 2019), sorption of cadmium and
other metals becomes more limited with decreasing pH. In addition, decreasing pH may lead to
desorption of metals, which could cause increasing metal concentrations. Decreasing pH and
associated desorption of metals could account for some of the observed increase in cadmium
concentrations in MW-25.
3.4 Indicator Parameter Evaluation
A summary of statistical analysis of indicator parameters is included in Appendix C-1.
Appendix C-2 presents a descriptive statistics comparison for pH and indicator parameters from
the New Wells Background Report (INTERA, 2008a), the 2012 SAR (INTERA, 2012a), and this
SAR. Data used in the analysis and data removed prior to analysis are presented in Appendices
C-3 and C-4, respectively. The distribution and identification of outliers and extreme outliers in
indicator parameter concentration datasets are demonstrated in the box plots included in Appendix
C-5. Histograms and timeseries plots are included in Appendix C-6 and C-7, respectively.
Groundwater elevation is plotted against time in Figure 2.

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page 9 Blanding, Utah September 23, 2019
Indicator parameters in MW-25 exhibit no trend (chloride), significant decreasing trends (fluoride
and sulfate), and a significant increasing trend (uranium) (Appendix C-1). Uranium
concentrations were increasing at the time of the New Wells Background Report, though not
significantly (INTERA, 2008a). The slopes of the significantly trending indicator parameters are
not steep and summary statics show that concentrations have not changed notably over time
(Appendices C-7 and C-2, respectively). The indicator parameter results suggest that MW-25 is
unlikely to be impacted by potential tailings seepage.
3.5 Groundwater Elevation
Groundwater elevations in MW-25 are presented in Figure 2. Groundwater elevations have been
decreasing since a peak in 2012. This change is likely a result of the removal of the wildlife ponds,
which removed the source of natural recharge to the groundwater, and increased groundwater
pumping related to the ongoing corrective action activities at the Mill site. The variations in
groundwater elevation do not appear to be related to the observed behavior of cadmium, pH, or
the indicator parameters in MW-25.
3.6 Cadmium
The cadmium dataset for MW-25 contains 108 data points at the time of this SAR. The current
GWCL was calculated using only 10 data points. As mentioned above, variability in cadmium
concentrations is visible after the laboratory change in fourth quarter of 2012. Descriptive statistics
from three datasets are compared in Appendix B-4: (1) the New Wells Background Report dataset,
(2) the complete dataset, and (3) post-fourth quarter of 2012 dataset. All datasets are normally or
lognormally distributed and have very similar mean concentrations and standard deviations. The
complete dataset exhibits a statistically significant increasing trend (Appendix B-10). This
increasing trend was observed at the time of the New Wells Background Report (Appendix D),
although it was not significant. As noted in Section 3.4, the overall stability of indicator parameter
concentrations in MW-25 suggests that the source of increased cadmium is not due to potential
tailings seepage.
A discussion of sources of naturally occurring cadmium and its behavior with decreasing pH is
included in Section 3.4.2 of the SAR for MW-11 and MW-24 (INTERA, 2019). Like at MW-24,
increased pyrite oxidation and an associated decrease in pH may cause increased dissolution of
cadmium-bearing minerals in the Burro Canyon Formation and decreased attenuation of cadmium
by sorption. These combined processes may contribute to the gradual, but significantly increasing
trend of cadmium in MW-25. In addition to geochemical processes, cadmium exceedances likely
result from additional data that capture the natural variability of cadmium concentrations in this
well relative to the original GWCL based on 10 data points. Because cadmium concentrations are
most likely due to natural variation and site-wide influences, a revised GWCL for cadmium is

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page 10 Blanding, Utah September 23, 2019
proposed. The current GWCL is 1.5 µg/L. The proposed revised GWCL is 2.5 µg/L, which is the
fractional approach under Utah Administrative Code R317-6-4-4.6(B)(2). The proposed revised
GWCL was calculated by a modified approach in accordance with the DWMRC-approved
Flowsheet due to the significantly increasing trend in the complete data set (Appendix E). A
discussion of the modified approach for cadmium is included in Section 4.0.

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page 11 Blanding, Utah September 23, 2019
4.0 CALCULATION OF GROUNDWATER COMPLIANCE LIMITS
The findings of analyses discussed above support the following conclusions: (1) exceedances of
the cadmium GWCL for MW-25 are likely the result of natural variability and site-wide oxidation
of pyrite resulting in decreases in pH; (2) concentrations of indicator parameters in MW-25 have
not changed significantly since the time of the Background Report (INTERA, 2008), the
University of Utah Study, or recent SARs; and (3) MW-25 is not being impacted by potential
tailings system seepage. Therefore, a revised GWCL for cadmium in MW-25 is proposed.
According to the DWMRC-approved Flowsheet (Appendix E), if an increasing trend is present, a
modified approach should be considered for determining GWCLs. Flowsheet analysis was
performed on two data sets during this SAR. Appendix B-1 presents the summary of those
analyses for the complete data set and the post-2012 data set. Although there is more variability
observed in the post-2012 data set, the flowsheet GWCL for that data set is only 0.01 µg/L greater
than the current GWCL, and therefore not an ideal data set from which to calculate a revised
GWCL. The complete data set, which is normally distributed and exhibits a significant increasing
trend (Appendix B-1), is recommended for calculation of a revised GWCL for cadmium in MW-
25. The Flowsheet (Appendix E) calculations along with the proposed GWCLs using a modified
approach in accordance with the DWMRC-approved Flowsheet are presented in Appendix B-1
and Table 2.
Table 2. Proposed Revised GWCL.
Well Parameter Current GWCL
Flowsheet Revised GWCL Rationale
Proposed
Modified Approach GWCL
Modified Approach Rationale
MW-25 Cadmium (µg/L) 1.5 1.6 Mean + 2 Standard Deviations 2.5 Fraction of GWQS
Notes:
µg/L= micrograms per liter

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page 12 Blanding, Utah September 23, 2019
5.0 CONCLUSIONS AND RECOMMENDATIONS
The Mill site was recently thoroughly studied in the Background Reports (INTERA, 2007a, 2007b,
2008), in various SARs, and in the University of Utah Study (Hurst and Solomon, 2008). The
Background Reports and the University of Utah Study concluded that groundwater at the Mill site
has not been impacted by Mill operations. All of these studies also acknowledged that there are
natural influences on the Mill site that have given rise to increasing trends and general variability
of background groundwater at the Mill site.
The focus of this SAR was, therefore, to identify any changes in the circumstances identified in
those studies. Evaluation of cadmium and indicator parameters in MW-25 was performed in
accordance with the DWMRC-approved Flowsheet (Appendix E). The current GWCL was
established using 10 data points. The current data set has over 100 data points and contains enough
data to demonstrate natural variability of cadmium concentrations in MW-25. Cadmium in MW-
25 exhibits a significantly increasing trend when considering the complete dataset. An increasing
trend was also observed at the time of the New Wells Background Report (INTERA, 2008). pH in
MW-25 is decreasing and the mobility of cadmium tends to increase as pH decreases. The indicator
parameter chloride is exhibiting no trend and fluoride and sulfate are decreasing significantly.
Uranium is significantly increasing and was identified as increasing at the time of the New Wells
Background Report (INTERA, 2008). The slopes of significantly trending indicator parameters
are not steep and summary statics show that concentrations have not changed notably over time
(Appendices C-7 and C-2, respectively). Due to relatively stable concentrations of indicator
parameters in MW-25 since the New Well Background Report, the increasing trend in cadmium
is most likely not related to potential tailings seepage. The exceedances of cadmium in MW-25
are likely due to both geochemical processes associated with pyrite oxidation and site-wide
decreasing pH and analytical effects, which include more precise analytical methods and
instrumentation, resulting in a larger dataset with greater variability. The slope of the increasing
cadmium trend for MW-25 is not as steep as that observed for MW-24 (INTERA, 2019); however,
in both cases, increasing cadmium concentrations could result from mobilization of natural sources
of cadmium within the Burro Canyon Formation.
INTERA recommends adopting the proposed revised GWCL for MW-25 using a modified
approach for trending constituents in accordance with the Flowsheet (Appendix E). Regular
revisions to GWCLs is consistent with the USEPA Unified Guidance (USEPA, 2009). Such
revisions account for variability in larger datasets and minimize unwarranted OOC status.

Source Assessment Report for Cadmium in MW-25 White Mesa Uranium Mill Page 13 Blanding, Utah September 23, 2019
6.0 REFERENCES
Hurst, T.G., and Solomon, D.K., 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. Prepared by Department of Geology and Geophysics, University of Utah.
Hydro Geo Chem (HGC), 2012. Investigation of Pyrite in the Perched Zone, White Mesa
Uranium Mill Site, Blanding, Utah.
––––––, 2018. White Mesa Uranium Mill Nitrate Monitoring Report Third Quarter 2018.
INTERA Incorporated, 2007a. Revised Background Groundwater Quality Report: Existing Wells for Denison Mines (USA) Corp.’s White Mesa Uranium Mill Site, San Juan
County, Utah.
––––––, 2007b. Revised Addendum: Evaluation of Available Pre-Operational and Regional Background Data, Background Groundwater Quality Report: Existing Wells for Denison Mines (USA) Corp.’s Mill Site, San Juan County, Utah.
––––––, 2008. Revised Addendum: Background Groundwater Quality Report: New Wells for
Denison Mines (USA) Corp.’s Mill Site, San Juan County, Utah.
––––––, 2009. Contaminant Investigation Report, White Mesa Uranium Mill Site, Blanding Utah.
––––––, 2012a. Source Assessment Report White Mesa Uranium Mill Blanding, Utah.
––––––, 2012b. pH Report White Mesa Uranium Mill Blanding, Utah.
______, 2016. Source Assessment Report for MW-18 and MW-24 White Mesa Uranium Mill
Blanding, Utah.
––––––, 2019. Source Assessment Report for MW-11 and MW-24 White Mesa Uranium Mill. June 27.
United States Environmental Protection Agency (“USEPA”), 2009. Statistical Analysis of
Groundwater Monitoring Data at RCRA Facilities, Unified Guidance. EPA-530-R-09-
007.
Utah Administrative Code (“UAC”). Rule R317-6. Ground Water Quality Protection. May 2019. https://rules.utah.gov/publicat/code/r317/r317-006.htm#T7
Williamson, M. A., Rimstidt, J. D., 1994. The Kinetics and Electrochemical Rate-Determining
Step of Aqueous Pyrite Oxidation. Geochimica et Cosmochimica Acta, 58, 5443-5454.
FIGURES
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MW-33
MW-32
MW-31MW-29
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MW-27
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MW-12 MW-11MW-05
MW-04
MW-02
MW-01
MW-03A
MW-14
MW-30
MW-35
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Figure 2. Groundwater Elevation in MW-25
Source Assessment Report for MW-25
White Mesa Uranium Mill Blanding, Utah
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APPENDIX A
GWCL Exceedances through Second Quarter 2019
Under the March 19, 2019 GWDP
APPENDIX A
GWCL Exceedances Through Second Quarter 2019 Under the March 19, 2019 GWDP
Monitoring Well
(Water Class)Constituent Exceeding GWCL
GWCL in
January 19,
2018 GWDP
Q1 2019
Sample
Date
Q1 2019
Result
February
2019
Monthly
Sample
Date
February
2019
Monthly
Result
March 2019
Monthly
Sample
Date
March 2019
Monthly
Result
Q2 2019
Sample
Date
Q2 2019
Result
May 2019
Monthly
Sample
Date
May 2019
Monthly
Result
June 2019
Monthly
Sample
Date
June 2019
Monthly
Result
MW-11 (Class II) Manganese (ug/L) 164.67 1/15/2019 181 2/13/2019 211 3/6/2019 170 4/24/2019 181 5/7/2019 210 6/3/2019 210
MW-25 (Class III) Cadmium (ug/L) 1.5 1/16/2019 1.32 2/12/2019 1.52 3/5/2019 1.54 4/10/2019 1.30 5/8/2019 1.41 6/4/2019 1.47
Nitrate + Nitrite (as N) (mg/L)0.62 2.21 0.967 3.22 3.00 0.986 3.16
Chloroform (ug/L)70 1200 1300 1290 4140 1140 778
Chloride (mg/L)58.31 70.7 57.2 60.4 82.0 73.0 72.6
Methylene Chloride (ug/L)5 3.24 1.91 1.45 4.16 1.69 <1.00
Nitrogen, Ammonia as N 0.92 0.938 NA NA 0.104 0.479 0.0919
Nitrate + Nitrite (as N) (mg/L)2.5 17.9 18.2 16.2 18.5 17.9 15.8
Chloride (mg/L)128 157 167 160 138 175 165
Selenium (ug/L)47.2 48.6 NA NA 53.6 47.1 49.9
Uranium (ug/L)8.32 9.07 9.09 8.39 8.62 8.15 8.88
Field pH (S.U.)6.47 - 8.5 6.60 6.46 6.97 7.06 7.00 7.12
Nitrate + Nitrite (as N) (mg/L)5 19.0 18.6 18.5 19.7 18.9 19.7
Chloride (mg/L)143 283 296 322 294 346 325
MW - 36 (Class III)Field pH (S.U.)6.49 - 8.5 1/23/2019 6.35 NS NA NS NA 4/18/2019 7.05 5/21/2019 6.73 6/3/2019 7.01
MW-05 (Class II)Uranium (ug/L) 7.5 1/17/2019 0.557 NS NA NS NA 4/24/2019 0.959 NS NA NS NA
MW-12 (Class III) Uranium (ug/L) 23.5 1/21/2019 23.6 NS NA NS NA 4/25/2019 23.2 NS NA NS NA
Beryllium (ug/L)2 3.37 NA NA 2.83 NA NA
Cadmium (ug/L)6.43 8.34 NA NA 8.24 NA NA
Fluoride (mg/L)0.47 NA NA NA 0.839 NA NA
Nickel (mg/L)50 NA NA NA 63.9 NA NA
Thallium (ug/L)2.01 2.72 NA NA 2.73 NA NA
Field pH (S.U.)5.03 - 8.5 4.63 NA NA 4.53 NA NA
Nitrate + Nitrite (as N) (mg/L)5.6 6.40 NA NA 6.33 NA NA
Chloride (mg/L)38 31.0 NA NA 32.0 NA NA
Chloride (mg/L)105 127 NA NA 165 NA NA
Cadmium (ug/L)5.2 4.76 NA NA 5.11 NA NA
Selenium (ug/L)11.1 NA NA NA 12.4 NA NA
Gross Alpha (pCi/L)2.42 NA NA NA 1.94 NA NA
Uranium (ug/L)4.9 7.12 NA NA 9.60 NA NA
MW-32 (Class III)Chloride (mg/L)35.39 1/22/2019 35.6 NS NA NS NA 4/9/2019 34.5 NS NA NS NA
MW-35 (Class ll)Nitrogen, Ammonia as N 0.14 1/16/2019 0.100 NS NA NS NA 4/18/2019 0.0634 NS NA NS NA
Notes:
NS= Not Required and Not Sampled
NA= Not Applicable
Exceedances are shown in yellow
5/2/2019 NS NS
4/23/2019 NS NS
4/24/2019 NS NS
Q2 2019 Results
4/24/2019 5/7/2019 6/4/2019
Required Quarterly Sampling Wells
Required Semi-Annual Sampling Wells
4/9/2019 5/7/2019 6/3/2019
4/10/2019 5/7/2019 6/3/2019
NS NS
1/23/2019 NS NS
1/21/2019 NS NS
1/22/2019
MW-24 (Class III)
MW-27 (Class III)
MW-28 (Class III)
Pursuant to the DWMRC letter of May 22, 2019, this constituent will no longer be monitored on an accelerated schedule. This constituent will be dropped from this report
after this quarter.
Q1 2019 Results
1/17/2019 2/13/2019 3/6/2019
1/16/2019 2/13/2019 3/6/2019MW-30 (Class II)
MW-31 (Class III) 1/15/2019 2/12/2019 3/5/2019
MW-26 (Class III)
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 1 of 1
APPENDIX B
Geochemical Analysis for Cadmium in MW-25
APPENDIX B-1
Summary of Geochemical Analysis for Cadmium in MW-25
Data Set Wp S p
MW-25 All Cadmium µg/L 108 0% 1.38 0.09 0.99 0.63 Normal 1029 3.2E-03 5.89E-03 Significant 1.6 1.5 1.6 Mean + 2 SD 2.50 Fractional Approach
MW-25 Oct 2012 to Present Cadmium µg/L 79 0% 1.39 0.09 0.98 0.29 Normal 165 0.24 0.63 Not Significant 1.6 1.5 1.6 Mean + 2 SD
Notes:
%ND = percent of non-detected values p = probability
mg/L = milligrams per liter W = Shapiro Wilk test value
µg/L = micrograms per liter S = Mann-Kendall statistic
s.u. = standard units
N = number of valid data points
Distribution = Distribution as determined by the Shapiro-Wilk distribution test for constituents with % Detect > 50% and N>8
Mean = The arithmatic mean as determined for normally or log-normally distributed constituents with % Detect > 50%
Standard Deviation = The standard deviation as determined for normally or log-normally distributed constituents with % Detect > 85%
Highest Historical Value = The highest observed value for constituents with % Detect < 50%
Proposed
Modified
Approach
GWCL
Modified Approach
GWCL Rationalea
Current
GWCL
Flowsheet
GWCL
Flowsheet GWCL
Rationale
Standard
Deviation
(SD)
Well Constituent N
% Non-
Detected
Values
MeanUnits
Shapiro-Wilk Test for Normality Normally or
Lognormally
Distributed?
Mann KendallTrend Analysis Significant Trend
Highest
Historical
Value
(HHV)
Linear P
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 1 of 1
APPENDIX B-2
Comparison of Calculated and Measured TDS in MW-25
Well
Number Sample Date Alkalinity
(mg/L)
Calcium
(mg/L)
Chloride
(mg/L)
Magnesium
(mg/L)
Potassium
(mg/L)
Sodium
(mg/L)
Sulfate
(mg/L)
Measured
TDS (mg/L)
Calculated
TDS (mg/L)Ratio
MW-25 6/23/2005 392 358 34 128 9.1 282.0 1600 2860 2803 98%
MW-25 9/22/2005 403 376 34 135 9.6 285.0 1670 2890 2913 101%
MW-25 12/13/2005 396 386 33 139 10.0 290.0 1860 2850 3114 109%
MW-25 3/22/2006 406 370 32 132 9.7 291.0 1710 2850 2951 104%
MW-25 6/20/2006 409 378 32 138 10.2 284.0 1680 2850 2931 103%
MW-25 9/12/2006 398 385 30 135 10.8 287.0 1570 2800 2816 101%
MW-25 10/24/2006 405 400 33 138 10.0 295.0 1880 2740 3161 115%
MW-25 3/16/2007 390 386 32 135 10.1 289.0 1750 2970 2992 101%
MW-25 6/20/2007 403 395 31 140 9.9 269.0 1740 2900 2988 103%
MW-25 8/27/2007 412 390 33 136 9.5 274.0 1850 2810 3105 110%
MW-25 10/25/2007 410 392 32 115 10.1 272.0 1710 2750 2941 107%
MW-25 3/18/2008 415 353 32 120 9.8 306.0 1750 2710 2986 110%
MW-25 3/18/2008 413 345 31 117 9.5 298.0 1760 2630 2974 113%
MW-25 6/12/2008 381 383 25 130 9.5 306.0 1610 2770 2844 103%
MW-25 8/4/2008 400 391 28 134 10.0 310.0 1710 2700 2983 110%
MW-25 2/3/2009 392 331 31 116 8.4 255.0 1630 2750 2763 100%
MW-25 5/13/2009 399 333 30 116 8.5 279.0 1690 2710 2856 105%
MW-25 8/24/2009 418 361 30 121 9.9 310.0 1580 2740 2830 103%
MW-25 10/13/2009 412 352 34 116 9.8 296.0 1650 2690 2870 107%
MW-25 2/3/2010 432 351 31 116 9.5 300.0 1630 2670 2870 107%
MW-25 4/28/2010 424 368 31 122 9.7 317.0 1660 2780 2932 105%
MW-25 9/8/2010 435 367 31 125 9.6 306.0 1760 2790 3034 109%
MW-25 11/10/2010 413 354 31 116 9.3 277.0 1650 2800 2850 102%
MW-25 2/2/2011 405 358 30 119 9.3 298.0 1690 2720 2909 107%
MW-25 4/4/2011 408 354 31 117 9.7 310.0 1620 2900 2850 98%
MW-25 8/3/2011 382 367 32 123 9.8 310.0 1660 2830 2884 102%
MW-25 10/4/2011 387 354 32 120 9.2 276.0 1680 2700 2858 106%
MW-25 2/14/2012 404 371 30 123 9.6 314.0 1630 2770 2882 104%
MW-25 5/2/2012 410 351 30 118 11.9 269.0 1670 2850 2860 100%
MW-25 7/10/2012 396 321 33 117 9.3 290.0 1620 2780 2786 100%
MW-25 11/12/2012 400 358 29 122 9.4 296.0 1680 2750 2894 105%
MW-25 2/20/2013 398 364 36 120 10.5 301.0 1730 2770 2960 107%
MW-25 5/14/2013 425 367 28 124 9.2 323.0 1350 2880 2626 91%
MW-25 7/10/2013 427 346 28 113 10.0 278.0 1320 2840 2522 89%
MW-25 11/19/2013 437 324 29 110 9.6 276.0 1450 2900 2636 91%
MW-25 3/10/2014 394 349 32 124 9.6 298.0 1560 2810 2766 98%
MW-25 6/2/2014 393 336 31 125 8.9 298.0 1560 2820 2752 98%
MW-25 9/3/2014 438 319 30 120 9.4 283.0 1530 2640 2729 103%
MW-25 11/4/2014 447 331 30 112 9.4 272.0 1750 2670 2951 111%
MW-25 2/4/2015 394 339 31 120 10.0 291.0 1620 2760 2805 102%
MW-25 4/7/2015 415 343 31 116 9.6 310.0 1580 2760 2805 102%
MW-25 8/10/2015 422 365 37 120 10.3 300.0 1560 2660 2814 106%
MW-25 11/11/2015 397 361 30 118 9.0 283.0 1750 2570 2948 115%
MW-25 2/8/2016 398 359 32 122 9.5 302.0 1680 2760 2902 105%
MW-25 5/3/2016 399 350 31 122 10.0 307.0 1730 2580 2949 114%
MW-25 8/17/2016 398 342 32 119 10.2 291.0 1670 2590 2862 111%
MW-25 11/2/2016 406 342 33 116 10.5 293.0 1330 2650 2530 95%
MW-25 2/7/2017 376 325 31 114 11.1 308.0 1320 2480 2485 100%
MW-25 5/1/2017 388 333 31 113 9.7 292.0 1490 2660 2657 100%
MW-25 8/14/2017 395 334 33 109 9.4 304.0 1800 2470 2984 121%
MW-25 11/1/2017 399 342 31 121 9.4 292.0 1490 2600 2685 103%
MW-25 2/19/2018 404 350 31 122 10.3 292.0 1490 2610 2699 103%
MW-25 4/17/2018 395 354 34 120 10.2 294.0 1580 2860 2787 97%
MW-25 9/10/2018 410 359 34 122 9.4 305.0 1640 2640 2880 109%
MW-25 10/24/2018 376 392 30 132 10.2 323.0 1530 2480 2793 113%
MW-25 1/16/2019 403 365 31 126 10.2 317.0 1530 2510 2782 111%
MW-25 4/10/2019 390 364 30 115 9.6 283.0 1450 2520 2642 105%
MW-25 7/15/2019 400 398 34 136 10.6 313.0 1660 2630 2952 112%
Notes:
mg/L = milligrams per liter
TDS = total dissolved solids
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 1 of 1
APPENDIX B-3
Charge Balance Calculations for Major Cations and Anions in MW-25
Well Sample
Date
Calcium
(meq/L)
Sodium
(meq/L)
Magnesium
(meq/L)
Potassium
(meq/L)
Total
Cation
Charge
(meq/L)
HCO3
(meq/L)
Chloride
(meq/L)
SO4
(meq/L)
Total
Anion
Charge
(meq/L)
Charge
Balance
Error
MW-25 6/23/2005 17.9 12.27 10.53 0.23 40.89 -6.42 -0.96 -33.31 40.70 0.24%
MW-25 9/22/2005 18.8 12.40 11.11 0.25 42.51 -6.60 -0.96 -34.77 42.33 0.21%
MW-25 12/13/2005 19.3 12.61 11.44 0.26 43.57 -6.49 -0.93 -38.73 46.15 -2.88%
MW-25 3/22/2006 18.5 12.35 10.86 0.25 41.92 -6.65 -0.90 -35.60 43.16 -1.45%
MW-25 6/20/2006 18.9 12.35 11.35 0.26 42.83 -6.70 -0.90 -34.98 42.58 0.29%
MW-25 9/12/2006 19.2 12.48 11.11 0.28 43.08 -6.52 -0.85 -32.69 40.06 3.63%
MW-25 10/24/2006 20.0 12.83 11.35 0.26 44.40 -6.64 -0.93 -39.14 46.71 -2.53%
MW-25 3/16/2007 19.3 12.57 11.11 0.26 43.20 -6.39 -0.90 -36.44 43.73 -0.61%
MW-25 6/20/2007 19.7 11.70 11.52 0.25 43.18 -6.60 -0.87 -36.23 43.71 -0.60%
MW-25 8/27/2007 19.5 11.92 11.19 0.24 42.81 -6.75 -0.93 -38.52 46.20 -3.81%
MW-25 10/25/2007 19.6 11.83 9.46 0.26 41.11 -6.72 -0.90 -35.60 43.22 -2.51%
MW-25 3/18/2008 17.6 13.31 9.87 0.25 41.05 -6.80 -0.90 -36.44 44.14 -3.63%
MW-25 3/18/2008 17.2 12.96 9.63 0.24 40.05 -6.77 -0.87 -36.64 44.29 -5.03%
MW-25 6/12/2008 19.1 13.31 10.70 0.24 43.36 -6.24 -0.71 -33.52 40.47 3.45%
MW-25 8/4/2008 19.5 13.48 11.02 0.26 44.28 -6.56 -0.79 -35.60 42.95 1.52%
MW-25 11/10/2008 19.1 13.96 10.61 0.25 43.94 -6.42 -0.85 -37.48 44.75 -0.91%
MW-25 2/3/2009 16.5 11.09 9.54 0.21 37.37 -6.42 -0.87 -33.94 41.24 -4.92%
MW-25 5/13/2009 16.6 12.14 9.54 0.22 38.51 -6.54 -0.85 -35.19 42.57 -5.00%
MW-25 8/24/2009 18.0 13.48 9.95 0.25 41.71 -6.85 -0.85 -32.90 40.59 1.35%
MW-25 10/13/2009 17.6 12.88 9.54 0.25 40.23 -6.75 -0.96 -34.35 42.06 -2.22%
MW-25 2/3/2010 17.5 13.05 9.54 0.24 40.35 -7.08 -0.87 -33.94 41.89 -1.87%
MW-25 4/28/2010 18.4 13.79 10.04 0.25 42.44 -6.95 -0.87 -34.56 42.38 0.06%
MW-25 9/8/2010 18.3 13.31 10.28 0.25 42.15 -7.13 -0.87 -36.64 44.65 -2.87%
MW-25 11/10/2010 17.7 12.05 9.54 0.24 39.49 -6.77 -0.87 -34.35 42.00 -3.07%
MW-25 2/2/2011 17.9 12.96 9.79 0.24 40.85 -6.64 -0.85 -35.19 42.67 -2.17%
MW-25 4/4/2011 17.7 13.48 9.63 0.25 41.02 -6.69 -0.87 -33.73 41.29 -0.32%
MW-25 8/30/2011 18.3 13.48 10.12 0.25 42.17 -6.26 -0.90 -34.56 41.72 0.53%
MW-25 10/4/2011 17.7 12.01 9.87 0.24 39.78 -6.34 -0.90 -34.98 42.22 -2.98%
MW-25 2/14/2012 18.5 13.66 10.12 0.25 42.54 -6.62 -0.85 -33.94 41.40 1.35%
MW-25 5/2/2012 17.5 11.70 9.71 0.30 39.23 -6.72 -0.85 -34.77 42.34 -3.81%
MW-25 7/10/2012 16.0 12.61 9.63 0.24 38.50 -6.49 -0.93 -33.73 41.15 -3.33%
MW-25 11/12/2012 17.9 12.88 10.04 0.24 41.02 -6.56 -0.81 -34.98 42.35 -1.59%
MW-25 2/20/2013 18.2 13.09 9.87 0.27 41.40 -6.52 -1.02 -36.02 43.56 -2.55%
MW-25 5/14/2013 18.3 14.05 10.20 0.24 42.80 -6.96 -0.79 -28.11 35.87 8.82%
MW-25 7/10/2013 17.3 12.09 9.30 0.26 38.91 -7.00 -0.79 -27.48 35.27 4.91%
MW-25 11/19/2013 16.2 12.01 9.05 0.25 37.47 -7.16 -0.82 -30.19 38.17 -0.93%
MW-25 3/10/2014 17.4 12.96 10.20 0.25 40.82 -6.46 -0.89 -30.19 37.53 4.20%
MW-25 6/2/2014 16.8 12.96 10.28 0.23 40.24 -6.44 -0.87 -32.48 39.79 0.56%
MW-25 9/3/2014 15.9 12.31 9.87 0.24 38.34 -7.18 -0.85 -32.48 40.50 -2.74%
MW-25 11/4/2014 16.5 11.83 9.21 0.24 37.80 -7.33 -0.83 -31.86 40.02 -2.84%
MW-25 2/4/2015 16.9 12.66 9.87 0.26 39.70 -6.46 -0.86 -36.44 43.75 -4.85%
MW-25 4/7/2015 17.1 13.48 9.54 0.25 40.39 -6.80 -0.88 -33.73 41.41 -1.24%
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 1 of 2
APPENDIX B-3
Charge Balance Calculations for Major Cations and Anions in MW-25
Well Sample
Date
Calcium
(meq/L)
Sodium
(meq/L)
Magnesium
(meq/L)
Potassium
(meq/L)
Total
Cation
Charge
(meq/L)
HCO3
(meq/L)
Chloride
(meq/L)
SO4
(meq/L)
Total
Anion
Charge
(meq/L)
Charge
Balance
Error
MW-25 8/10/2015 18.2 13.05 9.87 0.26 41.40 -6.92 -1.04 -32.90 40.85 0.67%
MW-25 11/11/2015 18.0 12.31 9.71 0.23 40.26 -6.51 -0.84 -32.48 39.83 0.54%
MW-25 2/8/2016 17.9 13.14 10.04 0.24 41.33 -6.52 -0.89 -36.44 43.85 -2.96%
MW-25 5/3/2016 17.5 13.35 10.04 0.26 41.11 -6.54 -0.87 -34.98 42.39 -1.53%
MW-25 8/17/2016 17.1 12.66 9.79 0.26 39.77 -6.52 -0.91 -36.02 43.45 -4.42%
MW-25 11/2/2016 17.1 12.74 9.54 0.27 39.62 -6.65 -0.92 -34.77 42.35 -3.32%
MW-25 2/7/2017 16.2 13.40 9.38 0.28 39.28 -6.16 -0.86 -27.48 34.51 6.46%
MW-25 5/1/2017 16.6 12.70 9.30 0.25 38.86 -6.36 -0.87 -31.02 38.26 0.79%
MW-25 8/14/2017 16.7 13.22 8.97 0.24 39.10 -6.47 -0.92 -37.48 44.87 -6.88%
MW-25 11/1/2017 17.1 12.70 9.95 0.24 39.96 -6.54 -0.88 -31.02 38.44 1.94%
MW-25 2/19/2018 17.5 12.70 10.04 0.26 40.47 -6.62 -0.87 -31.02 38.51 2.48%
MW-25 4/17/2018 17.7 12.79 9.87 0.26 40.59 -6.47 -0.95 -32.90 40.32 0.33%
MW-25 9/10/2018 17.9 13.27 10.04 0.24 41.46 -6.72 -0.96 -34.15 41.83 -0.44%
MW-25 10/24/2018 19.6 14.05 10.86 0.26 44.73 -6.16 -0.85 -31.86 38.87 7.02%
MW-25 1/16/2019 18.2 13.79 10.37 0.26 42.63 -6.60 -0.87 -31.86 39.33 4.03%
MW-25 4/10/2019 18.2 12.31 9.46 0.25 40.18 -6.39 -0.85 -30.19 37.43 3.54%
MW-25 7/15/2019 19.9 13.61 11.19 0.27 44.93 -6.56 -0.97 -34.56 42.08 3.28%
Notes:
meq/L = milliequivalents per litre
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 2 of 2
APPENDIX B-4
Descriptive Statistics for Cadmium in MW-25
Well Number Data Set Analyte Units
% Non-
Detects N Distribution Mean
Min.
Conc.
Max.
Conc.
Std.
Dev.Range Geometric
Mean Skewness Q25 Median Q75
MW-25 2008 Background Report Cadmium µg/L 0 10 Normal or Lognormal 1.39 1.30 1.50 0.10 0.20 1.40 -0.40 1.40 1.40 1.40
MW-25 2019 SAR- All Cadmium µg/L 0 108 Normal 1.38 1.19 1.60 0.09 0.41 1.37 0.26 1.31 1.37 1.43
MW-25 2019 SAR - 2012 to present Cadmium µg/L 0 79 Normal 1.39 1.23 1.60 0.09 0.37 1.39 0.36 1.33 1.39 1.45
Notes
µg/L = micrograms per liter
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 1 of 1
APPENDIX B-5
MW-25 Data Used for Statistical Analysis
Well Date Sampled
Parameter
Name Report Result Report Units Qualifer
MW-25 6/23/2005 Cadmium 1.30 µg/L
MW-25 9/22/2005 Cadmium 1.36 µg/L
MW-25 12/13/2005 Cadmium 1.34 µg/L
MW-25 6/20/2006 Cadmium 1.45 µg/L
MW-25 9/12/2006 Cadmium 1.46 µg/L
MW-25 10/24/2006 Cadmium 1.36 µg/L
MW-25 3/16/2007 Cadmium 1.44 µg/L
MW-25 6/20/2007 Cadmium 1.39 µg/L
MW-25 8/27/2007 Cadmium 1.44 µg/L
MW-25 10/25/2007 Cadmium 1.37 µg/L
MW-25 3/18/2008 Cadmium 1.23 µg/L
MW-25 6/12/2008 Cadmium 1.19 µg/L
MW-25 8/4/2008 Cadmium 1.27 µg/L
MW-25 11/10/2008 Cadmium 1.20 µg/L
MW-25 2/3/2009 Cadmium 1.37 µg/L
MW-25 5/13/2009 Cadmium 1.24 µg/L
MW-25 8/24/2009 Cadmium 1.34 µg/L
MW-25 10/13/2009 Cadmium 1.32 µg/L
MW-25 2/3/2010 Cadmium 1.26 µg/L
MW-25 4/28/2010 Cadmium 1.44 µg/L
MW-25 9/8/2010 Cadmium 1.40 µg/L
MW-25 11/10/2010 Cadmium 1.26 µg/L
MW-25 2/2/2011 Cadmium 1.34 µg/L
MW-25 4/4/2011 Cadmium 1.27 µg/L
MW-25 8/30/2011 Cadmium 1.19 µg/L
MW-25 10/4/2011 Cadmium 1.27 µg/L
MW-25 2/14/2012 Cadmium 1.31 µg/L
MW-25 5/2/2012 Cadmium 1.33 µg/L
MW-25 7/10/2012 Cadmium 1.24 µg/L
MW-25 11/12/2012 Cadmium 1.56 µg/L
MW-25 2/20/2013 Cadmium 1.35 µg/L
MW-25 3/19/2013 Cadmium 1.40 µg/L
MW-25 4/17/2013 Cadmium 1.36 µg/L
MW-25 5/14/2013 Cadmium 1.52 µg/L
MW-25 6/24/2013 Cadmium 1.31 µg/L
MW-25 7/10/2013 Cadmium 1.41 µg/L
MW-25 8/19/2013 Cadmium 1.57 µg/L
MW-25 9/17/2013 Cadmium 1.31 µg/L
MW-25 10/22/2013 Cadmium 1.50 µg/L
MW-25 11/19/2013 Cadmium 1.35 µg/L
MW-25 12/17/2013 Cadmium 1.23 µg/L
MW-25 1/7/2014 Cadmium 1.39 µg/L
MW-25 2/13/2014 Cadmium 1.29 µg/L
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 1 of 3
APPENDIX B-5
MW-25 Data Used for Statistical Analysis
Well Date Sampled
Parameter
Name Report Result Report Units Qualifer
MW-25 3/10/2014 Cadmium 1.29 µg/L
MW-25 4/28/2014 Cadmium 1.51 µg/L
MW-25 5/13/2014 Cadmium 1.34 µg/L
MW-25 6/2/2014 Cadmium 1.24 µg/L
MW-25 7/28/2014 Cadmium 1.30 µg/L
MW-25 8/18/2014 Cadmium 1.30 µg/L
MW-25 9/3/2014 Cadmium 1.30 µg/L
MW-25 10/6/2014 Cadmium 1.41 µg/L
MW-25 11/4/2014 Cadmium 1.57 µg/L
MW-25 12/9/2014 Cadmium 1.27 µg/L
MW-25 1/20/2015 Cadmium 1.44 µg/L
MW-25 2/4/2015 Cadmium 1.33 µg/L
MW-25 3/4/2015 Cadmium 1.37 µg/L
MW-25 4/7/2015 Cadmium 1.27 µg/L
MW-25 5/11/2015 Cadmium 1.38 µg/L
MW-25 6/23/2015 Cadmium 1.42 µg/L
MW-25 7/6/2015 Cadmium 1.43 µg/L
MW-25 8/10/2015 Cadmium 1.41 µg/L
MW-25 9/15/2015 Cadmium 1.31 µg/L
MW-25 10/6/2015 Cadmium 1.50 µg/L
MW-25 11/11/2015 Cadmium 1.38 µg/L
MW-25 12/8/2015 Cadmium 1.45 µg/L
MW-25 1/19/2016 Cadmium 1.37 µg/L
MW-25 2/8/2016 Cadmium 1.51 µg/L
MW-25 3/2/2016 Cadmium 1.42 µg/L
MW-25 4/12/2016 Cadmium 1.39 µg/L
MW-25 5/3/2016 Cadmium 1.43 µg/L
MW-25 6/14/2016 Cadmium 1.43 µg/L
MW-25 7/12/2016 Cadmium 1.44 µg/L
MW-25 8/17/2016 Cadmium 1.37 µg/L
MW-25 9/13/2016 Cadmium 1.41 µg/L
MW-25 11/2/2016 Cadmium 1.33 µg/L
MW-25 12/5/2016 Cadmium 1.41 µg/L
MW-25 1/17/2017 Cadmium 1.42 µg/L
MW-25 2/7/2017 Cadmium 1.45 µg/L
MW-25 3/7/2017 Cadmium 1.46 µg/L
MW-25 4/4/2017 Cadmium 1.58 µg/L
MW-25 5/1/2017 Cadmium 1.35 µg/L
MW-25 6/6/2017 Cadmium 1.32 µg/L
MW-25 7/12/2017 Cadmium 1.42 µg/L
MW-25 8/14/2017 Cadmium 1.33 µg/L
MW-25 9/11/2017 Cadmium 1.51 µg/L
MW-25 10/2/2017 Cadmium 1.40 µg/L
MW-25 11/1/2017 Cadmium 1.40 µg/L
MW-25 12/4/2017 Cadmium 1.60 µg/L
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 2 of 3
APPENDIX B-5
MW-25 Data Used for Statistical Analysis
Well Date Sampled
Parameter
Name Report Result Report Units Qualifer
MW-25 1/23/2018 Cadmium 1.38 µg/L
MW-25 2/19/2018 Cadmium 1.28 µg/L
MW-25 3/7/2018 Cadmium 1.45 µg/L
MW-25 4/17/2018 Cadmium 1.38 µg/L
MW-25 5/14/2018 Cadmium 1.34 µg/L
MW-25 6/18/2018 Cadmium 1.38 µg/L
MW-25 7/23/2018 Cadmium 1.30 µg/L
MW-25 8/9/2018 Cadmium 1.36 µg/L
MW-25 9/10/2018 Cadmium 1.35 µg/L
MW-25 10/24/2018 Cadmium 1.30 µg/L
MW-25 11/13/2018 Cadmium 1.51 µg/L
MW-25 12/10/2018 Cadmium 1.49 µg/L
MW-25 1/16/2019 Cadmium 1.32 µg/L
MW-25 2/12/2019 Cadmium 1.52 µg/L
MW-25 3/5/2019 Cadmium 1.54 µg/L
MW-25 4/10/2019 Cadmium 1.30 µg/L
MW-25 5/8/2019 Cadmium 1.41 µg/L
MW-25 6/4/2019 Cadmium 1.47 µg/L
MW-25 7/15/2019 Cadmium 1.23 µg/L
MW-25 8/6/2019 Cadmium 1.37 µg/L
Notes:
D= Diluted
U = Not detected above method detection limit
µg/L = micrograms per liter
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 3 of 3
APPENDIX B-6
Data Removed from Analysis
Reason Location ID
Date
Sampled Parameter Name
Report
Result
Report
Units
Extreme Upper Outlier, not part of trend MW-25 3/22/2006 Cadmium 2.78 µg/L
Note:
µg/L = micrograms per liter
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 1 of 1
APPENDIX B-7
Box Plot of Cadmium in MW-25
Cadmium in MW-25 for All data
Cadmium in MW-25 for post-Oct 2012 Data Set
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 1 of 1
APPENDIX B-8
Box Plot of Cadmium All Groundwater Monitoring Wells
Note:
Cadmium data for all wells, extreme outliers removed if not part of trend
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 1 of 1
APPENDIX B-9
Histograms of Cadmium in MW-25
Cadmium in MW-25 for All data
Cadmium in MW-25 for post-Oct 2012 Data Set
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 1 of 1
APPENDIX B-10
Time Concentration Plots of Cadmium in MW-25
Indicates a detected result
Indicates a non‐detect result
Cadmium in MW-25 for All Data
Cadmium in MW-25 for post-Oct 2012 Data Set
Source Assessment Report for MW-25
White Mesa Uranium Mill Page 1 of 1
APPENDIX C
Geochemical Analysis for pH and Indicator Parameters in MW-25
APPENDIX C-1
Summary of Geochemical Analysis for pH and Indicator Parameters in MW-25
Wp r2 pS p
MW-25 Chloride (mg/L) 74 0% 31.1 1.91 0.95 8.20E-03 Not normal NA NA -62 3.88E-01 No Trend Not significant
MW-25 Fluoride (mg/L) 66 0% 0.32 0.03 0.95 1.27E-02 Not normal NA NA -625 2.72E-04 Decreasing Significant
MW-25 Sulfate (mg/L) 59 0% 1627 128 0.94 8.68E-03 Not normal NA NA -566 1.08E-04 Decreasing Significant
MW-25 Uranium (µg/L) 111 0% 6.21 0.48 0.98 5.05E-02 Normal NA NA 1258 6.78E-04 Increasing Significant
MW-25 pH (pH Units) 126 0% 6.59 0.25 0.99 1.96E-01 Normal NA NA -761 5.45E-02 Decreasing Not significant
Notes:
σ = sigma N = number of valid data points
%ND = percent of non-detected values p = probability
µg/L = micrograms per liter W = Shapiro-Wilk test value
mg/L = milligrams per liter r2 = The measure of how well the trendline fits the data where r2=1 represents a perfect fit.
S = Mann-Kendall statistic
a = A regression test was performed on data that was determined to have normal or log-normal distribution
b = The Mann-Kendall test was performed on data that are not normally or lognormally distributed
Standard
DeviationWell Constituent N
% Non-
Detected
Values
Mean
Least Squares
Regression Trend
Analysisa
Mann-Kendall Trend
Analysisb 2019
Significant
Trend?
Background
Report
Significant
Trend?
Shapiro-Wilk Test
for Normality Normally or
Lognormally
distributed?
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 1 of 1
APPENDIX C-2
Descriptive Statistics for pH and Indicator Parameters in MW-25
Well Number Data Set Analyte Units
% Non-
Detects N Distribution Mean
Min.
Conc.
Max.
Conc.
Std.
Dev.Range Geometric
Mean Skewness Q25 Median Q75
MW-25 2008 Background Report Chloride mg/L 0% 11 Normal or Lognormal 32.40 30 34 1.20 4 32.30 -0.40 32.0 32.0 33.0
MW-25 2012 SAR Chloride mg/L 0% 28 Not Normal 31.21 25 34 1.89 9 31.15 -1.17 30.0 31.0 32.0
MW-25 2019 SAR Chloride mg/L 0% 74 Not Normal 31.09 25 36.8 1.91 11.8 31.03 0.07 30.0 31.0 32.0
MW-25 2008 Background Report Fluoride mg/L 0% 11 Normal or Lognormal 0.30 0.30 0.4 0.0 0.2 0.30 1.10 0.300.3 0.4
MW-25 2012 SAR Fluoride mg/L 0% 29 Normal or Lognormal 0.32 0.28 0.37 0.0 0.095 0.33 -0.11 0.31 0.321 0.34
MW-25 2019 SAR Fluoride mg/L 0% 66 Not Normal 0.32 0.32 0.2 0.41 0.2 0.32 0.05 0.30 0.32 0.33
MW-25 2008 Background Report Sulfate mg/L 0% 11 Normal or Lognormal 1729.1 1570 1880 101.8 310 1726.40 0.10 1670 1710 1850
MW-25 2012 SAR Sulfate mg/L 0% 29 Normal or Lognormal 1692.7 1570 1880 80.39 310 1690.90 0.82 1630 1680 1740
MW-25 2019 SAR Sulfate mg/L 0% 58 Not Normal 1626.9 1320 1880 127.7 560 1621.83 -0.57 1560 1650 1710
MW-25 2008 Background Report Uranium µg/L 0% 11 Normal or Lognormal 5.90 5.4 6.4 0.30 0.9 5.90 -0.50 5.9 6.0 6.0
MW-25 2012 SAR Uranium µg/L 0% 40 Normal or Lognormal 6.10 4.8 7.06 0.50 2.29 6.09 -0.18 5.8 6.0 6.5
MW-25 2019 SAR Uranium µg/L 0% 110 Not Normal 6.21 4.77 7.6 0.48 2.8 6.19 -0.11 5.9 6.2 6.5
MW-25 2012 pH Report pH pH Units 0% 41 Normal or Lognormal 6.13 5.8 7.25 0.26 1.5 6.64 -0.63 6.5 6.6 6.8
MW-25 2019 SAR pH pH Units 0% 126 Normal or Lognormal 6.59 5.77 7.25 0.25 1.5 6.58 -0.07 6.5 6.6 6.7
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 1 of 1
APPENDIX C-3
Data Used for Statistical Analysis
Well ID Date Sampled Parameter Result Units Qualifer
MW-25 06/23/2005 Chloride 34.0 mg/L
MW-25 09/22/2005 Chloride 34.0 mg/L
MW-25 12/13/2005 Chloride 33.0 mg/L
MW-25 03/22/2006 Chloride 32.0 mg/L
MW-25 06/20/2006 Chloride 32.0 mg/L
MW-25 09/12/2006 Chloride 30.0 mg/L
MW-25 10/24/2006 Chloride 33.0 mg/L
MW-25 03/16/2007 Chloride 32.0 mg/L
MW-25 06/20/2007 Chloride 31.0 mg/L
MW-25 08/27/2007 Chloride 33.0 mg/L
MW-25 10/25/2007 Chloride 32.0 mg/L
MW-25 03/18/2008 Chloride 32.0 mg/L
MW-25 06/12/2008 Chloride 25.0 mg/L
MW-25 08/04/2008 Chloride 28.0 mg/L
MW-25 11/10/2008 Chloride 30.0 mg/L
MW-25 02/03/2009 Chloride 31.0 mg/L
MW-25 05/13/2009 Chloride 30.0 mg/L
MW-25 08/24/2009 Chloride 30.0 mg/L
MW-25 10/13/2009 Chloride 34.0 mg/L
MW-25 02/03/2010 Chloride 31.0 mg/L
MW-25 04/28/2010 Chloride 31.0 mg/L
MW-25 09/08/2010 Chloride 31.0 mg/L
MW-25 11/10/2010 Chloride 31.0 mg/L
MW-25 02/02/2011 Chloride 30.0 mg/L
MW-25 04/04/2011 Chloride 31.0 mg/L
MW-25 08/03/2011 Chloride 32.0 mg/L
MW-25 10/04/2011 Chloride 32.0 mg/L
MW-25 02/14/2012 Chloride 30.0 mg/L
MW-25 05/02/2012 Chloride 30.0 mg/L
MW-25 07/10/2012 Chloride 33.0 mg/L
MW-25 11/12/2012 Chloride 28.8 mg/L
MW-25 02/20/2013 Chloride 36.1 mg/L
MW-25 05/14/2013 Chloride 28.1 mg/L
MW-25 06/24/2013 Chloride 30.4 mg/L
MW-25 07/10/2013 Chloride 28.0 mg/L
MW-25 08/19/2013 Chloride 31.1 mg/L
MW-25 09/17/2013 Chloride 29.6 mg/L
MW-25 10/22/2013 Chloride 28.6 mg/L
MW-25 11/19/2013 Chloride 29.0 mg/L
MW-25 12/17/2013 Chloride 31.2 mg/L
MW-25 01/07/2014 Chloride 31.0 mg/L
MW-25 02/13/2014 Chloride 30.4 mg/L
MW-25 03/10/2014 Chloride 31.5 mg/L
MW-25 04/28/2014 Chloride 31.0 mg/L
MW-25 05/13/2014 Chloride 26.4 mg/L
MW-25 06/02/2014 Chloride 30.9 mg/L
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 1 of 10
APPENDIX C-3
Data Used for Statistical Analysis
Well ID Date Sampled Parameter Result Units Qualifer
MW-25 09/03/2014 Chloride 30.0 mg/L
MW-25 11/04/2014 Chloride 29.6 mg/L
MW-25 02/04/2015 Chloride 30.5 mg/L
MW-25 04/07/2015 Chloride 31.1 mg/L
MW-25 08/10/2015 Chloride 36.8 mg/L
MW-25 11/11/2015 Chloride 29.8 mg/L
MW-25 12/08/2015 Chloride 31.1 mg/L
MW-25 01/19/2016 Chloride 29.6 mg/L
MW-25 02/08/2016 Chloride 31.6 mg/L
MW-25 03/02/2016 Chloride 30.9 mg/L
MW-25 04/12/2016 Chloride 31.5 mg/L
MW-25 05/03/2016 Chloride 30.8 mg/L
MW-25 06/14/2016 Chloride 31.2 mg/L
MW-25 07/12/2016 Chloride 29.6 mg/L
MW-25 08/17/2016 Chloride 32.2 mg/L
MW-25 09/13/2016 Chloride 32.0 mg/L
MW-25 11/02/2016 Chloride 32.7 mg/L
MW-25 02/07/2017 Chloride 30.6 mg/L
MW-25 05/01/2017 Chloride 31.0 mg/L
MW-25 08/14/2017 Chloride 32.7 mg/L
MW-25 11/01/2017 Chloride 31.2 mg/L
MW-25 02/19/2018 Chloride 30.8 mg/L
MW-25 04/17/2018 Chloride 33.8 mg/L
MW-25 09/10/2018 Chloride 34.2 mg/L
MW-25 10/24/2018 Chloride 30.1 mg/L
MW-25 01/16/2019 Chloride 30.7 mg/L
MW-25 04/10/2019 Chloride 30.1 mg/L
MW-25 07/15/2019 Chloride 34.3 mg/L
MW-25 6/23/2005 Fluoride 0.31 mg/L
MW-25 9/22/2005 Fluoride 0.35 mg/L
MW-25 12/13/2005 Fluoride 0.34 mg/L
MW-25 3/22/2006 Fluoride 0.33 mg/L
MW-25 6/20/2006 Fluoride 0.33 mg/L
MW-25 9/12/2006 Fluoride 0.32 mg/L
MW-25 10/24/2006 Fluoride 0.32 mg/L
MW-25 3/16/2007 Fluoride 0.38 mg/L
MW-25 8/27/2007 Fluoride 0.36 mg/L
MW-25 10/25/2007 Fluoride 0.28 mg/L
MW-25 3/18/2008 Fluoride 0.34 mg/L
MW-25 6/12/2008 Fluoride 0.32 mg/L
MW-25 8/4/2008 Fluoride 0.32 mg/L
MW-25 11/10/2008 Fluoride 0.34 mg/L
MW-25 2/3/2009 Fluoride 0.35 mg/L
MW-25 5/13/2009 Fluoride 0.35 mg/L
MW-25 8/24/2009 Fluoride 0.32 mg/L
MW-25 10/13/2009 Fluoride 0.33 mg/L
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 2 of 10
APPENDIX C-3
Data Used for Statistical Analysis
Well ID Date Sampled Parameter Result Units Qualifer
MW-25 2/3/2010 Fluoride 0.31 mg/L
MW-25 4/28/2010 Fluoride 0.33 mg/L
MW-25 9/8/2010 Fluoride 0.34 mg/L
MW-25 11/10/2010 Fluoride 0.31 mg/L
MW-25 2/2/2011 Fluoride 0.31 mg/L
MW-25 4/4/2011 Fluoride 0.28 mg/L
MW-25 8/3/2011 Fluoride 0.31 mg/L
MW-25 10/4/2011 Fluoride 0.32 mg/L
MW-25 2/14/2012 Fluoride 0.34 mg/L
MW-25 5/2/2012 Fluoride 0.32 mg/L
MW-25 7/10/2012 Fluoride 0.30 mg/L
MW-25 11/12/2012 Fluoride 0.30 mg/L
MW-25 2/20/2013 Fluoride 0.32 mg/L
MW-25 5/14/2013 Fluoride 0.39 mg/L
MW-25 11/19/2013 Fluoride 0.33 mg/L
MW-25 12/17/2013 Fluoride 0.30 mg/L
MW-25 1/7/2014 Fluoride 0.30 mg/L
MW-25 2/13/2014 Fluoride 0.31 mg/L
MW-25 3/10/2014 Fluoride 0.36 mg/L
MW-25 4/28/2014 Fluoride 0.41 mg/L
MW-25 5/13/2014 Fluoride 0.32 mg/L
MW-25 6/2/2014 Fluoride 0.33 mg/L
MW-25 7/28/2014 Fluoride 0.30 mg/L
MW-25 8/18/2014 Fluoride 0.30 mg/L
MW-25 9/3/2014 Fluoride 0.30 mg/L
MW-25 11/4/2014 Fluoride 0.24 mg/L
MW-25 2/4/2015 Fluoride 0.28 mg/L
MW-25 4/7/2015 Fluoride 0.29 mg/L
MW-25 11/11/2015 Fluoride 0.30 mg/L
MW-25 2/8/2016 Fluoride 0.32 mg/L
MW-25 5/3/2016 Fluoride 0.30 mg/L
MW-25 8/17/2016 Fluoride 0.32 mg/L
MW-25 11/2/2016 Fluoride 0.33 mg/L
MW-25 2/7/2017 Fluoride 0.26 mg/L
MW-25 5/1/2017 Fluoride 0.32 mg/L
MW-25 8/14/2017 Fluoride 0.31 mg/L
MW-25 2/19/2018 Fluoride 0.28 mg/L
MW-25 3/7/2018 Fluoride 0.32 mg/L
MW-25 4/17/2018 Fluoride 0.36 mg/L
MW-25 5/14/2018 Fluoride 0.35 mg/L
MW-25 8/9/2018 Fluoride 0.24 mg/L
MW-25 9/10/2018 Fluoride 0.24 mg/L
MW-25 10/24/2018 Fluoride 0.31 mg/L
MW-25 11/13/2018 Fluoride 0.31 mg/L
MW-25 12/10/2018 Fluoride 0.30 mg/L
MW-25 1/16/2019 Fluoride 0.30 mg/L
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 3 of 10
APPENDIX C-3
Data Used for Statistical Analysis
Well ID Date Sampled Parameter Result Units Qualifer
MW-25 4/10/2019 Fluoride 0.32 mg/L
MW-25 7/15/2019 Fluoride 0.30 mg/L
MW-25 06/23/2005 Sulfate 1600 mg/L
MW-25 09/22/2005 Sulfate 1670 mg/L D
MW-25 12/13/2005 Sulfate 1860 mg/L D
MW-25 03/22/2006 Sulfate 1710 mg/L D
MW-25 06/20/2006 Sulfate 1680 mg/L D
MW-25 09/12/2006 Sulfate 1570 mg/L D
MW-25 10/24/2006 Sulfate 1880 mg/L D
MW-25 03/16/2007 Sulfate 1750 mg/L D
MW-25 06/20/2007 Sulfate 1740 mg/L D
MW-25 08/27/2007 Sulfate 1850 mg/L D
MW-25 10/25/2007 Sulfate 1710 mg/L D
MW-25 03/18/2008 Sulfate 1750 mg/L D
MW-25 06/12/2008 Sulfate 1610 mg/L D
MW-25 08/04/2008 Sulfate 1710 mg/L D
MW-25 11/10/2008 Sulfate 1800 mg/L D
MW-25 02/03/2009 Sulfate 1630 mg/L D
MW-25 05/13/2009 Sulfate 1690 mg/L D
MW-25 08/24/2009 Sulfate 1580 mg/L D
MW-25 10/13/2009 Sulfate 1650 mg/L D
MW-25 02/03/2010 Sulfate 1630 mg/L D
MW-25 04/28/2010 Sulfate 1660 mg/L D
MW-25 09/08/2010 Sulfate 1760 mg/L D
MW-25 11/10/2010 Sulfate 1650 mg/L D
MW-25 02/02/2011 Sulfate 1690 mg/L D
MW-25 04/04/2011 Sulfate 1620 mg/L D
MW-25 08/03/2011 Sulfate 1660 mg/L D
MW-25 10/04/2011 Sulfate 1680 mg/L D
MW-25 02/14/2012 Sulfate 1630 mg/L D
MW-25 05/02/2012 Sulfate 1670 mg/L D
MW-25 07/10/2012 Sulfate 1620 mg/L D
MW-25 11/12/2012 Sulfate 1680 mg/L
MW-25 02/20/2013 Sulfate 1730 mg/L
MW-25 05/14/2013 Sulfate 1350 mg/L
MW-25 07/10/2013 Sulfate 1320 mg/L
MW-25 11/19/2013 Sulfate 1450 mg/L
MW-25 02/13/2014 Sulfate 1450 mg/L
MW-25 03/10/2014 Sulfate 1560 mg/L
MW-25 06/02/2014 Sulfate 1560 mg/L
MW-25 09/03/2014 Sulfate 1530 mg/L
MW-25 11/04/2014 Sulfate 1750 mg/L
MW-25 02/04/2015 Sulfate 1620 mg/L
MW-25 04/07/2015 Sulfate 1580 mg/L
MW-25 08/10/2015 Sulfate 1560 mg/L
MW-25 11/11/2015 Sulfate 1750 mg/L
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 4 of 10
APPENDIX C-3
Data Used for Statistical Analysis
Well ID Date Sampled Parameter Result Units Qualifer
MW-25 02/08/2016 Sulfate 1680 mg/L
MW-25 05/03/2016 Sulfate 1730 mg/L
MW-25 08/17/2016 Sulfate 1670 mg/L
MW-25 11/02/2016 Sulfate 1330 mg/L
MW-25 02/07/2017 Sulfate 1320 mg/L
MW-25 05/01/2017 Sulfate 1490 mg/L
MW-25 08/14/2017 Sulfate 1800 mg/L
MW-25 11/01/2017 Sulfate 1490 mg/L
MW-25 02/19/2018 Sulfate 1490.00 mg/L
MW-25 04/17/2018 Sulfate 1580.00 mg/L
MW-25 09/10/2018 Sulfate 1640.00 mg/L
MW-25 10/24/2018 Sulfate 1530.00 mg/L
MW-25 01/16/2019 Sulfate 1530.00 mg/L
MW-25 04/10/2019 Sulfate 1450.00 mg/L
MW-25 07/15/2019 Sulfate 1660.00 mg/L
MW-25 06/23/2005 Uranium 5.87 µg/L
MW-25 09/22/2005 Uranium 6.04 µg/L
MW-25 12/13/2005 Uranium 5.99 µg/L
MW-25 03/22/2006 Uranium 5.42 µg/L
MW-25 06/20/2006 Uranium 6.36 µg/L
MW-25 09/12/2006 Uranium 5.90 µg/L
MW-25 10/24/2006 Uranium 5.57 µg/L
MW-25 03/16/2007 Uranium 6.01 µg/L
MW-25 06/20/2007 Uranium 5.86 µg/L
MW-25 08/27/2007 Uranium 6.27 µg/L
MW-25 10/25/2007 Uranium 6.02 µg/L
MW-25 03/18/2008 Uranium 5.94 µg/L
MW-25 06/12/2008 Uranium 6.08 µg/L
MW-25 08/04/2008 Uranium 5.56 µg/L
MW-25 11/10/2008 Uranium 5.35 µg/L
MW-25 02/03/2009 Uranium 5.87 µg/L
MW-25 05/13/2009 Uranium 5.70 µg/L
MW-25 08/24/2009 Uranium 6.02 µg/L
MW-25 10/13/2009 Uranium 6.28 µg/L
MW-25 02/03/2010 Uranium 5.93 µg/L
MW-25 04/28/2010 Uranium 6.43 µg/L
MW-25 09/08/2010 Uranium 6.57 µg/L
MW-25 11/10/2010 Uranium 5.89 µg/L
MW-25 01/11/2011 Uranium 7.02 µg/L
MW-25 02/02/2011 Uranium 4.77 µg/L
MW-25 03/15/2011 Uranium 6.80 µg/L
MW-25 04/04/2011 Uranium 5.56 µg/L
MW-25 05/11/2011 Uranium 6.72 µg/L
MW-25 06/20/2011 Uranium 7.06 µg/L
MW-25 07/06/2011 Uranium 6.74 µg/L
MW-25 08/30/2011 Uranium 6.37 µg/L
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 5 of 10
APPENDIX C-3
Data Used for Statistical Analysis
Well ID Date Sampled Parameter Result Units Qualifer
MW-25 09/07/2011 Uranium 5.96 µg/L
MW-25 10/04/2011 Uranium 5.27 µg/L
MW-25 11/09/2011 Uranium 6.56 µg/L
MW-25 12/12/2011 Uranium 6.10 µg/L
MW-25 01/25/2012 Uranium 6.60 µg/L
MW-25 02/14/2012 Uranium 6.50 µg/L
MW-25 03/14/2012 Uranium 6.93 µg/L
MW-25 04/09/2012 Uranium 6.52 µg/L
MW-25 05/02/2012 Uranium 5.90 µg/L
MW-25 06/18/2012 Uranium 7.60 µg/L
MW-25 07/10/2012 Uranium 6.45 µg/L
MW-25 08/06/2012 Uranium 6.72 µg/L
MW-25 09/18/2012 Uranium 6.01 µg/L
MW-25 10/22/2012 Uranium 6.37 µg/L
MW-25 11/12/2012 Uranium 6.61 µg/L
MW-25 12/24/2012 Uranium 4.83 µg/L
MW-25 01/22/2013 Uranium 5.97 µg/L
MW-25 02/20/2013 Uranium 5.39 µg/L
MW-25 03/19/2013 Uranium 5.68 µg/L
MW-25 04/17/2013 Uranium 5.56 µg/L
MW-25 05/14/2013 Uranium 5.88 µg/L
MW-25 06/24/2013 Uranium 5.35 µg/L
MW-25 07/10/2013 Uranium 6.22 µg/L
MW-25 08/19/2013 Uranium 6.42 µg/L
MW-25 09/17/2013 Uranium 5.99 µg/L
MW-25 10/22/2013 Uranium 5.94 µg/L
MW-25 11/19/2013 Uranium 7.13 µg/L
MW-25 02/13/2014 Uranium 5.83 µg/L
MW-25 03/10/2014 Uranium 6.26 µg/L
MW-25 05/13/2014 Uranium 7.43 µg/L
MW-25 06/02/2014 Uranium 6.07 µg/L
MW-25 07/28/2014 Uranium 5.90 µg/L
MW-25 08/18/2014 Uranium 6.10 µg/L
MW-25 09/03/2014 Uranium 6.00 µg/L
MW-25 10/06/2014 Uranium 6.67 µg/L
MW-25 11/04/2014 Uranium 6.04 µg/L
MW-25 12/09/2014 Uranium 5.75 µg/L
MW-25 01/20/2015 Uranium 6.54 µg/L
MW-25 02/04/2015 Uranium 6.81 µg/L
MW-25 03/04/2015 Uranium 6.43 µg/L
MW-25 04/07/2015 Uranium 5.86 µg/L
MW-25 05/11/2015 Uranium 6.38 µg/L
MW-25 06/23/2015 Uranium 5.88 µg/L
MW-25 07/06/2015 Uranium 6.25 µg/L
MW-25 08/10/2015 Uranium 6.39 µg/L
MW-25 09/15/2015 Uranium 6.20 µg/L
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 6 of 10
APPENDIX C-3
Data Used for Statistical Analysis
Well ID Date Sampled Parameter Result Units Qualifer
MW-25 10/06/2015 Uranium 6.40 µg/L
MW-25 11/11/2015 Uranium 6.19 µg/L
MW-25 12/08/2015 Uranium 6.00 µg/L
MW-25 01/19/2016 Uranium 6.54 µg/L
MW-25 02/08/2016 Uranium 6.16 µg/L
MW-25 03/02/2016 Uranium 6.22 µg/L
MW-25 04/12/2016 Uranium 6.03 µg/L
MW-25 05/03/2016 Uranium 6.30 µg/L
MW-25 06/14/2016 Uranium 5.99 µg/L
MW-25 07/12/2016 Uranium 6.64 µg/L
MW-25 08/17/2016 Uranium 6.33 µg/L
MW-25 09/13/2016 Uranium 6.48 µg/L
MW-25 11/02/2016 Uranium 6.48 µg/L
MW-25 12/05/2016 Uranium 6.70 µg/L
MW-25 01/17/2017 Uranium 6.54 µg/L
MW-25 02/07/2017 Uranium 6.60 µg/L
MW-25 03/07/2017 Uranium 6.39 µg/L
MW-25 04/04/2017 Uranium 6.65 µg/L
MW-25 05/01/2017 Uranium 6.27 µg/L
MW-25 06/06/2017 Uranium 6.12 µg/L
MW-25 07/12/2017 Uranium 6.66 µg/L
MW-25 08/14/2017 Uranium 6.31 µg/L
MW-25 09/11/2017 Uranium 6.12 µg/L
MW-25 10/02/2017 Uranium 6.72 µg/L
MW-25 11/01/2017 Uranium 5.98 µg/L
MW-25 12/04/2017 Uranium 6 µg/L
MW-25 01/23/2018 Uranium 7 µg/L
MW-25 02/19/2018 Uranium 6 µg/L
MW-25 04/17/2018 Uranium 7 µg/L
MW-25 09/10/2018 Uranium 6 µg/L
MW-25 10/24/2018 Uranium 6 µg/L
MW-25 01/16/2019 Uranium 6 µg/L
MW-25 04/10/2019 Uranium 7 µg/L
MW-25 07/15/2019 Uranium 7 µg/L
MW-25 06/23/2005 pH 7 pH Units
MW-25 09/22/2005 pH 7 pH Units
MW-25 12/13/2005 pH 7 pH Units
MW-25 03/22/2006 pH 7 pH Units
MW-25 06/20/2006 pH 7 pH Units
MW-25 09/12/2006 pH 7 pH Units
MW-25 10/24/2006 pH 7 pH Units
MW-25 03/16/2007 pH 7 pH Units
MW-25 06/20/2007 pH 7 pH Units
MW-25 08/27/2007 pH 7 pH Units
MW-25 10/25/2007 pH 6 pH Units
MW-25 03/18/2008 pH 7 pH Units
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 7 of 10
APPENDIX C-3
Data Used for Statistical Analysis
Well ID Date Sampled Parameter Result Units Qualifer
MW-25 06/12/2008 pH 7 pH Units
MW-25 08/04/2008 pH 7 pH Units
MW-25 11/10/2008 pH 7 pH Units
MW-25 11/19/2008 pH 7 pH Units
MW-25 02/03/2009 pH 7 pH Units
MW-25 05/13/2009 pH 6.6 pH Units
MW-25 08/12/2009 pH 6.6 pH Units
MW-25 08/24/2009 pH 6.5 pH Units
MW-25 10/13/2009 pH 6.5 pH Units
MW-25 02/03/2010 pH 6.5 pH Units
MW-25 04/28/2010 pH 7.2 pH Units
MW-25 09/08/2010 pH 6.6 pH Units
MW-25 11/10/2010 pH 6.4 pH Units
MW-25 01/11/2011 pH 6.4 pH Units
MW-25 03/15/2011 pH 6.8 pH Units
MW-25 04/04/2011 pH 6.7 pH Units
MW-25 05/11/2011 pH 6.1 pH Units
MW-25 06/20/2011 pH 5.8 pH Units
MW-25 07/06/2011 pH 6.3 pH Units
MW-25 08/03/2011 pH 6.4 pH Units
MW-25 08/30/2011 pH 6.5 pH Units
MW-25 09/07/2011 pH 6.5 pH Units
MW-25 10/04/2011 pH 6.6 pH Units
MW-25 11/09/2011 pH 6.5 pH Units
MW-25 12/12/2011 pH 6.9 pH Units
MW-25 01/25/2012 pH 6.6 pH Units
MW-25 02/14/2012 pH 6.8 pH Units
MW-25 04/09/2012 pH 6.6 pH Units
MW-25 05/02/2012 pH 6.7 pH Units
MW-25 07/10/2012 pH 6.9 pH Units
MW-25 08/06/2012 pH 6.6 pH Units
MW-25 09/18/2012 pH 6.5 pH Units
MW-25 10/22/2012 pH 6.5 pH Units
MW-25 11/12/2012 pH 6.5 pH Units
MW-25 01/22/2013 pH 6.7 pH Units
MW-25 02/20/2013 pH 6.6 pH Units
MW-25 03/19/2013 pH 6.4 pH Units
MW-25 04/17/2013 pH 7.0 pH Units
MW-25 06/24/2013 pH 6.7 pH Units
MW-25 07/10/2013 pH 6.3 pH Units
MW-25 08/19/2013 pH 6.7 pH Units
MW-25 09/17/2013 pH 6.5 pH Units
MW-25 10/22/2013 pH 6.8 pH Units
MW-25 11/19/2013 pH 6.6 pH Units
MW-25 12/17/2013 pH 6.7 pH Units
MW-25 01/07/2014 pH 6.4 pH Units
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 8 of 10
APPENDIX C-3
Data Used for Statistical Analysis
Well ID Date Sampled Parameter Result Units Qualifer
MW-25 02/13/2014 pH 6.1 pH Units
MW-25 03/10/2014 pH 6.3 pH Units
MW-25 04/28/2014 pH 7.2 pH Units
MW-25 05/13/2014 pH 6.8 pH Units
MW-25 06/02/2014 pH 6.7 pH Units
MW-25 07/28/2014 pH 6.4 pH Units
MW-25 08/18/2014 pH 7.2 pH Units
MW-25 09/03/2014 pH 6.5 pH Units
MW-25 10/06/2014 pH 6.5 pH Units
MW-25 11/04/2014 pH 6.3 pH Units
MW-25 12/09/2014 pH 6.4 pH Units
MW-25 01/20/2015 pH 6.2 pH Units
MW-25 02/04/2015 pH 6.5 pH Units
MW-25 03/04/2015 pH 6.3 pH Units
MW-25 04/07/2015 pH 6.5 pH Units
MW-25 05/11/2015 pH 6.5 pH Units
MW-25 06/01/2015 pH 6.6 pH Units
MW-25 06/23/2015 pH 6.5 pH Units
MW-25 07/06/2015 pH 6.7 pH Units
MW-25 08/10/2015 pH 6.5 pH Units
MW-25 09/15/2015 pH 6.6 pH Units
MW-25 10/06/2015 pH 6.5 pH Units
MW-25 11/11/2015 pH 6.8 pH Units
MW-25 12/08/2015 pH 6.4 pH Units
MW-25 01/19/2016 pH 6.2 pH Units
MW-25 02/08/2016 pH 6.5 pH Units
MW-25 03/02/2016 pH 6.6 pH Units
MW-25 04/12/2016 pH 6.5 pH Units
MW-25 05/03/2016 pH 6.2 pH Units
MW-25 06/14/2016 pH 6.3 pH Units
MW-25 07/12/2016 pH 6.2 pH Units
MW-25 08/17/2016 pH 6.6 pH Units
MW-25 09/13/2016 pH 6.2 pH Units
MW-25 10/04/2016 pH 6.7 pH Units
MW-25 11/02/2016 pH 6.7 pH Units
MW-25 12/05/2016 pH 6.7 pH Units
MW-25 01/17/2017 pH 6.4 pH Units
MW-25 02/07/2017 pH 6.3 pH Units
MW-25 03/07/2017 pH 6.6 pH Units
MW-25 04/04/2017 pH 6.0 pH Units
MW-25 05/01/2017 pH 6.5 pH Units
MW-25 06/06/2017 pH 6.6 pH Units
MW-25 07/12/2017 pH 6.8 pH Units
MW-25 08/14/2017 pH 6.2 pH Units
MW-25 09/11/2017 pH 6.2 pH Units
MW-25 10/02/2017 pH 6.6 pH Units
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 9 of 10
APPENDIX C-3
Data Used for Statistical Analysis
Well ID Date Sampled Parameter Result Units Qualifer
MW-25 11/01/2017 pH 6.8 pH Units
MW-25 12/04/2017 pH 6.9 pH Units
MW-25 01/23/2018 pH 6.1 pH Units
MW-25 02/19/2018 pH 6.9 pH Units
MW-25 03/07/2018 pH 6.5 pH Units
MW-25 04/17/2018 pH 6.5 pH Units
MW-25 05/14/2018 pH 6.7 pH Units
MW-25 06/18/2018 pH 6.8 pH Units
MW-25 07/23/2018 pH 6.9 pH Units
MW-25 08/09/2018 pH 6.6 pH Units
MW-25 09/10/2018 pH 6.7 pH Units
MW-25 10/24/2018 pH 6.4 pH Units
MW-25 11/13/2018 pH 6.8 pH Units
MW-25 12/10/2018 pH 6.8 pH Units
MW-25 01/16/2019 pH 6.5 pH Units
MW-25 02/12/2019 pH 6.4 pH Units
MW-25 03/05/2019 pH 6.8 pH Units
MW-25 04/10/2019 pH 6.8 pH Units
MW-25 05/08/2019 pH 6.6 pH Units
MW-25 06/04/2019 pH 6.7 pH Units
MW-25 07/15/2019 pH 6.6 pH Units
MW-25 08/06/2019 pH 7.1 pH Units
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 10 of 10
Note:
D = Diluted
APPENDIX C-4
Indicator Parameter Data Removed from Analysis
Reason Location ID Date Sampled Parameter Name
Report
Result
Report
Units
Extreme Upper Outlier, not part of trend MW-25 7/10/2013 Fluoride 0.53 mg/L
Extreme Lower Outlier, not part of trend MW-25 8/10/2015 Fluoride 0.19 mg/L
Extreme Upper Outlier, not part of trend MW-25 11/1/2017 Fluoride 0.57 mg/L
Extreme Lower Outlier, not part of trend MW-25 6/18/2018 Fluoride 0.13 mg/L
Extreme Lower Outlier, not part of trend MW-25 7/23/2018 Fluoride 0.13 mg/L
Extreme Upper Outlier, not part of trend MW-25 06/20/2007 Fluoride 0.43 mg/L
Extreme Upper Outlier, not part of trend MW-25 5/14/2013 pH 7.8 pH Units
Extreme Upper Outlier, not part of trend MW-25 4/28/2014 Uranium 10.6 µg/L
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 1 of 1
APPENDIX C-5
Box Plots for pH and Indicator Parameters in MW-25
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 1 of 3
APPENDIX C-5
Box Plots for pH and Indicator Parameters in MW-25
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 2 of 3
APPENDIX C-5
Box Plots for pH and Indicator Parameters in MW-25
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 3 of 3
APPENDIX C-6
Histograms for pH and Indicator Parameters in MW-25
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 1 of 3
APPENDIX C-6
Histograms for pH and Indicator Parameters in MW-25
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 2 of 3
APPENDIX C-6
Histograms for pH and Indicator Parameters in MW-25
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 3 of 3
APPENDIX C-7
Time Series Plots and Linear Regressions for pH and Indicator Parameters in MW-25
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 1 of 2
APPENDIX C-7
Time Series Plots and Linear Regressions for pH and Indicator Parameters in MW-25
Notes:
Indicates a detected result
Indicates a non‐detect result
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 2 of 2

APPENDIX D
Time Concentration Plots Compared to Background Report Plots
APPENDIX D
Time Concentration Plots Compared to Background Report Plots
Cadmium in MW-25 from 2019 SAR
Cadmium in MW-25 from Existing Wells Background Report
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 1 of 5
APPENDIX D
Time Concentration Plots Compared to Background Report Plots
Chloride in MW-25 from 2019 SAR
Chloride in MW-25 from New Wells Background Report
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 2 of 5
APPENDIX D
Time Concentration Plots Compared to Background Report Plots
Fluoride in MW-25 from 2019 SAR
Fluoride in MW-25 from New Wells Background Report
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 3 of 5
APPENDIX D
Time Concentration Plots Compared to Background Report Plots
Sulfate in MW-25 from 2019 SAR
Sulfate in MW-25 from New Wells Background Report
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 4 of 5
APPENDIX D
Time Concentration Plots Compared to Background Report Plots
Uranium in MW-25 from 2019 SAR
Uranium in MW-25 from New Wells Background Report
Source Assesment Report for MW-25
White Mesa Uranium Mill Page 5 of 5

APPENDIX E
Flowsheet
(Groundwater Data Preparation and Statistical Process Flow for Calculating
Groundwater Protection Standards, White Mesa Mill Site (INTERA, 2007a)
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
If chloride, sulfate, or TDS, Remove from Dataset
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
Appendix E. Flowsheet
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).
Database of Wells and Analytes Listed in the Statement of Basis
APPENDIX F
Input and Output Files (Electronic Only)