DRC-2020-011934 - 0901a06880cc83a6

Energy Fuels Resources (USA) Inc.
225 Union Blvd. Suite 600
Lakewood, CO, US, 80228
303 974 2140
w ww.energyfuels.com ENERGY FUELS
June 24, 2020
DRC-2012O-ol.93
Div of Waste Management
and Radiation Control
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
JUN 2 6 2020
Re: Transmittal of Source Assessment Report for MW-31 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-31 at the White Mesa Mill. This SAR addresses the constituents that were identified as
exceeding the GWCL in the 4th Quarter 2019 as described in the Division of Waste Management and Radiation
Control ("DWMRC")-approved Q4 2019 Plan and Time Schedule. EFRI submitted the Plan and Time Schedule
for MW-31 on February 27, 2020. DWMRC approval of the Plan and Time Schedule was received by EFRI on
March 26, 2020. 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,
9104itike-Liti,
ENERGY FUELS RESOURCES (USA) INC.
Kathy Weinel
Quality Assurance Manager
CC: David C. Frydenlund
Paul Goranson
Terry Slade
Logan Shurnway
Scott Bakken
Stewart Smith (HGC)
June 24, 2020
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
Energy Fuels Resources (USA) Inc.
225 Union Blvd. Suite 600
Lakewood, CO, US, 80228
303 974 2140
www.enern:yfuel..com
Re: Transmittal of Source Assessment Report for MW-31 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-31 at the White Mesa Mill. This SAR addresses the constituents that were identified as
exceeding the GWCL in the 4th Quarter 2019 as described in the Division of Waste Management and Radiation
Control ("DWMRC")-approved Q4 2019 Plan and Time Schedule. EFRI submitted the Plan and Time Schedule
for MW-31 on February 27, 2020. DWMRC approval of the Plan and Time Schedule was received by EFRI on
March 26, 2020. 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,
c/(M;iv~
ENERGY FUELS RESOURCES (USA) INC.
Kathy Weinel
Quality Assurance Manager
CC: David C. Frydenlund
Paul Goranson
Terry Slade
Logan Shumway
Scott Bakken
Stewart Smith (HGC)
SOURCE ASSESSMENT REPORT
FOR MW-31
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
June 24, 2020

Source Assessment Report for MW-31 White Mesa Uranium Mill, Blanding, Utah
SOURCE ASSESSMENT REPORT FOR MW-31
WHITE MESA URANIUM MILL
Blanding, Utah

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

Prepared Under the Supervision of:

___________________________________
Bryn E. Kimball, PG
Utah Registration Number 10823695-2250 Expires 03/31/2021

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah ES-i June 24, 2020
EXECUTIVE SUMMARY
This Source Assessment Report (“SAR”) is an assessment of the sources, extent, and potential
dispersion of sulfate and total dissolved solids (“TDS”) in MW-31 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. Each of these constituents
occur naturally at the Mill (INTERA, 2008) and have exhibited exceedances of the applicable
Groundwater Compliance Limits (“GWCLs”).
MW-31 has been included in multiple recent investigations and reports including the New Wells
Background Report (INTERA, 2008), an isotopic investigation (Hurst and Solomon, 2008), and
four SAR reports (INTERA, 2012a, 2013, 2015, 2017). Sulfate and TDS in MW-31 were most
recently assessed and included in the 2017 SAR. The 2017 SAR concluded that increasing
concentrations of sulfate and TDS could be attributed to natural background and site-wide
influences (oxidation of pyrite and decreasing pH) or to impacts at the Mill site that are already
being addressed with an existing corrective action (nitrate/chloride plume capture). In a letter dated
March 20, 2018, the State of Utah Division of Waste Management and Radiation Control
(“DWMRC”) stated, “it appears that Mill activities are not influencing SAR studied concentrations
at monitoring well MW-31.” The 2017 SAR and the associated modified GWCLs, as presented
in the March 20, 2018 letter from DWMRC, were approved.
Increasing trends in concentrations have continued in MW-31, prompting additional exceedances
and out-of-compliance (“OOC”) status and resulting in the need for this SAR. Analytical results
for constituents included in this SAR exhibit increases in concentrations over time, which are likely
due to the location of this well within the nitrate/chloride plume and the result of oxidation of
pyrite in the formation around and upgradient of this well. To a lesser extent, increased frequency
of sampling and well redevelopment have also likely affected the behavior of constituents in
MW-31. In addition, changes in analytical methods and/or changing the analytical laboratory may
affect the concentrations of constituents reported for MW-31.
As the results of this analysis will demonstrate, concentrations of sulfate and TDS in MW-31 are
within the range of site-wide background and are likely influenced by oxidation of pyrite. Mass
balance calculations (Appendix E) demonstrate that concentrations in MW-31 are not consistent
with impacts from potential tailings system seepage. Once again, this SAR concludes that the
exceedances of sulfate and TDS in MW-31 can be attributed to natural background and site-wide
influences (oxidation of pyrite and decreasing pH) or to impacts at the Mill site that are already
being addressed with an existing corrective action (nitrate/chloride plume capture). The
conclusions of this analysis are consistent with conclusions presented in the Background Reports
(INTERA 2007a, 2007b, 2008) and other recent analyses.

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah ES-ii June 24, 2020
In accordance with the DWMRC-approved Flowsheet (from INTERA [2007a], included as
Appendix H), increasing trends necessitate a modified approach for calculation of GWCLs. The
modification in this approach uses a more recent dataset (collected after May 2014) and the greater
of (1) mean concentration plus two standard deviations (“mean + 2σ”), (2) highest historical value,
(3) background x 1.5, (4) the fractional approach, or (5) the upper tolerance limit to 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’s Unified Guidance (USEPA, 2009).
Such revisions account for the trends and minimize unwarranted OOC status in such wells.

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah i June 24, 2020
TABLE OF CONTENTS
EXECUTIVE SUMMARY ..................................................................................................... ES-i
LIST OF TABLES ........................................................................................................................ ii
LIST OF FIGURES ...................................................................................................................... ii
LIST OF APPENDICES .............................................................................................................. ii
ABBREVIATIONS AND ACRONYMS .................................................................................... iv
1.0 INTRODUCTION............................................................................................................. 1
1.1 Source Assessment Report Organization ................................................................ 3
1.2 Limitations Statement ............................................................................................. 4
2.0 CATEGORIES AND APPROACH FOR ANALYSIS .................................................. 5
2.1 Approach for Analysis ............................................................................................ 5 2.2 Approach for Setting Revised GWCLs ................................................................... 7
2.3 University of Utah Study ........................................................................................ 7
3.0 RESULTS OF ANALYSIS............................................................................................... 9
3.1 Site-Wide Decreasing pH ....................................................................................... 9 3.2 Changes in Groundwater in MW-31 ..................................................................... 10 3.3 Indicator Parameter Analysis ................................................................................ 10
3.4 pH Analysis ........................................................................................................... 12 3.5 Mass Balance Analyses......................................................................................... 12 3.6 Summary of Results .............................................................................................. 15 3.6.1 Sulfate ...................................................................................................... 15 3.6.2 Total Dissolved Solids ............................................................................. 15
4.0 CALCULATION OF GROUNDWATER COMPLIANCE LIMITS ........................ 16
4.1 Evaluation of Modified Approaches to Calculation of GWCLs for Trending Constituents........................................................................................................... 16 4.2 Proposed Revised GWCLs ................................................................................... 18
5.0 CONCLUSIONS AND RECOMMENDATIONS ........................................................ 19
6.0 REFERENCES ................................................................................................................ 21

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah ii June 24, 2020
LIST OF TABLES
Table 1. White Mesa Uranium Mill SARs ...................................................................................... 2
Table 2. Proposed GWCLs ........................................................................................................... 18
Table 3. MW-31 Summary of Findings ........................................................................................ 20 LIST OF FIGURES
Figure 1 Location of White Mesa Mill Site Figure 2 Exceedances and Proximity of MW-31 to Chloride Plume
Figure 3 Exceedances and Proximity of MW-31 to Nitrate Plume Figure 4 Groundwater Elevation over Time in MW-31 Figure 5 Groundwater Elevation Contours Figure 6 Ratio of Chloride to Fluoride Concentrations in MW-31 Figure 7 Ratio of Chloride to Sulfate Concentrations in MW-31
Figure 8 Ratio of Chloride to Uranium Concentrations in MW-31 LIST OF APPENDICES
Appendix A GWCL Exceedances for Fourth Quarter 2019 under the March 19, 2019 GWDP
Appendix B Statistical Analysis for MW-31 SAR Constituents
B-1 Statistical Analysis Summary Table B-2 Comparison of Calculated and Measured TDS for Samples with Complete Major Ions B-3 Charge Balance Calculations
B-4 Descriptive Statistics
B-5 Data Used for Statistical Analysis B-6 Box Plots for MW-31 SAR Constituents B-7 Box Plots for SAR Constituents in MW-31 and in Upgradient and Downgradient Wells
B-8 Box Plots for SAR Constituents in All Groundwater Monitoring Wells
B-9 Histograms B-10 Linear Regressions B-11 Time Series with Events
Appendix C Statistical Analysis for Indicator Parameters in MW-31
C-1 Indicator Parameter Analysis Summary Table
C-2 Descriptive Statistics of Indicator Parameters in MW-31 C-3 Data Used for Statistical Analysis C-4 Data Omitted from Statistical Analysis C-5 Box Plots for Indicator Parameters in MW-31

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah iii June 24, 2020
C-6 Box Plots for Indicator Parameters in MW-31 and Upgradient and
Downgradient Wells C-7 Piper Diagram for Cell 1, MW-31, and Upgradient and Downgradient Wells C-8 Histograms for Indicator Parameters in MW-31 C-9 Time Series Plots for Lognormally or Normally Distributed Constituents
C-10 Time Series with Events
Appendix D pH Analysis D-1 pH Analysis Summary Table D-2 Data Used for Analysis D-3 Box Plots for pH
D-4 Histograms for pH
D-5 Linear Regressions for pH
Appendix E Mass Balance Calculations Appendix F Flowsheet (Groundwater Data Preparation and Statistical Process Flow for
Calculating Groundwater Protection Standards, White Mesa Mill Site [INTERA, 2007a])
Appendix G Flowsheet Analysis for Post-Inflection Data (Modified Approach) for Purposes of Calculating GWCLs G-1 Descriptive Statistics for Modified GWCL Data Set and All Data
G-2 Data Used for Modified Approach
G-3 Box Plots for Modified Data Set G-4 Histograms for Modified Data Set G-5 Linear Regressions for Modified Data Set
Appendix H Input and Output Files (Electronic Only)

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah iv June 24, 2020
ABBREVIATIONS AND ACRONYMS
μg/L micrograms per liter
95-UTL 95% upper tolerance limit
Background Reports collectively refers to relevant background reports for this well and site: the Existing Wells Background Report (INTERA, 2007a), the Regional Background Report (INTERA, 2007b), and the New Wells Background Report
(INTERA, 2008)
CAP Corrective Action Plan CFCs chlorofluorocarbons CIR Contaminant Investigation Report
DF dilution factor 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) Inc. Existing Wells Background Report INTERA (2007a)
Flowsheet Groundwater Data Preparation and Statistical Process Flow
for Calculating Groundwater Protection Standards, White
Mesa Mill Site, San Juan County, Utah
GWCL Groundwater Compliance Limit GWDP State of Utah Ground Water Discharge Permit UGW370004
GWQS Groundwater Quality Standard
INTERA INTERA Incorporated
mg/L milligrams per liter Mill White Mesa Uranium Mill
New Wells Background Report INTERA (2008)
OOC out of compliance
pH Report INTERA (2012b)
Pyrite Report HGC (2012a)
Q4 2019 Plan and Time Schedule plan and time schedule for MW-31 for the fourth quarter of 2019 Q4 2019 Exceedance Notice exceedance notice submitted by EFRI January 31, 2020
Regional Background Report INTERA (2007b)
SAR Source Assessment Report

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah v June 24, 2020
ACRONYMS AND ABBREVIATIONS (Continued)
TDS Total Dissolved Solids
THF Tetrahydrofuran
UAC Utah Administrative Code University of Utah Study Hurst and Solomon, (2008) USEPA United States Environmental Protection Agency

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 1 June 24, 2020
1.0 INTRODUCTION
Energy Fuels Resources (USA) Inc. (“EFRI”) operates the White Mesa Uranium Mill (the “Mill”),
located near Blanding, Utah (Figure 1). Groundwater 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 sulfate and total dissolved solids (“TDS”) in groundwater compliance monitoring well
MW-31. The sulfate and TDS exceedances were addressed in previous SARs, but have exceeded
the recalculated groundwater compliance limits (“GWCLs”) specified in those SARs due to
statistically significant trends noted in those previous studies.
Part I.G.2 of the GWDP provides that an out-of-compliance (“OOC”) status exists when the
concentration of a constituent in two consecutive samples from a compliance monitoring point
exceeds a GWCL in Table 2 of the GWDP. 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 site and developing GWCLs under the GWDP. As required by then Part I.H.3 of the GWDP,
EFRI submitted the following three “Background Reports” to the Director (the “Director”) of the
State of Utah Division of Waste Management and Radiation Control (“DWMRC”)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):
• A revised background groundwater quality report: Existing Wells for Denison Mines (USA)
Corp.’s Mill Site, San Juan County, Utah, October 2007, prepared by INTERA
Incorporated (INTERA) (the “Existing Wells Background Report”).
• A revised addendum: Evaluation of Available Pre-Operational and Regional Background
Data, Background Groundwater Quality Report: Existing Wells for Denison Mines (USA)
Corp.’s Mill Site, San Juan County, Utah, November 16, 2007, prepared by INTERA (the
“Regional Background Report”).
• A revised addendum: Background Groundwater Quality Report: New Wells for Denison
Mines (USA) Corp.’s Mill Site, San Juan County, Utah, April 30, 2008, prepared by
INTERA (the “New Wells Background Report”).
Based on a review of the Background Reports and other information and analyses, the Director re-
opened the GWDP and modified the GWCLs to be equal to the mean concentration plus two standard

1 Formerly referred to as the State of Utah Division of Radiation Control.

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 2 June 24, 2020
deviations (“mean + 2σ ”) 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 plans and time schedules and the
associated SARs for White Mesa Uranium Mill are summarized in Table 1:
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 Se - MW-31
8/28/2013 Q1 2013 9/17/2013 12/17/2013 1/7/2014 THF - 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 SO4 - 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 U - MW-28
5/19/2015 Q1 2015 8/11/2015 Due 12/9/15* 2/19/2016 Se, SO4, TDS, pH - MW-31
9/10/2015 Q2 2015 11/10/2015 No SAR - install packer No SAR - install packer Cd, Zn, Be, Ni - MW-03
12/3/2015 Q3 2015 2/25/2016 No SAR - install packer NO SAR SO4- MW-3
3/3/2016 Q4 2015 4/4/2016 6/24/2016 12/20/2016
SO4- MW-18 F, Cd, Tl, and pH-
MW-24
3/10/2017 Q4 2016 5/23/2017 8/20/2017 3/20/2018 Se, SO4, TDS, and U in MW-31
3/2/2018 Q4 2017 3/30/2018 6/25/2018 7/25/2018 F- MW-14
8/28/2018 Q2 2018 10/18/2018 1/16/2019 7/9/2019 U, Se, pH - MW-30
12/5/2018 Q3 2018 3/5/2019 6/27/2019 9/5/2019** Tl, Cd, pH - MW-24
2/21/2019 Q4 2018 3/5/2019 6/27/2019 9/5/2019 Mn - MW-11
5/13/2019 Q1 2019 6/26/2019 9/23/2019 11/26/2019 Cd - MW-25
2/27/2020 Q4 2019 3/26/2020 TDS, SO4 - MW-31
5/21/2020 Q1 2020 Se, U - MW-28
Notes: *30-day extension for SAR; ** Installed MW-24A

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 3 June 24, 2020
On January 31, 2020, EFRI submitted a notice (the “Q4 2019 Exceedance Notice”) 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 the fourth quarter of
2019, and indicating which of those constituents had two consecutive exceedances as of that
quarter. A plan and time schedule for the fourth quarter of 2019 (“Q4 2019 Plan and Time
Schedule”) covered new dual exceedances of sulfate and TDS at MW-31. The MW-31 Q4 2019
Plan and Time Schedule was submitted on February 27, 2020, and was approved by the DWMRC
in correspondence dated March 26, 2020.
This SAR addresses the constituents that were identified as new dual exceedances or as exceeding
the previously revised GWCLs in the Q4 2019 Exceedance Notice as described in the DWMRC-
approved Q4 2019 Plan and Time Schedule.
1.1 Source Assessment Report Organization
A description of the approach used for analysis is provided in Section 2, the results of the analysis
are presented in Section 3, the calculation of GWCLs is provided in Section 4, and conclusions
and recommendations are presented in Section 5. Section 6 lists references cited in the SAR.
The appendices comprise the analyses performed for this Report and are organized in the following
manner: Appendix A contains a table showing exceedances for Fourth Quarter 2019 under the
March 19, 2019 GWDP. Appendix B contains the geochemical analysis performed on sulfate and
TDS in MW-31. Appendix C contains the indicator parameter analysis performed on MW-31.
Appendix D contains the pH analysis performed on MW-31. Appendix E contains mass balance
calculations. Appendix F contains the Groundwater Data Preparation and Statistical Process
Flow for Calculating Groundwater Protection Standards, White Mesa Mill Site, San Juan County,
Utah (“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, 1989, 1992, 2009). This Flowsheet was approved by DWMRC prior
to completion of the Background Reports. Appendix G contains analyses of two modified data
sets (post October 2012 and post May 2014) to address revising GWCLs for constituents with
increasing trends. Appendix H 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 software package “R.” R is a free statistical package
that allows the analyst to perform statistical analysis and format and output graphs more effectively
than the Statistica software package used in the past. Input and output files included in
Appendix H can be imported into either R or Statistica to replicate the results presented in this
SAR.

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 4 June 24, 2020
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 MW-31 White Mesa Uranium Mill Blanding, Utah 5 June 24, 2020
2.0 CATEGORIES AND APPROACH FOR ANALYSIS
Generally, OOC constituents and wells can be grouped into five categories:
Constituents in wells with previously identified rising trends.
Constituents in pumping wells.
Constituents potentially impacted by decreasing trends in pH across the Mill site.
Newly installed wells with interim GWCLs.
Other constituents and wells.
This SAR addresses two constituents in one well (sulfate and TDS in MW-31). These constituents
fall into category five: other constituents and wells. It is important to note that sulfate and TDS
also fall within the first and third categories: constituents in wells with previously identified rising
trends and constituents potentially impacted by decreasing trends in pH across the Mill site. The
pH is decreasing site-wide, likely due to oxidation of pyrite in the aquifer (HGC, 2012a). Sulfate
and increased TDS are also products of pyrite oxidation. Increased sulfate and TDS concentrations
may also be due to the location of MW-31 within the downgradient toe of the nitrate/chloride
plume (Figure 2 and Figure 3).
Additional factors that may have contributed to a potential change in behavior of groundwater
conditions and reported constituent concentrations in MW-31 include the following: (1) the 2011
well redevelopment project, which took place in April and May of 2011 (HGC, 2011); (2) the
change in analytical laboratory in 2012; (3) groundwater elevations that increased until 2013
(Figure 4) as a result of former wildlife pond seepage (HGC, 2014); (4) groundwater elevations
that have decreased since 2013 (Figure 4) as a result of cessation of water delivery to the wildlife
ponds in 2012 (HGC, 2014); and (5) the addition of several pumping wells under the
nitrate/chloride and chloroform Corrective Action Plans (“CAP”) subsequent to the fourth quarter
of 2012. A more detailed discussion of these variables is presented in Section 3.1 of the 2015 SAR
(INTERA, 2015).
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 caused by background 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

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 6 June 24, 2020
appropriate, a revised GWCL is proposed to reflect changes in background conditions at the Mill
site.
Assessments for potential sources of increasing concentrations of sulfate and TDS in MW-31 have
been performed in SARs produced in 2012, 2013, 2015, and 2017 (INTERA, 2012a, 2013, 2015,
2017). Assessment of the site-wide pH trend has been performed in PH Report White Mesa
Uranium Mill, Blanding, Utah (the “pH Report”) and Investigation of Pyrite in the Perched Zone,
White Mesa Uranium Mill Site (the “Pyrite Report,” HGC, 2012a). The analysis performed in this
SAR considers all available data to date to help determine if there have been any changes in
potential tailings system seepage indicator parameters (e.g., chloride, sulfate, fluoride, and
uranium) since the date of the New Wells Background Report and the approved SARs that may
suggest a change in the behavior of the groundwater in the 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 those groundwater monitoring wells at the Mill impacted by the chloride plume
(EFRI, 2020). Sulfate and fluoride are useful indicator parameters under geochemical conditions
allowing conservative (i.e., non-reactive) behavior. Uranium behavior may range from
conservative to non-conservative depending on the geochemical conditions.
Groundwater impacted by 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, it is
typically retarded behind chloride, fluoride, and sulfate due to possible sorption 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 constituent concentrations would indicate
that there has been no impact from the tailings system, a rising trend in concentrations could also
be due to natural influences (see Section 12.0 of INTERA, 2007a).
The evaluation of SAR parameters and indicator parameters in MW-31 was supported by a
statistical analysis that followed the process outlined in the Flowsheet (INTERA, 2007a) attached
as Appendix F. As discussed in Section 1.1, the Flowsheet was designed based on USEPA’s
Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities, Unified Guidance
(USEPA, 1989, 1992, 2009), and was approved by DWMRC prior to completion of the
Background Reports (INTERA, 2007a, 2007b, 2008).

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 7 June 24, 2020
2.2 Approach for Setting Revised GWCLs
If the preceding approach resulted in the conclusion that the previous analysis in the Background
Reports or most recently approved SARs has not changed, or that the OOC status of sulfate or
TDS in MW-31 is due to natural or other site-wide influences that are already being addressed by
corrective action, then new GWCLs may be proposed for the constituents. In proposing revised
GWCLs, INTERA has adopted the approach in the DWMRC-approved Flowsheet, 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 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, 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,
tailings solution and surface water samples were collected from 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,
sulfur-34 and oxygen-18 of sulfate, trace metals (uranium, manganese, and selenium), and
chlorofluorocarbons (“CFCs”). The 15 wells sampled included MW-31.
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.
With respect to CFC age dating, MW-31 was found to exhibit CFC recharge dates of the 1960s
and 1970s, indicating that the water in that well predated construction of the Mill in 1980. Tritium
was not detected in MW-31, indicating that impacts from wide-scale atmospheric injection of

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 8 June 24, 2020
tritium during aboveground thermonuclear weapons testing in the 1950s and 1960s, expected to
be found in surface waters such as solutions in the Mill’s tailings system, were not observed in that
well.
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. 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 ðD and ð18O suggest mixing between wildlife pond recharge and older groundwater in MW-19 and MW-27. D34S-SO4 and ð18O-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.
It should be further noted that, subsequent to the University of Utah Study, EFRI submitted a
Nitrate Groundwater Contamination Investigation Report, White Mesa Uranium Mill Site,
Blanding, Utah, dated December 30, 2009 (INTERA, 2009) (“CIR”), relating to the
nitrate/chloride plume at the Mill site.

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 9 June 24, 2020
3.0 RESULTS OF ANALYSIS
This section describes the potential geochemical influences on groundwater in MW-31 and results of
the analysis, summaries of which are provided in Appendix B-1, Appendix C-1, and Appendix D-
1. Supporting analyses are presented in Appendix E and Appendix G.
3.1 Site-Wide Decreasing pH
A general discussion of the site-wide pH trend is necessary because decreasing pH is one of the
most important contributors to increasing concentrations of the SAR parameters. A decreasing
trend in pH has been observed in almost every groundwater monitoring well across the Mill site,
including upgradient and far downgradient monitoring wells (INTERA, 2012b). The Pyrite Report
(HGC, 2012a) attributed the decline in pH across the Mill site to the site-wide existence and
oxidation of pyrite in the perched aquifer monitored at the site. This report showed that pyrite was
observed in cuttings of at least 14 monitoring wells, including MW-26 (HGC, 2012a), which is
upgradient of MW-31 (Figure 5).
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)
Reaction 1 will increase hydrogen ion concentrations, which results in decreasing pH. Increasing
concentrations of sulfate and TDS may also be a direct result of pyrite oxidation. Sulfate is a
product of reaction 1, so increasing sulfate concentrations may be due to increased site-wide pyrite
oxidation. The acidity produced during reaction 1 may also lead to increased mineral dissolution
overall (Brantley, 2008), which usually leads to increased TDS concentrations.
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) changing water levels and
incorporation of oxygen in air-filled pore spaces into groundwater; (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 below.
Pyrite may also oxidize in the presence of bacteria and nitrate according to the following reaction
(Hayakawa et al., 2013):
5FeS2 + 15NO3- + 10H2O  15/2N2 + 10SO42- + 5Fe(OH)3 + 5H+ (reaction 2)

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 10 June 24, 2020
Reaction 2 could be occurring in the parts of the aquifer impacted by the nitrate plume (Figure 3),
potentially causing further oxidation and dissolution of pyrite and subsequent decreasing pH and
increasing sulfate and TDS concentrations. As discussed in HGC (2017), the stability of nitrate
concentrations in MW-30 and MW-31, which are located at the downgradient toe of the nitrate
plume, could be due to nitrate degradation through oxidation of pyrite.
Pyrite oxidation by nitrate may occur by another pathway that consumes acid and produces sulfate
(Spiteri et al., 2008), as discussed in HGC (2017):
5FeS2 + 14NO3- + 4H+  7N2 + 10SO42- + 5Fe2+ + 2H2O (reaction 3)

The relative dominance of pyrite oxidation by dissolved oxygen (producing acid and sulfate by
reaction 1) and/or by nitrate (producing acid and sulfate by reaction 2; or producing sulfate but
consuming acid by reaction 3) may result in sulfate production with or without a decrease in pH.
3.2 Changes in Groundwater in MW-31
The behavior of groundwater has changed since the time of the Background Reports, but to a lesser
extent since recent SAR evaluations. Section 3.1 of the 2015 SAR describes in detail the changes,
events, and other factors that may be influencing the behavior of constituents in this well,
including:
• Sampling frequency (monthly monitoring commenced in 2010).
• Well redevelopment in 2011.
• Hydraulic influences (Figure 4).
• Geochemical influences.
• Analytical changes.
3.3 Indicator Parameter Analysis
Concentrations of parameters monitored in well MW-31 vary from concentrations observed at the
time of the Background Reports. The changes in concentrations are most likely attributable to a
combination of the influences discussed in Section 3.1 of the 2015 SAR: the proximity to the
chloride/nitrate plume and changing hydrologic and geochemical conditions due to pumping wells,
increased sample frequency, removal of recharge from the wildlife ponds, well rehabilitation, and
the oxidation of pyrite leading to decreasing pH and increasing concentrations. For these reasons,
the typical suite of indicator parameters of potential tailings system seepage may be impacted by
other processes. A summary of geochemical analysis of indicator parameters is included in
Appendix C-1. Appendix C-2 presents a descriptive statistics comparison for indicator

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 11 June 24, 2020
parameters from the New Wells Background Report and the 2012, 2013, 2015, and 2017 SARs.
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 data sets are demonstrated in the box plots included in Appendix C-5. Data from
additional monitoring wells were plotted alongside indicator parameters for MW-31 (Appendix
C-6). The additional wells and the areas they represent are the following: (1) MW-1, MW-18, and
MW-19 as upgradient wells; (2) MW-20 and MW-3A as downgradient wells; and (3) MW-22 as
a downgradient and far cross-gradient well (grouped with the other downgradient wells). This
comparison illustrates that fluoride, sulfate, and uranium concentrations in MW-31 are well within
the range of site-wide background concentrations. Chloride concentrations are above the range for
site-wide background, consistent with the location of MW-31 within the nitrate/chloride plume.
As the mass balance evaluation demonstrates (Section 3.5), the concentrations of constituents that
are increasing and/or exceeding GWCLs in MW-31 are not the result of potential tailings system
seepage. A Piper diagram, which can be used to distinguish between different waters, is presented
in Appendix C-7. The diagram illustrates that the geochemical signature of major ions in solution
differs between MW-31 and Cell 1.
Chloride concentrations in MW-31 exhibit a statistically significant increasing trend (see
Appendix C-9 for a time series). Fluoride concentrations are decreasing significantly in MW-31.
Sulfate and uranium concentrations in MW-31 are relatively low for the Mill site (Appendix B-8
and Appendix C-6), but show significant increasing trends at the time of this SAR. Time series
plots with vertical lines to indicate events that may have contributed to observed changes in
indicator parameters are included in Appendix C-10.
Current sulfate concentrations in MW-31 are among the lowest at the Mill site. A box plot showing
sulfate concentrations in all monitoring wells at the Mill site is included in Appendix B-8. Other
monitoring wells show sulfate concentrations that are three to seven times higher than those in
MW-31 (see Table 7 of the 2012 SAR). Sulfate is also significantly increasing in a number of
wells at the Mill site, including upgradient and far downgradient wells. See, for example, the
indicator parameter analyses for MW-18 included in the 2012 SAR, which show a significantly
increasing trend in sulfate and suggest that there are natural influences at the site that can influence
sulfate concentrations. Specifically, as noted by DWMRC in their approval letter of the MW-18
SAR, based on review of water level elevations included in the Mill site Quarterly Groundwater
Reports, upgradient wells are not likely to be impacted by current Mill activities. The elevations
at monitoring wells MW-l, MW-18 and MW-19 are higher than water elevations in the Burro
Canyon Aquifer beneath all of the Mill tailings cells. Those monitoring wells are located north and
northeast of the tailings cells, and local groundwater flow is to the south-southwest

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 12 June 24, 2020
(DWMRC, 2013). The widespread occurrence of pyrite in the Burro Canyon Formation and the
Dakota Sandstone (which host the perched groundwater monitored at the Mill site) can contribute
to decreasing pH and increasing sulfate in wells at the Mill site (HGC, 2012a; reaction 1). Increased
concentrations of sulfate, as well as chloride and TDS, are expected due to site-wide pyrite
oxidation and the location of MW-31 within the nitrate/chloride plume.
Uranium concentration trends are highly variable site-wide. An evaluation of uranium
concentrations over time was included for all groundwater monitoring wells at the Mill site in
Appendix F of the 2017 SAR (INTERA, 2017). Uranium concentrations in MW-31 are relatively
low for the site and exhibit a statistically significant upward trend first identified during the 2015
SAR (INTERA, 2015). Box plots showing uranium in all of the groundwater monitoring wells at
the Site are plotted in Appendix C-6. These box plots illustrate that uranium concentrations in
MW-31 are within the range of background concentrations.
With the exception of chloride, and despite any increasing trends, indicator parameters in MW-31
remain amongst the lowest at the Mill site (Appendix C-6) and are not present in concentrations
that would be expected if they were due to potential tailings system seepage (Section 3.5).
3.4 pH Analysis
A pH analysis was also performed for MW-31 (Appendix D). The pH analysis included creating
box plots to identify and omit extreme outliers, performing the Shapiro-Wilk test of normality
(Shapiro and Wilk, 1965), and testing for trends using either the least squares regression or the
Mann-Kendall trend method (see Appendices D-1 through D-5). The results of the pH analysis in
MW-31 show a significant decreasing trend in pH. The data appear to show more variance
beginning in 2010 (Appendix D-5), which corresponds to the increase in monthly sampling
frequency implemented that year.
3.5 Mass Balance Analyses
The 2017 SAR for MW-31 included a mass balance analysis where fluoride concentrations in
MW-31 were predicted by assuming a hypothetical situation under which potential tailings system
seepage has entered the groundwater and has become diluted during transport before reaching
MW‐31. Predicted fluoride concentrations were based on the dilution factors calculated for other
indicator parameters (uranium, chloride, and sulfate) using average Cell 1 concentrations and
current MW-31 concentrations. Because the conditions in MW-31 have not changed substantially
since 2017, the mass balance analysis in the 2017 SAR remains valid. This mass balance analysis
has been updated with more recent concentration values in this SAR.
The mass balance model is based on current concentrations of fluoride, uranium, chloride, and
sulfate in MW-31 and mean concentrations of the same constituents in Cell 1 water. The mean

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 13 June 24, 2020
concentrations in Cell 1 were based on data collected between 2003 and 2019 (EFRI 2019).
Samples of tailings system water have produced variable results between 2003 and 2019, so
average concentrations were used to describe the tailings system water. The model calculates
estimated fluoride contributions to MW‐31 groundwater from hypothetical tailings system seepage
based on measured concentrations of chloride, sulfate, and uranium. The model assumes potential
tailings system seepage has entered the groundwater and has become diluted during transport
before reaching MW‐31 and that this occurred far enough in the past to potentially reach MW‐31
at the present time. Therefore, the most recent analyses of MW‐31 groundwater were selected to
represent modern MW‐31 water.
For this mass balance calculation, indicator parameters are assumed to be conservative tracers
(INTERA, 2007a) and not subject to attenuation during transport. Therefore, if the tailings are a
source of contamination at MW‐31, the concentration of fluoride in MW‐31 is expected to be
proportional to the concentration of uranium, chloride, and sulfate in the tailings system water.
Although this model assumes only hypothetical tailings seepage and dilution of natural
groundwater at MW‐31, recent analyses show that more likely sources of increasing constituent
concentrations in this well include the chloride/nitrate plume (discussed below) and oxidization of
naturally occurring pyrite associated with decreasing pH.
Model calculations are presented in Appendix E. The mass balance calculations are based on
dilution factors (DF) computed as the ratio of a particular constituent’s current (Q2 2020)
concentration in MW-31 to its average concentration in the Cell 1 tailings solution since 2003. The
DFs calculated for all indicator parameters based on the ratio of Cell 1 and MW-31 constituent
concentrations vary by four orders of magnitude.
Based on the computed DFs for uranium, chloride, and sulfate, the predicted MW-31 fluoride
concentrations are 0.087, 35, and 15 milligrams per liter (mg/L), respectively. The most recent
observed concentration of fluoride in MW-31 is 0.632 mg/L. The dissimilarity between predicted
and observed fluoride concentrations and the large range in calculated dilution factors for the four
indicator parameters indicate that potential tailings system seepage is an unlikely contributor to
the groundwater chemistry of MW-31. Instead, fluoride concentrations in MW-31 are similar to
most natural waters (< 1 mg/L; Hem 1985) and are more consistent with natural processes.
In addition, if the same mass balance methodology is applied to uranium, the predicted MW-31
uranium concentrations range from 112 micrograms per liter (μg/L) (based on the fluoride DF) to
6,179 μg/L (based on the chloride DF). All of the predicted concentrations of uranium substantially
exceed the most recent observed uranium concentration of approximately 16 μg/L.

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 14 June 24, 2020
Fluoride concentrations at MW-31 are stable to decreasing (Appendix C-9), which is inconsistent
with potential tailings system seepage. Because concentrations of chloride are increasing and
fluoride is stable to decreasing, the ratio of chloride to fluoride concentrations is increasing
(Figure 6). If the chloride in MW-31 resulted from a potential tailings solution impact, the
MW-31 chloride to fluoride ratio would be decreasing (rather than increasing) because the chloride
to fluoride ratio in Cell 1 (approximately 11 based on average concentrations) is much lower than
the ratio at MW-31 (595 as of Q2 2020, Figure 6). In other words, if chloride to fluoride ratios
represent geochemical signatures, then it appears that MW-31 is not inheriting the signature of
tailings solution. The increase in the chloride to fluoride ratio at MW-31 is, however, consistent
with the position of MW-31 in the downgradient toe of the nitrate/chloride plume and the ongoing
downgradient migration of the plume. As discussed in Nitrate Contamination Investigation Report
White Mesa Uranium Mill Site, Blanding, Utah (INTERA, 2009), the nitrate/chloride plume
originated primarily from a pre-Mill source. This source (the historical pond) was located
approximately 500 feet upgradient (northeast) of Cell 1 (INTERA, 2009).
Finally, the ratios of other indicator parameters in MW-31 also differ substantially from ratios of
the same constituents in Cell 1 solutions. Like the ratio of chloride to fluoride described above
(Figure 6), the ratios of chloride to sulfate and chloride to uranium are shown for MW-31 and
average Cell 1 tailings solution in Figures 7 and 8, respectively. The average chloride to average
sulfate ratio in Cell 1 is approximately 0.14 while the Q2 2020 ratio in MW-31 is approximately
0.33; the ratio of average chloride to average uranium in Cell 1 is approximately 61 while the Q2
2020 ratio in MW-31 is approximately 24,260. The ratios of both chloride to sulfate and chloride
to uranium at MW-31 are increasing (Figures 7 and 8).
The increasing chloride to sulfate ratio is inconsistent with a Cell 1 impact because the ratio of
chloride to sulfate is lower in Cell 1 (0.14) than in MW-31 (0.33). Therefore, if Cell 1 were
potentially contributing chloride and sulfate to MW-31, the trend in the chloride to sulfate ratio
would be expected to decrease rather than increase. Likewise, the increasing ratio of chloride to
uranium concentrations at MW-31 could not result from a potential Cell 1 impact because the ratio
at MW-31 (24,260) is substantially larger than in Cell 1 (61).
Overall, the mass balance analysis indicates that potential tailings system seepage is an unlikely
contributor to the groundwater chemistry at MW-31. The nitrate/chloride plume and oxidation of
pyrite are the most likely cause of the increase in chloride, sulfate, and TDS measured in MW-31,
which is located in the downgradient toe of the plume where such increases would be expected (as
indicated above). This conclusion is consistent with previous mass balance analyses that were
based on nitrate concentrations within the nitrate/chloride plume as described below.

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 15 June 24, 2020
The nitrate mass balance calculation presented in the December 2009 CIR (INTERA, 2009)
suggested that groundwater mounding would occur underneath the tailings system if the
nitrate/chloride plume was caused by hypothetical tailings system seepage. The results of this
calculation predicted that a 5-foot groundwater mound would be expected if the nitrate/chloride
plume was caused by tailings system seepage. This nitrate mass balance calculation was updated
in the 2015 SAR (INTERA, 2015, Appendix F-2). Although a substantial groundwater mound was
predicted, such a mound has not been identified beneath the tailings cells (Figure 5).
3.6 Summary of Results
As the results of the analysis of SAR parameters in MW-31 demonstrate, increasing trends in
MW-31 are not consistent with potential tailings system seepage. A summary of conclusions for
each SAR parameter is included below.
3.6.1 Sulfate
Sulfate is naturally occurring in groundwater and is released into solution during the oxidation of
pyrite (reactions 1 through 3) and dissolution of common sulfate-bearing minerals such as gypsum
and anhydrite, both of which have been detected in the perched zone at the Mill (HGC, 2012a).
Sulfate concentrations in MW-31 are significantly increasing, although the concentrations remain
amongst the lowest at the Mill (Appendix B-8). These increasing concentrations are most likely
the result of pyrite oxidation.
3.6.2 Total Dissolved Solids
Appendix B-3 presents molar concentrations of the major cations and anions in MW-31 over time.
All of the major ions show increasing concentrations over time, and these ions make up the bulk
of measured TDS. This increase in TDS is consistent with decreasing pH because mineral
dissolution tends to increase with decreasing pH (Brantley, 2008). Appendix B-3 shows that the
most abundant cation is calcium, and the most abundant anions are chloride and sulfate. The source
of calcium is likely increased dissolution of calcite, the source of chloride is the chloride/nitrate
plume, and the source of sulfate is likely the oxidation of pyrite.

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 16 June 24, 2020
4.0 CALCULATION OF GROUNDWATER COMPLIANCE LIMITS
The findings of analyses discussed above support the conclusions that (1) MW-31 is not being
impacted by potential tailings system seepage, and (2) increasing concentrations of constituents in
MW-31 are the result of background and/or site-wide influences, such as the nitrate/chloride plume
and a site-wide decline in pH. Therefore, revision of GWCLs for SAR parameters in MW-31 is
proposed.
4.1 Evaluation of Modified Approaches to Calculation of GWCLs for Trending
Constituents
According to the DWMRC-approved Flowsheet (Appendix F), if an increasing trend is present, a
modified approach should be considered for determining GWCLs. Constituents included in this
SAR are exhibiting significantly increasing trends that can be attributed to one or more of the
following: (1) natural background conditions; (2) pyrite oxidation in the aquifer, which can
decrease pH, increase mobility of metals, and increase sulfate and TDS concentrations; (3) the
location of this well within the nitrate/chloride plume, which is actively being remediated
according to the CAP (HGC, 2012b); and/or (4) effects of recent events on groundwater in
MW-31; such as well redevelopment, increased sampling frequency, change in water levels, and
analytical method/laboratory change, as described in Section 3.1 of the 2015 SAR
(INTERA, 2015).
Therefore, the following alternative approaches to calculating GWCLs have been considered for
constituents in MW-31:
95% Upper Tolerance Limit (95-UTL).
The 95-UTL is one of several options for representing the upper bounds of a given dataset
(USEPA, 2009). The 95-UTL gives a 95% confidence that the UTL will contain at least 95% of
the distribution of observations in background. UTLs were calculated in USEPA’s free software
ProUCL. The ProUCL Version 5.0 Technical Guidance (USEPA, 2015) Chapter 3 describes how
the UTL is calculated based on distribution of the data.
1.5 times background concentration as defined in Utah Administrative Code (“UAC”)
R317-6-4.3.
The UAC R317-6-4.3 recognizes that “contaminants” may be present as part of naturally occurring
background conditions:
When a contaminant is present in a detectable amount as a background concentration, the concentration of the pollutant may not exceed the greater of 1.5

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 17 June 24, 2020
times the background concentration or 0.5 times the ground water quality standard
or background plus two standard deviations…
In this rule, background concentration is defined as the “concentration of a pollutant in ground
water upgradient or lateral hydraulically equivalent point from a facility, practice or activity which
has not been affected by that facility, practice or activity.” Background at the Mill has been
determined on an intrawell basis, as defined in the Background Reports. Therefore, to be
conservative, the mean concentration could be used as background for the purposes of this
calculation. The mean concentration would assume all data to date (or a data subset as described
below), after following the data quality steps of the Flowsheet.
Multiplying the mean concentration by 1.5 produces a GWCL that is greater than a GWCL
determined using mean + 2σ or the highest historical value. A greater GWCL decreases the
likelihood of false positives (exceedances) associated with increasing trends related to natural
background conditions or site-wide oxidation of pyrite.
Using recent data to calculate GWCLs.
This approach follows the DWMRC-approved Flowsheet (Appendix F) by taking into account
increasing trends and processing the data consistently with previously determined GWCLs. In this
approach, the complete data set, which exhibits an increasing trend over the history of the well
record, is divided into subsets of data based on identification of a point of inflection where the
results have shifted, or have been approved as background by the Director. This approach is
appropriate in wells that have been thoroughly investigated and where the causes of increasing
trends are not due to potential tailings system seepage or other Mill-related impacts that are not
already being addressed. For the purposes of this modified approach and to be consistent with
previous SARs, subsets of data from post October 2012 and post May 2014 were used to calculate
GWCLs (Appendix G).
These modified approaches have been considered for an achievable GWCL for parameters that are
increasing in concentration for reasons other than potential tailings system impact. MW-31 has
been thoroughly evaluated multiple times in recent years due to unachievable GWCLs. The most
appropriate GWCL that is achievable considering increasing trends is the highest of the following:
(1) mean + 2σ; (2) highest historical value; (3) fractional approach; (4) 1.5 times background; or
(5) the 95-UTL. This approach of choosing the highest value combines elements from the
Flowsheet and from previously approved GWCLs (DWMRC, 2016).

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 18 June 24, 2020
4.2 Proposed Revised GWCLs
In accordance with the Flowsheet, the increasing trends identified for sulfate and TDS warrant a
modified approach to the calculation of GWCLs. As discussed in detail in Section 3.0 and
demonstrated in Appendices B-11 and C-10, the changes observed in groundwater at MW-31 may
be attributable to many factors and events, several of which occurred between 2010 and 2014 and
correspond to changes in the chloroform CAP in 2014.
Increasing trends in MW-31 over time are not related to potential tailings system seepage. Sulfate
and TDS trends present in MW-31 likely result from the nitrate/chloride plume, which is being
addressed under a separate CAP, and oxidation of pyrite, which can contribute to increasing sulfate
and TDS concentrations while decreasing the pH.
Since the laboratory change in the fourth quarter of 2012, analytical methods and procedures have
been performed according to the Quality Assurance Plan. All parameters included in this SAR
have been monitored quarterly or monthly, resulting in a robust data set (over 40 N per data set
since June 2014). Subsets of data collected since October 2012 and June 2014 were analyzed for
trends (Appendix G). For all SAR parameters, concentrations are significantly increasing. For this
reason, the approach to calculation of GWCLs has been modified by using only data collected after
May 2014, and by choosing the greater of (1) mean + 2σ, (2) highest historical value, (3) fractional
approach, or (4) 1.5 times background. Flowsheet analysis has been performed for these data
subsets and the complete datasets and is summarized in Appendix B-1.
GWCLs determined according to the Flowsheet using all data to date, data after October 2012, and
data collected after May 2014 are presented in Appendix B-1. Based on this analysis, the proposed
GWCLs for sulfate and TDS are presented in the column titled “Modified Approach GWCL” in
Table 2.
Table 2. Proposed GWCLs
Parameter GWCLa
Flowsheet Revised GWCLb Rationale Modified Approach GWCLc
Modified Approach Rationale
Sulfate (mg/L) 993 1150 HHV 1170.5 Background x 1.5
TDS (mg/L) 2132 2650 HHV 2664 Background x 1.5
Notes: HHV = highest historical value. a = 2019 GWDP No.UGW370004. b = GWCL calculated using complete historical data set. c = Modified Approach calculated in accordance with the Flowsheet using more recent data (6/2014 to 1/2020) and choosing the highest of either the HHV, mean + 2σ, fractional approach, 95-UTL, or 1.5 x background.

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 19 June 24, 2020
5.0 CONCLUSIONS AND RECOMMENDATIONS
Background at the Mill site was thoroughly studied as described in the Background Reports
(INTERA, 2007a, 2007b, 2008) and in the University of Utah Study (Hurst and Solomon, 2008).
Conditions in MW-31 have been studied more recently as described in the 2012, 2013, 2015, and
2017 SARs (INTERA, 2012a, 2013, 2015, 2017). The Background Reports and the University of
Utah Study concluded that groundwater at the Mill site has not been impacted by Mill operations.
Those studies also acknowledged that there are natural influences operating at the Mill site that
have caused increasing trends and general variability of background groundwater quality at the
Mill site. The conclusion of the 2012, 2013, 2015, and 2017 SARs is that groundwater in MW-31
is not impacted by potential tailings system seepage. This conclusion is consistent with the
conclusions of the Background Reports and the University of Utah Study. MW-31 is located within
the nitrate/chloride plume that was identified in 2009, and is currently being addressed under a
separate corrective action (HGC, 2012b). Mass balance calculations have demonstrated that
concentrations of SAR parameters, indicator parameters (with the exception of chloride), and pH
in MW-31 are consistent with background groundwater concentrations across the Mill site, and
not the result of potential tailings system seepage. Chloride is being addressed under a separate
corrective action (HGC, 2012b), and is not attributed to potential tailings system seepage.
The focus of this SAR was to identify any changes in the circumstances identified in previous
studies. A change in concentrations of parameters in MW-31 can be observed after monthly
monitoring started in 2010, after the well redevelopment effort in 2011, after analytical changes in
2012, after the groundwater elevation peak in 2013, and after changes to the chloroform CAP in
2014.
Constituents included in this SAR exhibit significant increasing trends that can be attributed to one
or more of the following: (1) natural background conditions; (2) pyrite oxidation in the aquifer,
which can decrease pH, increase mobility of metals, and increase sulfate and TDS concentrations;
(3) the location of this well within the nitrate/chloride plume, which is actively being remediated
according to the CAP (HGC, 2012b); and/or (4) effects of recent events on groundwater in
MW-31 such as well redevelopment, increased sampling frequency, changes in water levels, and
analytical method/laboratory change, as described in Section 3.1 of the 2015 SAR
(INTERA, 2015). A site-wide comparison of concentrations in MW-31 shows that even with
significant increasing long-term trends, many of the constituents are present in concentrations less
than or within the range of site-wide background concentrations. Thus, increasing sulfate and TDS
concentrations in MW-31 over time are likely due to background influences, including the
decreasing trend in pH across the Mill site and the location of this well within the existing
nitrate/chloride plume, and not to potential tailings system seepage. Findings are summarized on
Table 3.

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 20 June 24, 2020
Table 3. MW-31 Summary of Findings
Out-of-Compliance Constituent Summary Path Forward
Sulfate Sulfate concentrations are likely due to a combination of the oxidation of pyrite, which releases sulfate, and the location of MW-31 within the nitrate/chloride plume. Sulfate concentrations in MW-31 remain among the lowest at the Mill site.
Modified approach GWCL; continue remedial action on the nitrate/chloride plume.
TDS TDS concentrations are impacted by the nitrate/chloride plume and increasing dissolved constituents from pyrite oxidation. TDS concentrations in MW-31 are among the lowest at the Mill site.
Modified approach GWCL; continue remedial action on the nitrate/chloride plume.

INTERA recommends adopting the revised GWCLs for MW-31 based on the modified approach
to address constituents with increasing trends in accordance with the Flowsheet. Regular revisions
to GWCLs for constituents in wells with significantly increasing trends due to background is
consistent with the USEPA’s Unified Guidance (USEPA, 2009). Such revisions account for the
trends and minimize unwarranted OOC status in such wells.

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 21 June 24, 2020
6.0 REFERENCES
Brantley, S. L., 2008. Kinetics of Mineral Dissolution. In Kinetics of Water-Rock Interaction.
Ed. S. L. Brantley, J. D. Kubicki, and A. F. White. New York: Springer, p. 151-210.
Division of Waste Management and Radiation Control (DWMRC), 2016. Letter RE: Energy Fuels Resources (USA) Inc. December 9, 2015, Transmittal of Source Assessment Report for Monitoring Well MW-31, White Mesa Uranium Mill Groundwater Discharge Permit No. UGW370004. February 19, 2016
––––––, 2013. Letter RE: Energy Fuels (USA) Inc. October 10, 2012 Source Assessment Report
White Mesa Uranium Mill and associated pH assessment documents (dated November 9, 2012 pH Report and December 7, 2012 Pyrite Investigation Report): DRC Findings. April 25, 2013
Energy Fuels Resources (USA) Inc. (EFRI), 2019. White Mesa Uranium Mill Annual Tailings
System Wastewater Monitoring Report.
––––––, 2020. First Quarter Nitrate Monitoring Report, White Mesa Uranium Mill
Hayakawa, A., Hatakeyama, M., Asano, R., Ishikawa, Y., and Hidaka, S., 2013. Nitrate Reduction Coupled with Pyrite Oxidation in the Surface Sediments of a Sulfide-rich Ecosystem. Journal of Geophysical Research: Biogeosciences, 118, 639-649.
Hem, J. D., 1985. Study and Interpretation of the Chemical Characteristics of Natural Water. United States Geological Survey Water-Supply Paper, 2254.
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), 2007. Site Hydrogeology and Estimation of Groundwater Travel Times in the Perched Zone, White Mesa Uranium Mill Site near Blanding, Utah.
––––––, 2011. Redevelopment of Existing Perched Monitoring Wells White Mesa Uranium Mill Near Blanding, Utah
––––––, 2012a. Investigation of Pyrite in the Perched Zone, White Mesa Uranium Mill Site,
Blanding, Utah.
––––––, 2012b. Corrective Action Plan for Nitrate White Mesa Uranium Mill, Near Blanding, Utah.
––––––, 2014. Hydrogeology Report for the White Mesa Uranium Mill, Blanding Utah.

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 22 June 24, 2020
––––––, 2017. Nitrate Corrective Action Plan Comprehensive Monitoring Evaluation (CACME)
Report, White Mesa Uranium Mill Near Blanding, Utah.
INTERA Incorporated (INTERA), 2007a. Revised Background Groundwater Quality Report: Existing Wells for Denison Mines (USA) Corp.’s White Mesa Uranium Mill Site, San Juan County, Utah.
______, 2007b. Evaluation of Available Pre-Operational and Regional Background Data,
Background Groundwater Quality Report: Existing Wells for Denison Mines (USA) Corp.’s Mill Site, San Juan County, Utah. November 16.
––––––, 2008. Revised Background Groundwater Quality Report: New Wells for Denison Mines (USA) Corp.’s White Mesa Uranium Mill Site, San Juan County, Utah.
––––––, 2009. Nitrate Groundwater Contamination 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.
––––––, 2013. Source Assessment Report for Selenium in MW-31 White Mesa Uranium Mill,
Blanding, Utah.
––––––, 2015. Source Assessment Report for MW-31 White Mesa Uranium Mill, Blanding, Utah.
______, 2016. Source Assessment Report for MW-18 and MW-24, White Mesa Uranium Mill, Blanding, Utah.
––––––, 2017. Source Assessment Report for MW-31 White Mesa Uranium Mill, Blanding,
Utah.
Shapiro, S.S., and Wilk, M.B., 1965. An Analysis of Variance Test for Normality (Complete Samples). Biometrika 52:591-611.
Spiteri, C., C.P. Slomp, C.P.,K. Tuncay, K., and C. Meile, C.,. 2008. Modeling Biogeochemical
Processes in Subterranean Estuaries: Effect of Flow Dynamics and Redox Conditions on
Submarine Groundwater Discharge of Nutrients. Water Resources Research, 2008, 44, W02430.
United States Environmental Protection Agency (USEPA), 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.
_____, 1992. Statistical Analysis of Ground-Water Monitoring Data at RCRA Facilities: Addendum to Interim Final Guidance, Office of Solid Waste, Permits and State Programs

Source Assessment Report for MW-31 White Mesa Uranium Mill Blanding, Utah 23 June 24, 2020
Division, U.S. Environmental Protection Agency, 401 M Street, S.W. Washington, D.C.
20460.
_____, 2009. Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities, Unified Guidance, EPA 530/R-09-007.
_____, 2015. Computing Upper Limits to Estimate Background Threshold Values Based Upon
Uncensored Data Sets without Nondetect Observations, in The ProUCL Version 5.0
Technical Guidance, EPA/600/R-07/041.
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
Cell No. 1
Cell No. 2
Cell No. 3
Cell No. 4A
Wild lifePond
Wild lifePond

Mill Site
Cell No. 4B
MW-40
MW-38
MW-39
MW-37
MW-36
MW-34
MW-33
MW-32
MW-31
MW-29
MW-28
MW-27
MW-26
MW-25
MW-24
MW-23
MW-22
MW-21
MW-20
MW-19
MW-18
MW-17MW-15
MW-12 MW-11MW-05
MW-04
MW-02
MW-01
MW-03A
MW-14
MW-30
MW-35
S:\ABQ\IUC-001-01-001 De nison Mine s\GIS\mapd oc s\2020_SAR s\MW-31\01_SAR MW31_Loc ationMap.mxd Date : 6/2/2020
Figu re 1Loc ation of White Me sa Mill Siteand Grou nd wate r Monitoring We llsWhite Me sa Uraniu m Mill
900 0 900
Fe e t
Sou rc e (s): Ae rial – ESR I Arc GIS online ;We lls – HGC, Inc ., May 2008 re port.
Grou nd wate r Monitoring We ll
IDAHOIDAHO
NEV
A
D
A
NEV
A
D
A
AR IZ ONAAR IZ ONA
WYOMINGWYOMING
UTAHUTAH
CO
L
O
R

A
D
O
CO
L
O
R

A
D
O
NEWNEWMEXICOMEXICO
White Me saUraniu m Mill
Cell No. 1
Cell No. 2
Cell No. 3
Cell No. 4A
Wild lifePond
Wild lifePond

Mill Site
Cell No. 4B
100
100
100
300
500
MW-01
MW-02
MW-03A
MW-04
MW-05 MW-11
MW-12
MW-14
MW-15 MW-17
MW-18
MW-19
MW-20
MW-21
MW-22
MW-23
MW-24
MW-25
MW-26
MW-27
MW-28
MW-29
MW-30 MW-32
MW-33 MW-34
MW-35
MW-36
MW-37
MW-38
MW-39
MW-40
MW-31
S :\ABQ\IUC-001-01-001 Denison Mines\GIS \m apd ocs\2020_S ARs\MW-31\02_S ARMW31_Ch lorid e.m x d Date: 6/3/2020
Fig ure 2Ex ceed ances and Prox im ity ofMW-31 to Ch lorid e Plum eWh ite Mesa Uranium Mill
1,000 0 1,000500
Feet
S ource(s): Aerial – ES RI ArcGIS online;Wells – HGC, Inc., May 2008 report;Nitrate and ch lorid e d ata collected Q1, 2020.
Leg end
Ground water Monitoring Well
Monitoring Well Ex ceed s: Ch lorid e,Nitrate, S ulfate, and TDS
Ch lorid e Contam ination Area Above100 m g /L
100 m g /L Ch lorid e Contour
Cell No. 1
Cell No. 2
Cell No. 3
Cell No. 4A
Wild lifePond
Wild lifePond

Mill Site
Cell No. 4B
10
10
10
5
20
30
5
30
5
MW-01
MW-02
MW-03A
MW-04
MW-05 MW-11
MW-12
MW-14
MW-15 MW-17
MW-18
MW-19
MW-20
MW-21
MW-22
MW-23
MW-24
MW-25
MW-26
MW-27
MW-28
MW-29
MW-30 MW-32
MW-33 MW-34
MW-35
MW-36
MW-37
MW-38
MW-39
MW-40
MW-31
S :\ABQ\IUC-001-01-001 Denison Mines\GIS \m apd ocs\2020_S ARs\MW-31\03_S ARMW31_Nitrate.m x d Date: 6/3/2020
Fig ure 3Ex ceed ances and Prox im ity ofMW-31 to Nitrate Plum eWh ite Mesa Uranium Mill
1,000 0 1,000500
Feet
S ource(s): Aerial – ES RI ArcGIS online;Wells – HGC, Inc., May 2008 report;Nitrate and ch lorid e d ata collected Q1, 2020.
Leg end
Ground water Monitoring Well
Monitoring Well Ex ceed s: Ch lorid e,Nitrate, S ulfate, and TDS
Nitrate Contam ination Area Above10 m g /L (d ash ed wh ere inferred )
10 m g /L Nitrate Contour
Figure 4
Groundwater Elevations over Time
at MW-31
White Mesa Uranium Mill
Service Layer Credits: Source: Esri,DigitalGlobe, GeoEye, Earthstar Geographics,CNES/Airbus DS, USDA, USGS, AeroGRID,IGN, and the GIS User Community
Figure 5
Groundwater Elevation Contours MW-31 SAR
MW-01
MW-02
MW-03A
MW-04
MW-05 MW-11MW-12
MW-14MW-15 MW-17
MW-18 MW-19
MW-20
MW-22
MW-23
MW-24
MW-25
MW-26
MW-27
MW-28
MW-29 MW-30
MW-31 MW-32
MW-34
MW-35
MW-36
MW-37
MW-38
MW-39
MW-40
5600
5500
5480
5460
5
5
6
0
5
5
4
0
5580
5
5
2
0
FILE: S:\ABQ\IUC-001-01-001 Denison Mines\GIS\mapdocs\2020_SARs\MW-31\04_SARMW31_GWelev.mxd Date: 6/2/2020
Source(s): Imagery from ArcGIS Online
2,000 0 2,000
Feet
Legend
Well Type
MW
PIEZ
TW4
TWN
Groundwater ElevationContour, ft amsl
Figure 6
Ratio of Chloride to Fluoride
Concentrations in MW-31
White Mesa Uranium Mill
0
100
200
300
400
500
600
700
800
900
1000
1/1/2005 1/1/2007 1/1/2009 1/1/2011 1/1/2013 1/1/2015 1/1/2017 1/1/20191/1/2021
ra
t
i
o
date
MW‐31 Cl/F
cell 1 average Cl/F
Linear (MW‐31 Cl/F)
Figure 7
Ratio of Chloride to Sulfate
Concentrations in MW-31
White Mesa Uranium Mill
0.00
0.10
0.20
0.30
0.40
0.50
1/1/2005 1/1/2007 1/1/2009 1/1/2011 1/1/2013 1/1/2015 1/1/2017 1/1/20191/1/2021
ra
t
i
o
date
MW‐31 Cl/SO4
average cell1 Cl/SO4
Linear (MW‐31 Cl/SO4)
Figure 8
Ratio of Chloride to Uranium
Concentrations in MW-31
White Mesa Uranium Mill
0
5000
10000
15000
20000
25000
30000
35000
1/1/2005 1/1/2007 1/1/2009 1/1/2011 1/1/2013 1/1/2015 1/1/2017 1/1/20191/1/2021
ra
t
i
o
date
MW‐31 Cl/U
average cell 1 Cl/U
Linear (MW‐31 Cl/U)
APPENDIX A
GWCL Exceedances for Fourth Quarter 2019
under the March 19, 2019 GWDP
APPENDIX A
GWCL Exceedances for Fourth Quarter 2019 under the March 19, 2019 GWDP
Monitoring Well
(Water Class)Constituent Exceeding GWCL GWCL in March
19, 2019 GWDP
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
Q3 2019
Sample
Date
Q3 2019
Result
August 2019
Monthly
Sample Date
August 2019
Monthly
Result
Sept. 2019
Monthly
Sample
Date
Sept. 2019
Monthly
Result
Q4 2019
Sample
Date
Q4 2019
Result
November
2019 Monthly
Sample Date
November
2019
Monthly
Result
December
2019
Monthly
Sample
Date
December
2019
Monthly
Result
Chloride (mg/L)39.16 34 NA NA 48.4 NA NA 30.8 39.1 35.4
Sulfate (mg/L)1309 1160 NA NA 1410 NA NA 1290 1140 1100
Manganese (ug/L)164.67 181 210 210 199 202 174 185 206 167Fluoride (mg/L)0.22 <0.100 NA NA 0.248 NA NA <0.100 0.127 0.120
Sulfate (mg/L)2330 1780 NA NA 2450 NA NA 2180 2110 2120
MW-25 (Class III) Cadmium (ug/L)1.5 4/10/2019 1.30 5/8/2019 1.41 6/4/2019 1.47 7/15/2019 1.23 8/6/2019 1.37 9/23/2019 1.38 10/9/2019 1.45 11/13/2019 1.36 12/4/2019 1.45Nitrate + Nitrite (as N) (mg/L)0.62 3.00 0.986 3.16 2.06 3.10 1.59 2.35 2.90 2.32Chloroform (ug/L)70 4140 1140 778 3110 1090 1540 1710 1280 1110Chloride (mg/L)58.31 82.0 73.0 72.6 75.2 83.5 62.1 73.8 62.3 57.7
Methylene Chloride (ug/L)5 4.16 1.69 <1.00 10.7 1.12 3.35 2.95 1.73 2.64
Nitrogen, Ammonia as N 0.92 0.104 0.479 0.0919 0.357 0.164 0.496 0.273 0.178 0.207
Nitrate + Nitrite (as N) (mg/L)2.5 18.5 17.9 15.8 19.3 15.8 17.9 18.2 17.2 17.8
Chloride (mg/L)128 138 175 165 181 190 176 170 180 185Selenium (ug/L)47.2 53.6 47.1 49.9 48.4 50.9 49.1 56.8 47.8 56.4Uranium (ug/L)8.32 8.62 8.15 8.88 9.03 9.39 8.12 8.69 9.29 8.99Field pH (S.U.)6.47 - 8.5 7.06 7.00 7.12 6.86 7.42 7.00 7.16 7.21 7.22Nitrate + Nitrite (as N) (mg/L)5 19.7 18.9 19.7 19.8 17.0 19.5 19.8 18.8 18.3Sulfate (mg/L)993 917 NA NA 1150 NA NA 1010 990 1020TDS (mg/L)2132 2080 NA NA 2580 NA NA 2280 2650 2030
Chloride (mg/L)143 294 346 325 374 372 365 318 338 343
Sulfate (mg/L)3146.21 2470 NA NA 3170 NA NA 2850 2590 2710
Field pH (S.U.)6.49 - 8.5 7.05 6.73 7.01 6.60 7.33 6.92 7.05 7.09 7.24
MW-12 (Class III)Uranium (ug/L)23.5 4/25/2019 23.2 NS NA NS NA 7/11/2019 23.1 NS NA NS NA 10/23/2019 21.6 NS NA NS NA
Beryllium (ug/L)2 2.83 NA NA 2.94 NA NA 3.25 NA NA
Cadmium (ug/L)6.43 8.24 NA NA 8.37 NA NA 9.31 NA NA
Fluoride (mg/L)0.47 0.839 NA NA 0.996 NA NA 0.667 NA NANickel (mg/L)50 63.9 NA NA 70.6 NA NA 75.4 NA NAManganese (ug/L)7507 7020 NA NA NA NA NA 7700 NA NA
Thallium (ug/L)2.01 2.73 NA NA 2.61 NA NA 2.88 NA NA
Field pH (S.U.)5.03 - 8.5 4.53 NA NA 5.03 NA NA 5.19 NA NA
MW-27 (Class III) Nitrate + Nitrite (as N) (mg/L) 5.6 4/23/2019 6.33 NS NA NS NA
7/12/2019
8/15/2019 6.50 NS NA NS NA 10/22/2019 6.27 NS NA NS NA
Chloride (mg/L)105 165 NA NA 133 NA NA 149 NA NA
Selenium (ug/L)11.1 12.4 NA NA 10.6 NA NA 16.5 NA NAGross Alpha (pCi/L)2.42 1.94 NA NA 1.20 NA NA <1.00 NA NAUranium (ug/L)4.9 9.60 NA NA 7.83 NA NA 12.4 NA NA
MW-32 (Class III)Chloride (mg/L)35.39 4/9/2019 34.5 NS NA NS NA 8/15/2019 35.7 NS NA NS NA 10/8/2019 35.3 NS NA NS NA
MW-35 (Class ll) Nitrogen, Ammonia as N 0.14 4/18/2019 0.0634 NS NA NS NA 7/11/2019 0.0935 NS NA NS NA 10/8/2019 <0.0500 NS NA NS NA
Notes:
NS= Not Required and Not SampledNA= Not Applicable
Exceedances are shown in yellow
10/22/2019 NS NS
Required Quarterly Sampling Wells
Required Semi-Annual Sampling Wells
11/6/2019 NS NS
10/9/2019 11/12/2019 12/3/2019
10/8/2019 11/13/2019 12/3/2019
10/9/2019 11/13/2019 12/4/2019
10/8/2019 11/13/2019 12/4/2019
Q4 2019 Results
10/15/2019 11/12/2019 12/3/2019
10/9/2019 11/13/2019 12/3/2019
MW-24 (Class III)
Q3 2019 Results
5/2/2019 NS NS
4/24/2019 NS NS
4/9/2019 5/7/2019
Q2 2019 Results
4/24/2019 5/7/2019
NS
7/18/2019 NS NS
9/24/2019
7/16/2019 8/6/2019 9/24/2019
7/15/2019 8/5/2019 9/23/2019
8/6/2019 9/23/2019
7/16/2019 8/6/2019
MW-11 (Class II)7/16/2019 8/5/2019 9/24/2019
MW-14 (Class III)
4/24/2019 5/7/2019 6/3/2019
4/23/2019 NS NS 7/15/2019 NS NS
MW-28 (Class III)
MW-26 (Class III)
MW-30 (Class II)
7/12/2019
8/16/2019 NS
7/16/2019MW-36 (Class III) 4/18/2019 5/21/2019 6/3/2019
MW-31 (Class III)
6/4/2019
5/7/2019 6/3/2019
6/3/2019
4/10/2019
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 1 of 1
APPENDIX B
Geochemical Analysis for SAR Parameters
in MW-31
Appendix B-1: Summary of Geochemical Analysis for Out of Compliance Constituents in MW-31
Wp Sp
MW-31 Sulfate Complete 126 0 668.9 160.9 0.9468 0.0001 No 6354 0 Increasing Yes 991 1003.3 1080 1150 993 1150 HHV
MW-31 Sulfate Post Sep 2012 85 0 741.2 148.2 0.9660 0.0243 No 2679 0 Increasing Yes 1038 1111.8 1120 1150 993 1150 HHVMW-31 Sulfate Post May 2014 65 0 780.3 145.8 0.9674 0.0843 Lognormal 1723 0 Increasing Yes 1071.9 1170.5 1099 1150 993 1071.9 Mean + 2σ 1170.5 Mean x 1.5
MW-31 Total Dissolved Solids Complete 127 0 1555.3 314 0.9420 0.0000 No 6481 0 Increasing Yes 2183 2333 2280 2650 2132 2650 HHV
MW-31 Total Dissolved Solids Post Sep 2012 85 0 1689.3 300 0.9567 0.0062 No 2870 0 Increasing Yes 2289 2534 2380 2650 2132 2650 HHV
MW-31 Total Dissolved Solids Post May 2014 65 0 1775.7 288 0.9460 0.0068 No 1684 0 Increasing Yes 2352 2664 2580 2650 2132 2650 HHV 2664 Mean x 1.5
Notes:
σ = sigma N = number of valid data points S = Mann-Kendall statistic
%ND = percent of non-detected values p = probability FA= Fraction of GWQS as defined in UAC R317-6
µg/L = micrograms per liter W = Shapiro Wilk test value NA= Not Applicable
mg/L = milligrams per liter r2 = The measure of how well the trendline fits the data where r2=1 represents a perfect fit.
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%
Flowsheet GWCL does not take into account increasing trends
§ = GWCL is based on the GWDP or most recent SARs, where applicable.
Constituent N
% Non-
Detected
Values
MeanWellData Set
Modified
Approach
GWCL
Rationale
Significant
Trend
Previously
Identified
Increasing
Trend?
Modified
Approach
GWCL*
Standard
Deviation
Highest
Historical
Value (HHV)
Mean + 2σ Current
GWCL §
Mann Kendall
Trend Analysis
Shapiro-Wilk Test for
Normality Normally or
Lognormally
distributed?
Upper
Tolerance
Limit (UTL)
Mean x 1.5 Flowsheet
GWCL Rationale
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 1 of 17
Appendix B-2: Comparison of Calculated and Measured TDS in MW-31
Date Sampled Alkalinity
(mg/L)
Calcium
(mg/L)
Chloride
(mg/L)
Potassium
(mg/L)
Magnesium
(mg/L)
Sodium
(mg/L)
Sulfate
(mg/L)
Measured TDS
(mg/L)
Calculated TDS
(mg/L)Ratio
8/24/2009 215 169 122 6.0 79.4 92.7 460 1230 1144 93%
10/14/2009 214 170 138 6.1 78.5 93.6 497 1160 1197 103%
2/9/2010 224 170 128 6.2 80.2 92.2 507 1150 1208 105%
4/20/2010 220 162 128 5.8 79.4 91.3 522 1220 1209 99%
9/13/2010 226 164 139 5.7 78.1 91 527 1330 1231 93%
11/9/2010 216 166 138 5.9 77.8 85.4 539 1320 1228 93%
2/1/2011 211 168 145 5.8 79.6 91.6 538 1220 1239 102%
4/1/2011 213 172 143 6.1 80.1 95 503 1370 1212 88%
8/2/2011 199 172 148 5.7 81.2 95.3 537 1300 1238 95%
10/3/2011 202 177 145 5.9 83.3 85.5 539 1320 1238 94%
2/13/2012 203 190 150 6.0 87.9 97.2 538 1240 1272 103%
5/2/2012 208 187 151 7.0 88 87.9 532 1410 1261 89%
7/9/2012 202 189 161 6.0 90.1 98 529 1400 1275 91%
11/6/2012 209.84 182 189 5.7 86.5 92.6 557 1230 1323 108%
2/19/2013 217.16 200 174 6.4 91.6 98.6 644 1390 1432 103%
5/13/2013 212.28 191 169 5.5 90.9 99.2 630 1540 1398 91%
7/9/2013 212.28 199 182 6.1 94.7 105 659 1510 1458 97%
11/18/2013 213.5 194 174 6.0 89.4 94.2 609 1320 1380 105%
3/10/2014 202.52 195 230 5.8 93.9 94.1 681 1490 1502 101%
6/2/2014 209.84 202 173 6.2 101 93.1 555 1520 1340 88%
9/3/2014 223.26 189 210 6.0 95.8 96.5 560 1460 1381 95%
11/4/2014 201.3 201 204 6.2 95.8 93.1 639 1520 1440 95%
2/2/2015 214.72 194 211 6.4 95.4 95 623 1520 1439 95%
4/7/2015 204.96 207 211 6.1 97.6 103 642 1680 1472 88%
8/10/2015 236.68 221 264 6.5 102 99.5 640 1530 1570 103%
11/09/2015 206 224 215 5.8 99.4 96.3 646 1460 1493 102%
2/15/2016 209 238 246 6.0 106 98.5 631 1490 1534 103%
5/3/2016 201 248 243 6.6 115 108 699 1550 1621 105%
8/16/2016 190 246 272 6.8 109 108 766 1710 1698 99%
11/1/2016 190 244 267 7.1 108 104 752 1690 1672 99%
2/7/2017 193 245 266 7.2 117 113 751 1680 1692 101%
5/1/2017 185 254 263 6.7 119 105 741 1820 1674 92%
8/14/2017 211 257 310 6.3 115 102 916 1780 1917 108%
11/1/2017 209 278 292 6.6 135 109 847 1770 1876 106%
2/20/2018 193.98 283 292 6.92 136 108 835 1930 1855 96%
4/17/2018 207.4 299 308 7.33 138 108 857 1980 1925 97%
9/10/2018 206.18 346 333 7.49 159 126 893 2100 2071 99%
10/24/2018 209.84 341 286 7.6 156 124 950 2000 2074 104%
1/15/2019 231.8 321 283 7.42 151 118 851 2030 1963 97%
4/10/2019 214.72 327 294 7.01 146 107 917 2080 2013 97%
7/15/2019 231.8 400 374 7.76 188 130 1150 2580 2482 96%
10/9/2019 225.7 346 318 6.63 167 124 1010 2280 2197 96%
1/14/2020 234.24 367 381 8.31 170 123 1120 2220 2404 108%
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 2 of 17
Appendix B-3: Charge Balance Calculations for Major Cations and Anions in MW-31
Well 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-31 6/22/2005 7.78 3.93 6.47 0.14 18.32 -2.77 -3.92 -10.49 17.18 3.20%
MW-31 3/19/2008 8.03 3.96 6.43 0.16 18.58 -3.47 -3.50 -10.85 17.82 2.10%
MW-31 6/3/2008 8.13 4.08 6.65 0.15 19.01 -3.23 -3.61 -10.70 17.54 4.02%
MW-31 8/4/2008 8.98 4.11 7.26 0.16 20.51 -3.44 -3.50 -10.39 17.33 8.40%
MW-31 11/11/2008 8.98 4.22 6.98 0.16 20.34 -3.36 -3.36 -11.26 17.98 6.17%
MW-31 2/3/2009 8.43 3.60 6.59 0.14 18.76 -3.36 -3.24 -10.16 16.76 5.63%
MW-31 5/13/2009 7.29 3.65 5.98 0.13 17.05 -3.43 -3.50 -10.26 17.19 -0.40%
MW-31 8/24/2009 8.43 4.03 6.53 0.15 19.15 -3.52 -3.44 -9.58 16.54 7.31%
MW-31 10/14/2009 8.48 4.07 6.46 0.16 19.17 -3.51 -3.89 -10.35 17.75 3.85%
MW-31 2/9/2010 8.48 4.01 6.60 0.16 19.25 -3.67 -3.61 -10.55 17.84 3.81%
MW-31 4/20/2010 8.08 3.97 6.53 0.15 18.74 -3.61 -3.61 -10.87 18.08 1.77%
MW-31 9/13/2010 8.18 3.96 6.43 0.15 18.71 -3.70 -3.92 -10.97 18.60 0.32%
MW-31 11/9/2010 8.28 3.71 6.40 0.15 18.55 -3.54 -3.89 -11.22 18.65 -0.28%
MW-31 2/1/2011 8.38 3.98 6.55 0.15 19.06 -3.46 -4.09 -11.20 18.75 0.83%
MW-31 4/1/2011 8.58 4.13 6.59 0.16 19.46 -3.49 -4.03 -10.47 18.00 3.91%
MW-31 8/2/2011 8.58 4.15 6.68 0.15 19.55 -3.26 -4.17 -11.18 18.62 2.46%
MW-31 10/3/2011 8.83 3.72 6.85 0.15 19.56 -3.31 -4.09 -11.22 18.62 2.45%
MW-31 2/13/2012 9.48 4.23 7.23 0.15 21.09 -3.33 -4.23 -11.20 18.76 5.86%
MW-31 5/2/2012 9.33 3.82 7.24 0.18 20.57 -3.41 -4.26 -11.08 18.74 4.65%
MW-31 7/9/2012 9.43 4.26 7.41 0.15 21.26 -3.31 -4.54 -11.01 18.86 5.97%
MW-31 11/6/2012 9.08 4.03 7.12 0.14 20.37 -2.82 -5.33 -11.60 19.75 1.56%
MW-31 2/19/2013 9.98 4.29 7.54 0.16 21.97 -2.92 -4.91 -13.41 21.23 1.70%
MW-31 5/13/2013 9.53 4.31 7.48 0.14 21.47 -2.85 -4.77 -13.12 20.73 1.73%
MW-31 7/9/2013 9.93 4.57 7.79 0.15 22.44 -2.85 -5.13 -13.72 21.70 1.67%
MW-31 11/18/2013 9.68 4.10 7.35 0.15 21.29 -2.87 -4.91 -12.68 20.45 1.99%
MW-31 3/10/2014 9.73 4.09 7.73 0.15 21.70 -2.72 -6.49 -14.18 23.39 -3.74%
MW-31 6/2/2014 10.08 4.05 8.31 0.16 22.60 -2.82 -4.88 -11.55 19.25 7.99%
MW-31 9/3/2014 9.43 4.20 7.88 0.15 21.66 -3.00 -5.92 -11.66 20.58 2.56%
MW-31 11/4/2014 10.03 4.05 7.88 0.16 22.12 -2.70 -5.75 -13.30 21.76 0.82%
MW-31 2/2/2015 9.68 4.13 7.85 0.16 21.82 -2.88 -5.95 -12.97 21.81 0.04%
MW-31 4/7/2015 10.33 4.48 8.03 0.16 22.99 -2.75 -5.95 -13.37 22.07 2.05%
MW-31 8/10/2015 11.03 4.33 8.39 0.17 23.91 -3.18 -7.45 -13.32 23.95 -0.07%
MW-31 11/09/2015 11.18 4.19 8.18 0.15 23.69 -2.77 -6.06 -13.45 22.28 3.07%
MW-31 2/15/2016 11.88 4.28 8.72 0.15 25.04 -2.80 -6.94 -13.14 22.88 4.50%
MW-31 5/3/2016 12.38 4.70 9.46 0.17 26.70 -2.70 -6.85 -14.55 24.11 5.10%
MW-31 8/16/2016 12.28 4.70 8.97 0.17 26.11 -2.56 -7.67 -15.95 26.18 -0.12%
MW-31 11/1/2016 12.18 4.52 8.89 0.18 25.77 -2.56 -7.53 -15.66 25.74 0.05%
MW-31 2/7/2017 12.23 4.92 9.63 0.18 26.95 -2.59 -7.50 -15.63 25.73 2.32%
MW-31 5/1/2017 12.67 4.57 9.79 0.17 27.20 -2.49 -7.42 -15.43 25.34 3.55%
MW-31 8/14/2017 12.82 4.44 9.46 0.16 26.88 -3.46 -8.74 -19.07 31.27 -7.55%
MW-31 11/1/2017 13.87 4.74 11.11 0.17 29.89 -3.42 -8.24 -17.63 29.29 1.01%
MW-31 2/20/2018 14.12 4.70 11.19 0.18 30.19 -3.18 -8.24 -17.38 28.80 2.35%
MW-31 4/17/2018 14.92 4.70 11.35 0.19 31.16 -3.40 -8.69 -17.84 29.93 2.01%
MW-31 9/10/2018 17.27 5.48 13.08 0.19 36.02 -3.38 -9.39 -18.59 31.36 6.91%
MW-31 10/24/2018 17.02 5.39 12.83 0.19 35.44 -3.44 -8.07 -19.78 31.29 6.22%
MW-31 1/15/2019 16.02 5.13 12.42 0.19 33.76 -3.80 -7.98 -17.72 29.50 6.74%
MW-31 4/10/2019 16.32 4.65 12.01 0.18 33.16 -3.52 -8.29 -19.09 30.90 3.52%
MW-31 7/15/2019 19.96 5.65 15.47 0.20 41.28 -3.80 -10.55 -23.94 38.29 3.75%
MW-31 10/9/2019 17.27 5.39 13.74 0.17 36.57 -3.70 -8.97 -21.03 33.70 4.08%
MW-31 1/14/2020 18.31 5.35 13.99 0.21 37.86 -3.84 -10.75 -23.32 37.91 -0.06%
Notes:
meq/L= milliequivalent per liter
HCO3 = Bicarbonate
SO4 = Sulfate
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 3 of 17
Appendix B-4: Descriptive Statistics for Out of Compliance Constituents in MW-31
Data Set 2020 SAR 2017 SAR 2015 SAR 2012 SAR
2008
Background
Report
2020 SAR 2017 SAR 2015 SAR 2012 SAR
2008
Background
Report
Analyte Sulfate Sulfate Sulfate Sulfate Sulfate
Total
Dissolved
Solids
Total
Dissolved
Solids
Total
Dissolved
Solids
Total
Dissolved
Solids
Total
Dissolved
Solids
Units mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L
% Non-Detects 0 0 0 0 0 0 0 0 0 0
N 126 100 77 39 10 127 100 78 51 10
Distribution Not normal or
lognormal
Not
normal or
lognormal
Not
normal or
lognormal
Not
normal or
lognormal
Not
normal or
lognormal
Not normal or
lognormal
Not
normal or
lognormal
normal or
lognormal
normal or
lognormal
Not
normal or
lognormal
Mean 669 1421 567 517 504 1555 1421 1364 1258 1265
Min. Conc.436 1150 436 436 436 1150 1150 1150 1110 1150
Max. Conc.1150 1820 691 552 532 2650 1820 1700 1460 1320
Std. Dev.161 161 65.1 24.2 27.8 314 161 125 76.5 50
Range 714 670 255 116 96.0 1500 670 550 350 170
Geometric Mean 652 1412 564 517 504 1527 1412 1358 1255 1264
Skewness 1.04 0.35 0.40 -1.3 -1.9 1.18 0.35 0.46 0.34 -1.60
Q25 537 1288 521 503 497 1310 1288 1270 1210 1240
Median 640 1410 541 522 513 1480 1410 1330 1240 1280
Q75 750 1530 630 538 522 1705 1530 1460 1300 1290
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill
Page 4 of 17
Appendix B-5: MW-31 Data Used for Analysis
Well Date Sampled Parameter Name Report
Result Report Units Qualifier
MW-31 6/22/2005 Sulfate 504 mg/l
MW-31 9/22/2005 Sulfate 436 mg/l D
MW-31 12/14/2005 Sulfate 509 mg/l D
MW-31 3/22/2006 Sulfate 485 mg/l D
MW-31 6/21/2006 Sulfate 522 mg/l D
MW-31 9/13/2006 Sulfate 516 mg/l D
MW-31 10/25/2006 Sulfate 526 mg/l D
MW-31 3/15/2007 Sulfate 516 mg/l D
MW-31 8/27/2007 Sulfate 532 mg/l D
MW-31 10/24/2007 Sulfate 497 mg/l D
MW-31 3/19/2008 Sulfate 521 mg/l D
MW-31 6/3/2008 Sulfate 514 mg/l D
MW-31 8/4/2008 Sulfate 499 mg/l D
MW-31 11/11/2008 Sulfate 541 mg/l D
MW-31 2/3/2009 Sulfate 488 mg/l D
MW-31 5/13/2009 Sulfate 493 mg/l D
MW-31 8/24/2009 Sulfate 460 mg/l D
MW-31 10/14/2009 Sulfate 497 mg/l D
MW-31 2/9/2010 Sulfate 507 mg/l D
MW-31 4/20/2010 Sulfate 522 mg/l D
MW-31 9/13/2010 Sulfate 527 mg/l D
MW-31 11/9/2010 Sulfate 539 mg/l D
MW-31 2/1/2011 Sulfate 538 mg/l D
MW-31 3/14/2011 Sulfate 531 mg/l D
MW-31 4/1/2011 Sulfate 503 mg/l D
MW-31 5/10/2011 Sulfate 512 mg/l D
MW-31 6/20/2011 Sulfate 540 mg/l D
MW-31 7/5/2011 Sulfate 532 mg/l D
MW-31 8/2/2011 Sulfate 537 mg/l D
MW-31 9/6/2011 Sulfate 541 mg/l D
MW-31 10/3/2011 Sulfate 539 mg/l D
MW-31 11/8/2011 Sulfate 552 mg/l D
MW-31 12/12/2011 Sulfate 530 mg/l D
MW-31 1/24/2012 Sulfate 539 mg/l D
MW-31 2/13/2012 Sulfate 538 mg/l D
MW-31 3/13/2012 Sulfate 517 mg/l D
MW-31 4/9/2012 Sulfate 547 mg/l D
MW-31 5/2/2012 Sulfate 532 mg/l D
MW-31 6/18/2012 Sulfate 497 mg/l D
MW-31 7/9/2012 Sulfate 529 mg/l D
MW-31 8/6/2012 Sulfate 571 mg/l D
MW-31 9/18/2012 Sulfate 561 mg/l D
MW-31 10/22/2012 Sulfate 545 mg/l
MW-31 11/6/2012 Sulfate 557 mg/l
MW-31 12/18/2012 Sulfate 664 mg/l
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 5 of 17
Appendix B-5: MW-31 Data Used for Analysis
Well Date Sampled Parameter Name Report
Result Report Units Qualifier
MW-31 1/22/2013 Sulfate 611 mg/l
MW-31 2/19/2013 Sulfate 644 mg/l
MW-31 3/19/2013 Sulfate 611 mg/l
MW-31 4/16/2013 Sulfate 668 mg/l
MW-31 5/13/2013 Sulfate 630 mg/l
MW-31 6/24/2013 Sulfate 659 mg/l
MW-31 7/9/2013 Sulfate 659 mg/l
MW-31 8/19/2013 Sulfate 656 mg/l
MW-31 9/17/2013 Sulfate 666 mg/l
MW-31 10/23/2013 Sulfate 637 mg/l
MW-31 11/18/2013 Sulfate 609 mg/l
MW-31 12/17/2013 Sulfate 656 mg/l
MW-31 1/7/2014 Sulfate 558 mg/l
MW-31 2/17/2014 Sulfate 480 mg/l
MW-31 3/10/2014 Sulfate 681 mg/l
MW-31 4/28/2014 Sulfate 527 mg/l
MW-31 5/13/2014 Sulfate 639 mg/l
MW-31 6/2/2014 Sulfate 555 mg/l
MW-31 7/28/2014 Sulfate 600 mg/l
MW-31 8/18/2014 Sulfate 620 mg/l
MW-31 9/3/2014 Sulfate 560 mg/l
MW-31 10/6/2014 Sulfate 606 mg/l
MW-31 11/4/2014 Sulfate 639 mg/l
MW-31 12/9/2014 Sulfate 687 mg/l
MW-31 1/20/2015 Sulfate 669 mg/l
MW-31 2/2/2015 Sulfate 623 mg/l
MW-31 3/3/2015 Sulfate 616 mg/l
MW-31 4/7/2015 Sulfate 642 mg/l
MW-31 5/11/2015 Sulfate 668 mg/l
MW-31 6/23/2015 Sulfate 691 mg/l
MW-31 7/6/2015 Sulfate 684 mg/l
MW-31 8/10/2015 Sulfate 640 mg/l
MW-31 9/15/2015 Sulfate 638 mg/l
MW-31 10/6/2015 Sulfate 655 mg/l
MW-31 11/9/2015 Sulfate 646 mg/l
MW-31 12/8/2015 Sulfate 690 mg/l
MW-31 1/19/2016 Sulfate 675 mg/l
MW-31 2/15/2016 Sulfate 631 mg/l
MW-31 3/2/2016 Sulfate 654 mg/l
MW-31 4/12/2016 Sulfate 715 mg/l
MW-31 5/3/2016 Sulfate 699 mg/l
MW-31 6/15/2016 Sulfate 748 mg/l
MW-31 7/12/2016 Sulfate 712 mg/l
MW-31 8/16/2016 Sulfate 766 mg/l
MW-31 9/13/2016 Sulfate 703 mg/l
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 6 of 17
Appendix B-5: MW-31 Data Used for Analysis
Well Date Sampled Parameter Name Report
Result Report Units Qualifier
MW-31 10/4/2016 Sulfate 720 mg/l
MW-31 11/1/2016 Sulfate 752 mg/l
MW-31 12/5/2016 Sulfate 748 mg/l
MW-31 1/17/2017 Sulfate 809 mg/l
MW-31 2/7/2017 Sulfate 751 mg/l
MW-31 3/6/2017 Sulfate 741 mg/l
MW-31 4/4/2017 Sulfate 758 mg/l
MW-31 5/1/2017 Sulfate 741 mg/l
MW-31 6/5/2017 Sulfate 808 mg/l
MW-31 7/11/2017 Sulfate 747 mg/l
MW-31 8/14/2017 Sulfate 916 mg/l
MW-31 9/11/2017 Sulfate 762 mg/l
MW-31 10/2/2017 Sulfate 823 mg/l
MW-31 11/1/2017 Sulfate 847 mg/l
MW-31 12/4/2017 Sulfate 825 mg/l
MW-31 1/24/2018 Sulfate 813 mg/l
MW-31 2/20/2018 Sulfate 835 mg/l
MW-31 4/17/2018 Sulfate 857 mg/l
MW-31 6/18/2018 Sulfate 976 mg/l
MW-31 7/23/2018 Sulfate 857 mg/l
MW-31 8/10/2018 Sulfate 841 mg/l
MW-31 9/10/2018 Sulfate 893 mg/l
MW-31 10/24/2018 Sulfate 950 mg/l
MW-31 11/13/2018 Sulfate 841 mg/l
MW-31 12/10/2018 Sulfate 905 mg/l
MW-31 1/15/2019 Sulfate 851 mg/l
MW-31 2/12/2019 Sulfate 893 mg/l
MW-31 3/5/2019 Sulfate 953 mg/l
MW-31 4/10/2019 Sulfate 917 mg/l
MW-31 7/15/2019 Sulfate 1150 mg/l
MW-31 10/9/2019 Sulfate 1010 mg/l
MW-31 11/12/2019 Sulfate 990 mg/l
MW-31 12/3/2019 Sulfate 1020 mg/l
MW-31 1/14/2020 Sulfate 1120 mg/l
MW-31 2/4/2020 Sulfate 1150 mg/l
MW-31 3/10/2020 Sulfate 1080 mg/l
MW-31 6/22/2005 Total Dissolved Solids 1290 mg/l
MW-31 9/22/2005 Total Dissolved Solids 1280 mg/l
MW-31 12/14/2005 Total Dissolved Solids 1290 mg/l
MW-31 3/22/2006 Total Dissolved Solids 1280 mg/l H
MW-31 6/21/2006 Total Dissolved Solids 1300 mg/l
MW-31 9/13/2006 Total Dissolved Solids 1320 mg/l
MW-31 10/25/2006 Total Dissolved Solids 1220 mg/l
MW-31 3/15/2007 Total Dissolved Solids 1280 mg/l
MW-31 8/27/2007 Total Dissolved Solids 1240 mg/l
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 8 of 17
Appendix B-5: MW-31 Data Used for Analysis
Well Date Sampled Parameter Name Report
Result Report Units Qualifier
MW-31 10/24/2007 Total Dissolved Solids 1150 mg/l
MW-31 3/19/2008 Total Dissolved Solids 1220 mg/l
MW-31 6/3/2008 Total Dissolved Solids 1180 mg/l
MW-31 8/4/2008 Total Dissolved Solids 1240 mg/l
MW-31 11/11/2008 Total Dissolved Solids 1220 mg/l
MW-31 2/3/2009 Total Dissolved Solids 1210 mg/l
MW-31 5/13/2009 Total Dissolved Solids 1230 mg/l
MW-31 8/24/2009 Total Dissolved Solids 1230 mg/l
MW-31 12/2/2009 Total Dissolved Solids 1160 mg/l
MW-31 2/9/2010 Total Dissolved Solids 1150 mg/l
MW-31 4/20/2010 Total Dissolved Solids 1220 mg/l
MW-31 9/13/2010 Total Dissolved Solids 1330 mg/l
MW-31 11/9/2010 Total Dissolved Solids 1320 mg/l
MW-31 1/10/2011 Total Dissolved Solids 1240 mg/l
MW-31 2/1/2011 Total Dissolved Solids 1220 mg/l
MW-31 3/14/2011 Total Dissolved Solids 1250 mg/l
MW-31 4/1/2011 Total Dissolved Solids 1370 mg/l
MW-31 5/10/2011 Total Dissolved Solids 1290 mg/l
MW-31 6/20/2011 Total Dissolved Solids 1330 mg/l
MW-31 7/5/2011 Total Dissolved Solids 1280 mg/l
MW-31 8/2/2011 Total Dissolved Solids 1300 mg/l
MW-31 9/6/2011 Total Dissolved Solids 1300 mg/l
MW-31 10/3/2011 Total Dissolved Solids 1320 mg/l
MW-31 11/8/2011 Total Dissolved Solids 1290 mg/l
MW-31 12/12/2011 Total Dissolved Solids 1330 mg/l
MW-31 1/24/2012 Total Dissolved Solids 1360 mg/l
MW-31 2/13/2012 Total Dissolved Solids 1240 mg/l
MW-31 3/13/2012 Total Dissolved Solids 1400 mg/l
MW-31 4/9/2012 Total Dissolved Solids 1380 mg/l
MW-31 5/2/2012 Total Dissolved Solids 1410 mg/l
MW-31 6/29/2012 Total Dissolved Solids 1460 mg/l
MW-31 7/9/2012 Total Dissolved Solids 1400 mg/l
MW-31 8/6/2012 Total Dissolved Solids 1400 mg/l
MW-31 9/18/2012 Total Dissolved Solids 1460 mg/l
MW-31 10/22/2012 Total Dissolved Solids 1320 mg/l
MW-31 11/6/2012 Total Dissolved Solids 1230 mg/l
MW-31 12/18/2012 Total Dissolved Solids 1270 mg/l
MW-31 1/22/2013 Total Dissolved Solids 1270 mg/l
MW-31 2/19/2013 Total Dissolved Solids 1390 mg/l
MW-31 3/19/2013 Total Dissolved Solids 1420 mg/l
MW-31 4/16/2013 Total Dissolved Solids 1260 mg/l
MW-31 5/13/2013 Total Dissolved Solids 1540 mg/l
MW-31 6/24/2013 Total Dissolved Solids 1380 mg/l
MW-31 7/9/2013 Total Dissolved Solids 1510 mg/l
MW-31 8/19/2013 Total Dissolved Solids 1440 mg/l
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 9 of 17
Appendix B-5: MW-31 Data Used for Analysis
Well Date Sampled Parameter Name Report
Result Report Units Qualifier
MW-31 9/17/2013 Total Dissolved Solids 1500 mg/l
MW-31 10/23/2013 Total Dissolved Solids 1460 mg/l
MW-31 11/18/2013 Total Dissolved Solids 1320 mg/l
MW-31 12/17/2013 Total Dissolved Solids 1500 mg/l
MW-31 1/7/2014 Total Dissolved Solids 1510 mg/l
MW-31 2/17/2014 Total Dissolved Solids 1460 mg/l
MW-31 3/10/2014 Total Dissolved Solids 1490 mg/l
MW-31 4/28/2014 Total Dissolved Solids 1440 mg/l
MW-31 5/13/2014 Total Dissolved Solids 1510 mg/l
MW-31 6/2/2014 Total Dissolved Solids 1520 mg/l
MW-31 7/28/2014 Total Dissolved Solids 1400 mg/l
MW-31 8/18/2014 Total Dissolved Solids 1410 mg/l
MW-31 9/3/2014 Total Dissolved Solids 1460 mg/l
MW-31 10/6/2014 Total Dissolved Solids 1420 mg/l
MW-31 11/4/2014 Total Dissolved Solids 1520 mg/l
MW-31 12/9/2014 Total Dissolved Solids 1450 mg/l
MW-31 1/20/2015 Total Dissolved Solids 1540 mg/l
MW-31 2/2/2015 Total Dissolved Solids 1520 mg/l
MW-31 3/3/2015 Total Dissolved Solids 1530 mg/l
MW-31 4/7/2015 Total Dissolved Solids 1680 mg/l
MW-31 5/11/2015 Total Dissolved Solids 1700 mg/l
MW-31 6/23/2015 Total Dissolved Solids 1630 mg/l
MW-31 7/6/2015 Total Dissolved Solids 1440 mg/l
MW-31 8/10/2015 Total Dissolved Solids 1530 mg/l
MW-31 9/15/2015 Total Dissolved Solids 1480 mg/l
MW-31 10/6/2015 Total Dissolved Solids 1540 mg/l
MW-31 11/9/2015 Total Dissolved Solids 1460 mg/l
MW-31 12/8/2015 Total Dissolved Solids 1580 mg/l
MW-31 1/19/2016 Total Dissolved Solids 1560 mg/l
MW-31 2/15/2016 Total Dissolved Solids 1490 mg/l
MW-31 3/2/2016 Total Dissolved Solids 1580 mg/l
MW-31 4/12/2016 Total Dissolved Solids 1710 mg/l
MW-31 5/3/2016 Total Dissolved Solids 1550 mg/l
MW-31 6/15/2016 Total Dissolved Solids 1580 mg/l
MW-31 7/12/2016 Total Dissolved Solids 1610 mg/l
MW-31 8/16/2016 Total Dissolved Solids 1710 mg/l
MW-31 9/13/2016 Total Dissolved Solids 1570 mg/l
MW-31 10/4/2016 Total Dissolved Solids 1670 mg/l
MW-31 11/1/2016 Total Dissolved Solids 1690 mg/l
MW-31 12/5/2016 Total Dissolved Solids 1670 mg/l
MW-31 1/17/2017 Total Dissolved Solids 1730 mg/l
MW-31 2/7/2017 Total Dissolved Solids 1680 mg/l
MW-31 3/6/2017 Total Dissolved Solids 1690 mg/l
MW-31 4/4/2017 Total Dissolved Solids 1660 mg/l
MW-31 5/1/2017 Total Dissolved Solids 1820 mg/l
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 10 of 17
Appendix B-5: MW-31 Data Used for Analysis
Well Date Sampled Parameter Name Report
Result Report Units Qualifier
MW-31 6/5/2017 Total Dissolved Solids 1710 mg/l
MW-31 7/11/2017 Total Dissolved Solids 1830 mg/l
MW-31 8/14/2017 Total Dissolved Solids 1780 mg/l
MW-31 9/11/2017 Total Dissolved Solids 1780 mg/l
MW-31 10/2/2017 Total Dissolved Solids 1760 mg/l
MW-31 11/1/2017 Total Dissolved Solids 1770 mg/l
MW-31 12/4/2017 Total Dissolved Solids 1910 mg/l
MW-31 1/24/2018 Total Dissolved Solids 1800 mg/l
MW-31 2/20/2018 Total Dissolved Solids 1930 mg/l
MW-31 4/17/2018 Total Dissolved Solids 1980 mg/l
MW-31 6/18/2018 Total Dissolved Solids 2010 mg/l
MW-31 7/23/2018 Total Dissolved Solids 2000 mg/l
MW-31 8/10/2018 Total Dissolved Solids 1980 mg/l
MW-31 9/10/2018 Total Dissolved Solids 2100 mg/l
MW-31 10/24/2018 Total Dissolved Solids 2000 mg/l
MW-31 11/13/2018 Total Dissolved Solids 1960 mg/l
MW-31 12/10/2018 Total Dissolved Solids 2090 mg/l
MW-31 1/15/2019 Total Dissolved Solids 2030 mg/l
MW-31 2/12/2019 Total Dissolved Solids 2090 mg/l
MW-31 3/5/2019 Total Dissolved Solids 2160 mg/l
MW-31 4/10/2019 Total Dissolved Solids 2080 mg/l
MW-31 7/15/2019 Total Dissolved Solids 2580 mg/l
MW-31 10/9/2019 Total Dissolved Solids 2280 mg/l
MW-31 11/12/2019 Total Dissolved Solids 2650 mg/l
MW-31 12/3/2019 Total Dissolved Solids 2030 mg/l
MW-31 1/14/2020 Total Dissolved Solids 2220 mg/l
MW-31 2/4/2020 Total Dissolved Solids 2240 mg/l
MW-31 3/10/2020 Total Dissolved Solids 2380 mg/l
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 11 of 17
Appendix B-6: Box Plots
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 12 of 17
:::::::::: C>
E
Q) -~
::i
(f)
::::::::::
1100
1000
900
800
700
600
500
E' 2500 .._....
(/)
"'O
0
(f)
"'O Q) >
0 (/)
(/)
0
ro -0 I-
2000
1500
Sulfate in MW-31
8
0
Percent nondetect: 0%
Min: 436, Mean: 668.86, Max: 1150, Std Dev: 160.92
Upper extreme threshold (Q75 + 3xH): 1389.25
Lower extreme threshold (Q25 -3xH): -101.75
Total Dissolved Solids in MW-31
0 0
0
Percent nondetect: 0%
Min: 1150, Mean: 1555.28, Max: 2650, Std Dev: 313.7
Upper extreme threshold (075 + 3xH): 2890
Lower extreme threshold (Q25 -3xH): 125
P'!-$INTERA
Appendix B-7: Box Plots for MW-31 and Upgradient and Downgradient Wells
Downgradient wells: MW-3A, MW-20, and MW-22.
Upgradient wells: MW-1, MW-18, and MW-19
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 13 of 17
Appendix B-8: Box Plots for SAR Parameters in Groundwater Monitoring Wells
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 14 of 17
Appendix B-11: Timeseries Plots with Events
Appendix B
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 17 of 17
APPENDIX C
Geochemical Analysis for Indicator Parameters in
MW-31
Appendix C-1: Summary of Geochemical Analysis for Indicator Parameters in MW-31
W p r2 p S p
MW-31 Chloride (mg/L)131 0 220 73.9 0.9532 0.0002 No NA NA 7448 0 Increasing Increasing No IncreasingMW-31 Fluoride (mg/L)59 0 0.809 0.103 0.9689 0.1355 Normal 0.540 3.4E-11 -1046 4.04E-12 Decreasing Decreasing No Decreasing
MW-31 Sulfate (mg/L)126 0 669 160.9 0.9468 0.0001 No NA NA 6354 0 Increasing Increasing No Increasing
MW-31 Uranium (µg/L)79 0 9.24 2.24 0.9548 0.0070 No NA NA 2307 0 Increasing Increasing No Increasing
Notes:
σ = sigma N = number of valid data points S = Mann-Kendall statistic
%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.
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
2020 Significant TrendStandard DeviationWellConstituentN
% Non-
Detected
Values
Mean
Least Squares Regression
Trend Analysisa
Mann-Kendall
Trend Analysisb 2017
Significant
Trend?
Background
Report Significant
Trend?
Shapiro-Wilk Test for
Normality Normally or
Lognormally
distributed?
2015
Significant
Trend?
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill
Appendix C-2: Descriptive Statistics of Indicator Parameters in MW-31
Data Set
Analyte Chloride Fluoride Sulfate Uranium Chloride Fluoride Sulfate Uranium Chloride Fluoride Sulfate Uranium Chloride Fluoride Sulfate Uranium Chloride Fluoride Sulfate Uranium
Units mg/L mg/L mg/L ug/L mg/L mg/L mg/L ug/L mg/L mg/L mg/L ug/L mg/L mg/L mg/L ug/L mg/L mg/L mg/L ug/L
% Non-Detects 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
N 131 59 126 79 98 47 99 54 76 41 77 42 50 31 47 32 10 10 10 10
Normally or Lognormallly Distributed?No Yes No No No Yes No Yes No No No Yes Yes No No Yes Yes No No Yes
Mean 219.63 0.81 668.86 9.24 186 0.818 601 7.96 167 0.84 567 7.5 146 0.86 527 7.3 133 0.91 504 7.6
Min. Conc.115 0.53 436 5.77 115 0.605 436 5.77 115 0.61 436 5.8 115 0.73 436 5.8 122 0.80 436 6.6
Max. Conc.381 1.18 1150 14.80 287 0.99 809 10.3 264 1.2 691 9.3 189 1.0 630 9.3 139 1.2 532 9.3
Std. Dev.73.92 0.10 160.92 2.24 47.7 0.080 87.9 1.08 35 0.09 65 0.8 18.1 0.06 34.5 0.74 5 0.12 28 0.75
Range 266.0 0.66 714 9.03 172 0.385 373 4.53 149 0.60 255 3.6 74.0 0.26 194 3.6 17 0.40 96 2.8
Geometric Mean 207.60 0.80 651.61 8.99 180 0.814 594 7.89 163 0.84 564 7.5 145 0.86 526 7.3 133 0.90 504 7.6
Skewness 0.45 0.40 1.04 0.76 0.37 -0.27 0.41 0.43 0.56 0.96 0.40 0.31 0.50 -0.17 0.56 0.73 -1.1 1.9 -1.9 1.2
Q25 149 0.74 537.25 7.34 144 0.763 528 7.14 138 0.78 521 7.0 132 0.83 507 6.9 131 0.85 497 7.2
Median 210 0.81 639.50 8.73 176 0.830 600 7.72 159 0.84 541 7.5 144 0.86 529 7.2 134 0.90 513 7.4
Q75 276 0.87 750.25 10.70 225.75 0.89 665.00 8.75 195 0.90 630 8.0 157 0.90 540 7.7 136 0.90 522 8.0
2017 SAR 2015 SAR 2013 SAR 2008 Background Report2020 SAR
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill
Appendix C-3: Data Used for Statistical Analysis
Well Sample Date Parameter Result Units Qualifier
MW-31 06/22/2005 Chloride 139 mg/l
MW-31 09/22/2005 Chloride 136 mg/l
MW-31 12/14/2005 Chloride 135 mg/l
MW-31 03/22/2006 Chloride 133 mg/l
MW-31 06/21/2006 Chloride 138 mg/l
MW-31 09/13/2006 Chloride 131 mg/l
MW-31 10/25/2006 Chloride 127 mg/l
MW-31 03/15/2007 Chloride 132 mg/l
MW-31 08/27/2007 Chloride 136 mg/l
MW-31 10/24/2007 Chloride 122 mg/l
MW-31 03/19/2008 Chloride 124 mg/l
MW-31 06/03/2008 Chloride 128 mg/l
MW-31 08/04/2008 Chloride 124 mg/l
MW-31 11/11/2008 Chloride 119 mg/l
MW-31 02/03/2009 Chloride 115 mg/l
MW-31 05/13/2009 Chloride 124 mg/l
MW-31 08/24/2009 Chloride 122 mg/l
MW-31 10/14/2009 Chloride 138 mg/l
MW-31 02/09/2010 Chloride 128 mg/l
MW-31 04/20/2010 Chloride 128 mg/l
MW-31 09/13/2010 Chloride 139 mg/l
MW-31 11/09/2010 Chloride 138 mg/l
MW-31 02/01/2011 Chloride 145 mg/l
MW-31 04/01/2011 Chloride 143 mg/l
MW-31 05/10/2011 Chloride 143 mg/l
MW-31 06/20/2011 Chloride 145 mg/l
MW-31 07/05/2011 Chloride 148 mg/l
MW-31 08/02/2011 Chloride 148 mg/l
MW-31 09/06/2011 Chloride 148 mg/l
MW-31 10/03/2011 Chloride 145 mg/l
MW-31 11/08/2011 Chloride 145 mg/l
MW-31 12/12/2011 Chloride 148 mg/l
MW-31 01/24/2012 Chloride 155 mg/l
MW-31 02/13/2012 Chloride 150 mg/l
MW-31 03/13/2012 Chloride 152 mg/l
MW-31 04/09/2012 Chloride 160 mg/l
MW-31 05/02/2012 Chloride 151 mg/l
MW-31 06/18/2012 Chloride 138 mg/l
MW-31 07/09/2012 Chloride 161 mg/l
MW-31 08/06/2012 Chloride 175 mg/l
MW-31 09/18/2012 Chloride 172 mg/l
MW-31 10/22/2012 Chloride 157 mg/l
MW-31 11/06/2012 Chloride 189 mg/l
MW-31 12/18/2012 Chloride 170 mg/l
MW-31 01/22/2013 Chloride 176 mg/l
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 3 of 23
Appendix C-3: Data Used for Statistical Analysis
Well Sample Date Parameter Result Units Qualifier
MW-31 02/19/2013 Chloride 174 mg/l
MW-31 03/19/2013 Chloride 168 mg/l
MW-31 04/16/2013 Chloride 171 mg/l
MW-31 05/13/2013 Chloride 169 mg/l
MW-31 06/24/2013 Chloride 179 mg/l
MW-31 07/09/2013 Chloride 182 mg/l
MW-31 08/19/2013 Chloride 183 mg/l
MW-31 09/17/2013 Chloride 193 mg/l
MW-31 10/23/2013 Chloride 188 mg/l
MW-31 11/18/2013 Chloride 174 mg/l
MW-31 12/17/2013 Chloride 203 mg/l
MW-31 01/07/2014 Chloride 194 mg/l
MW-31 02/17/2014 Chloride 197 mg/l
MW-31 03/10/2014 Chloride 230 mg/l
MW-31 04/28/2014 Chloride 230 mg/l
MW-31 05/13/2014 Chloride 200 mg/l
MW-31 06/02/2014 Chloride 173 mg/l
MW-31 07/28/2014 Chloride 200 mg/l
MW-31 08/18/2014 Chloride 210 mg/l
MW-31 09/03/2014 Chloride 210 mg/l
MW-31 10/06/2014 Chloride 205 mg/l
MW-31 11/04/2014 Chloride 204 mg/l
MW-31 12/09/2014 Chloride 215 mg/l
MW-31 01/20/2015 Chloride 226 mg/l
MW-31 02/02/2015 Chloride 211 mg/l
MW-31 03/03/2015 Chloride 209 mg/l
MW-31 04/07/2015 Chloride 211 mg/l
MW-31 05/11/2015 Chloride 225 mg/l
MW-31 06/23/2015 Chloride 228 mg/l
MW-31 07/06/2015 Chloride 222 mg/l
MW-31 08/10/2015 Chloride 264 mg/l
MW-31 09/15/2015 Chloride 231 mg/l
MW-31 10/06/2015 Chloride 222 mg/l
MW-31 11/09/2015 Chloride 215 mg/l
MW-31 12/08/2015 Chloride 231 mg/l
MW-31 01/19/2016 Chloride 228 mg/l
MW-31 02/15/2016 Chloride 246 mg/l
MW-31 03/02/2016 Chloride 228 mg/l
MW-31 04/12/2016 Chloride 254 mg/l
MW-31 05/03/2016 Chloride 243 mg/l
MW-31 06/15/2016 Chloride 252 mg/l
MW-31 07/12/2016 Chloride 241 mg/l
MW-31 08/16/2016 Chloride 272 mg/l
MW-31 09/13/2016 Chloride 254 mg/l
MW-31 10/04/2016 Chloride 260 mg/l
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 4 of 23
Appendix C-3: Data Used for Statistical Analysis
Well Sample Date Parameter Result Units Qualifier
MW-31 11/01/2016 Chloride 267 mg/l
MW-31 12/05/2016 Chloride 274 mg/l
MW-31 01/17/2017 Chloride 287 mg/l
MW-31 02/07/2017 Chloride 266 mg/l
MW-31 03/06/2017 Chloride 250 mg/l
MW-31 04/04/2017 Chloride 263 mg/l
MW-31 05/01/2017 Chloride 263 mg/l
MW-31 06/05/2017 Chloride 278 mg/l
MW-31 07/11/2017 Chloride 254 mg/l
MW-31 08/14/2017 Chloride 310 mg/l
MW-31 09/11/2017 Chloride 248 mg/l
MW-31 10/02/2017 Chloride 287 mg/l
MW-31 11/01/2017 Chloride 292 mg/l
MW-31 12/04/2017 Chloride 285 mg/l
MW-31 01/24/2018 Chloride 323 mg/l
MW-31 02/20/2018 Chloride 292 mg/l
MW-31 03/05/2018 Chloride 311 mg/l
MW-31 04/17/2018 Chloride 308 mg/l
MW-31 05/14/2018 Chloride 326 mg/l
MW-31 06/18/2018 Chloride 359 mg/l
MW-31 07/23/2018 Chloride 351 mg/l
MW-31 08/10/2018 Chloride 336 mg/l
MW-31 09/10/2018 Chloride 333 mg/l
MW-31 10/24/2018 Chloride 286 mg/l
MW-31 11/13/2018 Chloride 281 mg/l
MW-31 12/10/2018 Chloride 302 mg/l
MW-31 01/15/2019 Chloride 283 mg/l
MW-31 02/12/2019 Chloride 296 mg/l
MW-31 03/05/2019 Chloride 322 mg/l
MW-31 04/10/2019 Chloride 294 mg/l
MW-31 05/07/2019 Chloride 346 mg/l
MW-31 06/03/2019 Chloride 325 mg/l
MW-31 07/15/2019 Chloride 374 mg/l
MW-31 08/05/2019 Chloride 372 mg/l
MW-31 09/23/2019 Chloride 365 mg/l
MW-31 10/09/2019 Chloride 318 mg/l
MW-31 11/12/2019 Chloride 338 mg/l
MW-31 12/03/2019 Chloride 343 mg/l
MW-31 01/14/2020 Chloride 381 mg/l
MW-31 02/04/2020 Chloride 370 mg/l
MW-31 03/10/2020 Chloride 368 mg/l
MW-31 06/22/2005 Fluoride 0.83 mg/l
MW-31 09/22/2005 Fluoride 0.91 mg/l
MW-31 12/14/2005 Fluoride 0.85 mg/l
MW-31 03/22/2006 Fluoride 0.90 mg/l
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 5 of 23
Appendix C-3: Data Used for Statistical Analysis
Well Sample Date Parameter Result Units Qualifier
MW-31 06/21/2006 Fluoride 0.86 mg/l
MW-31 09/13/2006 Fluoride 0.94 mg/l
MW-31 10/25/2006 Fluoride 1.18 mg/l
MW-31 03/15/2007 Fluoride 0.94 mg/l
MW-31 08/27/2007 Fluoride 0.99 mg/l
MW-31 10/24/2007 Fluoride 0.85 mg/l
MW-31 03/19/2008 Fluoride 0.92 mg/l
MW-31 06/03/2008 Fluoride 0.94 mg/l
MW-31 08/04/2008 Fluoride 0.85 mg/l
MW-31 02/03/2009 Fluoride 0.91 mg/l
MW-31 05/13/2009 Fluoride 0.90 mg/l
MW-31 08/24/2009 Fluoride 0.89 mg/l
MW-31 10/14/2009 Fluoride 0.90 mg/l
MW-31 02/09/2010 Fluoride 0.88 mg/l
MW-31 04/20/2010 Fluoride 0.84 mg/l
MW-31 09/13/2010 Fluoride 0.89 mg/l
MW-31 11/09/2010 Fluoride 0.84 mg/l
MW-31 02/01/2011 Fluoride 0.83 mg/l
MW-31 04/01/2011 Fluoride 0.83 mg/l
MW-31 08/02/2011 Fluoride 0.80 mg/l
MW-31 10/03/2011 Fluoride 0.84 mg/l
MW-31 02/13/2012 Fluoride 0.86 mg/l
MW-31 05/02/2012 Fluoride 0.78 mg/l
MW-31 07/09/2012 Fluoride 0.78 mg/l
MW-31 11/06/2012 Fluoride 0.76 mg/l
MW-31 02/19/2013 Fluoride 0.73 mg/l
MW-31 05/13/2013 Fluoride 0.76 mg/l
MW-31 07/09/2013 Fluoride 0.84 mg/l
MW-31 11/18/2013 Fluoride 0.76 mg/l
MW-31 02/17/2014 Fluoride 0.81 mg/l
MW-31 03/10/2014 Fluoride 0.82 mg/l
MW-31 06/02/2014 Fluoride 0.74 mg/l
MW-31 09/03/2014 Fluoride 0.80 mg/l
MW-31 11/04/2014 Fluoride 0.61 mg/l
MW-31 02/02/2015 Fluoride 0.76 mg/l
MW-31 04/07/2015 Fluoride 0.75 mg/l
MW-31 08/10/2015 Fluoride 0.72 mg/l
MW-31 11/09/2015 Fluoride 0.68 mg/l
MW-31 02/15/2016 Fluoride 0.72 mg/l
MW-31 05/03/2016 Fluoride 0.76 mg/l
MW-31 08/16/2016 Fluoride 0.77 mg/l
MW-31 11/01/2016 Fluoride 0.74 mg/l
MW-31 02/07/2017 Fluoride 0.71 mg/l
MW-31 05/01/2017 Fluoride 0.69 mg/l
MW-31 08/14/2017 Fluoride 0.73 mg/l
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 6 of 23
Appendix C-3: Data Used for Statistical Analysis
Well Sample Date Parameter Result Units Qualifier
MW-31 11/01/2017 Fluoride 0.79 mg/l
MW-31 02/20/2018 Fluoride 0.81 mg/l
MW-31 04/17/2018 Fluoride 0.81 mg/l
MW-31 09/10/2018 Fluoride 0.66 mg/l
MW-31 10/24/2018 Fluoride 0.69 mg/l
MW-31 01/15/2019 Fluoride 0.70 mg/l
MW-31 04/10/2019 Fluoride 0.67 mg/l
MW-31 07/15/2019 Fluoride 0.89 mg/l
MW-31 10/09/2019 Fluoride 0.53 mg/l
MW-31 01/14/2020 Fluoride 0.78 mg/l
MW-31 06/22/2005 Sulfate 504 mg/l
MW-31 09/22/2005 Sulfate 436 mg/l D
MW-31 12/14/2005 Sulfate 509 mg/l D
MW-31 03/22/2006 Sulfate 485 mg/l D
MW-31 06/21/2006 Sulfate 522 mg/l D
MW-31 09/13/2006 Sulfate 516 mg/l D
MW-31 10/25/2006 Sulfate 526 mg/l D
MW-31 03/15/2007 Sulfate 516 mg/l D
MW-31 08/27/2007 Sulfate 532 mg/l D
MW-31 10/24/2007 Sulfate 497 mg/l D
MW-31 03/19/2008 Sulfate 521 mg/l D
MW-31 06/03/2008 Sulfate 514 mg/l D
MW-31 08/04/2008 Sulfate 499 mg/l D
MW-31 11/11/2008 Sulfate 541 mg/l D
MW-31 02/03/2009 Sulfate 488 mg/l D
MW-31 05/13/2009 Sulfate 493 mg/l D
MW-31 08/24/2009 Sulfate 460 mg/l D
MW-31 10/14/2009 Sulfate 497 mg/l D
MW-31 02/09/2010 Sulfate 507 mg/l D
MW-31 04/20/2010 Sulfate 522 mg/l D
MW-31 09/13/2010 Sulfate 527 mg/l D
MW-31 11/09/2010 Sulfate 539 mg/l D
MW-31 02/01/2011 Sulfate 538 mg/l D
MW-31 03/14/2011 Sulfate 531 mg/l D
MW-31 04/01/2011 Sulfate 503 mg/l D
MW-31 05/10/2011 Sulfate 512 mg/l D
MW-31 06/20/2011 Sulfate 540 mg/l D
MW-31 07/05/2011 Sulfate 532 mg/l D
MW-31 08/02/2011 Sulfate 537 mg/l D
MW-31 09/06/2011 Sulfate 541 mg/l D
MW-31 10/03/2011 Sulfate 539 mg/l D
MW-31 11/08/2011 Sulfate 552 mg/l D
MW-31 12/12/2011 Sulfate 530 mg/l D
MW-31 01/24/2012 Sulfate 539 mg/l D
MW-31 02/13/2012 Sulfate 538 mg/l D
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 7 of 23
Appendix C-3: Data Used for Statistical Analysis
Well Sample Date Parameter Result Units Qualifier
MW-31 03/13/2012 Sulfate 517 mg/l D
MW-31 04/09/2012 Sulfate 547 mg/l D
MW-31 05/02/2012 Sulfate 532 mg/l D
MW-31 06/18/2012 Sulfate 497 mg/l D
MW-31 07/09/2012 Sulfate 529 mg/l D
MW-31 08/06/2012 Sulfate 571 mg/l D
MW-31 09/18/2012 Sulfate 561 mg/l D
MW-31 10/22/2012 Sulfate 545 mg/l
MW-31 11/06/2012 Sulfate 557 mg/l
MW-31 12/18/2012 Sulfate 664 mg/l
MW-31 01/22/2013 Sulfate 611 mg/l
MW-31 02/19/2013 Sulfate 644 mg/l
MW-31 03/19/2013 Sulfate 611 mg/l
MW-31 04/16/2013 Sulfate 668 mg/l
MW-31 05/13/2013 Sulfate 630 mg/l
MW-31 06/24/2013 Sulfate 659 mg/l
MW-31 07/09/2013 Sulfate 659 mg/l
MW-31 08/19/2013 Sulfate 656 mg/l
MW-31 09/17/2013 Sulfate 666 mg/l
MW-31 10/23/2013 Sulfate 637 mg/l
MW-31 11/18/2013 Sulfate 609 mg/l
MW-31 12/17/2013 Sulfate 656 mg/l
MW-31 01/07/2014 Sulfate 558 mg/l
MW-31 02/17/2014 Sulfate 480 mg/l
MW-31 03/10/2014 Sulfate 681 mg/l
MW-31 04/28/2014 Sulfate 527 mg/l
MW-31 05/13/2014 Sulfate 639 mg/l
MW-31 06/02/2014 Sulfate 555 mg/l
MW-31 07/28/2014 Sulfate 600 mg/l
MW-31 08/18/2014 Sulfate 620 mg/l
MW-31 09/03/2014 Sulfate 560 mg/l
MW-31 10/06/2014 Sulfate 606 mg/l
MW-31 11/04/2014 Sulfate 639 mg/l
MW-31 12/09/2014 Sulfate 687 mg/l
MW-31 01/20/2015 Sulfate 669 mg/l
MW-31 02/02/2015 Sulfate 623 mg/l
MW-31 03/03/2015 Sulfate 616 mg/l
MW-31 04/07/2015 Sulfate 642 mg/l
MW-31 05/11/2015 Sulfate 668 mg/l
MW-31 06/23/2015 Sulfate 691 mg/l
MW-31 07/06/2015 Sulfate 684 mg/l
MW-31 08/10/2015 Sulfate 640 mg/l
MW-31 09/15/2015 Sulfate 638 mg/l
MW-31 10/06/2015 Sulfate 655 mg/l
MW-31 11/09/2015 Sulfate 646 mg/l
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 8 of 23
Appendix C-3: Data Used for Statistical Analysis
Well Sample Date Parameter Result Units Qualifier
MW-31 12/08/2015 Sulfate 690 mg/l
MW-31 01/19/2016 Sulfate 675 mg/l
MW-31 02/15/2016 Sulfate 631 mg/l
MW-31 03/02/2016 Sulfate 654 mg/l
MW-31 04/12/2016 Sulfate 715 mg/l
MW-31 05/03/2016 Sulfate 699 mg/l
MW-31 06/15/2016 Sulfate 748 mg/l
MW-31 07/12/2016 Sulfate 712 mg/l
MW-31 08/16/2016 Sulfate 766 mg/l
MW-31 09/13/2016 Sulfate 703 mg/l
MW-31 10/04/2016 Sulfate 720 mg/l
MW-31 11/01/2016 Sulfate 752 mg/l
MW-31 12/05/2016 Sulfate 748 mg/l
MW-31 01/17/2017 Sulfate 809 mg/l
MW-31 02/07/2017 Sulfate 751 mg/l
MW-31 03/06/2017 Sulfate 741 mg/l
MW-31 04/04/2017 Sulfate 758 mg/l
MW-31 05/01/2017 Sulfate 741 mg/l
MW-31 06/05/2017 Sulfate 808 mg/l
MW-31 07/11/2017 Sulfate 747 mg/l
MW-31 08/14/2017 Sulfate 916 mg/l
MW-31 09/11/2017 Sulfate 762 mg/l
MW-31 10/02/2017 Sulfate 823 mg/l
MW-31 11/01/2017 Sulfate 847 mg/l
MW-31 12/04/2017 Sulfate 825 mg/l
MW-31 01/24/2018 Sulfate 813 mg/l
MW-31 02/20/2018 Sulfate 835 mg/l
MW-31 04/17/2018 Sulfate 857 mg/l
MW-31 06/18/2018 Sulfate 976 mg/l
MW-31 07/23/2018 Sulfate 857 mg/l
MW-31 08/10/2018 Sulfate 841 mg/l
MW-31 09/10/2018 Sulfate 893 mg/l
MW-31 10/24/2018 Sulfate 950 mg/l
MW-31 11/13/2018 Sulfate 841 mg/l
MW-31 12/10/2018 Sulfate 905 mg/l
MW-31 01/15/2019 Sulfate 851 mg/l
MW-31 02/12/2019 Sulfate 893 mg/l
MW-31 03/05/2019 Sulfate 953 mg/l
MW-31 04/10/2019 Sulfate 917 mg/l
MW-31 07/15/2019 Sulfate 1150 mg/l
MW-31 10/09/2019 Sulfate 1010 mg/l
MW-31 11/12/2019 Sulfate 990 mg/l
MW-31 12/03/2019 Sulfate 1020 mg/l
MW-31 01/14/2020 Sulfate 1120 mg/l
MW-31 02/04/2020 Sulfate 1150 mg/l
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 9 of 23
Appendix C-3: Data Used for Statistical Analysis
Well Sample Date Parameter Result Units Qualifier
MW-31 03/10/2020 Sulfate 1080 mg/l
MW-31 06/22/2005 Uranium 6.56 µg/l
MW-31 09/22/2005 Uranium 7.25 µg/l
MW-31 12/14/2005 Uranium 7.27 µg/l
MW-31 03/22/2006 Uranium 8.04 µg/l
MW-31 06/21/2006 Uranium 9.32 µg/l
MW-31 09/13/2006 Uranium 8.03 µg/l
MW-31 10/25/2006 Uranium 7.71 µg/l
MW-31 03/15/2007 Uranium 7.60 µg/l
MW-31 08/27/2007 Uranium 7.18 µg/l
MW-31 10/24/2007 Uranium 7.20 µg/l
MW-31 03/19/2008 Uranium 7.02 µg/l
MW-31 06/03/2008 Uranium 6.95 µg/l
MW-31 08/04/2008 Uranium 6.77 µg/l
MW-31 11/11/2008 Uranium 6.35 µg/l
MW-31 02/03/2009 Uranium 7.08 µg/l
MW-31 05/13/2009 Uranium 6.76 µg/l
MW-31 08/24/2009 Uranium 6.97 µg/l
MW-31 10/14/2009 Uranium 6.97 µg/l
MW-31 02/09/2010 Uranium 7.12 µg/l
MW-31 04/20/2010 Uranium 6.74 µg/l
MW-31 09/13/2010 Uranium 7.23 µg/l
MW-31 11/09/2010 Uranium 6.72 µg/l
MW-31 02/01/2011 Uranium 5.77 µg/l
MW-31 04/01/2011 Uranium 6.81 µg/l
MW-31 08/02/2011 Uranium 7.68 µg/l
MW-31 10/03/2011 Uranium 8.87 µg/l
MW-31 02/13/2012 Uranium 7.96 µg/l
MW-31 05/02/2012 Uranium 7.34 µg/l
MW-31 07/09/2012 Uranium 8.17 µg/l
MW-31 11/06/2012 Uranium 8.73 µg/l
MW-31 02/19/2013 Uranium 7.33 µg/l
MW-31 05/13/2013 Uranium 7.63 µg/l
MW-31 07/09/2013 Uranium 7.90 µg/l
MW-31 11/18/2013 Uranium 9.03 µg/l
MW-31 02/17/2014 Uranium 7.65 µg/l
MW-31 03/10/2014 Uranium 7.96 µg/l
MW-31 06/02/2014 Uranium 7.72 µg/l
MW-31 09/03/2014 Uranium 8.40 µg/l
MW-31 11/04/2014 Uranium 7.71 µg/l
MW-31 02/02/2015 Uranium 8.00 µg/l
MW-31 04/07/2015 Uranium 8.07 µg/l
MW-31 08/10/2015 Uranium 8.76 µg/l
MW-31 11/09/2015 Uranium 8.72 µg/l
MW-31 02/15/2016 Uranium 8.41 µg/l
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 10 of 23
Appendix C-3: Data Used for Statistical Analysis
Well Sample Date Parameter Result Units Qualifier
MW-31 05/03/2016 Uranium 9.05 µg/l
MW-31 08/16/2016 Uranium 9.41 µg/l
MW-31 11/01/2016 Uranium 9.56 µg/l
MW-31 12/05/2016 Uranium 10.30 µg/l
MW-31 01/17/2017 Uranium 9.03 µg/l
MW-31 02/07/2017 Uranium 9.92 µg/l
MW-31 03/06/2017 Uranium 9.62 µg/l
MW-31 04/04/2017 Uranium 10.10 µg/l
MW-31 05/01/2017 Uranium 9.62 µg/l
MW-31 06/05/2017 Uranium 9.89 µg/l
MW-31 07/11/2017 Uranium 10.50 µg/l
MW-31 08/14/2017 Uranium 10.10 µg/l
MW-31 09/11/2017 Uranium 9.74 µg/l
MW-31 10/02/2017 Uranium 10.90 µg/l
MW-31 11/01/2017 Uranium 9.31 µg/l
MW-31 12/04/2017 Uranium 10.40 µg/l
MW-31 01/24/2018 Uranium 11.40 µg/l
MW-31 02/20/2018 Uranium 11.20 µg/l
MW-31 03/05/2018 Uranium 11.40 µg/l
MW-31 04/17/2018 Uranium 11.50 µg/l
MW-31 05/14/2018 Uranium 11.50 µg/l
MW-31 06/18/2018 Uranium 12.90 µg/l
MW-31 07/23/2018 Uranium 12.30 µg/l
MW-31 08/10/2018 Uranium 11.70 µg/l
MW-31 09/10/2018 Uranium 11.00 µg/l
MW-31 10/24/2018 Uranium 11.60 µg/l
MW-31 11/13/2018 Uranium 13.20 µg/l
MW-31 12/10/2018 Uranium 12.70 µg/l
MW-31 01/15/2019 Uranium 13.20 µg/l
MW-31 02/12/2019 Uranium 13.60 µg/l
MW-31 03/05/2019 Uranium 12.50 µg/l
MW-31 04/10/2019 Uranium 13.60 µg/l
MW-31 07/15/2019 Uranium 14.30 µg/l
MW-31 10/09/2019 Uranium 14.40 µg/l
MW-31 01/14/2020 Uranium 14.80 µg/l
Notes: D = field duplicate
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 11 of 23
Appendix C-4: Indicator Parameter Data Removed from Analysis
Reason Location ID Date Sampled Parameter Name Report Result Report Units
Extreme (Low)MW-31 11/11/2008 Fluoride 0.32 mg/L
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill
Appendix C-5: Box Plots for Indicator Parameters in MW-31
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 13 of 23
350
..-.. ::::: O> 300 .s
Q) 250 "'O ·;::
0
..c (.) 200
150
1.2
1.1
...-.. 1.0 ::::: O> .s 0 .9 Q)
"'O ·;:: 0 .8 0 ::i
LL 0.7
0.6
0 .5
Chloride in MW-31
Percent nondetect: 0%
o Outlier
• Extreme
Min: 115, Mean: 219.63, Max: 381 , Std Dev: 73.92
Upper extreme threshold (Q75 + 3xH): 657
Lower extreme threshold (Q25 -3xH): -232
Fluoride in MW-31
0
0
Percent nondetect: 0%
o Outlier
• Extreme
Min: 0.526, Mean: 0.81 , Max: 1.183244, Std Dev: 0.1
Upper extreme threshold (Q75 + 3xH): 1.2525
Lower extreme threshold (Q25 -3xH): 0.36
---=2#e lNTERA
Appendix C-5: Box Plots for Indicator Parameters in MW-31
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 14 of 23
1100
1000
:::::::: 900 O>
E .__.
800 Q) -~ 700 ::::J Cf) 600
500
14
..--... :::::::: 12 O> ::::J .__.
E 10 ::::J
c:: ro ,__
:::) 8
6
Sulfate in MW-31
8
0
Percent nondetect: 0%
o Outlier
• Extreme
Min: 436, Mean: 668.86, Max: 1150, Std Dev: 160.92
Upper extrema threshold (075 + 3xH): 1389.25
Lower extrema threshold (025 -3xH): -1 01.75
Uranium in MW-31
Percent nondetect: 0%
o Outlier
• Extreme
Min: 5.77, Mean: 9.24, Max: 14.8, Std Dev: 2.24
Upper extreme threshold (075 + 3xH): 20.795
Lower extreme threshold (025 -3xH): -2.76
---=2#e lNTERA
Appendix C-6: Box Plots for Indicator Parameters in MW-31 and Upgradient and Downgradient Wells
Downgradient wells: MW-3A, MW-20, and MW-22.
Upgradient wells: MW-1, MW-18, and MW-19
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 15 of 23
Appendix C-6: Box Plots for Indicator Parameters in MW-31 and Upgradient and Downgradient Wells
Downgradient wells: MW-3A, MW-20, and MW-22.
Upgradient wells: MW-1, MW-18, and MW-19
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 16 of 23
Appendix C-9: Time Series Plots and Linear Regressions for Indicator Parameters in MW-31
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 21 of 23
-14 ::::::: O> :::s 12
E 10 :::s
c ro 8 ..... => 6
Uranium in MW-31
-d:>v
~eft;
-~ 0 0 0 o 00 oa:>o
o ooo cJS> BoocfP o -o <oo
0 00 CD 0:0 Oo<D'b <t> 0 0 0
I
2005
I
2010
I
2015
Sample Date
I
2020
---=2#e lNTERA
Appendix C-10: Time Series with Events
Appendix C
Source Assesment Report for MW-31
White Mesa Uranium Mill Page 23 of 23
Sulfate in MW-31
• •
11 00 • -•
1000 -•
, • •• -:::::::: 900 O>
-• ....
E ._...
800 Q) -~
::i 700 (/)
600
... , ..
-...... .....
-.. ._,., ....... • t• t ··~· •• ::~ . --•
500 • • _. -41. •4 •• . . . ,. ... • .... 4 -.-• -• • ••• • • • •
I I I
2005 2010 2015 2020
Sample Date
Uranium in MW-31
• •• 14 ---• • • • ........... 12 :::::: O> ::I .__,
-., ..
• • E
::I 10 ·c ro ..._
=>
8
••• -•••• ·-· • • • • ~ • • • •• • • -•• •• • • -•• • • .4 •• .. -.. . -·· • • •
• • • • •• • -• 6
I I I I
2005 2010 2015 2020
2010-02-01 Monthly sampling
2011-05-03 Well redevelopment
2012-10-01 Lab change
Sample Date
2013-09-27 Peak groundwater elevation
2014-06-01 Five new ch loroform pumping wells brought online
---=2#e lNTERA
APPENDIX D
Geochemical Analysis for pH in
MW-31
Appendix D-1: pH Analysis Summary Table
W p
Normally or
Lognormally
distributed?
S p Trend
MW-31 pH 142 0 7.02 6.16 8.50 0.37 0.9616 0.0005 No -1605 0.0023 Decreasing Yes
Notes:
N = number of valid data points p = probability
W = Shapiro Wilk test value S = Mann-Kendall statistic
Shapiro-Wilk Test for Normality
Significant
Trend
Mann Kendall
Trend Analysis
Standard
DeviationWellConstituentN
% Non-
Detected
Values
Mean Minimum Maximum
Appendix D Source Assessment Report for MW-31White Mesa Uranium Mill
Appendix D-2: Field pH Measurements Used for pH Analysis
Location ID Field Parameter Date Measured Field Measurement
MW-31 pH 6/22/2005 7.27
MW-31 pH 9/22/2005 7.19
MW-31 pH 12/14/2005 7.30
MW-31 pH 3/22/2006 7.33
MW-31 pH 6/21/2006 7.15
MW-31 pH 9/13/2006 7.31
MW-31 pH 10/25/2006 7.26
MW-31 pH 3/15/2007 7.41
MW-31 pH 8/27/2007 7.08
MW-31 pH 10/24/2007 6.97
MW-31 pH 3/19/2008 6.95
MW-31 pH 6/3/2008 7.20
MW-31 pH 8/4/2008 7.20
MW-31 pH 11/10/2008 7.42
MW-31 pH 2/3/2009 7.30
MW-31 pH 5/13/2009 7.12
MW-31 pH 8/10/2009 7.34
MW-31 pH 8/24/2009 7.18
MW-31 pH 10/14/2009 7.05
MW-31 pH 12/2/2009 7.17
MW-31 pH 2/9/2010 6.96
MW-31 pH 4/20/2010 7.38
MW-31 pH 5/21/2010 6.95
MW-31 pH 6/15/2010 7.01
MW-31 pH 7/21/2010 7.80
MW-31 pH 8/24/2010 7.10
MW-31 pH 9/13/2010 7.66
MW-31 pH 9/21/2010 7.13
MW-31 pH 10/19/2010 6.92
MW-31 pH 11/9/2010 6.98
MW-31 pH 12/14/2010 6.95
MW-31 pH 1/10/2011 6.65
MW-31 pH 2/1/2011 7.21
MW-31 pH 3/14/2011 7.43
MW-31 pH 4/1/2011 7.01
MW-31 pH 5/10/2011 6.73
MW-31 pH 6/20/2011 6.16
MW-31 pH 7/5/2011 6.64
MW-31 pH 8/2/2011 6.67
MW-31 pH 9/6/2011 7.03
MW-31 pH 10/3/2011 7.28
MW-31 pH 11/8/2011 7.01
MW-31 pH 11/29/2011 7.34
MW-31 pH 12/12/2011 7.46
Appendix D
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 2 of 8
Appendix D-2: Field pH Measurements Used for pH Analysis
Location ID Field Parameter Date Measured Field Measurement
MW-31 pH 1/24/2012 6.78
MW-31 pH 2/13/2012 7.37
MW-31 pH 4/9/2012 7.14
MW-31 pH 5/2/2012 7.19
MW-31 pH 7/9/2012 7.53
MW-31 pH 8/6/2012 6.96
MW-31 pH 9/18/2012 7.10
MW-31 pH 10/22/2012 7.05
MW-31 pH 11/6/2012 7.04
MW-31 pH 12/18/2012 7.10
MW-31 pH 1/22/2013 6.90
MW-31 pH 2/19/2013 7.31
MW-31 pH 3/19/2013 7.22
MW-31 pH 4/16/2013 6.37
MW-31 pH 5/13/2013 7.92
MW-31 pH 6/24/2013 7.12
MW-31 pH 7/9/2013 6.98
MW-31 pH 8/19/2013 7.47
MW-31 pH 9/17/2013 7.09
MW-31 pH 10/23/2013 7.39
MW-31 pH 11/18/2013 6.99
MW-31 pH 12/17/2013 7.23
MW-31 pH 1/7/2014 7.11
MW-31 pH 2/17/2014 6.45
MW-31 pH 3/10/2014 6.53
MW-31 pH 4/28/2014 7.45
MW-31 pH 5/13/2014 6.83
MW-31 pH 6/2/2014 8.50
MW-31 pH 7/28/2014 6.92
MW-31 pH 8/18/2014 7.82
MW-31 pH 9/3/2014 7.11
MW-31 pH 10/6/2014 7.01
MW-31 pH 11/4/2014 6.69
MW-31 pH 12/9/2014 6.75
MW-31 pH 1/20/2015 6.47
MW-31 pH 2/2/2015 6.42
MW-31 pH 3/3/2015 6.35
MW-31 pH 4/7/2015 6.67
MW-31 pH 5/11/2015 6.74
MW-31 pH 6/1/2015 7.23
MW-31 pH 6/23/2015 7.15
MW-31 pH 7/6/2015 7.28
MW-31 pH 8/10/2015 6.80
MW-31 pH 9/15/2015 6.73
Appendix D
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 3 of 8
Appendix D-2: Field pH Measurements Used for pH Analysis
Location ID Field Parameter Date Measured Field Measurement
MW-31 pH 10/6/2015 6.47
MW-31 pH 11/9/2015 6.36
MW-31 pH 12/8/2015 6.70
MW-31 pH 1/19/2016 7.04
MW-31 pH 2/15/2016 7.27
MW-31 pH 3/2/2016 6.85
MW-31 pH 4/12/2016 6.93
MW-31 pH 5/3/2016 6.48
MW-31 pH 6/15/2016 7.09
MW-31 pH 7/12/2016 6.49
MW-31 pH 8/16/2016 6.92
MW-31 pH 9/13/2016 6.35
MW-31 pH 10/4/2016 7.05
MW-31 pH 11/1/2016 6.97
MW-31 pH 12/5/2016 6.80
MW-31 pH 1/17/2017 6.75
MW-31 pH 2/7/2017 6.20
MW-31 pH 3/6/2017 6.39
MW-31 pH 4/4/2017 6.16
MW-31 pH 5/1/2017 6.94
MW-31 pH 6/5/2017 6.96
MW-31 pH 7/11/2017 6.97
MW-31 pH 8/14/2017 6.29
MW-31 pH 9/11/2017 6.34
MW-31 pH 10/2/2017 7.01
MW-31 pH 11/1/2017 7.07
MW-31 pH 12/4/2017 7.54
MW-31 pH 1/24/2018 6.32
MW-31 pH 2/20/2018 7.35
MW-31 pH 3/5/2018 6.92
MW-31 pH 4/17/2018 6.75
MW-31 pH 5/14/2018 7.08
MW-31 pH 6/18/2018 7.21
MW-31 pH 7/23/2018 7.17
MW-31 pH 8/10/2018 7.02
MW-31 pH 9/10/2018 7.18
MW-31 pH 10/24/2018 6.59
MW-31 pH 11/13/2018 7.10
MW-31 pH 12/10/2018 7.03
MW-31 pH 1/15/2019 6.86
MW-31 pH 2/12/2019 6.24
MW-31 pH 3/5/2019 7.20
MW-31 pH 4/10/2019 7.30
MW-31 pH 5/7/2019 7.04
Appendix D
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 4 of 8
Appendix D-2: Field pH Measurements Used for pH Analysis
Location ID Field Parameter Date Measured Field Measurement
MW-31 pH 6/3/2019 7.04
MW-31 pH 7/15/2019 6.82
MW-31 pH 8/5/2019 7.44
MW-31 pH 9/23/2019 7.24
MW-31 pH 10/9/2019 7.23
MW-31 pH 11/12/2019 7.33
MW-31 pH 12/3/2019 7.30
MW-31 pH 1/14/2020 6.80
MW-31 pH 2/4/2020 7.24
MW-31 pH 3/10/2020 7.15
Appendix D
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 5 of 8
Appendix D-3: Box Plot for pH
Appendix D
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 6 of 8
8.5
8.0 .-.. (j) ::: c:: 7.5 ::>
I
Q. -7.0 I
Q.
6.5
pH in MW-31
0
0
Percent nondetect: 0%
Min: 6.16, Mean: 7.02, Max: 8.5, Std Dev: 0.37
Upper extreme threshold (075 + 3xH): 8.505
Lower extreme threshold (025 -3xH): 5.53
---=2#e lNTERA
APPENDIX E
Mass Balance in MW-31
Dilution Factors and Predicted Fluoride and Uranium Concentrations
Fluoride Uranium Chloride Sulfate
(mg/L) (ug/L)  (mg/L) (mg/L)
MW‐31 concentration (04/06/2020) 0.632 15.5 376 1130
Cell 1 concentration (2003 ‐ 2019 average) 2240 398000 24217 169662
Dilution factor (DF) = Cmw31/Ccell1 2.82E‐04 3.89E‐05 1.55E‐02 6.66E‐03
Fluoride Based 
on Uranium 
Dilution
Fluoride Based 
on Chloride 
Dilution
Fluoride Based 
on Sulfate 
Dilution
(mg/L) (mg/L) (mg/L)
Predicted diluted fluoride (Ccell1 F x DF)_0.087 35 15
Fluoride Uranium Chloride Sulfate
(mg/L) (ug/L)  (mg/L) (mg/L)
MW‐31 concentration (04/06/2020) 0.632 15.5 376 1130
Cell 1 concentration (2003 ‐ 2019 average) 2240 398000 24217 169662
Dilution factor (DF) = Cmw31/Ccell1 2.82E‐04 3.89E‐05 1.55E‐02 6.66E‐03
Uranium 
Based on 
Fluoride 
Dilution
Uranium 
Based on 
Chloride 
Dilution
Uranium 
Based on 
Sulfate 
Dilution
(ug/L) (ug/L) (ug/L)
Predicted diluted fluoride (Ccell1 U x DF)112 6,179 2,651
NOTES:
C mw31  = latest concentration at MW‐31
C cell1  = average concentration in Cell 1
ug/L = micrograms per liter
mg/L = milligrams per liter
Appendix E 
Source Assessment Report for MW‐31
White Mesa Uranium Mill
APPENDIX F
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 F. 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 G
Flowsheet Analysis for Post-Inflection Data
Appendix G-1: Descriptive Statistics for Modified GWCL Data Set and All Data
Data Set GWCL Subset
Post May 2014
GWCL Subset
Post Sep. 2012
ALL 2020 SAR
Data
GWCL Subset
Post May 2014
GWCL Subset
Post Sep. 2012
ALL 2020 SAR
Data
Analyte Sulfate Sulfate Sulfate Total Dissolved
Solids
Total
Dissolved
Solids
Total
Dissolved
Solids
Units mg/L mg/L mg/L mg/L mg/L mg/L
% Non-Detects 0 0 0 0 0 0
N 65 85 126 65 85 127
Distribution normal or
lognormal
Not
normal or
lognormal
Not
normal or
lognormal
Not
normal or
lognormal
Not
normal or
lognormal
Not
normal or
lognormal
Mean 780 741 669 1776 1689 1555
Min. Conc.555 480 436 1400 1230 1150
Max. Conc.1150 1150 1150 2650 2650 2650
Std. Dev.145.8 148.2 160.9 288 300 314
Range 595 670 714 1250 1420 1500
Geometric Mean 768 728 652 1754 1665 1527
Skewness 0.80 0.93 1.04 1.00 1.04 1.18
Q25 668 639 537 1540 1480 1310
Median 748 691 640 1700 1580 1480
Q75 857 835 750 1980 1830 1705
ALL 2020 SAR Data = All data with extremes removed
GWCL Subset Post 2012 = All data post September 2012
GWCL Subset Post 2014 = All data post May 2014
Appendix G
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 1 of 13
Appendix G-2: MW-31 Data Used for Analysis
Well Date
Sampled Parameter Name Report Result Report Units
MW-31 6/22/2005 Sulfate 504 mg/l
MW-31 9/22/2005 Sulfate 436 mg/l
MW-31 12/14/2005 Sulfate 509 mg/l
MW-31 3/22/2006 Sulfate 485 mg/l
MW-31 6/21/2006 Sulfate 522 mg/l
MW-31 9/13/2006 Sulfate 516 mg/l
MW-31 10/25/2006 Sulfate 526 mg/l
MW-31 3/15/2007 Sulfate 516 mg/l
MW-31 8/27/2007 Sulfate 532 mg/l
MW-31 10/24/2007 Sulfate 497 mg/l
MW-31 3/19/2008 Sulfate 521 mg/l
MW-31 6/3/2008 Sulfate 514 mg/l
MW-31 8/4/2008 Sulfate 499 mg/l
MW-31 11/11/2008 Sulfate 541 mg/l
MW-31 2/3/2009 Sulfate 488 mg/l
MW-31 5/13/2009 Sulfate 493 mg/l
MW-31 8/24/2009 Sulfate 460 mg/l
MW-31 10/14/2009 Sulfate 497 mg/l
MW-31 2/9/2010 Sulfate 507 mg/l
MW-31 4/20/2010 Sulfate 522 mg/l
MW-31 9/13/2010 Sulfate 527 mg/l
MW-31 11/9/2010 Sulfate 539 mg/l
MW-31 2/1/2011 Sulfate 538 mg/l
MW-31 3/14/2011 Sulfate 531 mg/l
MW-31 4/1/2011 Sulfate 503 mg/l
MW-31 5/10/2011 Sulfate 512 mg/l
MW-31 6/20/2011 Sulfate 540 mg/l
MW-31 7/5/2011 Sulfate 532 mg/l
MW-31 8/2/2011 Sulfate 537 mg/l
MW-31 9/6/2011 Sulfate 541 mg/l
MW-31 10/3/2011 Sulfate 539 mg/l
MW-31 11/8/2011 Sulfate 552 mg/l
MW-31 12/12/2011 Sulfate 530 mg/l
MW-31 1/24/2012 Sulfate 539 mg/l
MW-31 2/13/2012 Sulfate 538 mg/l
MW-31 3/13/2012 Sulfate 517 mg/l
MW-31 4/9/2012 Sulfate 547 mg/l
MW-31 5/2/2012 Sulfate 532 mg/l
MW-31 6/18/2012 Sulfate 497 mg/l
MW-31 7/9/2012 Sulfate 529 mg/l
MW-31 8/6/2012 Sulfate 571 mg/l
MW-31 9/18/2012 Sulfate 561 mg/l
MW-31 10/22/2012 Sulfate 545 mg/l
MW-31 11/6/2012 Sulfate 557 mg/l
MW-31 12/18/2012 Sulfate 664 mg/l
Appendix G
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 2 of 13
Appendix G-2: MW-31 Data Used for Analysis
Well Date
Sampled Parameter Name Report Result Report Units
MW-31 1/22/2013 Sulfate 611 mg/l
MW-31 2/19/2013 Sulfate 644 mg/l
MW-31 3/19/2013 Sulfate 611 mg/l
MW-31 4/16/2013 Sulfate 668 mg/l
MW-31 5/13/2013 Sulfate 630 mg/l
MW-31 6/24/2013 Sulfate 659 mg/l
MW-31 7/9/2013 Sulfate 659 mg/l
MW-31 8/19/2013 Sulfate 656 mg/l
MW-31 9/17/2013 Sulfate 666 mg/l
MW-31 10/23/2013 Sulfate 637 mg/l
MW-31 11/18/2013 Sulfate 609 mg/l
MW-31 12/17/2013 Sulfate 656 mg/l
MW-31 1/7/2014 Sulfate 558 mg/l
MW-31 2/17/2014 Sulfate 480 mg/l
MW-31 3/10/2014 Sulfate 681 mg/l
MW-31 4/28/2014 Sulfate 527 mg/l
MW-31 5/13/2014 Sulfate 639 mg/l
MW-31 6/2/2014 Sulfate 555 mg/l
MW-31 7/28/2014 Sulfate 600 mg/l
MW-31 8/18/2014 Sulfate 620 mg/l
MW-31 9/3/2014 Sulfate 560 mg/l
MW-31 10/6/2014 Sulfate 606 mg/l
MW-31 11/4/2014 Sulfate 639 mg/l
MW-31 12/9/2014 Sulfate 687 mg/l
MW-31 1/20/2015 Sulfate 669 mg/l
MW-31 2/2/2015 Sulfate 623 mg/l
MW-31 3/3/2015 Sulfate 616 mg/l
MW-31 4/7/2015 Sulfate 642 mg/l
MW-31 5/11/2015 Sulfate 668 mg/l
MW-31 6/23/2015 Sulfate 691 mg/l
MW-31 7/6/2015 Sulfate 684 mg/l
MW-31 8/10/2015 Sulfate 640 mg/l
MW-31 9/15/2015 Sulfate 638 mg/l
MW-31 10/6/2015 Sulfate 655 mg/l
MW-31 11/9/2015 Sulfate 646 mg/l
MW-31 12/8/2015 Sulfate 690 mg/l
MW-31 1/19/2016 Sulfate 675 mg/l
MW-31 2/15/2016 Sulfate 631 mg/l
MW-31 3/2/2016 Sulfate 654 mg/l
MW-31 4/12/2016 Sulfate 715 mg/l
MW-31 5/3/2016 Sulfate 699 mg/l
MW-31 6/15/2016 Sulfate 748 mg/l
MW-31 7/12/2016 Sulfate 712 mg/l
MW-31 8/16/2016 Sulfate 766 mg/l
MW-31 9/13/2016 Sulfate 703 mg/l
MW-31 10/4/2016 Sulfate 720 mg/l
Appendix G
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 3 of 13
Appendix G-2: MW-31 Data Used for Analysis
Well Date
Sampled Parameter Name Report Result Report Units
MW-31 11/1/2016 Sulfate 752 mg/l
MW-31 12/5/2016 Sulfate 748 mg/l
MW-31 1/17/2017 Sulfate 809 mg/l
MW-31 2/7/2017 Sulfate 751 mg/l
MW-31 3/6/2017 Sulfate 741 mg/l
MW-31 4/4/2017 Sulfate 758 mg/l
MW-31 5/1/2017 Sulfate 741 mg/l
MW-31 6/5/2017 Sulfate 808 mg/l
MW-31 7/11/2017 Sulfate 747 mg/l
MW-31 8/14/2017 Sulfate 916 mg/l
MW-31 9/11/2017 Sulfate 762 mg/l
MW-31 10/2/2017 Sulfate 823 mg/l
MW-31 11/1/2017 Sulfate 847 mg/l
MW-31 12/4/2017 Sulfate 825 mg/l
MW-31 1/24/2018 Sulfate 813 mg/l
MW-31 2/20/2018 Sulfate 835 mg/l
MW-31 4/17/2018 Sulfate 857 mg/l
MW-31 6/18/2018 Sulfate 976 mg/l
MW-31 7/23/2018 Sulfate 857 mg/l
MW-31 8/10/2018 Sulfate 841 mg/l
MW-31 9/10/2018 Sulfate 893 mg/l
MW-31 10/24/2018 Sulfate 950 mg/l
MW-31 11/13/2018 Sulfate 841 mg/l
MW-31 12/10/2018 Sulfate 905 mg/l
MW-31 1/15/2019 Sulfate 851 mg/l
MW-31 2/12/2019 Sulfate 893 mg/l
MW-31 3/5/2019 Sulfate 953 mg/l
MW-31 4/10/2019 Sulfate 917 mg/l
MW-31 7/15/2019 Sulfate 1150 mg/l
MW-31 10/9/2019 Sulfate 1010 mg/l
MW-31 11/12/2019 Sulfate 990 mg/l
MW-31 12/3/2019 Sulfate 1020 mg/l
MW-31 1/14/2020 Sulfate 1120 mg/l
MW-31 2/4/2020 Sulfate 1150 mg/l
MW-31 3/10/2020 Sulfate 1080 mg/l
MW-31 6/22/2005 Total Dissolved Solids 1290 mg/l
MW-31 9/22/2005 Total Dissolved Solids 1280 mg/l
MW-31 12/14/2005 Total Dissolved Solids 1290 mg/l
MW-31 3/22/2006 Total Dissolved Solids 1280 mg/l
MW-31 6/21/2006 Total Dissolved Solids 1300 mg/l
MW-31 9/13/2006 Total Dissolved Solids 1320 mg/l
MW-31 10/25/2006 Total Dissolved Solids 1220 mg/l
MW-31 3/15/2007 Total Dissolved Solids 1280 mg/l
MW-31 8/27/2007 Total Dissolved Solids 1240 mg/l
MW-31 10/24/2007 Total Dissolved Solids 1150 mg/l
MW-31 3/19/2008 Total Dissolved Solids 1220 mg/l
Appendix G
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 4 of 13
Appendix G-2: MW-31 Data Used for Analysis
Well Date
Sampled Parameter Name Report Result Report Units
MW-31 6/3/2008 Total Dissolved Solids 1180 mg/l
MW-31 8/4/2008 Total Dissolved Solids 1240 mg/l
MW-31 11/11/2008 Total Dissolved Solids 1220 mg/l
MW-31 2/3/2009 Total Dissolved Solids 1210 mg/l
MW-31 5/13/2009 Total Dissolved Solids 1230 mg/l
MW-31 8/24/2009 Total Dissolved Solids 1230 mg/l
MW-31 12/2/2009 Total Dissolved Solids 1160 mg/l
MW-31 2/9/2010 Total Dissolved Solids 1150 mg/l
MW-31 4/20/2010 Total Dissolved Solids 1220 mg/l
MW-31 9/13/2010 Total Dissolved Solids 1330 mg/l
MW-31 11/9/2010 Total Dissolved Solids 1320 mg/l
MW-31 1/10/2011 Total Dissolved Solids 1240 mg/l
MW-31 2/1/2011 Total Dissolved Solids 1220 mg/l
MW-31 3/14/2011 Total Dissolved Solids 1250 mg/l
MW-31 4/1/2011 Total Dissolved Solids 1370 mg/l
MW-31 5/10/2011 Total Dissolved Solids 1290 mg/l
MW-31 6/20/2011 Total Dissolved Solids 1330 mg/l
MW-31 7/5/2011 Total Dissolved Solids 1280 mg/l
MW-31 8/2/2011 Total Dissolved Solids 1300 mg/l
MW-31 9/6/2011 Total Dissolved Solids 1300 mg/l
MW-31 10/3/2011 Total Dissolved Solids 1320 mg/l
MW-31 11/8/2011 Total Dissolved Solids 1290 mg/l
MW-31 12/12/2011 Total Dissolved Solids 1330 mg/l
MW-31 1/24/2012 Total Dissolved Solids 1360 mg/l
MW-31 2/13/2012 Total Dissolved Solids 1240 mg/l
MW-31 3/13/2012 Total Dissolved Solids 1400 mg/l
MW-31 4/9/2012 Total Dissolved Solids 1380 mg/l
MW-31 5/2/2012 Total Dissolved Solids 1410 mg/l
MW-31 6/29/2012 Total Dissolved Solids 1460 mg/l
MW-31 7/9/2012 Total Dissolved Solids 1400 mg/l
MW-31 8/6/2012 Total Dissolved Solids 1400 mg/l
MW-31 9/18/2012 Total Dissolved Solids 1460 mg/l
MW-31 10/22/2012 Total Dissolved Solids 1320 mg/l
MW-31 11/6/2012 Total Dissolved Solids 1230 mg/l
MW-31 12/18/2012 Total Dissolved Solids 1270 mg/l
MW-31 1/22/2013 Total Dissolved Solids 1270 mg/l
MW-31 2/19/2013 Total Dissolved Solids 1390 mg/l
MW-31 3/19/2013 Total Dissolved Solids 1420 mg/l
MW-31 4/16/2013 Total Dissolved Solids 1260 mg/l
MW-31 5/13/2013 Total Dissolved Solids 1540 mg/l
MW-31 6/24/2013 Total Dissolved Solids 1380 mg/l
MW-31 7/9/2013 Total Dissolved Solids 1510 mg/l
MW-31 8/19/2013 Total Dissolved Solids 1440 mg/l
MW-31 9/17/2013 Total Dissolved Solids 1500 mg/l
MW-31 10/23/2013 Total Dissolved Solids 1460 mg/l
MW-31 11/18/2013 Total Dissolved Solids 1320 mg/l
Appendix G
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 5 of 13
Appendix G-2: MW-31 Data Used for Analysis
Well Date
Sampled Parameter Name Report Result Report Units
MW-31 12/17/2013 Total Dissolved Solids 1500 mg/l
MW-31 1/7/2014 Total Dissolved Solids 1510 mg/l
MW-31 2/17/2014 Total Dissolved Solids 1460 mg/l
MW-31 3/10/2014 Total Dissolved Solids 1490 mg/l
MW-31 4/28/2014 Total Dissolved Solids 1440 mg/l
MW-31 5/13/2014 Total Dissolved Solids 1510 mg/l
MW-31 6/2/2014 Total Dissolved Solids 1520 mg/l
MW-31 7/28/2014 Total Dissolved Solids 1400 mg/l
MW-31 8/18/2014 Total Dissolved Solids 1410 mg/l
MW-31 9/3/2014 Total Dissolved Solids 1460 mg/l
MW-31 10/6/2014 Total Dissolved Solids 1420 mg/l
MW-31 11/4/2014 Total Dissolved Solids 1520 mg/l
MW-31 12/9/2014 Total Dissolved Solids 1450 mg/l
MW-31 1/20/2015 Total Dissolved Solids 1540 mg/l
MW-31 2/2/2015 Total Dissolved Solids 1520 mg/l
MW-31 3/3/2015 Total Dissolved Solids 1530 mg/l
MW-31 4/7/2015 Total Dissolved Solids 1680 mg/l
MW-31 5/11/2015 Total Dissolved Solids 1700 mg/l
MW-31 6/23/2015 Total Dissolved Solids 1630 mg/l
MW-31 7/6/2015 Total Dissolved Solids 1440 mg/l
MW-31 8/10/2015 Total Dissolved Solids 1530 mg/l
MW-31 9/15/2015 Total Dissolved Solids 1480 mg/l
MW-31 10/6/2015 Total Dissolved Solids 1540 mg/l
MW-31 11/9/2015 Total Dissolved Solids 1460 mg/l
MW-31 12/8/2015 Total Dissolved Solids 1580 mg/l
MW-31 1/19/2016 Total Dissolved Solids 1560 mg/l
MW-31 2/15/2016 Total Dissolved Solids 1490 mg/l
MW-31 3/2/2016 Total Dissolved Solids 1580 mg/l
MW-31 4/12/2016 Total Dissolved Solids 1710 mg/l
MW-31 5/3/2016 Total Dissolved Solids 1550 mg/l
MW-31 6/15/2016 Total Dissolved Solids 1580 mg/l
MW-31 7/12/2016 Total Dissolved Solids 1610 mg/l
MW-31 8/16/2016 Total Dissolved Solids 1710 mg/l
MW-31 9/13/2016 Total Dissolved Solids 1570 mg/l
MW-31 10/4/2016 Total Dissolved Solids 1670 mg/l
MW-31 11/1/2016 Total Dissolved Solids 1690 mg/l
MW-31 12/5/2016 Total Dissolved Solids 1670 mg/l
MW-31 1/17/2017 Total Dissolved Solids 1730 mg/l
MW-31 2/7/2017 Total Dissolved Solids 1680 mg/l
MW-31 3/6/2017 Total Dissolved Solids 1690 mg/l
MW-31 4/4/2017 Total Dissolved Solids 1660 mg/l
MW-31 5/1/2017 Total Dissolved Solids 1820 mg/l
MW-31 6/5/2017 Total Dissolved Solids 1710 mg/l
MW-31 7/11/2017 Total Dissolved Solids 1830 mg/l
MW-31 8/14/2017 Total Dissolved Solids 1780 mg/l
MW-31 9/11/2017 Total Dissolved Solids 1780 mg/l
Appendix G
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 6 of 13
Appendix G-2: MW-31 Data Used for Analysis
Well Date
Sampled Parameter Name Report Result Report Units
MW-31 10/2/2017 Total Dissolved Solids 1760 mg/l
MW-31 11/1/2017 Total Dissolved Solids 1770 mg/l
MW-31 12/4/2017 Total Dissolved Solids 1910 mg/l
MW-31 1/24/2018 Total Dissolved Solids 1800 mg/l
MW-31 2/20/2018 Total Dissolved Solids 1930 mg/l
MW-31 4/17/2018 Total Dissolved Solids 1980 mg/l
MW-31 6/18/2018 Total Dissolved Solids 2010 mg/l
MW-31 7/23/2018 Total Dissolved Solids 2000 mg/l
MW-31 8/10/2018 Total Dissolved Solids 1980 mg/l
MW-31 9/10/2018 Total Dissolved Solids 2100 mg/l
MW-31 10/24/2018 Total Dissolved Solids 2000 mg/l
MW-31 11/13/2018 Total Dissolved Solids 1960 mg/l
MW-31 12/10/2018 Total Dissolved Solids 2090 mg/l
MW-31 1/15/2019 Total Dissolved Solids 2030 mg/l
MW-31 2/12/2019 Total Dissolved Solids 2090 mg/l
MW-31 3/5/2019 Total Dissolved Solids 2160 mg/l
MW-31 4/10/2019 Total Dissolved Solids 2080 mg/l
MW-31 7/15/2019 Total Dissolved Solids 2580 mg/l
MW-31 10/9/2019 Total Dissolved Solids 2280 mg/l
MW-31 11/12/2019 Total Dissolved Solids 2650 mg/l
MW-31 12/3/2019 Total Dissolved Solids 2030 mg/l
MW-31 1/14/2020 Total Dissolved Solids 2220 mg/l
MW-31 2/4/2020 Total Dissolved Solids 2240 mg/l
MW-31 3/10/2020 Total Dissolved Solids 2380 mg/l
Appendix G
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 7 of 13
Appendix G‐3: Box Plots
Sulfate in MW-31 for All data
Sulfate in MW-31 Post September 2012
Sulfate in MW-31 Post May 2014
Appendix G
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 8 of 13
Appendix G‐3: Box Plots
Total Dissolved Solids in MW-31 Post May 2014
Total Dissolved Solids in MW-31 for All data
Total Dissolved Solids in MW-31 Post September 2012
Appendix G
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 9 of 13
Appendix G‐4: Histograms
Sulfate in MW-31 for All data
Sulfate in MW-31 Post September 2012
Sulfate in MW-31 Post May 2014
Appendix G
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 10 of 13
Appendix G‐4: Histograms
Total Dissolved Solids in MW-31 for All data
Total Dissolved Solids in MW-31 Post September 2012
Total Dissolved Solids in MW-31 Post May 2014
Appendix G
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 11 of 13
Appendix G‐5: Linear Regression Analysis
Sulfate in MW-31 for All data
Sulfate in MW-31 Post September 2012
Sulfate in MW-31 Post May 2014
Appendix G
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 12 of 13
Appendix G‐5: Linear Regression Analysis
Total Dissolved Solids in MW-31 for All data
Total Dissolved Solids in MW-31 Post September 2012
Total Dissolved Solids in MW-31 Post May 2014
Appendix G
Source Assessment Report for MW-31
White Mesa Uranium Mill Page 13 of 13
APPENDIX H
Input and Output Files (Electronic Only)