DRC-2024-004813

March 4, 2024
Sent VIA E-MAIL AND EXPEDITED DELIVERY
Mr. Doug Hansen
Director
Division of Waste Management and Radiation Control
Utah Department of Environmental Quality
195 North 1950 West
Salt Lake City, UT 84114-4880
Energy Fuels Resources (USA) Inc.
225 Union Blvd. Suite 600
Lakewood, CO, US, 80228
303 974 2140
ww .enern.yfuels.com
Re: Transmittal of Source Assessment Report for MW-03A White Mesa Mill Groundwater Discharge
Permit UGW370004
Dear Mr. Hansen :
Enclosed are two copies of Energy Fuels Resource (USA) Inc.'s ("EFRl's") Source Assessment Report
("SAR") for MW-OJA at the White Mesa Mill. This SAR addresses the constituent that was identified as
exceeding the GWCL in the 3rd Quarter 2023 as described in the Division of Waste Management and Radiation
Control ("DWMRC")-approved Q3 2023 Plan and Time Schedule. EFRI submitted the Plan and Time Schedule
on November 15, 2023. DWMRC approval of the Plan and Time Schedule was received by EFRI on December
5, 2023. 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,
1<raty 1v~
ENERGY FUELS RESOURCES (USA) INC.
Kathy W einel
Director, Regulatory Compliance
CC : Jordan App
David Frydenlund
Garrin Palmer
Logan Shumway
Scott Bakken
Stewart Smith (HGC)
Angie Persico (lntera)
DRC-2024-004813
White Mesa Uranium Mill
State of Utah Groundwater Discharge Permit No. UGW370004
Source Assessment Report Under Part I.G.4
For Exceedances in MW-03A in the Third Quarter of2023
Prepared by:
?-l!tN:RGYFUELS
Energy Fuels Resources (USA) Inc.
225 Union Boulevard, Suite 600
Lakewood, CO 80228
March 4, 2024
EXECUTIVE SUMMARY
This Source Assessment Report ("SAR") is an assessment of the sources, extent, and potential
dispersion of selenium in MW-03A 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. Selenium in MW-03A has exhibited exceedances of the
applicable Groundwater Compliance Limits ("GWCLs").
MW-03A has been included in multiple recent investigations and reports, including the Revised
Background Groundwater Quality Report for New Wells (INTERA, 2008), an isotopic
investigation (Hurst and Solomon, 2008), a 2012 SAR (INTERA, 2012a), pH Report (INTERA,
2012b), and a 2014 SAR (INTERA, 2014). Analysis of indicator parameters shows that chloride
and sulfate concentrations are stable and fluoride and uranium concentrations are decreasing.
Stable to decreasing indicator parameters demonstrates that MW-03A is unimpacted by the
Tailings Management System ("TMS"). In addition, the 2008 Hurst and Solomon isotopic study,
noted that MW-03A was tritium-free, contained small amounts of chlorofluorocarbons ("CFCs"),
and did not bear isotopic signatures similar to those of either the tailings cells or the wildlife pond,
which suggests that trace metal concentrations and trends in the groundwater system near MW-
03A result from natural, background influences.
The site-wide analyses provided in the Background Reports, SARs, Pyrite Report and other
recent information and investigations at the site, also indicate that exceedances in MW-03A are
likely due to natural background influences that impact the geochemical conditions at MW-03A
(including changing water levels and enhanced oxygen transport to groundwater via the well
casing). Naturally-occurring selenium is likely mobilized by enhanced oxygen transport to
groundwater near the well. Factors that contributed to changes in groundwater conditions at
MW-03A are discussed in more detail in Section 3.0 of this SAR.
As the results of this analysis will demonstrate, trends in MW-03A are the result of background
conditions unrelated to potential seepage from the disposal of materials in the TMS. In addition,
selenium detected in MW-03A is within the range of site-wide conditions.
Revising the GWCLs to reflect the variations in selenium in MW-03A 1s proposed. In
accordance with the DWMRC-approved Flowsheet (from INTERA [2007a], included as
Appendix D), increasing trends may necessitate a modified approach, which has been approved
in previous SARs, for calculation of GWCLs. A modified approach for calculating a revised
GWCL for selenium in MW-03A used the greater of (1) mean plus two standard deviations, (2)
highest historical value, or (3) mean x 1.5 to determine representative and appropriate GWCLs
from a post-inflection subset of data. Regular revisions to GWCLs for constituents in wells with
significantly increasing trends over time due to background is consistent with the United States
ES-i
Environmental Protection Agency ("USEP A") Unified Guidance (USEP A , 2009). Such revisions
account for variability in larger datasets and minimize unwarranted out-of-compliance status.
ES-ii
TABLE OF CONTENTS
1.0 INTRODUCTION ................................................................................................................ 1
1.1 Source Assessment Report Organization .......................................................................... 2
2.0 CATEGORIES AND APPROACHES FOR ANALYSIS ................................................... 3
2.1 Approach for Analysis ...................................................................................................... 4
2.2 Approach for Setting Revised GWCLs ............................................................................. 5
2.3 University of Utah Study .................................................................................................. 5
3.0 RESULTS OF ANALYSIS .................................................................................................. 7
3 .1 Site-Wide pH Changes ...................................................................................................... 7
3.1.1 pH Decrease Prior to 2016 .............................................................................................. 7
3.1.2 pH Increase Post-2016 .................................................................................................... 8
3.2 Changes in Groundwater ................................................................................................... 9
3 .3 Indicator Parameter Analysis .......................................................................................... 10
3 .4 Mass Balance Analyses ................................................................................................... 11
3. 5 Summary of Results ........................................................................................................ 12
3.5.1 Selenium at MW-03A ................................................................................................... 12
4.0 CALCULATIONS OF GROUNDWATER COMPLIANCE LIMITS .............................. 13
4.1 Modified Approach to Calculation of GWCLs for Trending Constituents ......................... 13
4.2 Proposed Revised GWCL .................................................................................................... 15
5.0 CONCLUSIONS AND RECOMENDATIONS ................................................................. 15
6.0 SIGNATURE AND CERTIFICATION ............................................................................. 17
7.0 REFERENCES ................................................................................................................... 19
Table 1
Figure lA
Figure lB
Figure lC
Figure 2
Figure 3
Figure 4
Figure SA
Figure SB
Figure SC
Figure 6
LIST OF TABLES
Proposed Revised GWCLs for MW-03A
LIST OF FIGURES
White Mesa Site Plan Showing Locations of Perched Wells and Piezometers
Kriged 4th Quarter, 2023 Water Levels and Plume Boundaries, White Mesa Site
Kriged 4th Quarter, 2011 Water Levels and Plume Boundaries, White Mesa Site
MW-03A Groundwater Elevations
MW-03A Selenium Over Time
MW-03A pH Over Time
MW-03A Chloride and Fluoride Over Time
MW-03A Sulfate Over Time
MW-03A Uranium Over Time
MW-03A Manganese Over Time
LIST OF APPENDICES
Appendix A Statistical Analysis for Selenium in MW-03A
A-1 Summary of Statistical Analysis for Out of Compliance Constituents in MW-
03A
A-2 Comparison of Calculated and Measured TDS in MW-03A
A-3 Charge Balance Calculations for Major Cations and Anions in MW-03A
A-4 Descriptive Statistics for Selenium in MW-03A
A-S MW-03A Data Used for Statistical Analysis
A-6 Data Removed from Analysis
A-7 Outlier Evaluation for Selenium in MW-03A
A-8 Box Plots Showing Sitewide Selenium distribution in Groundwater
Monitoring Wells
A-9 Histograms of MW-03A
A-10 Timeseries Plots ofMW-03A
Appendix B Statistical Analysis for Indicator Parameters in MW-03A
B-1 Summary of Statistical Analysis for Indicator Parameters in MW-03A
B-2 Descriptive Statistics for Indicator Parameters in MW-03A
B-3 MW-03A Indicator Parameter Data Used for Analysis
B-4 Indicator Parameter Data Removed from Analysis
B-S Box Plots for Indicator Parameters in MW-03A
B-6 Histograms for Indicator Parameters in MW-03A
B-7 Timeseries Plots for Indicator Parameters in MW-03A
Appendix C Mass Balance Calculations
11
Appendix D Flowsheet (Groundwater Data Preparation and Statistical Process Flow for
Calculating Groundwater Protection Standards, White Mesa Mill Site
[INTERA, 2007a])
Appendix E Input and Output Files (Electronic Only)
111
ACRONYM LIST
Background Reports
CAP
CFCs
CIR
DI
Director
DWMRC
EFRI
GWCL
GWDP
GWQS
µg/L
mg/L
Mill
Ql
Q2
Q3
Q4
SAR
TDS
TMS
USEPA
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)
Corrective Action Plan
chlorofluorocarbons
Contaminant Investigation Report
Deionized
Director of the Division of Waste Management and Radiation Control
State of Utah Division of Waste Management and Radiation Control
Energy Fuels Resources (USA) Inc.
Groundwater Compliance Limit
State of Utah Ground Water Discharge Permit UGW370004
Groundwater Quality Standard
micrograms per liter
milligrams per liter
White Mesa Uranium Mill
first quarter
second quarter
third quarter
fourth quarter
Source Assessment Report
Total Dissolved Solids
Tailings Management System
United States Environmental Protection Agency
1.0 INTRODUCTION
Energy Fuels Resources (USA) Inc. ("EFRI") operates the White Mesa Uranium Mill
(the "Mill"), located near Blanding, Utah (Figure IA). Groundwater at the Mill is
regulated under the State of Utah Groundwater Discharge Permit UGW370004 (the
"GWDP"). This is the Source Assessment Report ("SAR") required under Part I.G.4 of
the GWDP relating to Part I.G.2 of the GWDP with respect to selenium in MW-03A.
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 Groundwater Compliance Limit ("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 for the existing wells, 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 three "Background
Groundwater Quality Reports" (INTERA 2007a, 2007b, 2008) (collectively, the
"Background Reports") to the Director (the "Director") of the State of Utah Division of
Waste Management and Radiation Control ("DWMRC") (the Director was formerly the
Executive Secretary of the Utah Radiation Control Board and the Co-Executive Secretary
of the Utah Water Quality Board).
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 deviations ("mean + 2cr") or the equivalent for each
constituent in each well (both existing and new wells), based on an "intra-well" approach.
That is, the compliance status for each constituent in a well is determined based on
current concentrations of that constituent in that well compared to the historic
concentrations for that constituent in that well, rather than compared to the concentrations
of the same constituent in other monitoring wells. The modified GWCLs became
effective on January 20, 2010. On January 19, 2018, March 19, 2019, and March 8, 2021,
revised GWDPs were issued, which set revised GWCLs for certain constituents in certain
monitoring wells as approved by the Director through previously approved SARs relating
to those constituents in those wells. GWCLs apply to groundwater monitoring wells
located in the perched aquifer at the Mill.
1
Figure lB is a site map showing perched well and piezometer locations, fourth quarter
("Q4") 2023 perched groundwater elevations, and other relevant site features, such as the
locations of formerly used (unlined) wildlife ponds, the historical pond, and the
boundaries of two shallow groundwater plumes (the nitrate/chloride plume and the
chloroform plume) which are under active remediation by pumping. Specifically, Figure
lB shows the commingled nitrate and chloride components of the nitrate/chloride plume.
Figure 1 C shows the same features as Figure 1 B, except that water levels and plume
boundaries are as they existed just prior to cessation of water delivery to the wildlife
ponds in the first quarter ("Q 1 ") of 2012. As shown in Figures 1 B and 1 C, perched
groundwater flows generally to the southwest across the site, and the nitrate/chloride
plume extends more than 1,000 feet upgradient of the Tailings Management System
("TMS") indicating an upgradient source. As discussed in HGC (2022), the chloroform
plume originated from disposal of laboratory wastes to two former sanitary leach fields
that were used prior to Mill construction and operation.
Groundwater quality at individual wells is impacted by transient conditions at the site.
Currently the perched groundwater system that is monitored at the site does not approach
steady state over much of the monitored area. A large part of the site perched water
system is in a transient state and affected by long-term changes in water levels due to past
and current activities unrelated to the disposal of materials to the TMS. Changes in water
levels have historically been related to seepage from the unlined wildlife ponds; however
past impacts related to the historical pond, and to a lesser extent formerly used sanitary
leach fields, have also influenced water levels, as discussed in HGC (2022). Water levels
have decreased at some locations due to chloroform and nitrate pumping and reduced
recharge from the wildlife ponds.
Figure 2 is a plot of groundwater elevations over time at MW-03A since installation in
2005. Groundwater levels have increased by approximately 1.5 feet at MW-03A since the
well was installed. As discussed above, water level increases are attributable to former
wildlife pond recharge.
1.1 Source Assessment Report Organization
Analyses of SAR parameters and indicator parameters in MW-03A were performed. A
description of the approach used for analysis is provided in Section 2.0, and the results of
the analyses are presented in Section 3.0. The calculation of GWCLs is discussed in
Section 4.0, and conclusions and recommendations are reviewed in Section 5.0. Section
6.0 provides signature and certification of this document, and Section 7.0 provides a list
of references cited in this SAR.
2
The appendices comprise the analyses performed for this SAR and are organized in the
following manner: Appendix A contains the statistical analysis performed on selenium in
MW-03A. Appendix B contains the indicator parameter analysis performed on MW-
03A. Appendix C summarizes the mass balance analysis. Appendix D 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
("USEP A") Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities,
Unified Guidance (USEP A, 2009), which was approved by DWMRC prior to completion
of the Background Reports. Appendix E 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 E can be imported into either R or Statistica to
replicate the results presented in this SAR.
2.0 CATEGORIES AND APPROACHES FOR ANALYSIS
Previously EFRI has categorized wells and constituents in five categories as follows:
I. Constituents Potentially Impacted by Decreasing pH Trends Across the Site
2. Newly Installed Wells with Interim GWCLs
3. Constituents in Wells with Previously Identified Rising Trends
4. Pumping Wells
5. Other Constituents
Selenium can fall within the first category when downward pH trends are noted, and pl-{
in MW-03A does exhibit a decreasing trend during certain time periods; although the
overall trend is nearly flat. Selenium in MW-03A can also fall within the third category:
constituents in wells with previously identified rising trends, because a rising trend was
noted for selenium in the 2012 SAR. Due to the multiple categories that are applicable to
selenium in MW-03A, for this SAR the fifth category, 'Other Constituents', will be used.
Assessment of this constituent in MW-03A will follow the process noted below.
The location of MW-03A is important when determining potential sources of
contamination. MW-03A is far downgradient of the TMS. MW-03A is also far
downgradient of the nitrate/chloride plume. Due to its far downgradient position, and
3
rates of groundwater migration that are on the order of a foot per year in the area
downgradient (south-southwest) of the TMS (HGC, 2022), neither the nitrate/chloride
plume nor any solutions potentially released from the TMS, could have impacted MW-
03A during the approximate 43 year period of Mill operation.
Figure 3 is a plot of MW-03A selenium concentrations over time. The consecutive
exceedances of selenium in MW-03A are likely due to background influences potentially
resulting from enhanced oxygen delivery to the perched groundwater zone via the well
casing. As discussed in Bailey et al (2009), selenium is mobile under oxidizing
conditions. Enhanced oxygen delivery would increase dissolved oxygen concentrations in
groundwater and could release naturally-occurring selenium, including selenium
contained as a contaminant in naturally-occurring pyrite in the Burro Canyon Formation,
which hosts perched groundwater at the site. Stable to declining indicator parameters
chloride, fluoride, sulfate and uranium at MW-03A demonstrate that increases in
selenium cannot result from potential TMS seepage. Given the stable to declining
indicator parameters, and recent analyses and investigations at the site, there is no
indication that the exceedances of selenium in MW-03A are due to Mill-related impacts
or to any potential TMS seepage.
2.1 Approach for Analysis
The first step in the analysis is to assess the potential sources for the exceedances to
determine whether they are due to background influences or Mill activities. If the
exceedances are determined to be within natural variability or due to site-wide influences,
then it is not necessary to perform further evaluations on the extent and potential
dispersion of the contamination or to perform an evaluation of potential remedial actions.
Monitoring will continue and, where appropriate, revised GWCLs are proposed to reflect
changes in background conditions.
The analysis performed in this SAR considers all available data to date to evaluate the
behavior of the constituents in the well. Analysis will determine if there have been any
changes in the behavior of potential TMS seepage indicator parameters ( e.g., chloride,
sulfate, fluoride, and uranium) since the date of the Background Reports that may suggest
a change in the behavior of the groundwater in MW-03A.
As discussed in the Background Reports (INTERA, 2007a, 2007b, 2008), indicator
parameters of potential TMS seepage include chloride, sulfate, fluoride, and uranium.
Chloride is typically the best indicator of potential TMS seepage. Statistical analysis for
selenium in MW-03A shows that while selenium concentrations have a significantly
increasing trend today, they did not have a significantly increasing trend at the time of the
New Wells Background Report (INTERA, 2008). None of the indicator parameters in
4
MW-03A are showing significantly increasing trends today or at the time of the New
Wells Background Report. Currently, chloride and sulfate are stable and uranium and
fluoride have significantly decreasing trends. Stable to decreasing concentrations of
indicator parameters demonstrates that MW-03A is unimpacted by the TMS.
The evaluation of SAR and indicator parameters in MW-03A was supported by a
statistical analysis that followed the process outlined in the Flowsheet (INTERA, 2007a),
a copy of which is attached as Appendix D. The Flowsheet was designed based on
USEPA's Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities,
Unified Guidance (USEP A, 2009), and was approved by DWMRC prior to completion of
the Background Reports.
2.2 Approach for Setting Revised GWCLs
If the preceding approach resulted in the conclusion that the analysis in the Background
Reports has not changed, or that the increasing concentrations of selenium in MW-03A
are due to natural, background variability ( or changes) in groundwater; geochemical
changes caused by the downgradient migration of the nitrate/chloride plume; or site-wide
influences such as the oxidation of pyrite; then a new GWCL may be proposed. In
proposing revised GWCLs, the DWMRC-approved Flowsheet approach was adopted,
including the last decision of the process that directs the analyst to consider a modified
approach to determining a G WCL if an increasing trend is present ( or decreasing trend in
the case of pH).
Appendix A-1 summarizes the statistical analysis for selenium in MW-03A and presents
the revised GWCLs for those constituents, based on the Flowsheet. A modified approach
for selenium is being proposed to address issues with revising GWCLs in constituents
with significantly increasing trends and to minimize unwarranted out-of-compliance
situations.
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 TMS is occurring.
To evaluate sources of solute concentrations at the Mill, extremely low-yielding wells
such as MW-03A, were sampled by lowering the pump to the bottom of the well, at
5
which time well MW-03A was pumped to approximately 1 m above the bottom of the
well screen. After three days of recovery, MW-03A was sampled using the dedicated
pump in the well. In addition, surface water samples were collected from TMS cells 1, 3,
and 4A, and two wildlife ponds. 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").
Specifically regarding MW-03A Hurst and Solomon stated that,
The majority of wells that exceeded water quality standards were tritium-
free, contained very small amounts of CFCs, and did not bear isotopic
signatures similar to those of either the tailings cells or the wildlife ponds.
This suggests natural, background values of trace metal contamination in
the groundwater system.
Hurst and Solomon (2008, page iii) concluded generally that,
[t]he data show that groundwater at the Mill is largely older than 50
years, based on apparent recharge dates from chlorofluorocarbons and
tritium concentrations. Wells exhibiting groundwater that has recharged
within the last 50 years appears to be a result of recharge from wildlife
ponds near the site. Stable isotope fingerprints do not suggest
contamination of groundwater by tailings cell leakage, evidence that is
corroborated by trace metal concentrations similar to historically-
observed observations.
Hurst and Solomon (2008) conclude 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 oD and 6 18 0 suggest mixing between wildlife pond
recharge and older groundwater in MW-19 and MW-27. D34S-SO4 and
o18 O-SO4fingerprints 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.
6
It should be further noted that, subsequent to the University of Utah Study, EFRI
submitted a Contaminant Investigation Report, White Mesa Uranium Mill Site, Blanding
Utah, dated December 30, 2009 (INTERA, 2009) ("CIR"), in connection with the
nitrate/chloride plume at the Mill site. The CIR discusses the presence of a historical
pond that existed for many years at a location upgradient from MW-27 (Figures IB and
IC), which was much closer to MW-27 than the wildlife ponds. This historical pond was
a contributor of surface water to MW-27.
3.0 RESULTS OF ANALYSIS
This section describes the geochemical influences on groundwater in MW-03A and
results of the analyses, summaries of which are provided in Appendix A-1, and
Appendix B-1 and discussed further below.
3.1 Site-Wide pH Changes
As discussed below, pH in nearly all MW-series monitoring wells was decreasing prior to
about 2016. This has resulted in mobilization of pH-sensitive metals and increases in
concentrations of these metals in groundwater. However, since about 2016, the site-wide
decreasing pH trend has reversed in nearly all MW-series monitoring wells (including
MW-03A), with post-2016 pH generally stable to increasing.
3.1.1 pH Decrease Prior to 2016
As has been documented in INTERA (2012), a decreasing trend in pH was observed in
almost every groundwater monitoring well across the site, including upgradient and far
cross-and downgradient monitoring wells; and decreasing pH is one of the most
important contributors to increasing concentrations of many naturally-occurring
parameters.
Hydro Geo Chem, Inc. (["HGC"], 2012a) ("The Pyrite Report") attributed the decline in
pH across the Mill site to the site-wide existence and oxidation of pyrite in the perched
groundwater monitored at the site. Based on HGC (2012a) pyrite has been noted in
approximately 213 of the lithologic logs for wells installed at the site since 1999, and
verified by laboratory analysis in core and cuttings from at least 25 monitoring wells. As
discussed in the Pyrite Report, pyrite was detected by the laboratory in a core sample
from MW-03A collected near the base of the Burro Canyon Formation.
Pyrite will oxidize according to the following reaction (Williamson and Rimstidt, 1994):
7
Reaction 1 will increase hydrogen ion ( acid) concentrations, which results in decreasing
pH. Oxidation of pyrite and the resulting decrease in pH enables subsequent pH-
dependent reactions to occur, including the mobilization of naturally-occurring metals
and metalloids in the formation (McClean and Bledsoe, 1992). In addition, pyrite
typically contains many contaminants including selenium (Curti, 2013; Deditius et al,
2011; Diener et al 2012; Grant et al, 2021; Keith, 2018) that are released upon pyrite
oxidation. As discussed in EFRI (2021), bottle-roll tests using 'generic' pyrite resulted in
bottle-roll solutions initially consisting of laboratory-grade deionized ("DI") water
generating as much as 64.9 µg/L selenium from the 'generic' pyrite sample; and as much
as 303 µg/L selenium from a pyritic core sample.
The causes for site-wide oxidation of pyrite include processes that increase oxygen
transport to groundwater. Monitoring well casings themselves provide direct conduits for
oxygen to impact groundwater in the immediate vicinities of the wells. Additional factors
that increase oxygen transport to groundwater include: (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 treatment of the nitrate/chloride plume; and (4) the
introduction of oxygen during increased sampling of monitoring wells (INTERA, 2012).
Many of these mechanisms, in particular changing water levels, are impacting MW-03A.
I
Water levels at many site wells increased due to former seepage from the northern
wildlife ponds located upgradient of the TMS. As shown in Figure 2, as a result of former
wildlife pond seepage and expansion of the resulting perched groundwater mound, water
levels at MW-03A increased by approximately 1.5 feet since installation.
3.1.2 pH Increase Post-2016
Although prior to about 2016 pH in nearly all MW-series monitoring wells was
decreasing, since about 2016, the site-wide decreasing pH trend has reversed in nearly all
MW-series monitoring wells (including MW-03A), with post-2016 pH generally stable to
increasing. As shown in Figure 4, prior to about 2011, pH at MW-03A was decreasing
significantly; between 2011 and late 2016, pH was noisy but relatively stable; and
subsequently, pH generally increased. The post-2016 generally increasing pH is
inconsistent with a TMS source as TMS solutions have a low pH, and mixing of potential
seepage of TMS solution with groundwater would cause a decrease (rather than increase)
in pH. The generally increasing post-2016 pH shows that MW-03A is unimpacted by the
TMS, consistent with the decreasing to stable indicator parameters in MW-03A (Figures
5A through 5C and Appendix B).
8
3.2 Changes in Groundwater
As discussed in Section 1, Figure 1B shows water levels and chloroform, nitrate and
chloride plume boundaries for the fourth quarter of 2023. Figure lC shows the same
features as Figure 1 B, except that water levels and plume boundaries are as they existed
just prior to cessation of water delivery to the wildlife ponds. A comparison between
Figure 1B and Figure lC shows the substantial changes in water levels that have occurred
in about 12 years due cessation of water delivery to the wildlife ponds. Currently,
although water levels have declined substantially in the center of the perched
groundwater mound associated with the northern wildlife ponds, water levels have not
returned to pre-pond seepage conditions, and consequently the groundwater mound is still
expanding.
The transient status of a large portion of the perched water system, manifested in long-
term changes in saturated thicknesses and rates of groundwater flow, results in trends in
pH and in the concentrations of many dissolved constituents that are unrelated to site
operations. Changes in saturated thicknesses and rates of groundwater flow can result in
changes in concentrations of dissolved constituents (or pH) for many reasons. For
example, as discussed in HGC (2012), groundwater rising into a vadose zone having a
different chemistry than the saturated zone will result in changes in pH and groundwater
constituent concentrations. If the rise in groundwater represents a long-term trend, long-
term changes in groundwater constituent concentrations ( or pH) result.
As discussed above, water levels have increased at MW-03A by about 1.5 feet since
installation (Figure 2). In addition, pH has been variable at MW-03A as shown in Figure
4. Prior to about 2011, pH at MW-03A was decreasing significantly; between 2011 and
late 2016, pH was noisy but relatively stable; and subsequently, pH generally increased.
Overall, pH has been relatively flat. The increases in water levels and changing trends in
pH indicate variable background conditions that could cause changes in many monitored
parameters, including selenium.
Selenium in MW-03A displays variable behavior, as it generally increased through 2016;
then generally decreased through 2019; and subsequently began to increase (Figure 3).
November of 2019 has been identified as a point of inflection representing the recent
increase in selenium concentrations. Overall, selenium displays an increasing trend.
However, indicator parameters chloride, fluoride, sulfate and uranium (Figures 5A
through 5C), discussed in detail in Section 3.3, show overall stable to decreasing trends,
indicating that, whatever the cause of increasing selenium, it cannot result from potential
TMS seepage. The trend of increasing selenium concentrations in MW-03A is likely the
result of mobilization from natural sources within the Burro Canyon Formation hosting
9
perched groundwater at the site. Naturally-occurring selenium sources include naturally-
occurring pyrite in the formation.
Selenium is a common contaminant in pyrite as discussed in Curti (2013); Deditius et al
(2011); Diener et al (2012); Grant et al (2021); and Keith (2018); and selenium
mobilization may result in whole or in part by oxidation of naturally-occurring pyrite in
the formation near MW-03A.
As discussed in Bailey et al (2009), selenium is mobile under oxidizing conditions
resulting from the presence of dissolved oxygen or nitrate in the groundwater; and
dissolved oxygen in groundwater near MW-03A is likely to increase as a result of oxygen
transport to groundwater via the well casing. Factors conducive to enhanced oxygen
transport to groundwater in the vicinity of any particular well are discussed in the Pyrite
Report. Specific factors discussed in the Pyrite Report that are expected to increase
oxygen transport to groundwater near MW-03A include (but are not limited to): 1) low
permeability and consequent low rates of groundwater movement through the well; 2)
large proportion of the well screen extending into the vadose zone; and 3) water levels
rising into a relatively oxygen-rich vadose zone. An increase in oxygen concentrations in
groundwater near MW-03A is also expected to be enhanced by the relatively small
saturated thickness measured at the well.
That oxygen concentrations (and oxidizing conditions) have been generally increasing at
MW-03A is consistent with the generally decreasing manganese concentrations at the
well displayed in Figure 6. Manganese is a redox sensitive metal that is relatively mobile
in the absence of oxygen and relatively immobile when oxygen is present (Brown et al,
2019; USGS, 2019).
3.3 Indicator Parameter Analysis
A summary of statistical analysis of indicator parameters for MW-03A is included in
Appendix B. The complete data set, indicated as "All 2023 SAR Data," and the post-
inflection data sets for MW-03A were evaluated for each indicator parameter and are
summarized in Appendix B-1. Appendix B-2 presents a descriptive statistics comparison
for MW-03A indicator parameters from the Existing Wells Background Report
(INTERA, 2007a), the 2012 SAR (INTERA, 2012a), and this SAR. Note that the 2017
SAR was in an abbreviated format which did not include indicator parameter evaluation.
Data used in the indicator parameter analysis are presented in Appendix B-3. The
distribution and identification of outliers and extreme outliers in indicator parameter
concentration datasets are demonstrated in the box plots included in Appendix B-5.
Histograms and time series plots are included in Appendix B-6 and B-7, respectively.
Complete data sets for MW-03A indicator parameters demonstrate that chloride, sulfate,
and pH are stable and uranium and fluoride have significantly decreasing trends
(Appendix B-1). Trend analysis of the post-November 2019 indicator parameter subsets
show decreasing trends for chloride, sulfate, and uranium, and no trend for either fluoride
or pH, further demonstrating stable to decreasing concentrations in indicator parameters
during this time period. The stable to decreasing behavior of indicator parameters
indicates that MW-03A is unimpacted by any potential seepage from the TMS.
Furthermore, an isotopic investigation (Hurst and Solomon, 2008) indicated that MW-
03A was tritium-free, contained small amounts of CFCs, and did not bear isotopic
signatures similar to those of either the tailings cells or the wildlife pond, which suggests
that trace metal concentrations and trends in the groundwater system near MW-03A result
from natural, background influences.
3.4 Mass Balance Analyses
Based on the data shown in Figure 2, water levels at MW-03A have risen by
approximately 1.5 feet, causing the saturated thickness to increase by approximately 13
%. TMS solutions contain chloride, a conservative solute, at an average concentration
exceeding 27,200 mg/L. If the water level changes at MW-03A were due to potential
TMS seepage, and resulted in a mixture containing approximately 13% TMS solution,
chloride concentrations at MW-03A would be approximately 3,600 mg/L, rather than the
fourth quarter, 2023 value of approximately 62 mg/L. Similarly, based on the average
concentrations (since 2003) in TMS solutions, the fluoride concentration would be
approximately 420 mg/L (rather than the fourth quarter, 2023 value of approximately 0. 7
mg/L); the sulfate concentration would exceed 25,300 mg/L (rather than the fourth
quarter, 2023 value of approximately 3,370 mg/L); the uranium concentration would
exceed 48,500 µg/L (rather than the fourth quarter, 2023 value of approximately 18.9
µg/L); and the selenium concentration would exceed 1,270 µg/L rather than the fourth
quarter, 2023 value of 132 µg/L). These calculations (summarized in Table C.l of
Appendix C) demonstrate that the observed increases in water levels at MW-03A do not
result from potential TMS seepage.
In addition, as discussed above, chloride and sulfate are stable and uranium and fluoride
have significantly decreasing trends (Figures 5A through 5C and Appendix B). Overall,
the mass balance analyses and geochemical considerations demonstrate that potential
TMS seepage is not a contributor to the groundwater chemistry at MW-03A.
11
3.5 Summary of Results
As will be discussed below, mcreases m selenium at MW-03A are the result of
background conditions unrelated to disposal of materials to the TMS.
Statistical analysis of selenium in MW-03A was performed for the complete historical
data set and for a more recent post-inflection data set containing data from November
2019 -present (Appendix A-1). Data used in the analysis are presented in Appendix A-
S. Data sets exhibit the following characteristics: (1) the complete data set has a non-
parametric distribution with a significantly increasing trend and (2) the post-November
2019 subset is normally distributed with a significantly increasing trend.
3.5.1 Selenium at MW-03A
As discussed above, analysis of indicator parameters shows that chloride and sulfate are
stable and uranium and fluoride have significantly decreasing trends. Stable to decreasing
indicator parameters demonstrate that MW-03A is unimpacted by TMS solutions and that
increases in selenium result from factors unrelated to disposal of materials in the TMS. In
addition, an isotopic investigation (Hurst and Solomon, 2008) indicated that MW-03A
was tritium-free, contained small amounts of CFCs, and did not bear isotopic signatures
similar to those of either the tailings cells or the wildlife pond, which suggests that trace
metal concentrations and trends in the groundwater system near MW-03A result from
natural, background influences. Furthermore, mass balance analysis indicates that water
level increases at MW-03A cannot result from TMS seepage, as concentrations of
chloride, fluoride, sulfate uranium and selenium would be one to several orders of
magnitude larger than the measured concentrations of these constituents.
Increasing selenium concentrations at MW-03A likely result from increasingly oxidizing
groundwater conditions near the well that are caused by enhanced oxygen transport to
groundwater near the well. Increasingly oxidizing conditions are expected to mobilize
naturally-occurring selenium in the formation hosting perched groundwater at the site
(including selenium present as a contaminant in naturally-occurring pyrite). Factors
expected to increase oxygen transport to groundwater near the well include (but are not
limited to): 1) low permeability and consequent low rates of groundwater movement
through the well; 2) large proportion of the well screen extending into the vadose zone;
and 3) water levels rising into a relatively oxygen-rich vadose zone. An increase in
oxygen concentrations in groundwater near MW-03A is also expected to be enhanced by
the relatively small saturated thickness measured at the well; and is consistent with
decreasing manganese concentrations at the well.
12
3.5.1.1 Summary of Factors Demonstrating no Impact to MW-03A From the TMS
The following factors indicate that changes in constituent concentrations at MW-03A do
not result from potential TMS seepage:
1. Indicator parameters chloride and sulfate are stable and uranium and fluoride have
significantly decreasing trends.
2. pH has been generally stable to increasing since 2016.
3. Increasing water levels related to former wildlife pond recharge are expected to
impact the MW-03A groundwater chemistry and contribute to trends in dissolved
constituents.
4. Mass balance analysis indicates that water level increases at MW-03A do not
result from potential TMS seepage.
Because increasing concentrations of selenium in MW-03A are not the result of potential
TMS seepage, a revised GWCL for selenium is proposed. Section 4 presents the methods
used to calculate a GWCL using a modified approach for trending constituents, in
accordance with the Flowsheet.
4.0 CALCULATIONS OF GROUNDWATER COMPLIANCE LIMITS
Because selenium in MW-03A is increasing significantly due to naturally occurring
conditions unrelated to potential seepage from the TMS (Appendix A-1, and A-10), the
Flowsheet (Appendix D) dictates that a modified approach should be used to calculate a
GWCL. Section 4.1 describes the rationale used to select a modified approach for
calculating a GWCL for selenium in MW-03A.
4.1 Modified Approach to Calculation of GWCLs for Trending Constituents
According to the DWMRC-approved Flowsheet, if an increasing trend is present, a
modified approach should be considered for determining GWCLs. The modified
approach used for selenium in MW-03A includes calculating a revised GWCL by
selecting the greater of (1) mean + 2cr, (2) highest historical value, or (3) mean x 1.5
using a complete dataset or subset of the data defined by a point of inflection to
determine representative and appropriate GWCLs for trending constituents.
As discussed in Section 3.2, selenium in MW-03A exhibits a significantly increasing
trend that can be attributed to conditions that are mobilizing naturally occurring selenium,
in the vicinity of MW-03A. A point of inflection was identified in late 2019 when
groundwater levels in MW-03A began to stabilize near 5472.9 ft amsl and an upward
trend in selenium concentrations was observed. The data subset from November 2019 to
13
November 2023 is believed to be representative of current conditions and appropriate for
calculating a revised selenium GWCL.
The USEP A Guidance recommends testing datasets for outliers and removing outliers
only when they exhibit much higher or lower concentrations than the rest of the dataset.
The USEPA Guidance recommends two outlier tests: Dixon's test, which is best for
smaller datasets, and Rosner's test, which is better for larger datasets. Dixon's test was
performed on the post-inflection dataset and Rosner's tests was performed on the full
dataset for selenium in MW-03A using ProUCL software. Both outlier tests assume that
the dataset without the suspected outliers is normally distributed, though the ProUCL
software performs the analysis regardless of the distribution type. In addition, outliers
were evaluated with boxplots and probability plots generated in R (Appendix A-7).
In boxplots used for outlier analysis (Appendix A-7), non-extreme outliers are shown as
open circles and extreme outliers are shown as stars. Extreme outliers are those greater
than the value representing the 75th quartile plus three times the interquartile range, or
lower than the value representing the 25th quartile minus three times the interquartile
range. Probability plots were also used to evaluate outliers. The probability plots
(Appendix A-7) show theoretical quantiles on the x-axis, assuming a normal or log
normal distribution, and sample quantiles on the y-axis. The probability plots also show a
theoretical normal distribution regression line. Generally, most of the measured results
plot near this line, whether they form a linear pattern or not. Outliers tend to plot farther
from this line than the rest of the dataset. Probability plots were used to evaluate outliers,
as well as to provide a visualization of whether the dataset fits a normal or log normal
distribution model.
Outliers were evaluated on a case-by-case basis considering the results of the outlier test
performed in ProUCL, boxplots, and probability plots. Outliers are typically removed
from analysis only when all of the following criteria are met: (1) outliers appeared to be
extreme in boxplots; (2) outliers appeared to be extreme in probability plots; and (3) the
results from Rosner's or Dixon's test indicated the value is an outlier at the 1 %
significance level. One outlier was identified in the full data set, and although two
potential outliers were identified in the post-inflection data set, the result of the Dixon's
outlier test indicated that neither of the two potential outliers were an outlier at 1 %
significance level, therefore no post-inflection data were removed from analysis.
Although the full data set and the post-inflection (post-November 2019) subset were
evaluated, the modified approach for the proposed GWCL is based on the highest
historical value of the post-November 2019 data subset.
14
Calculation of GWCLs using a modified approach decreases the likelihood of false
positives ( exceedances) associated with increasing trends related to natural background
conditions including site-wide oxidation of pyrite. The proposed GWCL maintains the
intra-well approach that has been established for compliance at the Mill, combining
elements from the Flowsheet and from previously approved GWCLs calculated using a
modified approach. The flowsheet calculations and the proposed GWCLs using the
modified approach, are presented in Appendix A-1 and Table 1, respectively.
4.2 Proposed Revised GWCL
A proposed revised GWCL was determined using a modified approach in accordance with
the Flowsheet, as presented in Table 1.
Table 1
Proposed Revised GWCLs for MW-03A
W II Parameter Current Proposed R t· 1 e (units) GWCL GWCL a wna e
MW-03A Selenium
(µg/L) 109.58 171.0
5.0 CONCLUSIONS AND RECOMENDATIONS
Modified Approach (highest
historical value)
using post-November 2019
subset
The Mill site was thoroughly studied in the Background Reports (INTERA, 2007a,
2007b, 2008, 2014), in various SARs, and in the University of Utah Study (Hurst and
Solomon, 2008). The Background Reports and the University of Utah Study concluded
that groundwater at the Mill site, including groundwater sampled at MW-03A, has not
been impacted by Mill operations. Both of those studies also acknowledged that there are
natural influences at play at the Mill site that have caused increasing trends and general
variability of background groundwater quality at the Mill site.
The focus of this SAR was, therefore, to identify any changes in the circumstances
identified in those studies. Evaluation of SAR parameters and indicator parameters in
MW-03A were performed in accordance with the DWMRC-approved Flowsheet
(Appendix D).
The analysis of MW-03A data indicates that increasing selenium concentrations are the
result of natural, background influences. Mechanisms likely include mobilization of
15
naturally-occurring selenium within the formation, and/or mobilization from naturally-
occurring pyrite in the formation, as a result of enhanced oxygen delivery to groundwater
in the vicinity of MW-03A via the well casing. That increasing selenium and water levels
at MW-03A cannot result from potential seepage from the TMS is demonstrated by stable
to decreasing indicator parameters chloride, fluoride, sulfate and uranium; and by mass
balance analysis that indicates chloride, fluoride, sulfate, uranium and selenium
concentrations would be one to several orders of magnitude higher than measured if the
water level increases were caused by potential TMS seepage.
EFRI recommends adopting the revised GWCLs for MW-03A in accordance with the
Flowsheet. Regular revisions to GWCLs are consistent with the USEPA Unified
Guidance (USEP A, 2009). Such revisions account for variability in larger datasets and
minimize unwarranted out-of-compliance status.
16
7.0 REFERENCES
Bailey, Ryan T.; Brent M. Cody; and Timothy K. Gates, 2009. Mobilization and Reactive
Transport of Selenium in a Stream-aquifer System: From Field Monitoring
Toward Remediation Modeling. Hydrology Days, 2009.
Brown, Craig J.; Jeannie R. B. Barlow; Charles A Cravatta III; and Bruce D. Lindsey,
2019. Factors affecting the occurrence oflead and manganese in untreated
drinking water from Atlantic and Gulf Coastal Plain aquifers, eastern United
States-Dissolved oxygen and pH framework for evaluating risk of elevated
concentrations. Applied Geochemistry, Vol. 101, February 2019, pp 88-102
Curti, E.; L. Aimoz; and A. Kitamura 2013. Selenium Uptake into Natural Pyrite. Journal
ofRadioanalytical and Nuclear Chemistry, 295 (3), pp 1855-1665.
Deditius, Artur P; Satoshi Utsonomiya; Martin Reich; Stephen E Kesler; Rodney C
Ewing; Robert Hough; and John Walshe, 2011. Trace Metal Nanoparticles in
Pyrite. Ore Geology Reviews, Vol. 42, Issue 1, Nov. 2011, pp 32-46.
Diener, A; T. Neuman; U. Kramar; and D. Schild, 2012. Structure of Selenium
Incorporated in Pyrite and Mackinawite as Determined by XAFS Analysis. J.
Contam. Hydrol., May 15, 2012, 133:30-9.
Energy Fuels Resources (USA) Inc. (EFRI), 2020a. White Mesa Uranium Mill Annual
Tailings System Wastewater Monitoring Report.
---, 2020b. Source Assessment Report for Exceedances in MW-28.
---, 2021. White Mesa Uranium Mill MW-24A Report, State of Utah Groundwater
Discharge Permit No. UGW 370004, June 14, 2021.
---, 2022. Source Assessment Report for Exceedances in MW-11.
Grant, Hannah L J; Mark D Hannington; and Sven Petersen, 2021. The Sequestration of
Trace Elements in Pyrite From Modem and Ancient Volcanic-Hosted Massive
Sulfide Deposits.
https :/ /2021. goldschmidt.info/ goldschmidt/2021 /meetingapp.cgi/paper/8302
Hydro Geo Chem, Inc. (HGC) 2012a. Investigation of Pyrite in the Perched Zone. White
Mesa Uranium Mill Site. Blanding, Utah. December 7, 2012.
---, 2022. Hydrogeology of the White Mesa Uranium Mill, Blanding, Utah. July 13,
2022.
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.
19
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. PH Report White Mesa Uranium Mill, Blanding, Utah.
---, 2012b. Source Assessment Report White Mesa Uranium Mill Site, Blanding,
Utah.
---, 2014. Source Assessment Report White Mesa Uranium Mill Site, Blanding,
Utah.
---, 2019. Source Assessment Report for MW-11 and MW-24 White Mesa Uranium
Mill Blanding, Utah.
Keith , Manuel; Daniel J Smith; Gawen, RT Jenkin; Davis A Holwell; and Mathew D
Dye, 2018. A review of Te and Se Systematics in Hydrothermal Pyrite From
Precious Metal Deposits: Insights into Ore-Forming Processes. Ore Geology
Reviews, Vol 96, May 2018, pp 269-282. Kolle, W., P. Werner, 0. Strebel, and J.
Bottcher. 1983. Denitrification in a reducing aquifer. Vom Wasser 1983, 61, 125-
147.
McClean, Joan E. and Bert E. Bledsoe, 1992. Behavior of Metals in Soils. USEP A
Groundwater Issue EPA/540/S-92/018, October 1992.
United States Environmental Protection Agency (USEPA) Office of Radiation and Indoor
Air Radiation Protection Division, 2008. Technical Report on Technologically
Enhanced Naturally-Occurring Radioactive Materials From Uranium Mining
Volume 2: Investigation of Potential Health, Geographic, and Environmental
Issues of Abandoned Uranium Mines. EPA-402-R-08-005, April 2008.
__ , 1989. Statistical Analysis of Groundwater 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.
20
__ , 1992. Statistical Analysis of Ground-Water Monitoring Data at RCRA Facilities:
Addendum to Interim Final Guidance, Office of Solid Waste, Permits and State
Programs Division, U.S. Environmental Protection Agency, 401 M Street, S.W.
Washington, D.C. 20460.
--~ 2005. Partition Coefficients for Metals in Surface Water, Soil, and Waste. U.S.
Environmental Protection Agency Office of Research and Development
Washington, D.C. 20460 .
__ , 2009. Statistical Analysis of Groundwater Monitoring Data at RCRA Facilities,
Unified Guidance, EPA 530/R-09-007.
United States Geological Survey, 2019. Oxidation/Reduction (Redox) Water Resources
Mission Area, February 27, 2019.
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.
21
FIGURES
APPENDICES
APPENDIX A
Appendix A-1: Summary of Statistical Analysis for Selenium in MW-03A
Well Data Set Constituent Units N
% Non-
Da1ec1.1>d
Values
Mean Stsndard
Devia tl on
Shapiro-Wilk Test for
Normality
w p
Normally or
Log normally
distributed?
MW-03A Full Selenium µg/L 59 2% 88.13 23.15 3.77E-13 Not normal
MW-03A Post-November 2019
Notes:
cr = si gma
µg/L = micrograms per liter
N = number of valid data points
FD = field duplicate
Selenium µg/L 10 0% 97.48 34.12 0.98 l.18E-03
p = probability
W = Shapiro Wilk test value
S = Mann-Kendall statistic
Distribution = Distribution as determined by the Shapiro-Wilk distribution test for constituents with % Detect> 50% and N>B
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> 50%
HHV = Highest Historical Value. The highest observed value for constituents with % Detect> 50%
Post-November 2019 = All data post November 2019
Appendix A
Source Assessment Report for MW-03a
White Mesa Uranium Mill
Normal
Mann Kendall
Trend Analysis Linear Trend Analysis
s p r2
333 0.015 NA NA
35 0.0012 0.65 5.09E-03
Significant
Trend
Increasing
Increasing
Previously
Identified
Increasing
Trend?
Yes
Yes
Current
GWCL'
Mean x
Mean+ 2o 1.5
109.58 134.43 132.19
109.58 165.71 146.22
r2 = The measure of how well the trendline fits the data where r2=1 represents a perfect fit.
FA= Fraction of GWQS as defined in UAC R317-6
NA= Not Applicable
Page 1 of 12
Highest
Historical
Value (HHV)
171.0
171.0
Fractional
Approach
GWCL
25.0
25.0
Flowsheet
GWCL
171.00
165.71
Rationale Modified GWCL Rationale
HHV 171.00 HHV
Mean+ 2cr 1'11.00 HHV
.-1-s lNTERA
Appendix A-2: Comparison of Calculated and Measured TDS in MW-03A
Alkalinity Calcium Well Date Sampled (mg/Las
HCO3 )
(mg/L)
----
MW-03a 6/23/2005 170 441
MW-03a 9/25/2005 342 471
MW-03a 12/14/2005 302 482
MW-03a 3/27/2006 323 480
MW-03a 6/25/2006 375 443
MW-03a 9/19/2006 356 467
MW-03a 10/26/2006 409 460
MW-03a 3/14/2007 381 478
MW-03a 10/31/2007 324 479
MW-03a 5/28/2008 384 496
MW-03a 11/3/2008 287 498
MW-03a 2/9/2009 265 481
MW-03a 5/28/2009 306 436
MW-03a 8/18/2009 305 486
MW-03a 10/28/2009 424 478
MW-03a 5/4/2010 436 487
MW-03a 11/22/2010 346 463
MW-03a 4/13/2011 375 473
MW-03a 10/11/2011 376 474
MW-03a 5/15/2012 386 477
MW-03a 11/29/2012 396.5 469
MW-03a 5/23/2013 435.54 436
MW-03a 12/11/2013 384.3 446
MW-03a 5/30/2014 414.8 465
MW-03a 11/13/2014 451.4 580
MW-03a 4/23/2015 407.48 490
MW-03a 11/4/2015 400.16 464
MW-03a 4/27/2016 352.58 484
MW-03a 11/8/2016 296.46 438
MW-03a 4/26/2017 353.8 448
MW-03a 10/25/2017 418.46 447
MW-03a 4/25/2018 400.16 465
MW-03a 11/1/2018 400.16 512
MW-03a 5/2/2019 463.6 512
MW-03a 11/6/2019 585.6 433
MW-03a 4/13/2020 385.52 477
MW-03a 10/26/2020 453.84 474
MW-03a 4/27/2021 417.24 468
MW-03a 11/10/2021 380.64 483
MW-03a 4/27/2022 400.16 208
MW-03a 10/19/2022 358.68 426
MW-03a 4/27/2023 355.02 388
Appendix A
Source Assessment Report for MW-03A
White Mesa Uranium Mill
Chloride Potassium Magnesium Sodium Sulfate
(mg/L) (mg/L) (mg/L) (mg/L) (mg/L)
---
63 26.4 284 698 3380
64 26.6 298 715 3560
60 26.6 314 707 3520
56 26.7 318 706 3490
61 30.2 282 679 3510
70 27.7 293 722 3440
57 26.8 288 737 3270
62 26.9 309 754 3810
60 29.3 310 741 3470
61 28.6 306 827 3550
56 28.6 310 811 3570
49 28.6 320 761 3730
60 28.1 303 674 3640
57 28.6 308 764 3840
42 28.0 298 773 3870
57 28.2 302 840 3680
59 27.8 312 754 3850
65 28.6 295 814 3350
59 27.3 301 708 3750
62 33.5 305 748 3220
67.1 28.1 295 818 2780
55.9 25.4 280 789 3120
60.9 27.8 296 781 3360
64.2 27.2 302 772 3830
59.7 26.5 385 977 3770
64.6 28.1 310 825 3720
59.5 27.3 296 732 3380
62.6 28.3 309 770 3580
67.4 27.8 304 669 3440
64.3 29.5 293 769 3450
58.2 30.6 288 760 3340
65.1 25.4 286 794 2810
55.7 30.0 311 859 3090
62.5 28.9 307 947 3450
58 .8 43.0 261 741 3730
60.1 29.7 288 897 3410
57.8 28.7 305 765 3430
62.5 33.9 277 810 3250
61.6 27.1 291 829 3550
57.3 12.0 130 753 3280
55.5 25.5 264 773 3520
60.7 24.8 255 716 3530
Page 2 of 12
-
Measured Calculated Ratio TDS (mg/L) TDS (mg/L)
5540 5062 91%
5560 5477 99%
5360 5412 101%
5410 5400 100%
5700 5380 94%
5580 5376 96%
5520 5248 95%
5770 5821 101%
5490 5413 99%
5070 5653 111%
5600 5561 99%
5690 5635 99%
5660 5447 96%
5760 5789 100%
5570 5913 106%
5860 5830 99%
5330 5812 109%
5720 5401 94%
5630 5695 101%
5730 5232 91%
5610 4854 87%
6020 5142 85%
5940 5356 90%
5790 5875 101%
5370 6250 116%
5410 5845 108%
5510 5359 97%
5260 5586 106%
5630 5243 93%
5280 5408 102%
5240 5342 102%
5190 4846 93%
5000 5258 105%
4880 5771 118%
5580 5852 105%
5300 5547 105%
3650 5514 151%
5270 5319 101%
5370 5622 105%
5080 4840 95%
5270 5423 103%
5570 5330 96%
,_Ss ,NTERA
Appendix A-3: Charge Balance Calculations for Major Cations and Anions in MW-03a
Well Date Calcium Sodium
, (meq/L) , (meq/L)
MW-03a 6/23/2005 22.01 30.48
MW-03a 9/25/2005 23.50 31.22
MW-03a 12/14/2005 24.05 30.87
MW-03a 3/27/2006 23.95 30.83
MW-03a 6/25/2006 22.11 29.65
MW-03a 9/19/2006 23.30 31.53
MW-03a 10/26/2006 22.95 32.18
MW-03a 3/14/2007 23.85 32.93
MW-03a 10/31/2007 23.90 32.36
MW-03a 5/28/2008 24.75 36.11
MW-03a 11/3/2008 24.85 35.41
MW-03a 2/9/2009 24.00 33.23
MW-03a 5/28/2009 21.76 29.43
MW-03a 8/18/2009 24.25 33.36
MW-03a 10/28/2009 23.85 33.76
MW-03a 5/4/2010 24.30 36.68
MW-03a 11/22/2010 23.10 32.93
MW-03a 4/13/2011 23.60 35.55
MW-03a 10/11/2011 23.65 30.92
MW-03a 5/15/2012 23.80 32.66
MW-03a 11/29/2012 23.40 35.72
MW-03a 5/23/2013 21.76 34.45
MW-03a 12/11/2013 22.26 34.10
MW-03a 5/30/2014 23.20 33.71
MW-03a 11/13/2014 28.94 42.66
MW-03a 4/23/2015 24.45 36.03
MW-03a 11/4/2015 23.15 31.97
MW-03a 4/27/2016 24.15 33.62
MW-03a 11/8/2016 21.86 29.21
MW-03a 4/26/2017 22.36 33.58
MW-03a 10/25/2017 22.31 33.19
MW-03a 4/25/2018 23.20 34.67
MW-03a 11/1/2018 25.55 37.51
MW-03a 5/2/2019 25.55 41.35
MW-03a 11/6/2019 21.61 32.36
MW-03a 4/13/2020 23.80 39.17
MW-03a 10/26/2020 23.65 33A1
MW-03a 4/27/2021 23.35 35.37
MW-03a 11/10/2021 24.10 36.20
MW-03a 4/27/2022 10.38 32.88
MW-03a 10/19/2022 21.26 33.76
MW-03a 4/27/2023 19.36 31.27
Appendix A
Source Assessment Report for MW-03a
White Mesa Uranium Mill
Magnesiu
m (meq/L)
23.36
24.52
25.83
26.16
23.20
24.11
23.69
25.42
25.50
25.17
25.50
26.33
24.93
25.34
24.52
24.85
25.67
24.27
24.76
25.09
24.27
23.04
24.35
24.85
31.67
25.50
24.35
25.42
25.01
24.11
23.69
23.53
25.59
25.26
21.47
23.69
25.09
22.79
23.94
10.70
21.72
20.98
Total Total
Potassium Cation HCO 3 Chloride SO4 Anion Charge Balance
(meq/L) Charge (meq/L) (meq/L) (meq/L) Charge Error
{meq/L) -{m_!1q/LJ -
0.68 76.53 -2.79 -1.78 -70.37 -74.94 1.05%
0.68 79.92 -5.60 -1.81 -74.12 -81.53 -1.00%
0.68 81.44 -4.95 -1.69 -73.29 -79.93 0.94%
0.68 81.63 -5.29 -1.58 -72.66 -79.54 1.30%
0.77 75.73 -6.15 -1.72 -73.08 -80.95 -3.33%
0.71 79.65 -5.83 -1.97 -71.62 -79.43 0.14%
0.69 79.52 -6.70 -1.61 -68.08 -76.39 2.00%
0.69 82.89 -6.24 -1.75 -79.33 -87.32 -2.60%
0.75 82.51 -5.31 -1.69 -72.25 -79.25 2.02%
0.73 86.77 -6.29 -1.72 -73.91 -81.93 2.87%
0.73 86.50 -4.70 -1.58 -74.33 -80.61 3.52%
0.73 84.29 -4.34 -1.38 -77.66 -83.38 0.54%
0.72 76.84 -5.01 -1.69 -75.79 -82.49 -3.55%
0.73 83.68 -5.00 -1.61 -79.95 -86.56 -1.69%
0.72 82.84 -6.95 -1.18 -80.57 -88.71 -3.42%
0.72 86.55 -7.15 -1.61 -76.62 -85.37 0.69%
0.71 82.41 -5.67 -1.66 -80.16 -87.49 -2.99%
0.73 84.15 -6.15 -1.83 -69.75 -77.73 3.97%
0.70 80.03 -6.16 -1.66 -78.08 -85.90 -3.54%
0.86 82.42 -6.33 -1.75 -67.04 -75.12 4.63%
0.72 84.11 -6.50 -1.89 -57.88 -66.27 11.86%
0.65 79.90 -7.14 -1.58 -64.96 -73.67 4.05%
0.71 81.42 -6.30 -1.72 -69.96 -77.97 2.17%
0.70 82.46 -6.80 -1.81 -79.74 -88.35 -3.45%
0.68 103.96 -7.40 -1.68 -78.49 -87.57 8.55%
0.72 86.70 -6.68 -1.82 -77.45 -85.95 0.43%
0.70 80.17 -6.56 -1.68 -70.37 -78.61 0.98%
0.72 83.92 -5.78 -1.77 -74.54 -82.08 1.11%
0.71 76.79 -4.86 -1.90 -71.62 -78.38 -1.02%
0.75 80.80 -5.80 -1.81 -71.83 -79.44 0.84%
0.78 79.97 -6.86 -1.64 -69.54 -78.04 1.22%
0.65 82.06 -6.56 -1.84 -58.51 -66.90 10.17%
0.77 89.41 -6.56 -1.57 -64.33 -72.46 10.47%
0.74 92.90 -7.60 -1.76 -71.83 -81.19 6.73%
1.10 76.54 -9.60 -1.66 -77.66 -88.92 -7.48%
0.76 87.43 -6.32 -1.70 -71.00 -79.01 5.06%
0.73 82.89 -7.44 -1.63 -71.41 -80.48 1.47%
0.87 82.38 -6.84 -1.76 -67.67 -76.27 3.85%
0.69 84.94 -6.24 -1.74 -73.91 -81.89 1.83%
0.31 54.26 -6.56 -1.62 -68.29 -76.46 -16.98%
0.65 77.38 -5.88 -1.57 -73.29 -80.73 -2.12%
0.63 72.24 -5.82 -1.71 -73.50 -81.03 -5.73%
Page 3 of 12 ra---¥,INTERA
Appendix A-5: MW-03a Data Used for Analysis
Well Date Sampled
MW-03a 6/23/2005
MW-03a 9/25/2005
MW-03a 12/14/2005
MW-03a 3/27/2006
MW-03a 6/25/2006
MW-03a 9/19/2006
MW-03a 10/26/2006
MW-03a 3/14/2007
MW-03a 10/31/2007
MW-03a 5/28/2008
MW-03a 8/12/2008
MW-03a 11/3/2008
MW-03a 2/9/2009
MW-03a 5/28/2009
MW-03a 8/18/2009
MW-03a 10/28/2009
MW-03a 5/4/2010
MW-03a 11/22/2010
MW-03a 2/16/2011
MW-03a 4/13/2011
MW-03a 8/11/2011
MW-03a 10/11/2011
MW-03a 3/1/2012
MW-03a 5/15/2012
MW-03a 7/19/2012
MW-03a 11/29/2012
MW-03a 3/13/2013
MW-03a 5/23/2013
MW-03a 7/19/2013
MW-03a 12/11/2013
MW-03a 3/5/2014
MW-03a 5/30/2014
MW-03a 9/17/2014
MW-03a 11/13/2014
MW-03a 2/12/2015
MW-03a 4/23/2015
MW-03a 7/29/2015
MW-03a 11/4/2015
MW-03a 2/16/2016
MW-03a 4/27/2016
MW-03a 9/22/2016
MW-03a 11/8/2016
MW-03a 2/9/2017
MW-03a 4/26/2017
MW-03a 8/17/2017
Appendix A
Source Assessment Report for MW-03a
White Mesa Uranium Mill
Parameter Name
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Page 5 of 12
Report Report Units Qualifier Result
82.0 ug/I
64.2 ug/I
5.0 ug/I u
71.2 ug/I
75.6 ug/1
79.1 ug/I
54.4 ug/I
74.0 ug/I
73.9 ug/I
73.4 ug/I
94.3 ug/I
89.0 ug/I
107.0 ug/1
102 .0 ug/1
90.4 ug/1
87.1 ug/1
81.4 ug/1
94.8 ug/1
99.0 ug/1
85.8 ug/1
88.5 ug/1
95.0 ug/I
65.8 ug/I
85 .1 ug/I
99.3 ug/1
111.0 ug/1
88.7 ug/1
75.6 ug/1
79.7 ug/1
77.9 ug/1
92.1 ug/I
104.0 ug/I
129.0 ug/1
88.5 ug/1
94.1 ug/1
101.0 ug/1
85.9 ug/I
91.7 ug/1
91.5 ug/I
103.0 ug/1
75.7 ug/1
142.0 ug/1
85.2 ug/1
93.9 ug/I
111.0 ug/I
a.-S;INTERA
Appendix A-5: MW-03a Data Used for Analysis
Well Date Sampled
MW-03a 10/25/2017
MW-03a 4/25/2018
MW-03a 11/1/2018
MW-03a 5/2/2019
MW-03a 11/6/2019
MW-03a 4/13/2020
MW-03a 10/26/2020
MW-03a 4/27/2021
MW-03a 11/10/2021
MW-03a 4/27/2022
MW-03a 10/19/2022
MW-03a 4/27/2023
MW-03a 7/12/2023
MW-03a 10/19/2023
Appendix A
Source Assessment Report for MW-03a
White Mesa Uranium Mill
Parameter Name
I
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Selenium
Page 6 of 12
Report Report Units Qualifier Result
89.6 ug/I
65.0 ug/I
69.4 ug/I
61.9 ug/I
55.4 ug/I
70.0 ug/I
100.0 ug/I
74.0 ug/I
75.5 ug/I
87.4 ug/I
97.5 ug/I
112.0 ug/I
171.0 ug/I
132.0 ug/I
p,,-'-INTERA
Appendix A-6: Data Removed from Analysis
Reason Location ID Date Sampled Parameter Name , Report Result Report Units
No extreme outliers for SAR arameters removed from anal sis
Appendix A
Source Assesment Report for MW-03a
White Mesa Uranium Mill Page 7 of 12 .-:-INTERA
Appendix A-8: Box Plots of MW-03a
-::::
O>
2-
E
.2
C
Q)
Q)
(/)
'a,
::,
E
.:!
C:
Q)
Q)
rJ)
Appendix A
150
100
50
0
Selenium in MW-03a for All Data
Selenium in MW-03a
•
0
•
Percent nondetect: 2%
o Outlier
♦ Extreme
Min : 5 , Mean: 88 .13 , Max : 171 , Std Dev : 23 .15
Upper extreme threshold (Q75 + 3xH): 166.35
Lower extreme threshold (Q25 -3xH): 7.44999999999999
Selenium in MW-03a Post November 2019
160
140
120
100
80
60
Selenium in MW-03a
0
Percent nondetect: 0%
o Outlier
♦ Extreme
Min: 55.4, Mean : 97.48 , Max: 171, Std Dev : 34.12
Upper extreme threshold (Q75 + 3xH): 212 .875
Lower extreme threshold (Q25 -3xH): -29 .5
Source Assessment Report for MW-03a
White Mesa Uranium Mill Page 9 of 12 ~-SslNTERA
:z: (/) )>
::J'" 0 "C
-· C "C
--, (D (DO :::J
::::0 (D a.
:::,, ..... -· <D _.... X
fG g: )>
(D
C Ill -, 1/1
II) 3 2. (D
C :::J
3 -
s: ~ =-c -o
-0
DJ CTQ
(D
I-'
0
s,
I-'
N
~
0 -,
s:
~
0
(,)
II)
II
2
-I
I
)> 2 =o Ill ,.
< ~ ~-Ql
C" ro
a.
Ill -Ill
C
CJ)
CD a.
:r MW-01 -
CT MW-02 -0 >< MW-03a -
"O MW-05 -0 -MW-11 -CJ)
MW-12 -
MW-14 -
MW-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 -
MW-41B -
Selenium (ug/L)
..... ..... N I\) (,)
01 0 01 0 01 0 0 0 0 0 0 0 0
I I I I I I I
• 0
~ .... mo m-~ X C --• c--[]]----, o • -, -CD -·
loff• 3 ~
(D ...
t[]]---, ..
IID)Or-------C[J-----.i • I[), • • + ♦
tl]io ♦
♦ ..
I .. +
[l-41>
►
r[}--,o
c-ffi-,
♦
fll}l
l{l]--00
r-(D--, 0
IP
r-[]-,
I
r··----c=[J --,
I
(/)
(D m :::, c:·
3
s: )>
0,, :::s ,,
-· (I)
-:::s Q C.
~-><"
:e t (I) ••
=m (/) 0
><
""C
0 ur
en :::r
0
~ -· :::s cc
en ;:;: ;
a:
(I)
en
(I) -(I)
:::s
C
3
C ;· -::::!. er
C -er
:::s -:::s
G)
0
C
:::s
C.
! -(I) ...
APPENDIXB
Appendix B-1: Summary of Statistical Analysis for Indicator Parameters in MW-03a
Well Data Set Constituent
ALL 2024 SAR Data
Post-November 2019 Chloride (mg/L)
ALL 2024 SAR Data Fluoride (mg/L)
Post-November 2019 Fluoride (mg/L)
MW-03a ALL 2024 SAR Data Sulfate (mg/L)
Post-November 2019 Sulfate (mg/L)
ALL 2024 SAR Data Uranium (µg/L)
Post-November 2019 Uranium (µgill
ALL 2024 SAR Data pH (µg/L)
Post-November 2019 pH (µg/L)
Notes:
a= sigma
%ND = percent of non-detected values
µg/L = micrograms per liter
¾Non-
N Detected Mean
Values
1 42 I o 1 60.0 1
8 0 59.3
42 0.047619 1.07
8 0.125 0.81
57 0 3480.4
8 0 3462.5
43 0.023256 19.6
8 0 18.6
61 0 6.6
9 0 6.8
Standard
Deviation
Shapiro-WIik Test
for Normallty
ra'.? µ
Q863 I 1.34E-04
2.4 0.975 9.32E-01
0.3 0.444 2.02E-11
0.4 0.720 3.78E-03
262.1 0.916 7.21E-04
155.5 0.955 7.61E-01
4.6 0.297 4.46E-13
1.5 0.895 2.62E-01
0.3 0.989 8.49E-01
0.2 0.948 6.73E-01
N = number of valid dala points
p = probability
W = Shapiro-Wilk lest value
Normally or
Log normally
distributed?
Normal
Nol normal
Not normal
Not normal
Normal
Not normal
Normal
Normal
Normal
Least Squares
Regression Trend
Analysis'
r' p
0.02 7.4E-01
NA NA
NA NA
NA NA
0.03 6.7E-01
NA NA
0.28 1.8E-01
NA NA
NA NA
S = Mann-Kendall statistic
FD= field duplicate
Mann-Kendall Trend
Analysisb
s p
O•
-4 0.36
-287 0.00
6 0.27
21088.33 0.07
0 0.50
9115 0.01
-15 0.040452
NA NA
_O __ ~
mg/L = milligrams per liler r2 = The measure of how well the lrendline fits the data where r2=1 represents a perfect fit ,
Appendix B
a = A regression test was performed on data that was determined lo have normal or log-normal distribution
b = The Mann-Kendall test was performed on data that are not normally or lognormally dislributed
Post-November 2019 = All data post November 2019
Source Assesment Report for MW-03a
White Mesa Uranium Mill Page 1 of 19
Background
Report
Significant
Trend?
No
No
No
No
No
No
No
Decreasing
Decreasing
2024 Significant Trend
I Not significanl
Not significant
Significantly decreasing
Not significant
Not significant
Not significant
Significanlly decreasing_
Significant (no trend)
NA
Not significant
~¥.INTERA
GEDSCIENCE & ENGINEEl=IING SOLUTIONS
Appendix B-3: MW-03a Indicator Parameter Data Used for Analysis
"" • IJ,:lf•
MW-03a 06/23/2005
MW-03a 09/25/2005
MW-03a 12/14/2005
MW-03a 03/27/2006
MW-03a 06/25/2006
MW-03a 09/19/2006
MW-0 a 0 I 0
MW-03a 03/14/2007
MW-03a 10/31/2007
-0 05/28/2008
MW-03a 11/03/2008
MW-03a 02/09/2009
MW-03a 05/28/2009
MW-03a 08/18/2009
MW-03a 10/28/2009
MW-03a 05/04/2010
MW-03a 11/22/2010
MW-03a 04/13/2011
MW-03a 10/11/2011
MW-03a 05/15/2012
MW-03a 11/29/2012
MW-03a 05/23/2013
MW-03a 12/11/2013
MW-03a 05/30/2014
MW-03a 11/13/2014
MW-03a 04/23/2015
MW-03a 11/04/2015
MW-03a 04/27/2016
MW-03a 11/08/2016
MW-03a 04/26/2017
MW-03a 10/25/2017
MW-03a 04/25/2018
MW-03a 11/01/2018
MW-03a 05/02/2019
MW-03a 11/06/2019
MW-03a 04/13/2020
MW-03a 10/26/2020
MW-03a 04/27/2021
MW-03a 11/10/2021
MW-03a 04/27/2022
MW-03a 10/19/2022
MW-03a 04/27/2023
MW-03a 06/23/2005
MW-03a 09/25/2005
MW-03a 12/14/2005
MW-03a 03/27/2006
MW-03a 06/25/2006
MW-03a 09/19/2006
Appendix B
Source Assesment Report for MW-03a
White Mesa Uranium Mill
r-:; 1..-; • ·~
Chloride 63.0 mQ/1
Chloride 64.0 mg/I
Chloride 60.0 mg/I
Chloride 56.0 mQ/1
Chloride 61.0 mg/I
Chloride 70.0 mg/I
11 ride 57.0 mQ/1
Chloride 62.0 mg/I
Chloride 60.0 mg/I
r 1. 1g/l
Chloride 56.0 mg/I
Chloride 49.0 mg/I
Chloride 60.0 mQ/1
Chloride 57.0 mg/I
Chloride 42.0 mg/I
C ri 57. mQ/1
Chloride 59.0 mg/I
Chloride 65.0 mg/I
C ri 5 . mQ/1
Chloride 62.0 mg/I
Chloride 67.1 mg/I
Chloride 55.9 mg/I
Chloride 60.9 mg/I
Chloride 64.2 mg/I
Chloride 59.7 mg/I
Chloride 64.6 mg/I
Chloride 59.5 mg/I
Chloride 62.6 mg/I
Chloride 67.4 mg/I
Chlorid mg/I
Chloride 58.2 mg/I
Chloride 65.1 mg/I
Chloride 55.7 mQ/1
Chloride 62.5 mg/I
Chloride 58.8 mg/I
Chloride 60.1 mQ/1
Chloride 57.8 mg/I
Chloride 62.5 19/1
Chloride 61.6 mQ/1
Chloride 57.3 mg/I
Chloride 55.5 mQ/1
Chloride 60.7 mg/I
Fluoride 1.6 mg/I
Fluoride 1.1 mQ/1
Fluoride 1.3 mg/I
Fluoride 1.4 mg/I
Fluoride 1.1 mg/I
Fluoride 0.0 mg/I u
Page 3 of 19 =-is,NTERA
Appendix B-3: MW-03a Indicator Parameter Data Used for Analysis
. ;T,jr.ll ■F.U·
-, .. 1 /_v06
-0 a 0 I /2007
MW-03a 10/31/2007
MW-03a 05/28/2008
MW-03a 1 03/2008
MW-03a 02/09/2009
MW-03a 05/28/2009
MW-03a 08/18/2009
MW-03a 10/28/2009
MW-03a 05/04/2010
MW-03a 11/22/2010
MW-03a 04/13/2011
MW-03a 10/11/2011
MW-03a 05/15/2012
MW-03a 11/29/2012
MW-03a 05/23/2013
MW-03a 12/11/2013
MW-03a 05/30/2014
MW-03a 11/13/2014
r~ - 3 04/23/2015
MW-03a 11/04/2015
MW-03a 04/27/2016
MW-03a 11/08/2016
MW-03a 04/26/2017
MW-03a 10/25/2017
MW-03a 04/25/2018
MW-03a 11/01/2018
MW-03a 05/02/2019
MW-03a 11/06/2019
MW-03a 04/13/2020
MW-03a 10/26/2020
MW-03a 04/27/2021
MW-03a 11/10/2021
MW-03a 04/27/2022
MW-03a 10/19/2022
MW-03a 04/27/2023
MW-03a 06/23/2005
MW-03a 09/25/2005
MW-03a 12/14/2005
MW-03a 03/27/2006
MW-03a 06/25/2006
MW-03a 09/19/2006
MW-03a 10/26/2006
MW-03a 03/14/2007
MW-03a 10/31/2007
MW-03a 05/28/2008
MW-03a 11/03/2008
MW-03a 02/09/2009
Appendix B
Source Assesment Report for MW-03a
White Mesa Uranium Mill
=-.■-. l ■■r• l(:J -■IU:lliif •
Fluoride 1.1 mg/I
Fluoride 1.2 mg/I
Fluoride 1.4 mg/I
Fluoride 1.0 mg/I
Fluoride 1.5 mg/I
Fluoride 1.5 mg/I
Fluoride 1.6 mg/I
Fluoride 1.4 mg/I
Fluoride .0 mg/I
Fluoride 0.9 mg/I
Fluoride 1.3 mg/I
Fluoride 1.1 mg/I
Fluoride 1.1 mg/I
Fluoride 1.1 mg/I
Fluoride 1.0 mg/I
Fluoride 1.0 mg/I
Fluoride 1.0 mg/I
Fluoride 1.0 mg/I
Fluoride 1.0 mg/I
Fluoride 0.9 mg/I
Fluoride 1.0 mg/I
Fluoride 1.1 mg/I
Fluoride 1.4 mg/I
Fluoride 1.1 mg/I
Fluoride 1.0 mg/I
Fluoride 1.3 mg/I
Fluoride 0.9 mg/I
Fluoride 1.0 mg/I
Fluoride 0.4 mg/I
Fluoride 0.9 mg/I
Fluoride 0.9 mg/I
Fluoride 1.0 mg/I
Fluoride 1.1 mg/I
Fluoride 0.1 mg/I u
Fluoride 1.4 mg/I
Fluoride 0.6 mg/I
Sulfate 3380.0 mg/I
Sulfate 3560.0 mg/I
Sulfate 3520.0 mg/I
Sulfate 3490.0 mg/I
Sulfate 3510.0 mg/I
Sulfate 3440.0 mg/I
Sulfate 3270.0 mg/I
Sulfate 3810.0 mg/I
Sulfate 3470.0 mg/I
Sulfate 3550.0 mg/I
Sulfate 3570.0 mg/I
Sulfate 3730.0 mg/I
Page 4 of 19 ~rrnE ~NTERA
Appendix B-3: MW-03a Indicator Parameter Data Used for Analysis
. mr,, P.111 F.I r-
05/28/2009
-a 08/18/2009
MW-03a 10/28/2009
MW-03a 05/04/2010
-03a 09/21/2010
MW-03a 11/22/2010
MW-03a 02/16/2011
MW-03a 04/13/2011
MW-03a 08/11/ 1
MW-03a 10/11/2011
MW-03a 03/01/2012
MW-03a 05/15/2012
MW-03a 07/19/2012
MW-03a 11/29/2012
MW-03a 03/13/ 1
MW-03a 05/23/2013
MW-03a 07/19/2013
MW-03a 12/11/2013
MW-03a 03/05/2014
MW-03a 05/30/2014
MW-03a 09/17/2014
MW-03a 11/13/2014
-3a 02/12/2015
MW-03a 04/23/2015
MW-03a 07/29/2015
-0 a 11/0 /2015
MW-03a 02/16/2016
MW-03a 04/27/2016
MW-03a 09/22/2016
MW-03a 11/08/2016
MW-03a 02/09/2017
MW-03a 04/26/2017
MW-03a 08/17/2017
MW-03a 10/25/2017
MW-03a 04/25/2018
MW-03a 11/01/2018
-I /2019
MW-03a 11/06/2019
MW-03a 04/13/2020
MW-03a 10/2 I 0
MW-03a 04/27/2021
MW-03a 11/10/2021
MW-03a 04/2 I 0 2
MW-03a 10/19/2022
MW-03a 04/27/2023
MW-03a 06/23/2005
MW-03a 09/25/2005
MW-03a 12/14/2005
Appendix B
Source Assesment Report for MW-03a
White Mesa Uranium Mill
,~. .. -. 1r:11 ■■1•
Sulfate 3640.0 mg/I
Sulfate 3840.0 mg/I
Sulfate 3870.0 mg/I
Sulfate 3680.0 mg/I
Sulfate 3630.0 mg/I
Sulfate 3850.0 mg/I
Sulfate 3730.0 mg/I
Sulfate 3350.0 mg/I
ul ~ 5 0. 1g/l
Sulfate 3750.0 mg/I
Sulfate 3020.0 mg/I
Sulfate 3 20. 1g/l
Sulfate 3700.0 mg/I
Sulfate 2780.0 mg/I
ul e 34 0. g/1
Sulfate 3120.0 mg/I
Sulfate 3670.0 mg/I
Sulfate 3360.0 mg/I
Sulfate 3100.0 mg/I
Sulfate 3830.0 mg/I
Sulfate 3350.0 mg/I
Sulfate 3770.0 mg/I
Sulfate 3450.0 mg/I
Sulfate 3720.0 mg/I
Sulfate 3860.0 mg/I
Sulfate 3380.0 mg/I
Sulfate 3580.0 mg/I
Sulfate 3580.0 mg/I
Sulfate 3390.0 mg/I
Sulfate 3440.0 mg/I
Sulfate 2800.0 mg/I
Sulfate 3450.0 mg/I
Sulfate 3740.0 mg/I
Sulfate 3340.0 mg/I
Sulfate 2810.0 mg/I
Sulfate 3090.0 mg/I
Sulfate 3450.0 mg/I
Sulfate 3730.0 mg/I
Sulfate 3410.0 mg/I
S I at mg/I
Sulfate 3250.0 mg/I
Sulfate 3550.0 mg/I
lfa 2 0. mg/
Sulfate 3520.0 mg/I
Sulfate 3530.0 mg/I
Uranium 35.2 ug/1
Uranium 19.7 ug/1
Uranium 0.3 ug/1 u
Page 5 of 19 .-:e ,NTERA
Appendix B-3: MW-Ola Indicator Parameter Data Used for Analysis
•Ill -■F.l•·
A .... 03/27/2006
-a 06/25/2006
MW-03a 09/19/2006
MW-03a 10/26/2006
MW-03a 03/14/2007
MW-03a 10/31/2007
MW-03a 05/28/2008
MW-03a 08/12/2008
MW-03a 1/ I
MW-03a 02/09/2009
MW-03a 05/28/2009
MW-03a /1 / 9
MW-03a 10/28/2009
MW-03a 05/04/2010
MW-03a 11/22/2010
MW-03a 04/13/2011
MW-03a 10/11/2011
MW-03a 05/1 / 12
MW-03a 11/29/2012
MW-03a 05/23/2013
MW-03a 12/11/2013
MW-03a 05/30/2014
MW-03a 11/13/2014
MW-03a 04/23/2015
MW-03a 11/04/2015
-a I 7/2 1
MW-03a 11/08/2016
MW-03a 04/26/2017
MW-03a 10/25/2017
MW-03a 04/25/2018
MW-03a 11/01/2018
MW-03a 05/02/2019
MW-03a 11/06/2019
MW-03a 04/13/2020
MW-03a 10/26/2020
MW-03a 04/27/2021
MW-03a 11/10/2021
MW-03a 04/27/2022
MW-03a 10/19/2022
MW-03a 04/27/2023
Appendix B
Source Assesment Report for MW-03a
White Mesa Uranium Mill
1-.. 1..:1 , ••• • -IIJF.lnm:I
Uranium 19.9 ug/I
Uranium 28.2 ug/I
Uranium 25.4 ug/I
Uranium 24.2 ug/I
Uranium 21.9 ug/I
Uranium 22.9 ug/I
Uranium 22.4 ug/I
Uranium 19.0 ug/I
rmi m 17. ug/I
Uranium 16.5 ug/I
Uranium 17.0 ug/I
r ni m 17.0 ug/I
Uranium 19.5 ug/I
Uranium 19.5 ug/I
r im 19.2 ug/I
Uranium 19.7 ug/I
Uranium 18.1 ug/I
Uranium 2.1 ug/I
Uranium 22.4 ug/I
Uranium 18.5 ug/I
Uranium 24.3 ug/I
Uranium 20.1 ug/I
Uranium 16.7 ug/I
Uranium 20.3 ug/I
Uranium 19.3 ug/I
Uranium 7. ug/
Uranium 16.1 ug/I
Uranium 19.2 ug/I
Uranium 16.1 ug/I
Uranium 19.3 ug/I
Uranium 18.6 ug/I
Uranium 19.0 ug/I
Uranium 19.6 ug/I
Uranium 19.6 ug/I
Uranium 16.8 ug/I
Uranium 20.3 ug/I
Uranium 19.2 ug/I
Uranium 19.0 ug/I
Uranium 18.0 ug/I
Uranium 16.2 UQ/I
Page 6 of 19 ...-¾#slNIE.:IA
Appendix B-5: Box Plots for Indicator Parameters in MW-03a
,......_
:::::
Cl
E -Q)
"O ·;::
.Q
.c
(.)
-:::::::
Cl
E -Q)
"C ·c
..Q
..c
(.)
Appendix B
70
65
60
55
50
45
Chloride in MW-03a for All Data
Chloride in MW-03a
0
0
Percent nondetect: 0%
o Outlier
• Extreme
Min: 42, Mean: 60.05, Max: 70, Std Dev: 4.81
Upper extreme threshold (Q75 + 3xH): 78.025
Lower extreme threshold (Q25 -3xH): 41.975
Ch loride in MW-03a Post November 2019
62
61
60
59
58
57
56
Chloride in MW-03a
Percent nondetect: 0%
o Outlier
• Extreme
Min: 55.5, Mean: 59.29, Max: 62.5, Std Dev: 2.36
Upper extreme threshold (Q75 + 3xH): 70.675
Lower extreme threshold (025 -3xH): 47.925
Source Assessment Report for MW-03a
White Mesa Uranium Mill Page 8 of 19 --¼INTERA
Appendix B-5: Box Plots for Indicator Parameters in MW-03a
Appendix B
1.5
.........
::::::::
O>
_§_ 1.0
Q)
"C ·;;::
0
:J
u:::: 0.5
• 0.0
Fluoride in MW-03a for All Data
Fluoride in MW-03a
0
0 •
Percent nondetect: 5%
o Outlier
• Extreme
Min: 0.020307443494044, Mean: 1.07, Max: 1.6, Std Dev: 0.33
Upper extreme threshold (Q75 + 3xH): 2.21
Lower extreme threshold (Q25 -3xH): 0.0749999999999995
Fluoride in MW-03a Post November 2019
1.4
1.2 -1.0 ::::
Cl
E -0.8 Q)
"C ·;;:: 0.6 0
:J u::: 0.4
0.2
Fluoride in MW-03a
Percent nondetect: 12%
o Outlier
• Extreme
Min: 0.1, Mean: 0.81, Max: 1.36, Std Dev: 0.41
Upper extreme threshold (Q75 + 3xH): 2.6235
Lower extreme threshold (Q25 -3xH): -1.048
Source Assessment Report for MW-03a
White Mesa Uranium Mill Page 9 of 19 ... ¥slNTERA
Appendix B-5: Box Plots for Indicator Parameters in MW-03a
-::::
O>
E -Q) -~
::J
Cl)
-'ai .s
.l!:!
~ ::::,
Cl)
Appendix B
3800
3600
3400
3200
3000
2800
Sulfate in MW-03a for All Data
Sulfate in MW-03a
Percent nondetect: 0%
o Outlier
• Extreme
Min: 2780, Mean: 3480.35, Max: 3870, Std Dev: 262.1
Upper extreme threshold (Q75 + 3xH): 4640
Lower extreme threshold (Q25 -3xH): 2400
Sulfate in_ IVIW-03a Post November 2019 ,
3700
3600
3500
3400
3300
Sulfate in MW-03a
Percent nondetect: 0%
o Outlier
♦ Extreme
Min: 3250, Mean: 3462.5, Max: 3730, Std Dev: 155.54
Upper extreme threshold (Q75 + 3xH): 4007.5
Lower extreme threshold (Q25 -3xH): 2905
Source Assessment Report for MW-03a
White Mesa Uranium Mill Page 10 of 19 ~¥.INTERA
Appendix 8-5: Box Plots for Indicator Parameters in MW-03a
-::::::::
Cl
2-
E
::J
C
ClJ ,_
=>
-'ai
2.
E
.2
C
(ti .... =>
Appendix B
35
30
25
20
15
10
5
0
Uranium in MW-03a for All Data
Uranium in MW-03a
•
• 8
•
Percent nondetect: 2%
o Outlier
• Extreme
Min: 0.3, Mean: 19.58, Max: 35.2, Std Dev: 4.62
Upper extreme threshold (Q75 + 3xH): 27.35
Lower extreme threshold (Q25 -3xH): 10.9
Uranium in MW-03a Post Uranium 2019
20
19
18
17
Uranium in MW-03a
Percent nondetect: 0%
o Outlier
• Extreme
Min: 16.2, Mean: 18.59, Max: 20.3, Std Dev: 1.45
Upper extreme threshold (Q75 + 3xH): 25.3
Lower extreme threshold (Q25 -3xH): 12
Source Assessment Report for MW-03a
White Mesa Uranium Mill Page 11 of 19 .-9¥slNTERA
Appendix B-7: Timeseries Plots for Indicator Parameters in MW-03a
----::::::::
0)
E -Q)
"O ·;:::
0
..c
(.)
----::::::::
0)
E
Chloride in MW-03a for All Data
70 -e
65 -~ ®
@@ @® 60 -
55 -
50 -
45 -
I
2005
@®
@
@
@
® ®
€)
I
2010
@
Chloride in MW-03a
®
®
®
@ ®
@ ®
@ ®
® ®
@
I
2015
Sample Date
®
Iii)
@
@
®
@ii@
®
I
2020
@ @
Chloride in MW-03a Post November 2019
Chloride in MW-Q3a
r =-0.1432 p = 0.7352 r = 0.0205
®
@@
Q)
"O ·;:::
62 -
61 -
60 -59 -~;®--.::... _______________ _j
Appendix B
0
..c
0
58 -
57 -
56 -
I
2020
Source Assessment Report for MW-03a
White Mesa Uranium Mill
I
2021
I
2022
Sample Date
Page 16 of 19
0
I
2023
~¾INTERA
Appendix 8-7: Timeseries Plots for Indicator Parameters in MW-03a
-::::::::
C)
E -Q)
"C ·c
0
::J
LL
-::::::::
C)
E -Q)
"O ·c
0
::J
LL
Appendix B
Fluoride in MW-03a for All Data
Fluoride in MW-03a
1.5 Q;)o
0 @ 0 (I 8 0 ~
® e@@ f) @ ®® @(I) 1.0 Ii @(ii) @@)®@)Ii®@®@ (f)
@@ •
0 .5 @
0.0
2005 2010 2015 2020
Sample Date
Fluoride in MW-03a Post November 2019
1.4
1.2 -
1.0 -
0.8 -
0.6 -
0.4 -®
0.2 -
I
2020
--
Fluoride in MW-03a
0
I I
2021 2022
Sample Date
u
I
2023
f)
@
0
Source Assessment Report for MW-03a
White Mesa Uranium Mill Page 17 of 19 ..-3:s lNTERA
APPENDIXC
Table C.1
Predicted MW-3A Concentrations Based on a Mass Balance Assuming a
TMS lmpact1
average 2 predicted Q4, 2023 measured
constituent concentration in MW-11
constituent concentration in TMS assuming TMS impact
chloride (mg/L) 27,274 3,600
fluoride (mg/L) 3,229 420
sulfate (mg/L) 172,787 25,394
uranium (ug/L) 373,395 48,558
selenium (ug/L) 8,930 1,276
1 assumes water level increase at MW-3A due to TMS impact
2 assumes conservative behavior (no sorption, hydrodynamic dispersion or degradation)
mg/L = milligrams per liter
ug/L = micrograms per liter
concentration
in MW-3A
62
0.70
3,370
18.9
132.0
APPENDIXD
APPENDIXE
Input and Output Files (Electronic Only)