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Home My WebLink AboutDRC-2021-006041 - 0901a06880e7a4f2Div of Waste Management and Radiation Control APR 3 0 2021 Energy Fuels Resources (USA) Inc. 225 Union Blvd. Suite 600 Lakewood, CO, US, 80225 ENERGYFUELS 3(13 974 2140 D RC-2021- oo(004-[ ergyfuels.coin April 29, 2021 Sent VIA E-MAIL AND OVERNIGHT DELIVERY Ms. Jalynn Knudsen Interim Director Division of Waste Management and Radiation Control Utah Department of Environmental Quality 195 North 1950 West Salt Lake City, UT 84116 Re: Transmittal of Source Assessment Report for MW-31 White Mesa Mill Groundwater Discharge Permit UGW370004 Dear Ms. Knudsen 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 3rd Quarter 2020 as described in the Division of Waste Management and Radiation Control ("DWMRC")-approved Q3 2020 Plan and Time Schedule. EFRI submitted the Plan and Time Schedule for MW-31 on November 18. 2020. DWMRC approval of the Plan and Time Schedule was received by EFRI on February 1, 2021. Each hardcopy report contains a CDs with a word searchable electronic copy of the report. If you should have any questions regarding this report plotaxe contact me, Yours very truly, ENERGY FUELS RFSOURCFS (USA) INC. Kathy weinel Quality Assurance Manager : David Frydenlund Garrin Palmer Terry Slade Logan Shumway Scou Bakken Stewart Smith (HGC) Angie Persico (Intera) Dear Ms. Knudsen White Mesa Uranium Mill State of Utah Groundwater Discharge Permit No. UGW370004 Source Assessment Report Under Part I.G.4 For Exceedances in MW-31 in the Third Quarter of 2020 Prepared by: Energy Fuels Resources (USA) Inc. 225 Union Boulevard, Suite 600 Lakewood, CO 80228 April 29, 2021 ES-i EXECUTIVE SUMMARY This Source Assessment Report (“SAR”) is an assessment of uranium in monitoring well 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. Uranium occurs naturally at the Mill (INTERA, 2008) and has exhibited exceedances of the applicable Groundwater Compliance Limits (“GWCLs”) in MW-31 and other wells, both upgradient and downgradient of Mill facilities due to natural background and site-wide influences. 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 five SAR reports (INTERA, 2012a, 2013, 2015, 2017, 2020). Sulfate and total dissolved solids (“TDS”) in MW-31 were most recently assessed and included in the 2020 SAR. The 2020 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 August 6, 2020, 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 2020 SAR and the associated modified GWCLs, as presented in the August 6, 2020 letter from DWMRC, were approved. Increasing trends in concentrations have continued in groundwater at MW-31, prompting additional exceedances and out-of-compliance (“OOC”) status and resulting in the need for this SAR. Because groundwater in MW-31 was recently evaluated, this SAR focuses on updated statistical analysis using newly available data since the 2020 SAR and a proposed revised GWCL for uranium. 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 with the results of the 2020 SAR, this analysis will demonstrate that concentrations of uranium in MW-31 are within the range of site-wide background. Mass balance calculations presented in Appendix E of the 2020 SAR 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 uranium 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. In accordance with the DWMRC-approved Flowsheet (from INTERA [2007a], included as Appendix C), increasing trends necessitate a modified approach for calculation of GWCLs. The ES-ii modification in this approach uses a more recent dataset (collected after July 2020) 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. i TABLE OF CONTENTS 1.0 INTRODUCTION.............................................................................................................. 1 1.1 Source Assessment Report Organization ......................................................................... 2 2.0 CATEGORIES AND APPROACH FOR ANALYSIS ................................................... 2 2.1 Approach for Analysis ..................................................................................................... 3 2.2 Approach for Setting Revised GWCLs ............................................................................ 3 2.3 University of Utah Study.................................................................................................. 4 3.0 RESULTS OF ANALYSIS................................................................................................ 4 3.1 Site-Wide Decreasing pH ................................................................................................. 4 3.2 Changes in Groundwater in MW-31 ................................................................................ 4 3.3 Indicator Parameter Analysis ........................................................................................... 5 3.4 Mass Balance Analyses .................................................................................................... 6 3.5 Summary of Results ......................................................................................................... 6 4.0 CALCULATIONS OF GROUNDWATER COMPLIANCE LIMITS ......................... 7 4.1 Evaluation of Modified Approaches to Calculation of GWCLs for Trending Constituents...................................................................................................................... 7 4.2 Proposed Revised GWCLs ............................................................................................... 8 5.0 CONCLUSIONS AND RECOMMENDATIONS ........................................................... 9 6.0 REFERENCES ................................................................................................................. 11 LIST OF TABLES Table 1. Proposed GWCL ............................................................................................................... 9 LIST OF FIGURES Figure 1 Location of White Mesa Mill Site and Groundwater Monitoring Wells Figure 2 Groundwater Elevation over Time in MW-31 ii LIST OF APPENDICES Appendix A Statistical Analysis for SAR and Indicator Parameters in MW-31 A-1 Summary of Statistical Analysis for SAR and Indicator Parameters in MW-31 A-2 Descriptive Statistics of SAR and Indicator Parameters in MW-31 A-3 Data Used for Statistical Analysis A-4 Data Removed from Analysis A-5 Box Plots for SAR and Indicator Parameters in MW-31 A-6 Histograms for SAR and Indicator Parameters in MW-31 A-7 Time Series Plots and Linear Regressions for SAR and Indicator Parameters in MW-31 A-8 Time Series Plots for SAR and Indicator Parameters in MW-31 with Events/Inflection Points Appendix B Statistical Analysis for Select Post-Inflection Uranium Datasets (Modified Approach) for Purposes of Calculating GWCL B-1 Summary of Statistical Analysis and GWCL Calculation for Data Subsets B-2 MW-31 Data Used for Analysis B-3 Box Plots for Select Uranium Datasets in MW-31 B-4 Histograms for Select Datasets in MW-31 B-5 Timeseries and Linear Regression Analysis for Select Uranium Datasets in MW-31 Appendix C Flowsheet (Groundwater Data Preparation and Statistical Process Flow for Calculating Groundwater Protection Standards, White Mesa Mill Site [INTERA, 2007a]) Appendix D Input and Output Files (Electronic Only) iii ACRONYM LIST 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 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. GWCL Groundwater Compliance Limit GWDP State of Utah Ground Water Discharge Permit UGW370004 GWQS Groundwater Quality Standard μg/L micrograms per liter mean + 2σ mean concentration plus two standard deviations mg/L milligrams per liter Mill White Mesa Uranium Mill OOC out of compliance SAR Source Assessment Report TDS Total Dissolved Solids UAC Utah Administrative Code TMS Tailings Management System University of Utah Study Hurst and Solomon, (2008) USEPA United States Environmental Protection Agency 1 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 uranium in groundwater compliance monitoring well MW-31. Uranium exceedances have been addressed in previous SARs, and recent concentrations 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 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 + 2σ”) or the equivalent for each constituent in each well, 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, and March 19, 2019, 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. On October 20, 2020, EFRI submitted a notice (the “Q3 2020 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 third quarter of 2020 and indicating which of those constituents had two consecutive exceedances as of that quarter. A plan and time schedule for the third quarter of 2020 (“Q3 2020 Plan and Time Schedule”) covered new dual exceedances of uranium 2 in MW-31. The MW-31 Q3 2020 Plan and Time Schedule was submitted on November 18, 2020, and was approved by the DWMRC in correspondence dated February 1, 2021 (DWMRC, 2021). Uranium concentrations in MW-31 exhibit a statistically significant upward trend first identified during the 2015 SAR (INTERA, 2015). Uranium was also addressed in the 2017 SAR and has exceeded the revised GWCL due to statistically significant trends noted in these previous studies. A comprehensive assessment of MW-31 was completed in June 2020. Since the June 2020 assessment was completed, only a few data points have been collected and the 2020 assessment remains current with no changes required. This SAR for the uranium exceedance will rely on the geochemical, pH, indicator parameter, and plume assessments included in the June 2020 SAR. This SAR will not repeat or reproduce the June 2020 assessments and will only include the relevant statistics and a recalculation of the GWCLs for uranium in MW-31. 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 statistical analysis for uranium and other indicator parameters in MW-31. Appendix B contains the statistical analysis performed on modified uranium datasets in MW-31 to address revising GWCLs for constituents with increasing trends. Appendix C 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 D 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 D can be imported into either R or Statistica to replicate the results presented in this SAR. 2.0 CATEGORIES AND APPROACH FOR ANALYSIS Previously EFRI has categorized wells and constituents in five categories as follows: • Constituents Potentially Impacted by Decreasing pH Trends Across the Site • Newly Installed Wells with Interim GWCLs 3 • Constituents in Wells with Previously Identified Rising Trends • Pumping Wells • Other Constituents This SAR addresses uranium in MW-31. This constituent falls into the third category: Constituents in Wells with Previously Identified Rising Trends. Additionally, uranium can fall within the first category when downward pH trends are noted. 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 appropriate, a revised GWCL is proposed to reflect changes in background conditions at the Mill site. The primary focus of a source assessment for uranium in MW-31 is to determine whether or not there is any new information that would suggest that the previous analysis conducted in the New Wells Background Report, SARs, pH Report (INTERA, 2012b), and Pyrite Report (HGC, 2012a) has changed since the date of those Reports. This assessment has been recently completed in June of 2020 and again as part of the Q3 2020 Plan and Time Schedule. In light of the conclusions and the lack of contradictory data, this assessment is considered complete. Based on those recent studies the evaluation contained within this SAR is focused on updated statistical analysis and recalculation of the GWCL for uranium per the DWMRC letter dated February 1, 2021 (DWMRC, 2021). The analysis performed in this SAR considers all available data to date. 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 C. 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). 2.2 Approach for Setting Revised GWCLs Since the recent assessments indicate that the previous analysis in the Background Reports has not changed, and that the OOC status of uranium in MW-31 is due to natural or other site-wide influences that are already being addressed by corrective action, then new GWCLs are being proposed for uranium. The revised GWCLs use the DWMRC-approved Flowsheet (Appendix C), including the last decision of the process that directs the analyst to consider a modified approach to determining a GWCL if an increasing trend (decreasing in the case of pH) is present. 4 2.3 University of Utah Study At the request of the DWMRC, T. Grant Hurst and D. Kip Solomon of the Department of Geology and Geophysics of the University of Utah performed a groundwater study (the “University of Utah Study”) at the Mill site in July 2007 (Hurst and Solomon, 2008). The purpose of this study was to characterize groundwater flow, chemical composition, noble gas composition, and water age to evaluate whether the increasing and elevated trace metal concentrations in monitoring wells at the Mill, all of which were identified in the Background Reports (INTERA, 2007a, 2007b, 2008), may indicate that potential seepage from the Tailings Management System (“TMS”) is occurring. The overall results and conclusions of this study, as well as the specific results related to MW-31, are included in Section 2.3 of the 2020 SAR. 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 A-1 and Appendix B-1. Supporting analyses are also presented in Appendices A-2, A-5, A-6, A-7, and A-8 as well as Appendices B-3, B-4, and B-5. 3.1 Site-Wide Decreasing pH A general discussion of the site-wide pH trend is included in Section 3.1 of the 2020 SAR. Although pH in MW-31 has an overall significantly decreasing trend when considering the entire historical dataset, more recent data show that pH is stable to increasing at near-neutral values. Statistical analysis of pH in MW-31 is included in Appendix A of this report. 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. • Geochemical influences. • Analytical changes. 5 3.3 Indicator Parameter Analysis As discussed in the Background Reports (INTERA, 2007a, 2007b, 2008), indicator parameters of potential TMS seepage include chloride, sulfate, fluoride, and uranium. Chloride is the best indicator of potential TMS seepage; however, chloride is problematic as an indicator parameter for those groundwater monitoring wells impacted by the chloride plume (EFRI, 2020a). 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 TMS is 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). Regardless, although the absence of a rising trend in constituent concentrations would indicate that there has been no impact from the TMS, a rising trend in concentrations could also result from natural influences (INTERA, 2007a, Section 12.0). 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 A-1. Appendix A-2 presents a descriptive statistics comparison for indicator parameters from the New Wells Background Report and the 2012, 2013, 2015, 2017, and 2020 SARs. Data used in the analysis and data removed prior to analysis are presented in Appendices A-3 and A-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 A-5. Data from additional monitoring wells were plotted alongside indicator parameters for MW-31 in Appendix C-6 of the 2020 SAR. 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 included in Section 3.5 of the 2020 SAR demonstrates, the concentrations of constituents that are increasing and/or exceeding GWCLs in MW-31 are not the result of potential tailings system seepage. 6 Chloride concentrations in MW-31 exhibit a statistically significant increasing trend (see Appendix A-7 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 as described below 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 A-8. 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 of the 2020 SAR. 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. Increased concentrations in MW-31 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 B-9 of the SAR for MW-28 (EFRI, 2020b). 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 of the 2020 SAR) and are not present in concentrations that would be expected if they were due to potential tailings system seepage (Section 3.5 of the 2020 SAR). 3.4 Mass Balance Analyses The 2020 SAR for MW-31 (INTERA, 2020), included a mass balance analysis. In light of the lack of contradictory data, the conclusions in the 2020 SAR are consistent with previous mass balance analyses that were based on nitrate concentrations within the nitrate/chloride plume as described in the December 2009 Nitrate Groundwater Contamination Investigation Report (INTERA, 2009). 3.5 Summary of Results As the results of the analysis of uranium and indicator parameters in MW-31 demonstrate, increasing trends in MW-31 are not consistent with potential TMS seepage. As noted in Section 3.3 above, uranium concentrations are relatively low for the site, and as shown in Appendix A are exhibiting a statistically significant increasing trend. 7 Notable changes in uranium concentration trends occur in 2014 at the time of the wellhead impact and repair, in 2017, and in 2020. The subset of data post-2020 that were analyzed alongside the complete data set and other selected data sets presented in Appendix B are normally distributed and exhibit an increasing trend. Furthermore, the mass balance analysis discussed in the 2020 SAR indicates that the MW-31 uranium concentrations are inconsistent with a potential TMS impact. 4.0 CALCULATIONS 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 the GWCL for uranium 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 C), 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 total dissolved solids (“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: 1. 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. 2. 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: 8 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 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 is proposed to 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. 3. Using recent data to calculate GWCLs. This approach follows the DWMRC-approved Flowsheet (Appendix C) 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 for uranium over the history of the well record, is divided into a subset of data based on identification of points of inflection where the results have shifted. This approach is appropriate in wells, such as MW-31, that have been thoroughly investigated and where the causes of increasing trends are not due to any potential TMS seepage or other Mill-related impacts that are not already being addressed. For purposes of this modified approach and to be consistent with previous SARs, three points of inflection were identified and evaluated in the uranium data sets, (Appendix B) in addition to the full data set. The post-July 2020 data set is normally distributed and exhibits an increasing trend. 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 in MW-31 (DWMRC, 2020). 4.2 Proposed Revised GWCLs In accordance with the Flowsheet, the increasing trend identified for uranium warrants a modified approach to the calculation of GWCLs. The complete uranium data set exhibits a significantly increasing trend with a non-parametric distribution. Post July-2020 data are increasing with a normal distribution. Considering the increasing trends, a modified approach of choosing the highest of the following: (1) fractional approach; (2) highest historical value; (3) mean + 2σ, calculated using either the full data set or a post 9 inflection data set; (4) 1.5 times background, calculated using either the full data set or a post inflection data set: or (5) the 95-UTL, calculated using either the full data set or a post inflection data set would be appropriate. Flowsheet analysis has been performed for these data subsets and the complete datasets and is summarized in Appendix A-1 and Appendix B-1. GWCLs determined according to the Flowsheet using all data to date and the post inflection data sets including the post July-2020 data are presented in Appendix B-1. The modified approach of 1.5 times background using the post-2020 data set is selected as the most appropriate GWCL (Table 1), because it is the greater of the approached listed above. As a result of this analysis, the proposed revised GWCL for uranium is set out in Table 1 below. Table 1. Proposed GWCL Parameter Current GWCLa Flowsheet Revised GWCL Rationale Uranium (µg/L) 15 29.03 1.5 x background of post-July 2020 data set Notes: a = 2021 GWDP No.UGW370004. µg/L = micrograms per liter 5.0 CONCLUSIONS AND RECOMMENDATIONS Background groundwater quality 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). The Background Reports and the University of Utah Study concluded that groundwater at the Mill site has not been impacted by Mill operations. These studies also acknowledged that there are natural influences operating at the Mill site that have caused increasing trends and general variability in background groundwater quality. Consistent with the conclusions of the Background Reports, the University of Utah Study, the conclusion of the 2020 SAR, and this SAR is that groundwater in MW-31 is not impacted by potential TMS seepage. Mass balance calculations have demonstrated that concentrations of uranium and indicator parameters are consistent with background groundwater concentrations, and not the result of potential TMS seepage. Constituents in MW-31 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 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 10 levels, analytical method/laboratory change, and changes in the CAP pumping, as described in Section 3.1 of the 2015 SAR (INTERA, 2015) and the 2020 SAR (INTERA, 2020). In addition to the above factors, a site-wide comparison of constituent concentrations in MW-31 shows that even though many constituents have significant increasing long-term trends, their concentrations are less than or within the range of site-wide background concentrations. This constitutes further evidence that increasing concentrations in MW- 31 are likely due to background influences and the location of this well within the existing nitrate/chloride plume, and not to potential TMS seepage. 11 6.0 REFERENCES Division of Waste Management and Radiation Control (DWMRC), 2020. Letter RE: Energy Fuels Resources (USA) Inc. June 24, 2020 Source Assessment Report for MW-31, White Mesa Uranium Mill Utah Groundwater Discharge Permit No. UGW370004 (Permit) ––––––, 2021. Letter RE: Energy Fuels Resources (USA) Inc. November 18, 2020, Transmittal of Plan and Time Schedule, Groundwater Discharge Permit No. UGW370004 (Permit) Energy Fuels Resources (USA) Inc. (EFRI), 2020a. First Quarter Nitrate Monitoring Report, White Mesa Uranium Mill ––––––, 2020b. White Mesa Uranium Mill State of Utah Groundwater Discharge Permit No. UGW370004 Source Assessment Report under Part I.G.4 For Exceedances in MW-28 in the First Quarter of 2020. HGC, 2012a. Investigation of Pyrite in the Perched Zone. White Mesa Uranium Mill Site. Blanding, Utah. December 7, 2012 _____, 2012b. Corrective Action Plan for Nitrate White Mesa Uranium Mill, Near Blanding, Utah. 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. 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. October 10, 2012. _____, 2012b. PH Report, White Mesa Uranium Mill, Blanding, Utah. 12 ––––––, 2013. Source Assessment Report for MW-31, White Mesa Uranium Mill, Blanding, Utah. August 30, 2013. ––––––, 2015. Source Assessment Report for MW-31, White Mesa Uranium Mill, Blanding, Utah. December 9, 2015. ––––––, 2017. Source Assessment Report for MW-31, White Mesa Uranium Mill, Blanding, Utah. August 20, 2017. ––––––, 2020. Source Assessment Report for MW-31, White Mesa Uranium Mill, San Juan County, Utah. June 24, 2020. United States Environmental Protection Agency (USEPA), 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. _____, 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. _____, 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. Office of Radiation and Indoor Air Radiation Protection Division. EPA-402-R-08-005, April 2008. _____, 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. FIGURES Cell No. 1 Cell No. 2 Cell No. 3 Cell No. 4A WildlifePond WildlifePond 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 Denison Mines\GIS\mapdocs\2020_SARs\MW-31\01_SARMW31_LocationMap.mxd Date: 6/2/2020 Figure 1Location of White Mesa Mill Siteand Groundwater Monitoring WellsWhite Mesa Uranium Mill 900 0 900 Feet Source(s): Aerial – ESRI ArcGIS online;Wells – HGC, Inc., May 2008 report. Groundwater Monitoring Well IDAHOIDAHO NEVADA NEVADA ARIZONAARIZONA WYOMINGWYOMING UTAHUTAH COLORADO COLORADO NEWNEWMEXICOMEXICO White MesaUranium Mill Figure 2 Groundwater Elevations over Time at MW-31 White Mesa Uranium Mill 5540 5541 5542 5543 5544 5545 5546 5547 5548 5549 5550 January‐06 January‐08 January‐10 January‐12 January‐14 January‐16 January‐18 January‐20 January‐22 Po t e n t i o m e t r i c S u r f a c e E l e v a t i o n (f t a m s l ) Date APPENDIX A Statistical Analysis for SAR and Indicator Parameters in MW-31 A-1 Summary of Statistical Analysis for SAR and Indicator Parameters in MW-31 A-2 Descriptive Statistics of SAR and Indicator Parameters in MW-31 A-3 Data Used for Statistical Analysis A-4 Data Removed from Analysis A-5 Box Plots for SAR and Indicator Parameters in MW-31 A-6 Histograms for SAR and Indicator Parameters in MW-31 A-7 Time Series Plots and Linear Regressions for SAR and Indicator Parameters in MW-31 A-8 Time Series Plots for SAR and Indicator Parameters in MW-31 with Events/Inflection Points Appendix A-1: Summary of Statistical Analysis for SAR and Indicator Parameters in MW-31 Wp r2 pSp MW-31 Uranium Complete 88 0 10.227386 3.6784765 0.9274888 0.0001044 No N/A N/A 3039 0 Increasing Yes 22.20 MW-31 Chloride (mg/L) Complete 142 0 229.80282 79.890017 0.9451017 2.195E-05 No N/A N/A 8669 0 Increasing Yes 381.00 MW-31 Fluoride (mg/L) EO Removed 63 0 0.8012179 0.1060507 0.9769008 0.2820837 Yes -1198 6.12727E-13 Decreasing No 1.18 MW-31 Sulfate (mg/L) Complete 137 0 699.81022 190.49813 0.9333576 4.363E-06 No N/A N/A 7564 0 Increasing Yes 1150.00 MW-31 pH (S.U.) Complete 153 0 7.0129412 0.3424887 0.9671726 0.0010354 No N/A N/A -1487 0.009523551 Decreasing N/A 8.23 Notes: σ = sigma.a = A regression test was performed on data that was determined to have normal or lognormal distribution. %ND = percent of non-detected values. b = The Mann-Kendall test was performed on data that are not normally or lognormally distributed. µg/L = micrograms per liter. Distribution = Distribution as determined by the Shapiro-Wilk distribution test for constituents with % Detect > 50% and N>8. mg/L = milligrams per liter. Mean = The arithmetic mean as determined for normally or lognormally distributed constituents with % Detect > 50%. N = number of valid data points. Standard Deviation = The standard deviation as determined for normally or lognormally distributed constituents with % Detect > 85%. NA= not applicable.Highest Historical Value = The highest observed value for constituents with % Detect < 50%. p = probability.r2 = The measure of how well the trendline fits the data where r2=1 represents a perfect fit. S = Mann-Kendall statistic. s.u. = standard units of pH. W = Shapiro-Wilk test value. Previously Identified Increasing Trend? Highest Historical Value (HHV) Standard Deviation Shapiro-Wilk Test for Normality Normally or Lognormally distributed? Least Squares Regression Trend Analysisa Mann-Kendall Trend Analysisb Significant TrendMeanWell Constituent Data Set N % Non- Detected Values Appendix A Source Assessment Report for MW-31 White Mesa Uranium Mill Page 1 of 1 Appendix A-2: Descriptive Statistics of SAR and Indicator Parameters in MW-31 Data Set Analyte Chloride Fluoride Sulfate Uranium pH 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 S.U. 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 00000 0000 0000 0000 0000 0000 N 142 63 137 88 153 131 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 No Yes No No No Yes No Yes No No No Yes Yes No No Yes Yes No No Yes Mean 229.80 0.80 699.81 10.23 7.01 219.63 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 0.526 436 5.77 6.16 115 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 1.1832 1150 22.2 8.23 381 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.79.89 0.1061 190.5 3.6785 0.3425 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 0.6572 714 16.43 2.07 266.0 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 216.11 0.7943 676.74 9.694 7.0046 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 0.3606 0.3539 0.9409 1.4194 -0.126 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 152.75 0.735 539 7.6225 6.83 149 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 222 0.806 655 9.04 7.04 210 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 290.75 0.86 813 11.525 7.23 276 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 2021 SAR 2017 SAR 2015 SAR 2013 SAR 2008 Background Report2020 SAR Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 1 of 1 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units MW-31 6/22/2005 Uranium 6.56 µg/L MW-31 9/22/2005 Uranium 7.25 µg/L MW-31 12/14/2005 Uranium 7.27 µg/L MW-31 3/22/2006 Uranium 8.04 µg/L MW-31 6/21/2006 Uranium 9.32 µg/L MW-31 9/13/2006 Uranium 8.03 µg/L MW-31 10/25/2006 Uranium 7.71 µg/L MW-31 3/15/2007 Uranium 7.60 µg/L MW-31 8/27/2007 Uranium 7.18 µg/L MW-31 10/24/2007 Uranium 7.20 µg/L MW-31 3/19/2008 Uranium 7.02 µg/L MW-31 6/3/2008 Uranium 6.95 µg/L MW-31 8/4/2008 Uranium 6.77 µg/L MW-31 11/11/2008 Uranium 6.35 µg/L MW-31 2/3/2009 Uranium 7.08 µg/L MW-31 5/13/2009 Uranium 6.76 µg/L MW-31 8/24/2009 Uranium 6.97 µg/L MW-31 10/14/2009 Uranium 6.97 µg/L MW-31 2/9/2010 Uranium 7.12 µg/L MW-31 4/20/2010 Uranium 6.74 µg/L MW-31 9/13/2010 Uranium 7.23 µg/L MW-31 11/9/2010 Uranium 6.72 µg/L MW-31 2/1/2011 Uranium 5.77 µg/L MW-31 4/1/2011 Uranium 6.81 µg/L MW-31 8/2/2011 Uranium 7.68 µg/L MW-31 10/3/2011 Uranium 8.87 µg/L MW-31 2/13/2012 Uranium 7.96 µg/L MW-31 5/2/2012 Uranium 7.34 µg/L MW-31 7/9/2012 Uranium 8.17 µg/L MW-31 11/6/2012 Uranium 8.73 µg/L MW-31 2/19/2013 Uranium 7.33 µg/L MW-31 5/13/2013 Uranium 7.63 µg/L MW-31 7/9/2013 Uranium 7.90 µg/L MW-31 11/18/2013 Uranium 9.03 µg/L MW-31 2/17/2014 Uranium 7.65 µg/L MW-31 3/10/2014 Uranium 7.96 µg/L MW-31 6/2/2014 Uranium 7.72 µg/L MW-31 9/3/2014 Uranium 8.40 µg/L MW-31 11/4/2014 Uranium 7.71 µg/L MW-31 2/2/2015 Uranium 8.00 µg/L MW-31 4/7/2015 Uranium 8.07 µg/L MW-31 8/10/2015 Uranium 8.76 µg/L MW-31 11/9/2015 Uranium 8.72 µg/L MW-31 2/15/2016 Uranium 8.41 µg/L Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 1 of 14 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units MW-31 5/3/2016 Uranium 9.05 µg/L MW-31 8/16/2016 Uranium 9.41 µg/L MW-31 11/1/2016 Uranium 9.56 µg/L MW-31 12/5/2016 Uranium 10.30 µg/L MW-31 1/17/2017 Uranium 9.03 µg/L MW-31 2/7/2017 Uranium 9.92 µg/L MW-31 3/6/2017 Uranium 9.62 µg/L MW-31 4/4/2017 Uranium 10.10 µg/L MW-31 5/1/2017 Uranium 9.62 µg/L MW-31 6/5/2017 Uranium 9.89 µg/L MW-31 7/11/2017 Uranium 10.50 µg/L MW-31 8/14/2017 Uranium 10.10 µg/L MW-31 9/11/2017 Uranium 9.74 µg/L MW-31 10/2/2017 Uranium 10.90 µg/L MW-31 11/1/2017 Uranium 9.31 µg/L MW-31 12/4/2017 Uranium 10.40 µg/L MW-31 1/24/2018 Uranium 11.40 µg/L MW-31 2/20/2018 Uranium 11.20 µg/L MW-31 3/5/2018 Uranium 11.40 µg/L MW-31 4/17/2018 Uranium 11.50 µg/L MW-31 5/14/2018 Uranium 11.50 µg/L MW-31 6/18/2018 Uranium 12.90 µg/L MW-31 7/23/2018 Uranium 12.30 µg/L MW-31 8/10/2018 Uranium 11.70 µg/L MW-31 9/10/2018 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 1/15/2019 Uranium 13.20 µg/L MW-31 2/12/2019 Uranium 13.60 µg/L MW-31 3/5/2019 Uranium 12.50 µg/L MW-31 4/10/2019 Uranium 13.60 µg/L MW-31 7/15/2019 Uranium 14.30 µg/L MW-31 10/9/2019 Uranium 14.40 µg/L MW-31 1/14/2020 Uranium 14.80 µg/L MW-31 4/6/2020 Uranium 15.50 µg/L MW-31 7/7/2020 Uranium 18.10 µg/L MW-31 8/10/2020 Uranium 19.70 µg/L MW-31 9/1/2020 Uranium 18.50 µg/L MW-31 10/19/2020 Uranium 19.30 µg/L MW-31 11/16/2020 Uranium 17.80 µg/L MW-31 12/7/2020 Uranium 19.50 µg/L MW-31 1/12/2021 Uranium 19.70 µg/L MW-31 2/9/2021 Uranium 22.20 µg/L Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 2 of 14 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units MW-31 6/22/2005 Chloride 139 mg/L MW-31 9/22/2005 Chloride 136 mg/L MW-31 12/14/2005 Chloride 135 mg/L MW-31 3/22/2006 Chloride 133 mg/L MW-31 6/21/2006 Chloride 138 mg/L MW-31 9/13/2006 Chloride 131 mg/L MW-31 10/25/2006 Chloride 127 mg/L MW-31 3/15/2007 Chloride 132 mg/L MW-31 8/27/2007 Chloride 136 mg/L MW-31 10/24/2007 Chloride 122 mg/L MW-31 3/19/2008 Chloride 124 mg/L MW-31 6/3/2008 Chloride 128 mg/L MW-31 8/4/2008 Chloride 124 mg/L MW-31 11/11/2008 Chloride 119 mg/L MW-31 2/3/2009 Chloride 115 mg/L MW-31 5/13/2009 Chloride 124 mg/L MW-31 8/24/2009 Chloride 122 mg/L MW-31 10/14/2009 Chloride 138 mg/L MW-31 2/9/2010 Chloride 128 mg/L MW-31 4/20/2010 Chloride 128 mg/L MW-31 9/13/2010 Chloride 139 mg/L MW-31 11/9/2010 Chloride 138 mg/L MW-31 2/1/2011 Chloride 145 mg/L MW-31 4/1/2011 Chloride 143 mg/L MW-31 5/10/2011 Chloride 143 mg/L MW-31 6/20/2011 Chloride 145 mg/L MW-31 7/5/2011 Chloride 148 mg/L MW-31 8/2/2011 Chloride 148 mg/L MW-31 9/6/2011 Chloride 148 mg/L MW-31 10/3/2011 Chloride 145 mg/L MW-31 11/8/2011 Chloride 145 mg/L MW-31 12/12/2011 Chloride 148 mg/L MW-31 1/24/2012 Chloride 155 mg/L MW-31 2/13/2012 Chloride 150 mg/L MW-31 3/13/2012 Chloride 152 mg/L MW-31 4/9/2012 Chloride 160 mg/L MW-31 5/2/2012 Chloride 151 mg/L MW-31 6/18/2012 Chloride 138 mg/L MW-31 7/9/2012 Chloride 161 mg/L MW-31 8/6/2012 Chloride 175 mg/L MW-31 9/18/2012 Chloride 172 mg/L MW-31 10/22/2012 Chloride 157 mg/L MW-31 11/6/2012 Chloride 189 mg/L MW-31 12/18/2012 Chloride 170 mg/L Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 3 of 14 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units MW-31 1/22/2013 Chloride 176 mg/L MW-31 2/19/2013 Chloride 174 mg/L MW-31 3/19/2013 Chloride 168 mg/L MW-31 4/16/2013 Chloride 171 mg/L MW-31 5/13/2013 Chloride 169 mg/L MW-31 6/24/2013 Chloride 179 mg/L MW-31 7/9/2013 Chloride 182 mg/L MW-31 8/19/2013 Chloride 183 mg/L MW-31 9/17/2013 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 1/7/2014 Chloride 194 mg/L MW-31 2/17/2014 Chloride 197 mg/L MW-31 3/10/2014 Chloride 230 mg/L MW-31 4/28/2014 Chloride 230 mg/L MW-31 5/13/2014 Chloride 200 mg/L MW-31 6/2/2014 Chloride 173 mg/L MW-31 7/28/2014 Chloride 200 mg/L MW-31 8/18/2014 Chloride 210 mg/L MW-31 9/3/2014 Chloride 210 mg/L MW-31 10/6/2014 Chloride 205 mg/L MW-31 11/4/2014 Chloride 204 mg/L MW-31 12/9/2014 Chloride 215 mg/L MW-31 1/20/2015 Chloride 226 mg/L MW-31 2/2/2015 Chloride 211 mg/L MW-31 3/3/2015 Chloride 209 mg/L MW-31 4/7/2015 Chloride 211 mg/L MW-31 5/11/2015 Chloride 225 mg/L MW-31 6/23/2015 Chloride 228 mg/L MW-31 7/6/2015 Chloride 222 mg/L MW-31 8/10/2015 Chloride 264 mg/L MW-31 9/15/2015 Chloride 231 mg/L MW-31 10/6/2015 Chloride 222 mg/L MW-31 11/9/2015 Chloride 215 mg/L MW-31 12/8/2015 Chloride 231 mg/L MW-31 1/19/2016 Chloride 228 mg/L MW-31 2/15/2016 Chloride 246 mg/L MW-31 3/2/2016 Chloride 228 mg/L MW-31 4/12/2016 Chloride 254 mg/L MW-31 5/3/2016 Chloride 243 mg/L MW-31 6/15/2016 Chloride 252 mg/L MW-31 7/12/2016 Chloride 241 mg/L MW-31 8/16/2016 Chloride 272 mg/L Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 4 of 14 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units MW-31 9/13/2016 Chloride 254 mg/L MW-31 10/4/2016 Chloride 260 mg/L MW-31 11/1/2016 Chloride 267 mg/L MW-31 12/5/2016 Chloride 274 mg/L MW-31 1/17/2017 Chloride 287 mg/L MW-31 2/7/2017 Chloride 266 mg/L MW-31 3/6/2017 Chloride 250 mg/L MW-31 4/4/2017 Chloride 263 mg/L MW-31 5/1/2017 Chloride 263 mg/L MW-31 6/5/2017 Chloride 278 mg/L MW-31 7/11/2017 Chloride 254 mg/L MW-31 8/14/2017 Chloride 310 mg/L MW-31 9/11/2017 Chloride 248 mg/L MW-31 10/2/2017 Chloride 287 mg/L MW-31 11/1/2017 Chloride 292 mg/L MW-31 12/4/2017 Chloride 285 mg/L MW-31 1/24/2018 Chloride 323 mg/L MW-31 2/20/2018 Chloride 292 mg/L MW-31 3/5/2018 Chloride 311 mg/L MW-31 4/17/2018 Chloride 308 mg/L MW-31 5/14/2018 Chloride 326 mg/L MW-31 6/18/2018 Chloride 359 mg/L MW-31 7/23/2018 Chloride 351 mg/L MW-31 8/10/2018 Chloride 336 mg/L MW-31 9/10/2018 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 1/15/2019 Chloride 283 mg/L MW-31 2/12/2019 Chloride 296 mg/L MW-31 3/5/2019 Chloride 322 mg/L MW-31 4/10/2019 Chloride 294 mg/L MW-31 5/7/2019 Chloride 346 mg/L MW-31 6/3/2019 Chloride 325 mg/L MW-31 7/15/2019 Chloride 374 mg/L MW-31 8/5/2019 Chloride 372 mg/L MW-31 9/23/2019 Chloride 365 mg/L MW-31 10/9/2019 Chloride 318 mg/L MW-31 11/12/2019 Chloride 338 mg/L MW-31 12/3/2019 Chloride 343 mg/L MW-31 1/14/2020 Chloride 381 mg/L MW-31 2/4/2020 Chloride 370 mg/L MW-31 3/10/2020 Chloride 368 mg/L MW-31 4/6/2020 Chloride 376 mg/L Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 5 of 14 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units MW-31 5/5/2020 Chloride 361 mg/L MW-31 6/2/2020 Chloride 377 mg/L MW-31 7/7/2020 Chloride 370 mg/L MW-31 8/10/2020 Chloride 368 mg/L MW-31 9/1/2020 Chloride 367 mg/L MW-31 10/19/2020 Chloride 345 mg/L MW-31 11/16/2020 Chloride 251 mg/L MW-31 12/7/2020 Chloride 311 mg/L MW-31 1/12/2021 Chloride 354 mg/L MW-31 2/9/2021 Chloride 380 mg/L MW-31 6/22/2005 Fluoride 0.83 mg/L MW-31 9/22/2005 Fluoride 0.91 mg/L MW-31 12/14/2005 Fluoride 0.85 mg/L MW-31 3/22/2006 Fluoride 0.90 mg/L MW-31 6/21/2006 Fluoride 0.86 mg/L MW-31 9/13/2006 Fluoride 0.94 mg/L MW-31 10/25/2006 Fluoride 1.18 mg/L MW-31 3/15/2007 Fluoride 0.94 mg/L MW-31 8/27/2007 Fluoride 0.99 mg/L MW-31 10/24/2007 Fluoride 0.85 mg/L MW-31 3/19/2008 Fluoride 0.92 mg/L MW-31 6/3/2008 Fluoride 0.94 mg/L MW-31 8/4/2008 Fluoride 0.85 mg/L MW-31 2/3/2009 Fluoride 0.91 mg/L MW-31 5/13/2009 Fluoride 0.90 mg/L MW-31 8/24/2009 Fluoride 0.89 mg/L MW-31 10/14/2009 Fluoride 0.90 mg/L MW-31 2/9/2010 Fluoride 0.88 mg/L MW-31 4/20/2010 Fluoride 0.84 mg/L MW-31 9/13/2010 Fluoride 0.89 mg/L MW-31 11/9/2010 Fluoride 0.84 mg/L MW-31 2/1/2011 Fluoride 0.83 mg/L MW-31 4/1/2011 Fluoride 0.83 mg/L MW-31 8/2/2011 Fluoride 0.80 mg/L MW-31 10/3/2011 Fluoride 0.84 mg/L MW-31 2/13/2012 Fluoride 0.86 mg/L MW-31 5/2/2012 Fluoride 0.78 mg/L MW-31 7/9/2012 Fluoride 0.78 mg/L MW-31 11/6/2012 Fluoride 0.76 mg/L MW-31 2/19/2013 Fluoride 0.73 mg/L MW-31 5/13/2013 Fluoride 0.76 mg/L MW-31 7/9/2013 Fluoride 0.84 mg/L MW-31 11/18/2013 Fluoride 0.76 mg/L MW-31 2/17/2014 Fluoride 0.81 mg/L Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 6 of 14 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units MW-31 3/10/2014 Fluoride 0.82 mg/L MW-31 6/2/2014 Fluoride 0.74 mg/L MW-31 9/3/2014 Fluoride 0.80 mg/L MW-31 11/4/2014 Fluoride 0.61 mg/L MW-31 2/2/2015 Fluoride 0.76 mg/L MW-31 4/7/2015 Fluoride 0.75 mg/L MW-31 8/10/2015 Fluoride 0.72 mg/L MW-31 11/9/2015 Fluoride 0.68 mg/L MW-31 2/15/2016 Fluoride 0.72 mg/L MW-31 5/3/2016 Fluoride 0.76 mg/L MW-31 8/16/2016 Fluoride 0.77 mg/L MW-31 11/1/2016 Fluoride 0.74 mg/L MW-31 2/7/2017 Fluoride 0.71 mg/L MW-31 5/1/2017 Fluoride 0.69 mg/L MW-31 8/14/2017 Fluoride 0.73 mg/L MW-31 11/1/2017 Fluoride 0.79 mg/L MW-31 2/20/2018 Fluoride 0.81 mg/L MW-31 4/17/2018 Fluoride 0.81 mg/L MW-31 9/10/2018 Fluoride 0.66 mg/L MW-31 10/24/2018 Fluoride 0.69 mg/L MW-31 1/15/2019 Fluoride 0.70 mg/L MW-31 4/10/2019 Fluoride 0.67 mg/L MW-31 7/15/2019 Fluoride 0.89 mg/L MW-31 10/9/2019 Fluoride 0.53 mg/L MW-31 1/14/2020 Fluoride 0.78 mg/L MW-31 4/6/2020 Fluoride 0.63 mg/L MW-31 7/7/2020 Fluoride 0.63 mg/L MW-31 10/19/2020 Fluoride 0.83 mg/L MW-31 1/12/2021 Fluoride 0.65 mg/L 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 Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 7 of 14 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units 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 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 Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 8 of 14 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units 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 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 Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 9 of 14 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units 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 4/6/2020 Sulfate 1130 mg/L MW-31 5/5/2020 Sulfate 1080 mg/L MW-31 6/2/2020 Sulfate 1130 mg/L MW-31 7/7/2020 Sulfate 1150 mg/L MW-31 8/10/2020 Sulfate 1100 mg/L MW-31 9/1/2020 Sulfate 1110 mg/L MW-31 10/19/2020 Sulfate 1100 mg/L MW-31 11/16/2020 Sulfate 676 mg/L MW-31 12/7/2020 Sulfate 922 mg/L MW-31 1/12/2021 Sulfate 1070 mg/L MW-31 2/9/2021 Sulfate 1130 mg/L MW-31 6/22/2005 pH 7.27 s.u. MW-31 9/22/2005 pH 7.19 s.u. MW-31 12/14/2005 pH 7.30 s.u. MW-31 3/22/2006 pH 7.33 s.u. MW-31 6/21/2006 pH 7.15 s.u. MW-31 9/13/2006 pH 7.31 s.u. MW-31 10/25/2006 pH 7.26 s.u. MW-31 3/15/2007 pH 7.41 s.u. MW-31 8/27/2007 pH 7.08 s.u. MW-31 10/24/2007 pH 6.97 s.u. Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 10 of 14 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units MW-31 3/19/2008 pH 6.95 s.u. MW-31 6/3/2008 pH 7.20 s.u. MW-31 8/4/2008 pH 7.20 s.u. MW-31 11/10/2008 pH 7.42 s.u. MW-31 2/3/2009 pH 7.30 s.u. MW-31 5/13/2009 pH 7.12 s.u. MW-31 8/10/2009 pH 7.34 s.u. MW-31 8/24/2009 pH 7.18 s.u. MW-31 10/14/2009 pH 7.05 s.u. MW-31 12/2/2009 pH 7.17 s.u. MW-31 2/9/2010 pH 6.96 s.u. MW-31 4/20/2010 pH 7.38 s.u. MW-31 5/21/2010 pH 6.95 s.u. MW-31 6/15/2010 pH 7.01 s.u. MW-31 7/21/2010 pH 7.80 s.u. MW-31 8/24/2010 pH 7.10 s.u. MW-31 9/13/2010 pH 7.66 s.u. MW-31 9/21/2010 pH 7.13 s.u. MW-31 10/19/2010 pH 6.92 s.u. MW-31 11/9/2010 pH 6.98 s.u. MW-31 12/14/2010 pH 6.95 s.u. MW-31 1/10/2011 pH 6.65 s.u. MW-31 2/1/2011 pH 7.21 s.u. MW-31 3/14/2011 pH 7.43 s.u. MW-31 4/1/2011 pH 7.01 s.u. MW-31 5/10/2011 pH 6.73 s.u. MW-31 6/20/2011 pH 6.16 s.u. MW-31 7/5/2011 pH 6.64 s.u. MW-31 8/2/2011 pH 6.67 s.u. MW-31 9/6/2011 pH 7.03 s.u. MW-31 10/3/2011 pH 7.28 s.u. MW-31 11/8/2011 pH 7.01 s.u. MW-31 11/29/2011 pH 7.34 s.u. MW-31 12/12/2011 pH 7.46 s.u. MW-31 1/24/2012 pH 6.78 s.u. MW-31 2/13/2012 pH 7.37 s.u. MW-31 4/9/2012 pH 7.15 s.u. MW-31 5/2/2012 pH 7.19 s.u. MW-31 7/9/2012 pH 7.53 s.u. MW-31 8/6/2012 pH 6.96 s.u. MW-31 9/18/2012 pH 7.10 s.u. MW-31 10/22/2012 pH 7.05 s.u. MW-31 11/6/2012 pH 7.04 s.u. MW-31 12/18/2012 pH 7.10 s.u. Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 11 of 14 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units MW-31 1/22/2013 pH 6.94 s.u. MW-31 2/19/2013 pH 7.32 s.u. MW-31 3/19/2013 pH 7.28 s.u. MW-31 4/16/2013 pH 6.37 s.u. MW-31 5/13/2013 pH 7.92 s.u. MW-31 6/24/2013 pH 7.10 s.u. MW-31 7/9/2013 pH 6.98 s.u. MW-31 8/19/2013 pH 7.36 s.u. MW-31 9/17/2013 pH 7.06 s.u. MW-31 10/23/2013 pH 7.35 s.u. MW-31 11/18/2013 pH 6.99 s.u. MW-31 12/17/2013 pH 7.23 s.u. MW-31 1/7/2014 pH 7.13 s.u. MW-31 2/17/2014 pH 6.45 s.u. MW-31 3/10/2014 pH 6.53 s.u. MW-31 4/28/2014 pH 7.45 s.u. MW-31 5/13/2014 pH 6.83 s.u. MW-31 6/2/2014 pH 8.23 s.u. MW-31 7/28/2014 pH 6.88 s.u. MW-31 8/18/2014 pH 7.60 s.u. MW-31 9/3/2014 pH 6.94 s.u. MW-31 10/6/2014 pH 6.97 s.u. MW-31 11/4/2014 pH 6.69 s.u. MW-31 12/9/2014 pH 6.73 s.u. MW-31 1/20/2015 pH 6.49 s.u. MW-31 2/2/2015 pH 6.42 s.u. MW-31 3/3/2015 pH 6.40 s.u. MW-31 4/7/2015 pH 6.80 s.u. MW-31 5/11/2015 pH 6.74 s.u. MW-31 6/1/2015 pH 7.14 s.u. MW-31 6/23/2015 pH 7.08 s.u. MW-31 7/6/2015 pH 7.22 s.u. MW-31 8/10/2015 pH 6.80 s.u. MW-31 9/15/2015 pH 6.73 s.u. MW-31 10/6/2015 pH 6.47 s.u. MW-31 11/9/2015 pH 6.36 s.u. MW-31 12/8/2015 pH 6.70 s.u. MW-31 1/19/2016 pH 7.04 s.u. MW-31 2/15/2016 pH 7.21 s.u. MW-31 3/2/2016 pH 6.83 s.u. MW-31 4/12/2016 pH 6.93 s.u. MW-31 5/3/2016 pH 6.48 s.u. MW-31 6/15/2016 pH 7.01 s.u. MW-31 7/12/2016 pH 6.49 s.u. Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 12 of 14 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units MW-31 8/16/2016 pH 6.92 s.u. MW-31 9/13/2016 pH 6.35 s.u. MW-31 10/4/2016 pH 6.99 s.u. MW-31 11/1/2016 pH 6.92 s.u. MW-31 12/5/2016 pH 6.79 s.u. MW-31 1/17/2017 pH 6.75 s.u. MW-31 2/7/2017 pH 6.30 s.u. MW-31 3/6/2017 pH 6.39 s.u. MW-31 4/4/2017 pH 6.26 s.u. MW-31 5/1/2017 pH 6.87 s.u. MW-31 6/5/2017 pH 6.90 s.u. MW-31 7/11/2017 pH 6.94 s.u. MW-31 8/14/2017 pH 6.29 s.u. MW-31 9/11/2017 pH 6.32 s.u. MW-31 10/2/2017 pH 7.01 s.u. MW-31 11/1/2017 pH 7.04 s.u. MW-31 12/4/2017 pH 7.31 s.u. MW-31 1/24/2018 pH 6.46 s.u. MW-31 2/20/2018 pH 7.25 s.u. MW-31 3/5/2018 pH 6.92 s.u. MW-31 4/17/2018 pH 6.75 s.u. MW-31 5/14/2018 pH 7.05 s.u. MW-31 6/18/2018 pH 7.18 s.u. MW-31 7/23/2018 pH 7.17 s.u. MW-31 8/10/2018 pH 7.00 s.u. MW-31 9/10/2018 pH 7.13 s.u. MW-31 10/24/2018 pH 6.59 s.u. MW-31 11/13/2018 pH 7.08 s.u. MW-31 12/10/2018 pH 7.03 s.u. MW-31 1/15/2019 pH 6.89 s.u. MW-31 2/12/2019 pH 6.24 s.u. MW-31 3/5/2019 pH 7.15 s.u. MW-31 4/10/2019 pH 7.29 s.u. MW-31 5/7/2019 pH 7.02 s.u. MW-31 6/3/2019 pH 7.02 s.u. MW-31 7/15/2019 pH 6.79 s.u. MW-31 8/5/2019 pH 7.44 s.u. MW-31 9/23/2019 pH 7.13 s.u. MW-31 10/9/2019 pH 7.23 s.u. MW-31 11/12/2019 pH 7.33 s.u. MW-31 12/3/2019 pH 7.29 s.u. MW-31 1/14/2020 pH 6.97 s.u. MW-31 2/4/2020 pH 7.26 s.u. MW-31 3/10/2020 pH 7.15 s.u. Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 13 of 14 Appendix A-3: Data Used for Statistical Analysis Well Sample Date Parameter Result Units MW-31 4/6/2020 pH 7.25 s.u. MW-31 5/5/2020 pH 6.60 s.u. MW-31 6/2/2020 pH 6.84 s.u. MW-31 7/7/2020 pH 7.44 s.u. MW-31 8/10/2020 pH 7.40 s.u. MW-31 9/1/2020 pH 7.12 s.u. MW-31 10/19/2020 pH 6.79 s.u. MW-31 11/16/2020 pH 7.12 s.u. MW-31 12/7/2020 pH 7.21 s.u. MW-31 1/12/2021 pH 7.20 s.u. MW-31 2/9/2021 pH 7.25 s.u. Notes: µg/L = micrograms per liter. mg/L = milligrams per liter. s.u. = standard units of pH. Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 14 of 14 Appendix A-4: 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 Note: mg/L = milligrams per liter. Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 1 of 1 Appendix A-5: Box Plots for SAR and Indicator Parameters in MW-31 Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 1 of 3 20 --::::: O> 2.. 15 E -~ C C1J .... ::> 10 350 ....-.. ::::: 300 O> E -Q) 250 "'O ·c _Q 200 ..c (.) 150 Uranium in MW-31 0 Percent nondetect: 0% o Outlier * Extreme Min: 5.77, Mean: 10.23, Max: 22.2, Std Dev: 3.68 Upper extreme threshold (Q75 + 3xH): 23.2325 Lower extreme threshold (Q25 -3xH): -4.085 Chloride in MW-31 Percent nondetect: 0% o Outlier * Extreme Min: 115, Mean: 229.8, Max: 381, Std Dev: 79.89 Upper extreme threshold (Q75 + 3xH): 704.75 Lower extreme threshold (Q25 -3xH): -261 .25 ~s lNTERA Appendix A-5: Box Plots for SAR and Indicator Parameters in MW-31 Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 2 of 3 1.2 1.1 .......... 1.0 :::::: 0) -S 0.9 Q) "'O 0.8 ·.::: 0 ::::, u:::: 0.7 0.6 0.5 1100 1000 .......... :::::: 900 0) -S Q) 800 _.. ~ 700 ::::, Cf) 600 500 Fluoride in MW-31 0 0 Percent nondetect: 0% o Outlier * Extreme Min: 0.526, Mean: 0.8, Max: 1.183244, Std Dev: 0.11 Upper extreme threshold (075 + 3xH): 1.235 Lower extreme threshold (025 -3xH): 0.36 Sulfate in MW-31 Percent nondetect: 0% o Outlier * Extreme Min: 436, Mean: 699.81, Max: 1150, Std Dev: 190.5 Upper extreme threshold (075 + 3xH): 1635 Lower extreme threshold (025 -3xH): -283 ~s lNTERA Appendix A-5: Box Plots for SAR and Indicator Parameters in MW-31 Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 3 of 3 8.0 i 7.5 C ::::> I s 7.0 I 0.. 6.5 pH in MW-31 0 0 0 Percent nondetect: 0% o Outlier * Extreme Min: 6.16, Mean: 7.01, Max: 8.23, Std Dev: 0.34 Upper extreme threshold (075 + 3xH): 8.43 Lower extreme threshold (025 -3xH): 5.63 ~s lNTERA Appendix A-6: Histograms for SAR and Indicator Parameters in MW-31 Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 1 of 3 >, (.) C (].) ::i CJ" (].) .... LL >, (.) C (].) ::i CJ" (].) .... LL LO N 0 N LO ....... 0 ....... LO 0 0.7 0.8 LO ....... 0 ....... LO 0 2.05 2.15 Uranium (ug/1) in MW-31 SW-W = 0.9275, p = 1 e-04 0.9 1.0 1.1 1.2 Log Result Chloride (mg/I) in MW-31 SW-W = 0.9451, p = 0 2.25 2.35 2.45 Log Result 1.3 1.4 2.55 ~ri lNTERA Appendix A-6: Histograms for SAR and Indicator Parameters in MW-31 Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 2 of 3 0 N >, L.C) (.) ....... C a, :::J CT' 0 a, ....... .... LL L.C) 0 0 C'0 >, (.) C a, 0 :::J N CT' a, .... LL 0 ....... 0 Fluoride {mg/I) in MW-31 SW-W = 0.9769, p = 0.2821 -0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 Log Result Sulfate {mg/I) in MW-31 SW-W = 0.9334, p = 0 2.60 2.65 2.70 2.75 2.80 2.85 2.90 2.95 3.00 3.05 3.10 Log Result ~--ri lNTERA Appendix A-6: Histograms for SAR and Indicator Parameters in MW-31 Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 3 of 3 0 C"') >, (.) C 0 Q) N ::, O"' Q) .... LL 0 ~ 0 pH (pH Units) in MW-31 SW-W = 0.9672, p = 0.001 0.78 0.80 0.82 0.84 0.86 0.88 0.90 0.92 Log Result ~--ri lNTERA Appendix A-7: Time Series Plots and Linear Regressions for SAR and Indicator Parameters in MW-31 Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 1 of 2 --20 :::::::: O> :::J --E 15 :::J C 10 ro ,.._ ::> 2005 --350 :::::::: O> E 300 --Q) 250 "O ·.:::: 200 0 .c 150 () 2005 1.2 --:::::::: 1.1 O> E 1.0 --0.9 Q) "O 0.8 ·.:::: 0 0.7 :::J LL 0.6 0.5 2005 2010 2010 Uranium in MW-31 2015 Sample Date Chloride in MW-31 2015 Sample Date Fluoride in MW-31 r = -0.7432 p = 0 r2 = 0.5524 2010 2015 Sample Date 2020 2020 2020 ~ri lNTERA Appendix A-7: Time Series Plots and Linear Regressions for SAR and Indicator Parameters in MW-31 Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 2 of 2 ..-1100 :::::: 1000 0) E 900 -(1) 800 -700 co ::!:::: 600 ::i Cf) 500 2005 ..-8.0 (/) :t::: C 7.5 => I 7.0 0.. -I 6.5 0.. 2005 2010 0 0 2010 Sulfate in MW-31 2015 Sample Date pH in MW-31 2015 Sample Date 2020 2020 ~ri lNTERA Appendix A-8: Time Series Plots for SAR and Indicator Parameters in MW-31 with Events/Inflection Points Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 1 of 3 20 -:::::::: 0) ::, -15 E ::, C ro .... ::, 10 350 -300 :::::::: 0) -S Q) 250 "'O ·c _Q ..c 0 200 150 Uranium in MW-31 -l; • •• • -•• • • .z-••• . .--: -•dt,_· • • ..... • • .... . ,. • •• ., ,, t .-.. ..._. -· '• ... • • • • • I I I I 2005 2010 2015 Sample Date 2020 Chloride in MW-31 • I • • .r, • • • • • ' . ' . •• • •• . ' . ,.. ••• . . .. .. , ... ... •c.e419 ,. ... • ... " • ..... . . . ' ...... . 2005 • 2010 2015 Sample Date -2010-02-01 Monthly sampling -2011-05-03 Well redevelopment -2012-10-01 Lab change -2013-09-27 Peak groundwater elevation 2014-06-01 Five new chloroform pumping wells brought online -2020-06-24 Previous MW-31 SAR 2020 ~,INTERA Appendix A-8: Time Series Plots for SAR and Indicator Parameters in MW-31 with Events/Inflection Points Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 2 of 3 1.2 1.1 --1.0 :::::: 0) E 0.9 -Q) l:J ·c 0.8 0 ::, u::: 0.7 0.6 0.5 1100 1000 --:::::: 900 0) E -Q) 800 ro !::!::::: ::, 700 Cf) 600 500 Fluoride in MW-31 -• - -• • • • • • • ..,4 . -• • • • • • • - - - I 2005 - - - - - - • • • •• • '. • -• • • •• •• • • ,. • • I 2010 • I 2015 Sample Date Sulfate in MW-31 • • • • ... • • .. • • • •• • I 2020 ••• . ., .. -• , • • •• • .... • ... ,, ...... .. .,,,,,.. .... ,., .... • • •• 4 . . ., . •• •• • -• .,., --......... 411 t • t• • • • • .,. ... I t• • 4 -."-• -• • • •• • • I 2005 • • I I 2010 2015 Sample Date -2010-02-01 Monthly sampling -2011-05-03 Well redevelopment -2012-10-01 Lab change -2013-09-27 Peak groundwater elevation I 2020 -2014-06-01 Five new chloroform pumping wells broughtonline -2020-06-24 Pr,evious MW-31 SAR ~,INTERA Appendix A-8: Time Series Plots for SAR and Indicator Parameters in MW-31 with Events/Inflection Points Appendix A Source Assesment Report for MW-31 White Mesa Uranium Mill Page 3 of 3 8.0 ~ 7.5 C => I -9: 7.0 I Q.. 6.5 pH in MW-31 It -• • • • -• • • • • • • ' • •• ,· ••••• • • • . . ,.. • • • • • " • - - I 2005 -• • • • '· ••• , • ' ... .. • • : •, • , .. , . •• t:~· .. . •• • ••• • I ... I • 4 ... ' t I••• •• • • . -• • ' • • ... , • I I 2010 2015 Sample Date -2010-02-01 Monthly sampli ng -2011-05-03 Well redevelopment -2012-10-01 Lab change -2013-09-27 Peak groundwater elevation • • • •• • • • • • I 2020 -2014-06-01 Five new chloroform pumping well s brought online -2020-06-24 Previous MW-31 SAR ~,INTERA APPENDIX B Statistical Analysis for Select Post-Inflection Uranium Datasets (Modified Approach) for Purposes of Calculating GWCL B-1 Summary of Statistical Analysis and GWCL Calculation for Data Subsets B-2 MW-31 Data Used for Analysis B-3 Box Plots for Select Uranium Datasets in MW-31 B-4 Histograms for Select Datasets in MW-31 B-5 Timeseries and Linear Regression Analysis for Select Uranium Datasets in MW-31 Appendix B-1: Summary of Statistical Analysis and GWCL Calculation for Data Subsets (Modified Approach) Wp r2 pS p MW-31 Uranium Complete 88 0 10.23 3.68 0.9275 0.0001 No N/A N/A 3039.00 0.00E+00 Increasing Yes 17.58 15.34 19.7 22.20 15 15 22.2 HHV MW-31 Uranium Post Sep 2012 59 0 11.67 3.69 0.9384 0.0050 No N/A N/A 1505.00 0.00E+00 Increasing Yes 19.05 17.51 19.7 22.20 15 15 22.2 HHV MW-31 Uranium Post May 2014 52 0 12.16 3.66 0.9427 0.0144 No N/A N/A 1175.00 0.00E+00 Increasing Yes 19.47 18.24 19.7 22.20 15 15 22.2 HHV MW-31 Uranium Post July 2020 8 0 19.35 1.37 0.8968 0.2704 Yes 0.3996 0.0927 13.00 6.73E-02 No Yes 22.09 29.03 23.71 22.20 15 15 22.2 HHV 29.03 Mean x 1.5 Notes:a = A regression test was performed on data that was determined to have normal or lognormal distribution. σ = sigma.b = The Mann-Kendall test was performed on data that are not normally or lognormally distributed. %ND = percent of non-detected values. Distribution = Distribution as determined by the Shapiro-Wilk distribution test for constituents with % Detect > 50% and N>8. µg/L = micrograms per liter.Mean = The arithmetic mean as determined for normally or lognormally distributed constituents with % Detect > 50%. FA= Fraction of GWQS as defined in UAC R317-6. Standard Deviation = The standard deviation as determined for normally or lognormally distributed constituents with % Detect > 85%. GWCL = Groundwater Compliance Limit. Highest Historical Value = The highest observed value for constituents with % Detect < 50%. HHV = Highest Historical Value.Flowsheet GWCL does not take into account increasing trends. mg/L = milligrams per liter.§ = GWCL is based on the March 2019 Groundwater Discharge Permit or most recent Source Assessment Reports, where applicable. N = number of valid data points.r2 = The measure of how well the trendline fits the data where r2=1 represents a perfect fit. NA= not applicable. p = probability. S = Mann-Kendall statistic. s.u. = standard units of pH. W = Shapiro-Wilk test value. Current GWCL § Flowsheet GWCL Rationale Modified Approach GWCL* Modified Approach GWCL Rationale Fractional Approach GWCL Standard Deviation Shapiro-Wilk Test for Normality Normally or Lognormally Distributed? Least Squares Regression Trend Analysisa Mann-Kendall Trend Analysisb Significant Trend Previously Identified Increasing Trend? Mean + 2σ Mean x 1.5 Upper Tolerance Limit (UTL) Highest Historical Value (HHV) MeanWell Constituent Data Set N % Non- Detected Values Appendix B Source Assessment Report for MW-31 White Mesa Uranium Mill Page 1 of 1 Appendix B-2: MW-31 Data Used for Analysis Well Date Sampled Parameter Name Report Result Report Units MW-31 1/12/2021 Uranium 19.70 µg/L MW-31 1/14/2020 Uranium 14.80 µg/L MW-31 1/15/2019 Uranium 13.20 µg/L MW-31 1/17/2017 Uranium 9.03 µg/L MW-31 1/24/2018 Uranium 11.40 µg/L MW-31 10/14/2009 Uranium 6.97 µg/L MW-31 10/19/2020 Uranium 19.30 µg/L MW-31 10/2/2017 Uranium 10.90 µg/L MW-31 10/24/2007 Uranium 7.20 µg/L MW-31 10/24/2018 Uranium 11.60 µg/L MW-31 10/25/2006 Uranium 7.71 µg/L MW-31 10/3/2011 Uranium 8.87 µg/L MW-31 10/9/2019 Uranium 14.40 µg/L MW-31 11/1/2016 Uranium 9.56 µg/L MW-31 11/1/2017 Uranium 9.31 µg/L MW-31 11/11/2008 Uranium 6.35 µg/L MW-31 11/13/2018 Uranium 13.20 µg/L MW-31 11/16/2020 Uranium 17.80 µg/L MW-31 11/18/2013 Uranium 9.03 µg/L MW-31 11/4/2014 Uranium 7.71 µg/L MW-31 11/6/2012 Uranium 8.73 µg/L MW-31 11/9/2010 Uranium 6.72 µg/L MW-31 11/9/2015 Uranium 8.72 µg/L MW-31 12/10/2018 Uranium 12.70 µg/L MW-31 12/14/2005 Uranium 7.27 µg/L MW-31 12/4/2017 Uranium 10.40 µg/L MW-31 12/5/2016 Uranium 10.30 µg/L MW-31 12/7/2020 Uranium 19.50 µg/L MW-31 2/1/2011 Uranium 5.77 µg/L MW-31 2/12/2019 Uranium 13.60 µg/L MW-31 2/13/2012 Uranium 7.96 µg/L MW-31 2/15/2016 Uranium 8.41 µg/L MW-31 2/17/2014 Uranium 7.65 µg/L MW-31 2/19/2013 Uranium 7.33 µg/L MW-31 2/2/2015 Uranium 8.00 µg/L MW-31 2/20/2018 Uranium 11.20 µg/L MW-31 2/3/2009 Uranium 7.08 µg/L MW-31 2/7/2017 Uranium 9.92 µg/L MW-31 2/9/2010 Uranium 7.12 µg/L MW-31 2/9/2021 Uranium 22.20 µg/L MW-31 3/10/2014 Uranium 7.96 µg/L MW-31 3/15/2007 Uranium 7.60 µg/L MW-31 3/19/2008 Uranium 7.02 µg/L MW-31 3/22/2006 Uranium 8.04 µg/L MW-31 3/5/2018 Uranium 11.40 µg/L Appendix B Source Assessment Report for MW-31 White Mesa Uranium Mill Page 1 of 2 Appendix B-2: MW-31 Data Used for Analysis Well Date Sampled Parameter Name Report Result Report Units MW-31 3/5/2019 Uranium 12.50 µg/L MW-31 3/6/2017 Uranium 9.62 µg/L MW-31 4/1/2011 Uranium 6.81 µg/L MW-31 4/10/2019 Uranium 13.60 µg/L MW-31 4/17/2018 Uranium 11.50 µg/L MW-31 4/20/2010 Uranium 6.74 µg/L MW-31 4/4/2017 Uranium 10.10 µg/L MW-31 4/6/2020 Uranium 15.50 µg/L MW-31 4/7/2015 Uranium 8.07 µg/L MW-31 5/1/2017 Uranium 9.62 µg/L MW-31 5/13/2009 Uranium 6.76 µg/L MW-31 5/13/2013 Uranium 7.63 µg/L MW-31 5/14/2018 Uranium 11.50 µg/L MW-31 5/2/2012 Uranium 7.34 µg/L MW-31 5/3/2016 Uranium 9.05 µg/L MW-31 6/18/2018 Uranium 12.90 µg/L MW-31 6/2/2014 Uranium 7.72 µg/L MW-31 6/21/2006 Uranium 9.32 µg/L MW-31 6/22/2005 Uranium 6.56 µg/L MW-31 6/3/2008 Uranium 6.95 µg/L MW-31 6/5/2017 Uranium 9.89 µg/L MW-31 7/11/2017 Uranium 10.50 µg/L MW-31 7/15/2019 Uranium 14.30 µg/L MW-31 7/23/2018 Uranium 12.30 µg/L MW-31 7/7/2020 Uranium 18.10 µg/L MW-31 7/9/2012 Uranium 8.17 µg/L MW-31 7/9/2013 Uranium 7.90 µg/L MW-31 8/10/2015 Uranium 8.76 µg/L MW-31 8/10/2018 Uranium 11.70 µg/L MW-31 8/10/2020 Uranium 19.70 µg/L MW-31 8/14/2017 Uranium 10.10 µg/L MW-31 8/16/2016 Uranium 9.41 µg/L MW-31 8/2/2011 Uranium 7.68 µg/L MW-31 8/24/2009 Uranium 6.97 µg/L MW-31 8/27/2007 Uranium 7.18 µg/L MW-31 8/4/2008 Uranium 6.77 µg/L MW-31 9/1/2020 Uranium 18.50 µg/L MW-31 9/10/2018 Uranium 11.00 µg/L MW-31 9/11/2017 Uranium 9.74 µg/L MW-31 9/13/2006 Uranium 8.03 µg/L MW-31 9/13/2010 Uranium 7.23 µg/L MW-31 9/22/2005 Uranium 7.25 µg/L MW-31 9/3/2014 Uranium 8.40 µg/L Appendix B Source Assessment Report for MW-31 White Mesa Uranium Mill Page 2 of 2 Appendix B-3: Box Plots for Select Uranium Datasets in MW-31 Uranium in MW-31 All Data Uranium in MW-31 Post September 2012 Appendix B Source Assessment Report for MW-31 White Mesa Uranium Mill Page 1 of 2 Appendix B-3: Box Plots for Select Uranium Datasets in MW-31 Uranium in MW-31 Post May 2014 Uranium in MW-31 Post July 2020 Appendix B Source Assessment Report for MW-31 White Mesa Uranium Mill Page 2 of 2 Appendix B-4: Histograms for Select Datasets in MW-31 Uranium in MW-31 All Data Uranium in MW-31 Post September 2012 Appendix B Source Assessment Report for MW-31 White Mesa Uranium Mill Page 1 of 2 Appendix B-4: Histograms for Select Datasets in MW-31 Uranium in MW-31 Post May 2014 Uranium in MW-31 Post July 2020 Appendix B Source Assessment Report for MW-31 White Mesa Uranium Mill Page 2 of 2 Appendix B-5: Timeseries and Linear Regression Analysis for Select Uranium Datasets in MW-31 Uranium in MW-31 All Data Uranium in MW-31 Post September 2012 Appendix B Source Assessment Report for MW-31 White Mesa Uranium Mill Page 1 of 2 Appendix B-5: Timeseries and Linear Regression Analysis for Select Uranium Datasets in MW-31 Uranium in MW-31 Post May 2014 Uranium in MW-31 Post July 2020 Appendix B Source Assessment Report for MW-31 White Mesa Uranium Mill Page 2 of 2 APPENDIX C 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 C. 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 D Input and Output Files (Electronic Only)