DRC-2024-005577

May 7, 2024
Kathy Weinel
Director of Regulatory Compliance
Energy Fuels Resources (USA) Inc.
225 Union Blvd., Suite 600
Lakewood, CO 80228
RE: Energy Fuels Resources (USA) Inc.March4, 2024, Source Assessment Report forSeleniuminMonitoring Well MW-03A, White Mesa Uranium MillUtah Groundwater Discharge Permit No. UGW370004
Dear Ms. Weinel:
The Utah Division of Waste Management and Radiation Controlhas reviewed the Energy Fuels Resources (USA) Inc. (EFR),March 4, 2024, document titled “White Mesa Uranium Mill, State of
Utah Groundwater Discharge Permit No. UGW370004, Source Assessment Report Under Part I.G.4 for Exceedances in MW-03Ain the Third Quarter of 2023” (SAR) (DRC-2024-004813). The SAR includes
an evaluation of out of compliance (OOC) parameterSelenium in monitoring well MW-03A.Monitoring Well MW-03A is located hydraulically downgradient from Cells4A and 4B.
Per the SAR, EFR finds thatMW-03A has not been impacted by seepage from the tailings cells. Current changes in groundwater chemistry and Selenium OOC at monitoring well MW-03A are due
to changing groundwater background conditions. Section 3.5.1.1 of the SAR includes discussion of the assessment and lists the four factors supporting that EFR conclusion. Specifically,
per the SAR:
“Indicator parameters chloride, and sulfate are stable and uranium and fluoride havesignificantly decreasing trends.
pH has been generally stable to increasing since 2016.
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.
Mass balance analysis indicates that water level increases at MW-03A do not result from potential TMS seepage.”
MW-03AStatistical Analysis
Based on Division review of the SAR,it was noted that statistical analysis was conducted for Selenium on the complete historic data set and for a post-November 2019, data set. After
November, 2019, a point of inflection is observed where groundwater levels in MW-03A began to stabilize and an increasing trend in Selenium concentration was observed.
The statistical analysis performed by EFR showed that Selenium concentration in MW-03A exhibited a non-parametric distribution and significantlyincreasing trend for the complete data
set. The post-November 2019 data set is normally distributed with a significantlyincreasing trend. The post-November 2019 data subset is believed to be representative of current conditions
and appropriate forcalculating a revised GWCL for Selenium.
The Division approved statistical flow chart for the White Mesa Mill groundwater monitoring wells clarifies that if an increasing trend is apparent for a constituent, then a modified
approach should be considered. The modified approach should allow for a GWCL which considers the increasing concentration, therefore, the proposed GWCL for Selenium in MW-03A was calculated
based on the highest historical value of the post-November 2019, data set. The calculations and findings are summarized on a table in the SAR (Appendix A-1 of the SAR).
EFR Statistical methods used in the SAR included:
1. Dixon's test, Rosner's test, and Probability Plots to evaluate outliers.
2. Descriptive statistics for the complete data set and post-inflection data set
3. Shapiro-Wilk Test for normality.
4. Mann-Kendall and Linear Trend Analysis.
Per Division review of the SAR and historical data for MW-03A, the out-of-compliance status for Selenium does not appear to be associated with contamination from a tailings wastewater
source. Division findings are detailed in a separate SAR review memorandum. Based on these findings it is appropriate to adjust the Permit groundwater compliance limit for Selenium
in MW-03A, consistent with the currently approved groundwater data statistical process flow chart for the Mill and associated guidance.
Approved Modified GWCL for Selenium in MW-03A
Per review of the statistical analysis and proposed modifications to the GWCL, the GWCL will be modified in the White Mesa Uranium Mill Ground Water Permit for Selenium in monitoring
well MW-03A as summarized in the table below:
Well Number
Parameter
Current GWCL
Modified GWCL
Method of Analysis
MW-03A
Selenium
109.58 µg/L
171 µg/L
Highest Historical Value*
*Based on the Highest Historical Value of the post November 2019 Selenium background data set
Note that the modified GWCL will not be effective until Permit renewal, and that the modified GWCLwill be subject to formal public notice and public participation requirements. These
Permit modifications are anticipated to be made during calendar year 2024.
If you have any questions, please call Chris Leahy at [phone].
Sincerely,
Adam Wingate, Uranium Recovery Manager
Division of Waste Management and Radiation Control
AJW/CL/wa
c: Grant Sunada, Health Director, San Juan Public Health Department
Ronnie Nieves, Environmental Health Director, San Juan Public Health Department
Curtis Page, District Engineer, UDEQ

Kathy Weinel, Regulatory Compliance Director, Energy Fuels Resources (USA) Inc. (Email and Hard Copy)
Scott Bakken, Energy Fuels Resources (Email, [e-mail])