DRC-2025-001611

May20, 2025
Kathy Weinel, Director of Quality Assurance
Energy Fuels Resources (USA) Inc.
225 Union Blvd., Suite 600
Lakewood, CO 80228
RE: Energy Fuels Resources (USA) Inc. March 10, 2025, Transmittal of Plan and Time Schedule
Groundwater Discharge Permit No. UGW370004
Project Number 479-2025-20
Dear Ms. Weinel:
In a report dated February 11, 2025, Energy Fuels Resources (USA) Inc. (EFRI)notified the Division of Waste Management and Radiation Control (Division) that total dissolved solids (TDS)
in MW-28entered out-of-compliance (OOC) status after exceeding the Groundwater Compliance Limit (GWCL) in the 4thQuarter 2024sampling event (DRC-2025-000480).Groundwater Discharge Permit
No. UGW370004 (Permit) conditionI.G.2. states that a well enters OOC status when the concentration of a pollutant exceeds a GWCL for two consecutive sampling events. Permit condition
I.G.4.c. requires EFRI to submit a plan and time schedule for completing a Source Assessment Report (SAR) for any well that enters OOC status.
On March 10, 2025, EFRI submitted a report titled Transmittal of Plan and Time Schedule under Utah Ground Water Discharge Permit UGW370004 Part I.G.4(c) White Mesa Mill (EFRI Plan)(DRC-2025-000843)
to theDivision in compliance with Permit condition I.G.4.c. The EFRI Plan outlines the investigation EFRI plans to conduct when evaluatingconsecutiveexceedances of theGWCL for TDS in
monitoring well MW-28.The EFRI Plan also proposes evaluating previous OOC constituents in MW-28, Uranium and Selenium. EFRI indicates theseOOC constituents were addressed in a previous
SAR, but both have exceeded therecalculated GWCLs specified in that SAR.
The table below summarizes the preliminary findings in the EFRI Plan:
Monitoring Well
Parameters
EFRI Noted Preliminary Findings
MW-28
TDS, Uranium, Selenium
MW-28 lies within the influence of the Nitrate/Chloride plume.
EFRI notes that concentration of indicator parameter sulfate in MW-28 is stable.
EFRI notes that the concentration of indicator parameter fluoride in MW-28 is decreasing.
EFRI notes that the concentration of indicator parameters chloride and uranium in MW-28 is increasing.
The EFRI Plan states that the increase in TDS concentration at MW-28 “could be attributed to natural background and site-wide influences such as oxidation of pyrite”OR impacts of the
Nitrate/chloride plume already being addressed underan existing corrective action.
The EFRI Plan states that the increase in Uranium and Selenium concentration at MW-28 are “attributable primarily to: the oxidation of naturally-occurring pyrite that contains Selenium
and Uranium as a contaminant; and mobilization of naturally occurring Selenium and Uranium by Nitrate as the Nitrate plume migrates towards MW-28.”
A Source Assessment Report (SAR) which will include a source investigation and statistical analysis, per Section 4 of the EFRI Plan, will be submitted to the Director within 90 days
after approval of the EFRI Plan.
As expressed in the table above, EFRI preliminary findings attribute the Uranium and Selenium increases at MW-28 to the oxidation of naturally-occurring pyrite that contains Selenium
and Uranium as a contaminant; and mobilization of naturally occurring Selenium and Uranium by Nitrate as the Nitrate plume migrates towards MW-28. During the review of the EFRI report,
The Division reviewed trends in groundwater levels and groundwater quality at MW-28 and at nearby wells with increasing Uranium and Selenium concentrations (MW-11, MW-30, and MW-31).

The Division noted that at MW-11 and MW-28, previous water level increases attributed to the wildlife ponds ceased around 2016, and the concentration of Nitrate was non-detect until
either 2014 (MW-28) or 2019 (MW-11), when increasing Nitrate trends began and have continued to present. This is also roughly when Uranium and Selenium began to be regularly detected
and increases in concentrations of both began. This would appear to support the preliminary findingmentioned above, as the Nitrate concentrations at MW-11 and MW-28 have increased since
about 2014 (MW-28) or 2019 (MW-11) while in conjunction, concentrations of Uranium and Selenium have steadily increased and water levels have flattened out.
However, the Division also noted that at MW-30 and MW-31,previous water level increases attributed to the wildlife ponds levelled off around 2014,and the concentration of Nitrate has
remained relatively steady(MW-30) or decreased slightly (MW-31) since 2005. Uranium and Selenium were already being detected at MW-30 and MW-31 in 2005, and concentrations are currently
still increasing. In other words, it appears that Nitrate concentration at MW-30 and MW-31 has remained flat (MW-30)or decreased slightly (MW-31) since 2005 while concentrations of
Uranium and Selenium have steadily increasedand water levels have flattened out (MW-30) or decreased slightly (MW-31). In other words, the saturated zone at MW-30 and MW-31 has not
increased since around 2014, the Nitrate concentration at these wells had remained relatively consistent since 2014, but Uranium and Selenium continue to increase. This would appear
to imply that a different mechanism is contributing to the increasing Uranium and Selenium concentrations.
In short, it appears that Nitrate could be responsible for increases in Uranium and Selenium concentrations at MW-11 and MW-28, but it is not as clear at MW-30 and MW-31, where Nitrate
has been in contact with the formation since at least 2005. Due to this discrepancy, the Division requests that EFRI please consider all four wells when conducting the sourceassessment
of exceedances at MW-28due to water level increases and/or oxidation of pyrite.
Based on review of the EFRI Plan it appears that the proposed activities are appropriate, and the EFRI Plan is hereby approved with the additional request of the Division above.
If you have any questions, please contactChris Leahy by email at [e-mail] or by phone at [phone].
Sincerely,
Adam Wingate, Uranium Recovery Section Manager
Division of Waste Management and Radiation Control
AJW/CL/wa
c: Dennis Shumway, San Juan Public Health Department
Mike Moulton, San Juan Public Health Department
Curtis Page, P.E., District Engineer, UDEQ
Kathy Weinel, Director of Regulatory Compliance, Energy Fuels Resources (USA) Inc.

(Email and Hard Copy) [e-mail]
Logan Shumway, Mill Manager, Energy Fuels Resources (USA) Inc.
(Email) [e-mail]