DRC-2018-002404 - 0901a068807caa6f

DRC-2018-002404 195 North 1950 West • Salt Lake City, UT Mailing Address: P.O. Box 144880 • Salt Lake City, UT 84114-4880
Telephone [phone] • Fax [phone] • T.D.D. [phone] www.deq.utah.gov Printed on 100% recycled paper
State of Utah
GARY R. HERBERT Governor SPENCER J. COX
Lieutenant Governor
Department of
Environmental Quality
Alan Matheson Executive Director DIVISION OF WASTE MANAGEMENT AND RADIATION CONTROL Scott T. Anderson Director

March 20, 2018

Kathy Weinel, Quality Assurance Manager
Energy Fuels Resources (USA) Inc.
225 Union Blvd., Suite 600
Lakewood, CO 80228
RE: Energy Fuels Resources (USA) Inc. August 21, 2017, Source Assessment Report for MW-31
Groundwater Discharge Permit No. UGW370004 (Permit)
White Mesa Uranium Mill
Dear Ms. Weinel:

The Division of Waste Management and Radiation Control has completed its review of the Energy Fuels
Resources’ (EFR) August 21, 2017 document titled Source Assessment Report for MW-31 White Mesa Uranium Mill (SAR). The SAR includes an assessment of selenium, sulfate, total dissolved solids (TDS) and uranium in monitoring well MW-31.

Source Assessment

It was noted that Energy Fuels provided a source assessment and calculated, by several methods, proposed revised Ground Water Compliance Limits (GWCLs) for selenium, sulfate, TDS and uranium
in monitoring well MW-31. Monitoring well MW-31 is located hydraulically downgradient from the
eastern portion of Cell 2 and from the mill processing areas and is within the defined nitrate/chloride
plume. In the SAR, EFR notes that all SAR parameters were identified as having an increasing
concentration trend since the development of the Existing Wells Background Report. Division data review confirms that the SAR parameters all show increasing concentration trends.

Based on the review of the SAR, it appears that Mill activities are not influencing SAR studied
concentrations at monitoring well MW-31. This is based on the findings of several lines of evidence in
the SAR including, 1) potential effects from a 2011 well redevelopment project; 2) a change in analytical laboratory in 2012; 3) addition of several pumping wells to the nitrate/ chloride and chloroform corrective action plan (2013, 2014, 2015); 4) decreasing pH trend effects on monitoring well
geochemistry; 5) evaluation of tailings solution indicator parameters (chloride, sulfate, fluoride and
uranium); 6) site-wide comparison of parameters in MW-31 and upgradient and downgradient wells

(MW-31 shows relatively low concentrations of SAR parameters); 7) potential effects of pyrite oxidation releasing selenium and sulfate, and other trace metals, into solution; 8) location of MW-31
within the nitrate/chloride plume; 9) findings of the 2007/2008 University of Utah Groundwater Study;
and, 10) mass balance Analyses

Statistical Analysis
Based on the review of the SAR statistical analysis, it was noted that analysis was conducted for the
complete historic data set for MW-31 and for a post October 2012 data set. The complete data set
showed normal or log normal distribution for uranium but not for selenium, sulfate or TDS. The
modified data set did show normality for selenium, sulfate, TDS and uranium. Statistical methods used included, 1) descriptive statistics for the complete and modified data sets; 2) mean and standard
deviation calculation; 3) Shapiro-Wilk Test for normality; and, 4) Mann-Kendall Trend Analysis (non-
normally distributed data sets). Proposed GWCLs were calculated based on Mean + 2 Standard
Deviation, Highest Historical Value, Fraction of Groundwater Standard, and Background Mean
Concentration times 1.5. The calculations and findings are summarized in a table in the SAR (Appendix B-1 of the SAR).

In accordance with the approved statistical flow chart for the White Mesa Mill groundwater monitoring
wells, it was noted that if an upward trend is apparent for an analyte, then a modified approach should be
considered. The modified approach should allow for a GWCL which considers the increasing concentrations. Based on this, EFR calculated GWCLs according to the Utah Groundwater Rules (Utah
Administrative Code R317-6) which allow maximums to be set according to Mean + 2 Standard
Deviations, 0.5 times the GWQS (Class III Water) or 1.5 times the background concentration. Division
findings note that setting the GWCL at a maximum value for these parameters is reasonable, given that
the wells will likely exceed a more conservative GWCL in a short period of time when considering the increasing trends. This is particularly the case for selenium and sulfate in MW-31which have relatively
stronger trends are present at higher concentrations.

Selenium and sulfate additionally show a defined change in background data pre October 2012. In
accordance with the EPA 2009 Unified Statistical Guidance Section 5.3, and based on verification that the increases are due to background influences, it is appropriate to use the data collected after the point
of inflection and therefore, GWCLs for selenium and sulfate will use the post 2012 data set. It should be
noted that the difference between the post 2012 data set mean and the complete data set mean are not
significantly different. The TDS time series plot does not show a clear point of inflection and the
complete data set will be used. Since uranium GWCL is being reset based on the fraction of the GWQS, the specific data sets are not used except for comparisons.

Therefore, when comparing the various calculated GWCLs, it is appropriate to set GWCLs for selenium
and sulfate and TDS according to 1.5 times background for post 2012 data sets (Se and SO4) or the
complete data set (TDS). Uranium will be set according to 0.5 times the GWQS. These values are in conformance with the approved statistical flow chart, the Utah Groundwater Rules, EPA Statistical
Guidance and consider the increasing data trends.

MW-31 Approved Modified GWCLs
Based on the review of the SAR regarding proposed modifications to the GWCLs and statistical analysis
of the data and a telephone conference with Division representatives and EFR representatives on March
8, 2018, it was agreed that the GWCLs will be modified in the White Mesa Uranium Mill Ground Water
Permit for monitoring well MW-31 as summarized on the table below:
Well Number Parameter Current GWCL Modified GWCL Method of Analysis
MW-31 Selenium 86.81 µg/L 119.4 µg/L Background X 1.5*
MW-31 Sulfate 697.6 mg/L 993 mg/L Background X 1.5*
MW-31 TDS 1700 mg/L 2132 mg/L Background X 1.5**
MW-31 Uranium 9.1µg/L 15 µg/L Fraction (0.5) of GWQS *Based on 1.5 times the mean of the post Oct. 2012 data set for MW-31
**Based on 1.5 times the mean of the complete data set for MW-31 Please note that the modified GWCLs will not be effective until future issuance of a revised
Groundwater Discharge Permit and that the modifications will be subject to formal public notice and
public participation requirements. This is expected to take place in fall or winter of 2018.
If you have any questions, please call Tom Rushing at [phone].
Sincerely,

Scott T. Anderson, Director
Division of Waste Management and Radiation Control

STA/TR/ka
c: Kirk Benge, Health Officer, San Juan Public Health Department
Rick Meyer, Environmental Health Director, San Juan Public Health Department Scott Hacking, P.E., DEQ District Engineer