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Home My WebLink AboutDRC-2024-006482 Salt Lake City, UT -4880 Telephone (801) 536-Fax (801) 536-T.D.D. (801) 536-4284 www.deq.utah.gov Printed on 100% recycled paper State of Utah SPENCER J. COX Governor DEIDRE HENDERSON Lieutenant Governor Department of Environmental Quality Kimberly D. Shelley Executive Director DIVISION OF WASTE MANAGEMENT AND RADIATION CONTROL Douglas J. Hansen Director MEMORANDUM TO: File THROUGH: Adam Wingate, Uranium Mills Recovery Manager Chris Leahy, Hydrogeologist, PG FROM: Dean Henderson, Hydrogeologist, PG DATE: July 15, 2024 SUBJECT: Division of Waste Management and Radiation Control (Division) Staff Review of the March 28, 2024, Chloroform Corrective Action Comprehensive Monitoring Evaluation (CACME) Report White Mesa Uranium Mill, near Blanding, Utah. Energy Fuels Resources (USA) Inc. (EFRI). Groundwater Corrective Action Plan (GCAP) found in Attachment 1 of the Stipulation and Consent Order (SCO) Docket No. UGW20-01. Based on the DWMRC staff review below it appears that the March 28, 2022, Chloroform CACME Report is in compliance with the GCAP found in Attachment 1 of the SCO Docket No. UGW20-01. REVIEW OF CACME 2024 GCAP Part III.H requires: -Year Corrective Action Comprehensive Monitoring Evaluation on or before March 31 2016, and every two-years thereafter, EFR shall submit a comprehensive An electronic copy of the Chloroform CACME 2024 report was submitted to the Director of Division of Waste Management and Radiation Control (Director) on March 29, 2024. A hard copy of the CACME 2024 was received by the Director on April 2, 2024 (DRC-2024-005132) and therefore meets the requirement in GCAP Part III.H. GCAP Part III.H.1 requires: monitoring performe Page 2 Summary and Interpretation Results Between the 4th Quarter 2012 and 4th Quarter 2023 Chloroform Groundwater Monitoring Since December 31, 2012, 44 quarterly chloroform groundwater monitoring reports (1 st quarter 2013 through 4th quarter 2023) have been submitted by EFRI. These monitoring reports were reviewed and approved by the Director and appeared to follow requirements in Parts III.A through E of the GCAP. Approval by the Director was documented with closeout letters for all 44 quarterly chloroform groundwater monitoring reports. The chloroform monitoring well network (Network) consists of 23 groundwater compliance monitoring wells, 5 groundwater performance monitor wells, and 15 groundwater pumping wells. At this time this Network controls, defines and bounds the chloroform plume. The chloroform monitoring network is summarized in Table 1 below. Table 1 Chloroform Groundwater Monitoring Network Wells Compliance Wells Performance Wells Pumping Wells MW-32 TW4-28 TW4-7 MW-4 TW4-39 TW4-3 TW4-30 TW4-10 MW-26 TW4-40 TW4-5 TW4-31 TW4-16 TW4-1 TW4-41 TW4-6 TW4-32 TW4-26 TW4-2 TW4-8 TW4-33 TW4-29 TW4-4 TW4-9 TW4-34 TW4-11 TW4-12 TW4-35 TW4-19 TW4-13 TW4-36 TW4-21 TW4-14 TW4-38 TW4-22 TW4-18 TW4-42 TW4-24 TW4-23 TW4-43 TW4-25 TW4-27 TW4-37 Chloroform pumping since 2003, the groundwater mound decay below the wildlife ponds since 2012, and nitrate pumping initiated in 2013 has resulted in decreasing trends in the hydraulic gradients and saturated thickness resulting in the reduction of groundwater flow through the chloroform plume. Between the 4th quarter 2012 and 4th quarter 2023, hydraulic gradients have been reduced between 10% to 34% and the average saturated thickness within the plume has decreased approximately 37%. In 2015, the background groundwater flow through the chloroform plume was calculated as approximately 3.4 gpm. The decreasing saturated thicknesses and hydraulic gradients in the plume has resulted in a 4th quarter 2023 calculated background flow of approximately 2.24 gpm. The chloroform pumping system is calculated to remove approximately 4.35 gpm (exceeding the background flow by 2.1 gpm) which indicates that the pumping system appears to be adequate to control the plume. With the use of kriged 4th quarter, 2023 water level contours, chloroform plume boundary, chloroform mass distribution and perched water level maps an estimated 77% of the plume area, and 92% of the plume mass are under hydraulic capture as of the 4th quarter of 2023. Page 3 Expansion of the chloroform plume boundaries between 1 st quarter 2012 and 4th quarter 2015 were relatively stable. Between the 4th quarter 2015 and 4th quarter 2017 the chloroform plume boundaries expanded eastward and cross-gradient in the vicinity of TW4-9, which may be the result of reduced dilution from northern wildlife ponds, and in the southerly downgradient vicinity of TW4-26, which is the result of more southerly gradients because of the decay of the southern wildlife pond. In October 2016 well TW4-38 was drilled and installed to bound the chloroform plume east of TW4-9. Chloroform concentrations collected in quarterly sampling events after TW4-38 was installed were <1.0 µg/l demonstrating that this well bounds the chloroform plume east of TW4-9. The southern portion of the plume is bounded by TW4-42 (non-detect for chloroform). TW4-40 was installed once concentrations at TW4--42 was installed once concentrations at TW4--40 was converted to a pumping well in May 2019. At the southeast extremity of the plume, relatively stable to decreasing chloroform at TW4-33 (no longer within the plume) and generally decreasing to stable concentrations at downgradient well TW4-29 suggest that chloroform migration may have been arrested at TW4-33 by TW4-4 and TW4-41 pumping. The decreasing to stable chloroform at TW4-29 results from a remnant of the plume that migrated downgradient from TW4-33 to TW4-29; then toward TW4-30 (which formerly bounded the plume to the east). Once chloroform concentrations at TW4-30 exceeded 70 ug/L for two consecutive quarters, new compliance well TW4-43 was installed approximately 200 feet east-southeast of TW4-30. Because chloroform concentrations at TW4-30 are again below 70 ug/L during the 3 rd quarter 2022, TW4-30 again bounds the plume to the southeast. Decreasing chloroform concentrations at downgradient well TW4-6 since the first quarter of 2015 and increasing to stable concentrations at TW4-26 since the first quarter of 2016 suggest that chloroform migration has been captured in the vicinity of TW4-6 by pumping wells TW4-4 and TW4-41. Chloroform trends at wells within and near the southern extremity of the plume are influenced by TW4- 4 and TW4-42 pumping. Continued migration of chloroform to the east in the vicinity of TW4-30 may change because hydraulic gradient near TW4-30 is now more southerly than easterly, by the influence on both TW4-4 and TW4-41 pumping and reduced wildlife pond recharge. TW4-40 began pumping during the second quarter of 2019. TW4-40 is located within the downgradient (southern) toe of the plume, south of TW4-26. Pumping of TW4-40 well help reduce and help prevent further downgradient plume migration. Chloroform detected in the vicinity of TW4-26 and TW4-40 appears to be within the hydraulic capture zone of TW4-40. It appears that the chloroform plume is under control, and it appears the GCAP is effective in protecting public health and the environment. In addition, natural attenuation by dilution, hydrodynamic dispersion, volatilization, and possible reductive dichlorination (abiotic degradation) suggest that all chloroform will be below the GCAL within 200 years. Therefore, continued implementation of the GCAP and the current pumping system is recommended. Page 4 GCAP Part III.H.2 requires: Review the chloroform mass removal rates resulting from pumping to evaluate the performance of the pumping Wells. In the event that the mass removal rates have dropped substantially, such evaluation shall include a determination whether the removal rates have dropped as a result of reduced concentrations within the plume, lost well productivities or a general reduction in Since 2003 the chloroform pumping system have removed approximately 1410 lbs. of chloroform from the plume. Since the 3rd quarter 2015, chloroform mass removal rates and the chloroform plume residual estimates have trended downward. This trend is a consequence of both reduced chloroform concentrations within the plume and reduced saturated thickness and decrease in hydraulic gradients due to pumping system and the termination of water delivered to the north and south wildlife ponds in March 2012. DWMRC CONCLUSIONS The DWMRC staff agrees with EFR that chloroform plume appears to be under control, and it appears the GCAP is effective in protecting public health and the environment. Continued implementation of the GCAP and the current pumping system should continue. Therefore, a letter will be drafted for the Division Director Signature, notifying EFR of the review and closing out the 2024 Chloroform Corrective Action Comprehensive Monitoring Evaluation (CACME) Report. Page 5 References Utah Division of Waste Management and Radiation Control, Stipulation and Consent Order Docket No. UGW20-01, Attachment 1, Groundwater Corrective Action Plan found in Attachment 1, September 14, 2015.