DRC-2022-022191 - 0901a0688110d0fb

October 24, 2022
Sent VIA E-MAIL AND EXPEDITED DELIVERY
Ms. Doug Hansen
Director
Division of Waste Management and Radiation Control
Utah Department of Environmental Quality 195 North 1950 West Salt Lake City, UT 84116
Energy Fuels Resources (USA) Inc. 225 Union Blvd. Suite 600 Lakewood, CO, US, 80228 303 974 2140 www.energyfuels.com
Div of Waste Management and Radiation Control
OCT 2 7 2022
Re: Monitor Well MW-41 Abandonment and Proposed MW-41A Location White Mesa Uranium Mill
Dear Mr. Hansen:
Pursuant to the telephone notice provided by Energy Fuels Resources (USA) Inc. ("EFRI") to the Division of Waste Management and Radiation Control ("DWMRC") staff on October 19, 2022 and October 20, 2022, EFRI is submitting this letter documenting the abandonment of monitoring well MW-41 and proposing the location for the replacement well MW-41A at the White Mesa Mill (the "Mill").
BACKGROUND
During discussions with DWMRC regarding the MW-24A Phase 2 investigation design, DWMRC requested the installation of another groundwater monitoring well down gradient of MW-24/MW-24A. The new well, MW-41, was installed down gradient from MW-24/MW-24A (in closer proximity to MW-
24 than MW-2) on July 20, 2022. Pursuant to discussions with DWMRC and the DWMRC February 2,
2022 letter which stated, "The additional monitoring well should be constructed to eliminate suspected
problems with well construction at MW-24/MW-24A (e.g. eliminate open well screen above the water
table)", EFRI planned to complete MW-41 using a shorter well screen to eliminate open well screen above the water table (i.e. submerged screened interval).
The primary purpose of eliminating open screen above the water table is to minimize transport of air into
the vadose zone in the vicinity of the well to in turn minimize oxygen transport to groundwater. As previously discussed, enhanced oxygen transport to groundwater near monitoring wells increases pyrite oxidation, lowers pH, and mobilizes trace metals contained in pyrite as well as pH sensitive metals that occur naturally in the formation hosting perched groundwater.
MW-41 drilling commenced on July 20, 2022, with EFRI collecting core during drilling. Water was encountered at 92 feet during the drilling. In an effort to eliminate open well screen above the water table, EFRI's geologist instructed the driller to screen the well from 100 feet to 130 feet (the total depth of the well).
Subsequent field activities conducted at the noted that the static water level in MW-41 was approximately
111 feet below top of casing ("btc"). A static water level of approximately 111 feet btc means that, as
DRC-2022-022191
MW-41
TW4-43
TWN-20
[]
perched monitoring well installed July, 2022 and proposed replacement location
temporary perched monitoring well installed September, 2021
temporary perched nitrate monitoring well installed April, 2021
MW.-24A perched monitoring well installed December 2019
TW4-42 ¢
TW4-40 EB
TW4-19 EB
MW-38 ◊
MW-5 •
TW4-12
TWN-7
PIEZ-1 g
temporary perched monitoring well installed April 2019
perched chloroform pumping well installed February 2018
perched chloroform or nitrate pumping well
perched monitoring well installed February 2018
perched monitoring well
temporary perched monitoring well
temporary perched nitrate monitoring well
perched piezometer
RUIN SPRING b seep or spring
DR-10
• MW-21
DR-11� . DR-12
• MW-3A
OR-13
OR-15 • HYDRO GEO CHEM,INC. • MW--01
a'lf,111:df �?!1TWN--05
D O TWN-20 TWN--07
• MW-18
•11�1:i.f!lliTWN-15
•!J/t,� TWN-10 1tli!J!.f
•
0 TWN-14
0 TWN--06 lWN--09
"141},"®i!J TWN--08.
. ' PIEZ--01
WHITE MESA SITE PLAN SHOWING LOCATIONS OF PERCHED WELLS AND PIEZOMETERS AND LOCATIONS
OF MW-41 AND PROPOSED REPLACEMENT
APPROVED DATE REFERENCE H:/718000/MW41/ Reinstallation/UMW41 location.srf
FIGURE