DWQ-2025-002901

STATEMENT OF BASISGROUND WATER DISCHARGE PERMIT UGW350015Kennecott Utah Copper LLC
Magna Process Water Reservoir
Magna, Utah
August, 2025
Introduction
The Division of Water Quality (DWQ) under the authority of the Utah Ground Water Quality Protection Rules1(Ground Water Rules) issues ground water discharge permits to facilities which
have a potential to discharge contaminants to ground water2. As defined by the Ground Water Rules, such facilities include mining operations3. The Ground Water Rules are based on an
anti-degradation strategy for ground water protection as opposed to non-degradation; therefore, discharge of contaminants to ground water may be allowed provided that current and future
beneficial uses of the ground water are not impaired and the other requirements of Rule 317-6-6.4.A are met4.Following this strategy, ground water is divided into classes based on its
quality5; and higher-quality ground water is given greater protection6 due to the greater potential for beneficial uses.
The Director has developed permit conditions consistent with R317-6 and appropriate to the nature of the mined materials, facility operations, maintenance, best available technology7
(BAT) and the hydrogeologic and climatic conditions of the site, to ensure that the operation would not contaminate ground water.
Basis for Permit RenewalThis Permit is being renewed in accordance with R317-6-6.7. However, a permit may be terminated or a renewal denied if any one of the four items in R317-6-6.8
applies:Noncompliance by the permittee with any condition of the Permit where the permittee has failed to take appropriate action in a timely manner to remedy the Permit violation;The
permittee’s failure in the application or during the Permit approval process to disclose fully all significant relevant facts at any time;A determination that the permitted facility
endangers human health or the environment and can only be regulated to acceptable levels by plan modification or termination; orThe permittee requests termination of the Permit.
Permit Changes and Modifications
No new facilities will be regulated under this Permit. Any reference to the Utah Copper Power Plant (UPP) has been removed from this permit application as the facility is the process
of being demolished.
Purpose
Past permitting of this area included the North Concentrator facilities consisting of the Bonneville Crushing Mill as well as the Magna Flotation Mill and Filter Plant and the Utah Copper
Power Plant (UPP). These mills and filter plant facilities ceased operations in 2001 with reclamation completed in 2007 while the UPP ceased operations in 2017 and is in various stages
of demolition. Currently in place is the Magna Process Water Reservoir, which includes containment and pumping facilities that route process water for Kennecott Utah Copper LLC(Kennecott)
operations.The Magna Reservoir facility, located north of the former UPPfacility, consists of two reservoirs located adjacent to each other. The reservoirs were constructed in 2011 to
primarily be operated in series with flow typically first entering Reservoir No. 1, flowing to Reservoir No. 2, and then to Pump Stations 3, 3A, and 3B. However, each reservoir has
an inlet, outlet, and overflow that can be isolated so that the reservoirscan be operated independently during periods of maintenance, modification, or repair. The reservoirs include
an identical, double containment liner system as the seepage barrier: A primary liner consisting of an 80-mil HDPE geomembrane with microspikes for surface traction is located on top.
A secondary liner consisting of a 60-mil HDPE geomembrane with drainage nubs is located beneath the primary liner.
The volume of any leakage is monitored by electrical controls in leak detection manholes that are linked to a programmable logic controller (PLC) located and monitored remotely at the
Tailings Control Room.
Hydrogeology
The Magna Process Water Reservoir facilities are located on the north flank of the Oquirrh Mountains. Immediately to the east and north of the site lie basin-fill sediments. Three
aquifer systems exist in the vicinity of the Magna Process Water Reservoir: the Bedrock Aquifer system associated with the Oquirrh Mountains, the confined Principal Aquifer, and the
unconfined Shallow Aquifer.
The Bedrock Aquifer beneath the facility is comprised of Paleozoic shale, quartzite, limestone, and dolomite. Recharge to the Bedrock Aquifer system is principally from precipitation
on the mountains to the south. Ground water in the bedrock system flow path discharges to the north of the Magna Process Water Reservoir facilities either directly to Adamson Spring
or passes into the Principal Aquifer and into Adamson Spring or the Clarification Canal at or near Pump Station #1.
The Principal Aquifer is a confined system which includes a gravel zone and lacustrine deposits. The gravel zone was most likely derived from erosion of the mountains during an extensive
low lake cycle. Many high yield water supply wells near the OquirrhMountains are completed in the gravel zone of the Principal Aquifer. The lacustrine zone consists of clay, silt and
interbedded fine sand. Principal ground water flow direction for this aquifer is northerly.
The Shallow Aquifer system consists of interbedded lacustrine Bonneville clay, silt, and fine sand. The exact depth of this system varies but is approximately the upper 35 to 50 feet
of saturated sediments. The potentiometric surface for the Shallow Aquifer system depicts lateral flow in a north and northeasterly direction with vertical ground water flow gradients
predominantly in an upward direction for the majority of wells completed in the shallow system.
The Little Valley area encompasses the surface drainage from the decommissioned Bonneville Mill. Recharge from rain and snow events that come in contact with the former ore storage
area or other decommissioned operations associated with Bonneville facilities would enter the bedrock system beneath the Little Valley area
Ground Water Quality
The water quality in the Bedrock, Principal, and Shallow Aquifers beneath and immediately adjacent to the Magna Reservoirfacilities is generally a Class II water with TDS values that
range from 1,000 mg/L in the southern area to near 2,000 mg/L in the northern area.Ground water concentrations of sulfate typically range from less than 100mg/L up to 500mg/l. In addition,
the seepage from the fresh waterUtah - Salt Lake Canal (Jordan River source) has an average sulfate concentration of approximately 400 mg/L. This appears to influence the ground water
quality in the area along the canal that is east of the permit boundary.
Concentrations of dissolved trace metals are relatively low. Cadmium, chromium, lead, mercury, and silver are near or below the minimum detection limit. Arsenic concentrations are
generally in the 0.005 to 0.016 mg/Lrange but well below the ground water quality standard of 0.05 mg/L. Dissolved copper concentrations range from non-detect to 0.02 mg/L. Selenium
concentrations range from non-detect to 0.025 mg/L.
Compliance Monitoring Program
A semiannual compliance monitoring program is required by the permit. ComplianceLimitshave been established following the specific rule of R317-6-6.4. The following parameters were
selected for compliance monitoring based on their high concentrations in the process water compared to concentrations in shallow ground water:TDS
Chloride
Sulfate
Alkalinity
Calcium

Magnesium
Potassium
Sodium
Dissolved Metals (arsenic, boron, lead, barium, cadmium, chromium, copper, selenium, and zinc)
Best Available Technology (BAT) and FacilityModificationsKennecott is in the process ofdemolishing the UPP BAT is applicable to management of the Magna Reservoirs and its conveyance
system.
Compliance Schedule Items