DWQ-2025-004412

Kennecott Bingham Canyon Mine and Water Collection System:
Dry Fork Management Plan
Operational Plan Summary
This plan targets groundwater monitoring and controls of historic mine impacted waters in the Dry Fork area. The management of these waters is separated into three areas:
Clean water capture upgradient of Dry Fork area;
Bedrock groundwater monitoring; and
Alluvial extraction of Dry Fork/Bingham Creek area mine groundwater.
The plan is formatted into five sections and summarizes well “as-built” specifications, pumping rates, historic concentrations of key analytes and geologic and hydrogeolgic conditions
where applicable. The five sections specifically addressed are:
Upgradient clean water capture;
Peripheral or lateral monitoring wells;
Alluvial pumping wells below the toe of Bingham Canyon waste rock disposal area;
Bedrock monitoring wells between Bingham Canyon waste rock disposal area and the Bingham Canyon cut-off wall; and
Bingham Canyon cut-off wall.
Historic Overview Including Geologic/Hydrologic Factors
Overview
Bedrock groundwater is known to have been impacted as a result of mining activities within the Dry Fork area. Efforts were made to monitor the extent of the contamination as well as
extract contaminated water with sulfate concentrations in excess of 20,000 mg/l. During the extraction period which lasted between 1960s and 2003, the geologic, hydrologic conditions
within the Dry fork area were studied extensively and are summarized in more detail below. Through various monitoring and extraction wells (Figure 2) the impacted groundwater was determined
to be confined to Bingham Canyon and its alluvial and bedrock flow path impeded by local structures resulting in mine contact waters reporting to down canyon alluvium. Mining operations
were modified in 2004 resulting in a change in Dry Fork plume management strategies. Kennecott placed waste rock in Bingham Canyon beginning in 1998 through the present, which covered
most of the monitoring wells in Bingham Canyon. Monitoring is now performed from wells at the mouth of the canyon.
Geologic Conditions
The geology of the Dry Fork area consists of Paleozoic sedimentary bedrock which is heavily folded and faulted. Two large fold structures are known to exist within Dry Fork Canyon: the
Copperton Anticline and the Copperton Overturn. The anticline is steeply dipping to the west and overturned on the east side. The Conger and Champion thrust faults cut across Bingham
Canyon. These structures generally impose down gradient bedrock barriers which minimize the migration of ground water deeper into bedrock to the east where it could impact the Salt Lake
Valley aquifer.
Hydrologic Conditions
Vertical head gradient at the confluence of Bingham Canyon and Dry Fork Canyon is predominantly upward and averages 0.026 ft/ft (not density corrected). The upward gradient is reflective
of a compilation of piezometer data collected from locations within the canyon both historic and current. The lower and most eastern part of Bingham Canyon has an upwards gradient as
large as 0.051 ft/ft (not density corrected). In these conditions, groundwater is reporting to alluvium where is can be captured in the alluvium pumping wells.
Waste rock was placed over approximately 100 feet of alluvial material in Bingham Canyon. Over this time period, the waste rock has drained meteoric water into the Bingham Canyon alluvial
material and into bedrock. This change has affected the hydraulic gradient somewhat such that the upward gradient has decreased. Kennecott believes the alluvial material is not fully
saturated and is partially influencing the water quality near the mouth of Bingham Canyon.
Monitoring Controls & Contingency Plan
Section 1: Upgradient Clean Water Capture
Two pumping wells are located upgradient of the Dry Fork dump area. The wells are COP2701 (Mid Valley Well) and COG1172 (Upper Dry Fork Well or Picnic Flats Well) as depicted in Figure
2. Well COG1172 is in the process of being replaced with a new extraction well (COG2865) located approximately 600 feet upgradient of COG1172. The purpose of the wells is to capture
clean water upgradient of the Dry Fork waste rock area prior to coming into contact with waste rock contact water (WRCW) as well as minimize hydraulic head pressure created by upgradient
groundwater sources in Dry Fork Canyon. Pumping on COP2701 began in the late 1990s, with an average monthly pumping rate of 130 gpm over the past 5 years when in use. Flow rates have
ranged from approximately100 to over 500 gpm. Pumping of COG1172 was re-established in 2007 and was implemented to supplement COP2701. The average flow rate (5 year rolling average)
for COG1172 based upon a monthly average is 50 gpm and has ranged between 40 to 70 gpm.
Table 1: Dry Fork Area Clean Water Capture Wells Summary Information
Well ID
COP2701
COG1172/Replacement Well COG2865
Alias
Mid Valley Well
Picnic Flats Well
General Location
300 ft upgradient of Dry Fork dump toe
1500 ft upgradient of COP2701
Coordinate
(state plane 83)
N 7378029.3
E 1459357.4
N 7378749.7
E 1458019.9
Years in Service
25

12
Surface elevation
6241
6341
Total Depth (ft)
345
962.8
Screen interval (ft)
20-275
80 – 952
Screened Lithology
Quartzitic alluvium/Quartzite
Quartzitic alluvium/Quartzite
Pump capacity (gpm)
500
375
Average Monthly pumping rate (gpm)¹
130
50
Average annual water volume removed (acre-feet)
200²
60³
Static Water Level (ft)
~110
100
¹Average pumping rate based upon months when pump is in service
²Average volume based upon 5 year rolling average annual data
³Average volume based upon 5 year rolling average annual data
Section 2: Peripheral Monitoring Well Controls
Peripheral monitoring of the Dry Fork area is performed through compliance monitoring wells COG2806A and B. The wells are located north and east of the Dry Fork Canyon and Bingham Canyon
intersect, as depicted in Figure 2, and both intervals are screened in quartzite. The wells are intended to monitor the potential lateral movement of mine impacted ground water originating
from Dry Fork Canyon. Groundwater monitoring wells ECG1106A & B, located approximately 600 feet north of ECG2787 and drilled in bedrock, can also be used as monitoring the northern/eastern
edge of the Dry Fork water quality. In addition, COG995A & B located adjacent and northwest of the waste rock and ECG2866 A & B located on the eastern extent of the waste rock in Bingham
Canyon are also used to monitor changes in water quality. The COG995 and ECG2866 sites are completed in bedrock and each have shown minimal changes in water quality over the past years.
Alluvial monitoring well ECG2854 and bedrock completion wells ECG2853A&B were located on top of the waste rock dump face, and the well casings had bent inward due to slight movements
in the waste rock dump. These wells were appropriately abandoned in September 2024.
Table 2: Peripheral Bedrock Monitoring Wells Summary Information
Well ID
COG2806A
COG2806B
General Location
NE corner of Dry Fork-Bingham Canyon Intersect
Same
Coordinate
(state plane 83)
N 7375371.5
E 1468620.3
Same
Years in Service
4
Same
Casing elevation
6228.91
6228.67
Total Depth (ft)
800
1108
Screen interval (ft)
760-800
1068-1108

Screen Lithology
Limey Quartzite
Quartzite
Average DTW (ft)
691
695
Monitoring of contaminated waters to the immediate south is precluded by active waste rock placement and historic waste rock disposal areas. The east side collection system is located
further south and east, which is comprised of a robust monitoring network of cut-off walls and monitoring wells. Bedrock groundwater contamination will be identified using these wells
and operational control structures.
Section 3: Alluvial Controls
Down Gradient of Bingham Canyon Waste Rock Disposal Area
Groundwater impact to the alluvial material is controlled with three pumping wells situated between the toe of Bingham Canyon waste rock disposal area and the Bingham Canyon Cut-off
Wall (COW) as depicted in Figure 2. Table 3 summarizes well statistics. The wells were placed to capture mine impacted water moving through alluvium and minimize water reporting to the
Bingham Canyon COW. The goal of the wells is to maximize alluvial extraction before mine impacted waters can enter the bedrock, however pumping rates for individual wells may vary or
cease all together based upon alluvial saturation conditions. There is no alluvial pumping located in Bingham Canyon between the Dry Fork pumping wells and ECG2866A & B. ECG2866A &
B were replaced by ECG2789A & B in 2020 to accommodate theinstallation of a new conveyor belt.
Table 3: Alluvial Pumping Wells Summary Information
Well ID
ECG2787¹
K83
ECG1185
Alias
NA
Curtis Springs
Copperton Channel
General Location
900 feet east of dump toe
3200 feet east of dump toe
3500 feet east of dump toe
Coordinate
(state plane 83)
N 7373909
E 1469365
N 7373754.9
E 1471616.3
N 7374630.6
E 1471905.2
Surface elevation
5496
5426
5509
Total Depth (ft)
130
109.8
200.7
Screen interval (ft)
75 – 129
46.5 – 96.5
130 – 200
Pump capacity (gpm)
260
300
30
Average Monthly pumping rate
120
2002
17
Average annual volume removed (acre-feet)
190
110

15
Average DTW (ft)
80
492
144
¹ Well performance statistics based upon 2019 annual reporting.
2This well operates when needed based on groundwater flow. This well has only beenoperated approximately 10 months since 2015 and monthly average is for months when pumped in 2019.
Section 4: Bedrock Controls
Down Gradient of Bingham Canyon Waste Rock Disposal Area
Five monitoring wells screened in bedrock act as early warning detection for impacts from Mine impacted water potentially impacting groundwater. The well locations are depicted in Figure
2.
Table 4a: Bedrock Monitoring Wells Summary Information
Well ID
ECG2789 A & B (to be replaced in 2020 with ECG2866)
ECG1100 A & B
K93
Comment
Paleozoic dual completion bedrock well
ECG1202 replacement
Paleozoic dual completion bedrock well
Paleozoic-Volcanic Bedrock contact
MDG1101 Replacement
General Location
Toe of Bingham Canyon dump
900 feet east of dump toe
2100 feet east of dump toe
Coordinate
(state plane 83)
N 7373789
E 1468530
N 7373797
E 1469391.8
N 7373736.3
E 1470610.3
Year built
2009
1994 (mod. 1997)
1968
Surface elevation
5558
5511
5451
Total Depth (ft)
730
861
765
Screen interval (ft)
A Completion
297 – 337
406 – 426
685 – 765
B Completion
675.7 – 715.7
828 – 857
NA
DTW (ft)
A Completion
108.2
90.2
14.8

B Completion
108.3
83.4
NA
Table 4b: Permit Limits for Bedrock Compliance Monitoring Wells
Well ID
Screen Lithology
Sampling Frequency
pH
TDS
(mg/l)
SO4
(mg/l)
Dissolved Cd (mg/l)
Dissolved Cu (mg/l)
Dissolved Zn (mg/l)
ECG1100A
Bedrock
Semi-annual
6.5-8.50
4148
2581
0.003
0.650
3.01
ECG1100B
Bedrock
Semi-annual
6.50-8.50
391
81
0.001
0.033
1.25
ECG2789A
(ECG2866A)
Bedrock
Semi-annual
TBD
TBD
TBD
TBD
TBD
TBD
ECG2789B
(ECG2866B)
Bedrock
Semi-annual
TBD
TBD
TBD
TBD
TBD
TBD
K93
Bedrock
Semi-annual
6.50-8.50
480
39

0.050
0.100
0.06
Bedrock Contamination Contingency Plan
The purpose of the bedrock monitoring wells is to monitor groundwater conditions relative to historic Dry Fork plume concentrations prior to 2003. The average sulfate concentration in
the Dry Fork plume has been known to be 20,000 mg/l. The following contingency measures will be used as a guide if the sulfate concentrations in bedrock as indicated by the above compliance
monitoring wells reach historic levels and action levels:
Evaluate potential risks to human health and the environment.
Evaluate potential contamination to waters of the state.
Assess the feasibility and effectiveness of extracting and treating ground water using wells or drains.
Petitioning of the Water Quality Board for an alternative Corrective Action Concentration Limits consistent with the risks identified.
Corrective Action Plans will be written in accordance with UCA R317-6-6.15 D and submitted for approval to the DWQ upon completion of the Contamination Investigation.
Section 5: Bingham Creek Cut-off Wall
The Bingham Creek COW is a concrete structure that spans Bingham Canyon and is built into volcanic bedrock, which has very low permeability. The wall is located approximately 5600 feet
down canyon from the toe of the waste rock disposal area as depicted in Figure 2. The wall is designed to capture alluvial water migrating down Bingham Canyon not captured by the alluvial
pumping wells up canyon. Water collected at the wall’s sump is removed through pumping. Pumping rates fluctuate seasonally and can be dependent upon the effectiveness of the alluvial
pumping wells in Bingham Canyon upgradient of the cutoff wall listed in Table 3.
Table 5: Bingham Creek Cut-off Wall Specifications
Site ID
ECP2562
Alias
Bingham Creek COW
General Location
5600 ft down gradient of dump toe
Coordinate
(state plane)
N 7373492.5
E 1473938.0
Years in Service
1995 to present
Surface elevation
5353
Total Depth (ft)
110
Pump capacity (gpm)
900 total (2 pumps)
Average Monthly pumping rate
300¹
Average annual volume removed (acre-feet)
513
Average DTW in sump (ft)
85
¹Average monthly pumping rate based upon 2019 monthly data.
The Bingham Creek Cut-off wall spans approximately 375 feet across Bingham Creek channel and is approximately 100 feet deep and built into volcanic bedrock. During excavation and construction
of the wall, the majority of the alluvial flow comes from the bottom 20 feet of coarsequartzitic gravel immediately above bedrock. Several previous borings/wells into the underlying
volcanic bedrock were exposed during the excavation for the wall and water flowed upward from the bedrock into the excavation area. Head measurements were not conducted on the upgradient
flow. Water quality from the upward flow had conductivities measuring less than 2,000 umhos/cm. After the cutoff wall was completed, down gradient monitoring wells completed in alluvium
and volcanic bedrock exhibited decreases in sulfate concentrations.
Reporting
Kennecott will follow guidelines set forth by permit # UGW350010 regarding compliance well monitoring and reporting and will be reported on a quarterly basis. Operational and monitoring
sites of the Dry Fork and Bingham drainage area will be sampled on an annual basis (if available to sample) for water quality as per Table 3 of the permit. Water flow data, specifically
average monthly pumping rates and corresponding annual totals will be tracked throughout the year for operational locations and reported in the annual report as well as associated water
quality data.