DAQ-2025-000591

Rio Tinto Kennecott, 4700 Daybreak Parkway, South Jordan, Utah, 84009
January 30, 2025
Mr. Bryce Bird, Director Department of Environmental Quality Division of Air Quality
195 N 1950 W Salt Lake City, UT 84116
Subject: Approval Order (AO) DAQE-AN0572018-06 Kennecott Utah Copper – Tailings Facility Tailings Quarterly Report – Fourth Quarter 2024
Dear Mr. Bird,
In compliance with Kennecott Utah Copper LLC (Kennecott) Approval Order (AO) DAQE-AN0572018-06, dated April 6, 2006, Kennecott is submitting the attached Tailings Quarterly Report to summarize applicable data for the fourth quarter of 2024.
• All monitoring and recordkeeping requirements were met during the
reporting period.
• Zero (0) acres were seeded during the reporting period
• Polymer or chemical dust suppressant was applied to a total of 85 acres during the reporting period; See Control Measures table for suppressant and polymer application acres.
• The 95% minimum wetness criterion was met as determined during the grid inspections conducted during the fourth quarter of 2024. Refer to the
attached surface wetness table.
• Kennecott continued to monitor weather conditions during the reporting period. Criteria for wind speeds were experienced on three (3) days during the quarter. o October 17, 2024
o October 23, 2024 o December 14, 2024 If you have any questions or need further information regarding this report, please feel free to contact Sean Daly at 801-204-2563.
Sincerely,
Paula H. Doughty Manager, Hydro, Tailings and Water Services
Attachment
Rio Tinto Kennecott 4700 Daybreak Parkway South Jordan, Utah 84009 Tel: [phone]

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KENNECOTT UTAH COPPER – TAILINGS QUARTERLY REPORT
4th Quarter Report – 2024 This report reviews dust control activities for the reduction of fugitive dust at the Kennecott Utah Copper Tailings Site and fulfils reporting requirements as outlined in the Approval Order (AO) for this facility. Control Measures
Area
Drill Seeding & Fertilizer (acres)
Hydro-seeding (acres)
Redrill (acres)
Total seeding (acres)
MCl, Pine Tar, Hy-Mulch, M-binder & Polymer Control (acres) North 0 0 0 0 85 South 0 0 0 0 0 The acreage listed above is displayed on the attached maps as required in the AO. No acres on the site were treated with lime and biosolids to enhance vegetative growth. Supplemental Dust Controls
In addition to the dust control methods outlined above, road watering was conducted as conditions warranted. Automatic high-pressure sprinklers were also used on inactive construction cells in the north area. Dike Interior Dust Control
The operational program of rotating tailings distribution from the peripheral discharge system continued during the quarter in the north area. Tailings distribution has been discontinued in the south area due to reclamation activities. Criteria For Wind Reporting During the fourth quarter of 2024, KUC monitored meteorological conditions. There were three (3) days during the period when the criteria for wind reporting was met. The AO combines the north impoundment with the south area and
defines criteria for winds greater than 25 mph for greater than one hour from any direction during which no precipitation occurred.
The analyses of tailings impoundment surface wetness for the fourth quarter of 2024 are detailed in the following table:

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WETNESS CATEGORY (%)
Date Deep Water Shallow Water Wet Saturated Wet, Unsaturated Treated/ Crusted All Dry
2024.10.31 31% 35% 28% 6% 0% 0%
2024.11.14 December 30% N/A 28% N/A 28% N/A 13% N/A
1% N/A 0% N/A

The observed tailings pond surface dryness is below the maximum allowable
surface dryness of 5%.

Docusign Envelope ID: 747C6D6B-6139-4C14-8D0B-5B9D96FABFCB
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KENNECOTT UTAH COPPER
DAILY WIND REPORT WITH HOURLY AVERAGES
TAILINGS IMPOUNDMENT STATION
Date: October 17, 2024
Date/Time (MDT)
Center Tails Station
Wind Speed Wind Direction
mph Degrees
10/17/2024 0:00 32.44 157.3
10/17/2024 1:00 25.72 289
10/17/2024 2:00 31.99 290
10/17/2024 3:00 21.03 286.3
10/17/2024 4:00 8.50 342.3
10/17/2024 5:00 4.92 344
10/17/2024 6:00 6.26 289.3
10/17/2024 7:00 12.75 309.2
10/17/2024 8:00 9.62 54.6
10/17/2024 9:00 6.26 247.8
10/17/2024 10:00 11.63 331.2
10/17/2024 11:00 8.05 355
10/17/2024 12:00 17.90 7.7
10/17/2024 13:00 14.32 5.4
10/17/2024 14:00 10.74 9.1
10/17/2024 15:00 5.37 94.9
10/17/2024 16:00 10.51 131.1
10/17/2024 17:00 12.97 120
10/17/2024 18:00 12.53 125.8
10/17/2024 19:00 4.47 124.6
10/17/2024 20:00 30.42 299.3
10/17/2024 21:00 34.45 339.4
10/17/2024 22:00 30.87 0.9
10/17/2024 23:00 29.97 350.8
Hrs ≥ 25 mph: 7
Daily Avg: 16.40
Max Wind & Corresponding Direction: 34.45 339.4

Docusign Envelope ID: 747C6D6B-6139-4C14-8D0B-5B9D96FABFCB
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KENNECOTT UTAH COPPER
DAILY WIND REPORT WITH HOURLY AVERAGES
TAILINGS IMPOUNDMENT STATION
Date: October 23, 2024
Date/Time (MDT)
Center Tails Station
Wind Speed Wind Direction
mph Degrees
10/23/2024 0:00 4.03 131.6
10/23/2024 1:00 4.25 212.1
10/23/2024 2:00 2.68 153
10/23/2024 3:00 5.14 227.5
10/23/2024 4:00 3.58 279.7
10/23/2024 5:00 3.36 160.4
10/23/2024 6:00 1.79 245.7
10/23/2024 7:00 3.58 232.4
10/23/2024 8:00 3.58 249.3
10/23/2024 9:00 4.03 244
10/23/2024 10:00 5.14 329.9
10/23/2024 11:00 9.62 303.9
10/23/2024 12:00 9.62 306.2
10/23/2024 13:00 8.95 325.9
10/23/2024 14:00 9.62 310.7
10/23/2024 15:00 9.17 312.7
10/23/2024 16:00 17.22 290.7
10/23/2024 17:00 11.18 284.9
10/23/2024 18:00 6.93 253.6
10/23/2024 19:00 4.03 231.3
10/23/2024 20:00 4.92 172.4
10/23/2024 21:00 20.58 134.5
10/23/2024 22:00 26.17 146.8
10/23/2024 23:00 23.26 168.8
Hrs ≥ 25 mph: 3
Daily Avg: 8.44
Max Wind & Corresponding Direction: 26.17 146.8

Docusign Envelope ID: 747C6D6B-6139-4C14-8D0B-5B9D96FABFCB
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KENNECOTT UTAH COPPER
DAILY WIND REPORT WITH HOURLY AVERAGES
TAILINGS IMPOUNDMENT STATION
Date: December 14, 2024
Date/Time (MDT)
Center Tails Station
Wind Speed Wind Direction
mph Degrees
12/14/2024 0:00 23.71 150.7
12/14/2024 1:00 18.34 161.5
12/14/2024 2:00 26.62 150.5
12/14/2024 3:00 30.87 164.3
12/14/2024 4:00 31.99 157.9
12/14/2024 5:00 24.61 171.3
12/14/2024 6:00 29.53 151.4
12/14/2024 7:00 20.36 186.8
12/14/2024 8:00 4.70 181.9
12/14/2024 9:00 6.26 207.4
12/14/2024 10:00 6.04 279.3
12/14/2024 11:00 6.49 290.6
12/14/2024 12:00 25.72 124.8
12/14/2024 13:00 36.46 144
12/14/2024 14:00 33.78 145.5
12/14/2024 15:00 36.91 153
12/14/2024 16:00 32.88 142.2
12/14/2024 17:00 29.75 147.5
12/14/2024 18:00 27.51 151.5
12/14/2024 19:00 33.11 182.7
12/14/2024 20:00 46.08 223.1
12/14/2024 21:00 35.12 240.7
12/14/2024 22:00 20.13 317.7
12/14/2024 23:00 9.17 356
Hrs ≥ 25 mph: 14
Daily Avg: 24.84
Max Wind & Corresponding Direction: 46.08 223.1

Docusign Envelope ID: 747C6D6B-6139-4C14-8D0B-5B9D96FABFCB
Kennecott North TailingsSurvey Department
NORTH
AMENDMENTS NTS 2024 SOILS 0
FOURTH QTR. POLYMER 2024
STEVE HUNTER
2024 PROJECTS
Docusign Envelope ID: 747C6D6B-6139-4C14-8D0B-5B9D96FABFCB
Kennecott North TailingsSurvey Department
NORTH
AMENDMENTS NTS 2024 SOILS 0
FOURTH QTR. PINETAR 2024
STEVE HUNTER
2024 PROJECTS
Docusign Envelope ID: 747C6D6B-6139-4C14-8D0B-5B9D96FABFCB