DAQ-2025-000600

Rio Tinto Kennecott Utah Copper, LLC. 4700 Daybreak Parkway, South Jordan, Utah 84009.
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Rio Tinto Kennecott
4700 Daybreak Parkway
South Jordan, Utah 84009

January 24th, 2025

Mr. Bryce Bird, Director
Utah Department of Environmental Quality
Division of Air Quality
P.O. Box 44820
Salt Lake City, UT 84114-4820
Attention: Mr. Connor Kijowski
Subject: Copperton Concentrator
Approval Order DAQE-AN105710049-24
Molybdenum Plant Wet Scrubbers Semi-Annual Report

Dear Mr. Bird:

In accordance with Condition II.B.1.d of Approval Order DAQE-AN105710049-24,
dated September 23, 2024 and 40 CFR 60.385(c), Kennecott Utah Copper (KUC) is
required, at least weekly, to monitor and record measurements of scrubber pressure loss
or gain and liquid flow rates differing by more than thirty percent (30%) from the
average obtained during the most recent performance tests. The most recent
performance tests for DC-04 and DC-190 were conducted in June and November 2002,
respectively.

A review of the records for the second half of 2024 (July through December) was
completed in January 2025. Records for the following wet scrubbers (permitted
emission sources) at the Copperton Concentrator were reviewed:

MP106 Product Molybdenum Dryer Venturi Scrubber (DC-04)
MP107 Product Molybdenum Dryer Venturi Scrubber (DC-190)

The monitored and recorded pressure and flow rate readings for the operating venturi
scrubbers (DC-04 and DC-190) were within acceptable ranges. No deviations occurred
during the second half of 2024 (July through December).

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Should you have any questions or need further information regarding this letter, please
contact me or Sean Daly at 801-204-2563.

Sincerely,

Brendan Murphy
General Manager – Minerals

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