DWQ-2025-002362

April 1, 2025

Cassady Kristensen
Rio Tinto Kennecott
Environment Business Partner
4700 Daybreak Parkway
South Jordan, Utah 84009
[e-mail]

Subject: Approval to Use - South East Waste Rock Dump Optimization Project

Dear Ms. Kristensen:

The Division of Water Quality (“Division”) issued a Construction Permit for the South East Waste Rock Dump Optimization Project (SEWOP) on March 28, 2024. The Division performed a final
inspection on March 4, 2025. On February 14, 2025, the Division received the As-Built Drawing Set entitled SEW Optimization Toe Drain Extension prepared by Sunrise Engineering.

Based on the final inspection and the review of the As-Built Drawing Set, DWQ approves the use of the SEWOP.

If you have any questions about this letter please contact me at [phone] or [e-mail].

Sincerely,

Woodrow W. Campbell, P.E.
Environmental Engineer
Ground Water Section

WWC/DLB/

cc: Via Email

Erdenebayar Naran, Rio Tinto ([e-mail])
 Jay Quintanilla, Rio Tinto ([e-mail])
Nathan Christensen, Sunrise Engineering ([e-mail])
Mazie Cox, DERR
Wayne Western, DOGM

DWQ-2025-002362