Rio Tinto announced plans to invest in its Kennecott operation near Salt Lake City, Utah, to strengthen its supply of copper in the United States by increasing production from underground mining and improving the health of key assets.

The company approved $498 million for the underground development and supporting infrastructure for the North Rim Skarn (NRS) area. Production from the NRS area will commence in 2024 and is expected to ramp up over two years, to deliver around 250,000 metric tons (mt) of additional mined copper over the next 10 years alongside open-cut operations.

In September 2022, Rio Tinto approved development capital totaling $55 million to start underground mining in the Lower Commercial Skarn (LCS) area. Underground production within the LCS area started in February 2023, and is expected to deliver a total of around 30,000 mt of additional mined copper through 2027.

The company said these two investments will support Kennecott in building a world-class underground mine that will leverage battery electric vehicle (BEV) technology, following a successful trial in 2022.

A $300 million rebuild is also underway at the Kennecott smelter. The rebuild is the largest in Kennecott’s history and commenced in May 2023. A further $120 million is being invested to upgrade the refinery tank house structure and update Kennecott’s molybdenum flotation circuit with a state-of-the-art, fully automated system. As the second largest copper producer in the U.S., Rio Tinto said the investment will allow Kennecott to continue to deliver a high-quality product to customers.

“We are investing to build a world-class underground mine at Kennecott and strengthen our processing facilities, to meet the growing demand for copper in the United States, a key material for domestic manufacturing and the energy transition,” Rio Tinto Copper COO Clayton Walker said. “This investment will position Kennecott to continue the strong contribution it has made as part of the Salt Lake Valley community for 120 years, injecting about $1.5 billion annually to the local Utah economy.”

Studies to inform decisions on the next phases of expanding underground production continue in parallel with work that is being advanced to extend open-pit mining at Kennecott beyond 2032.

The NRS has updated Indicated Mineral Resources of 10.8 million mt at 2.93% copper, 1.20 g/mt gold, 65.97 g/mt silver, 0.008 % molybdenum, and Inferred Mineral Resources of 7.7 million mt at 3.13% copper, 0.96 g/mt gold, 18.41 g/mt silver, and 0.005 % molybdenum identified based on additional drilling and an initial Probable Ore Reserve of 3 million mt at 2.39% copper, 1.77 g/mt gold, 18.59 g/mt silver, and 0.010 % molybdenum.