As much as 30 kt (33,000 st) of copper could be produced from expanded underground operations at Rio Tinto’s Kennecott operations near Salt Lake City, UT. On Sept. 27, Rio Tinto announced that it has approved a $55 million investment to begin underground mining and expand production at the mine.

The expansion is expected to add to overall copper production from 2023 to 2027 with the first ore to be produced in 2023 the company said in an announcement.

Underground mining will initially focus on an area known as the Lower Commercial Skarn (LCS), which will deliver a total of around 30 kt (33,000 st) of additional high quality mined copper through the period to 2027 alongside open cut operations. Full production is expected in the second half of the year. It will be processed through the existing facilities at Kennecott, one of only two operating copper smelters in the United States.
Kennecott holds the potential for significant and attractive underground development. The LCS is the first step toward this, with a mineral resource of 7.5 Mt (8.3 million st) at 1.9 percent copper, 0.84 g/t gold, 11.26 g/t silver, and 0.015 percent molybdenum identified based on drilling and a probable ore Reserve of 1.7 Mt (1.9 million st) at 1.9 percent copper, 0.71 g/t gold, 10.07 g/t silver, and 0.044 percent molybdenum.

Rio Tinto also announced that will begin trails with underground battery electric vehicles as part of the expansion. The battery electric vehicles will improve employee health and safety, increase productivity and reduce carbon emissions from future underground mining fleets. A battery electric haul truck and loader supplied by Sandvik Mining and Rock Solutions are being used to evaluate performance and suitability as part of underground development work.

“This investment will allow us to quickly bring additional volumes of high quality copper to the market and build our knowledge and capabilities as we evaluate larger scale underground mining at Kennecott,” Rio Tinto Copper chief executive Bold Baatar said. “We are progressing a range of options for a significant resource that is yet to be developed at Kennecott, which could extend our supply of copper and other critical materials needed for electric vehicles and renewable power technologies.

“Trialling underground battery electric vehicles is an exciting step in our work to create a safer workplace for our employees, increase the productivity of the mine and reduce emissions from our operations. We look forward to seeing their potential for deployment.”

Existing underground infrastructure is currently being extended to enable early access to the next underground resource and undertake characterization studies. A Feasibility Study to inform decisions on the next phase of underground production is expected to be completed in 2023. This will be one of several potential stages currently being investigated.

Feasibility studies are also being progressed to extend openpit mining at Kennecott beyond 2032.