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The company is also projecting that the incident – which was previously expected to reduce 2025 output by 33,000 tonnes – will cut around 25,000 tonnes of production in 2026, Máximo Pacheco told Fastmarkets.
Speaking in an interview in London, Pacheco said the operational disruption, which started in July, will also dent the Chilean miner’s earnings before interest, tax, depreciation and amortization (EBITDA) by around $500 million.
“At this stage, the priority for us is to make sure that we are working on restarting our operation in a very safe way,” he added.
The expanded estimate highlights the deepening operational consequences of the rock burst, which killed six miners earlier this year – the first such fatalities at El Teniente in 35 years.
The mine is one of the world’s largest underground copper operations and a key contributor to global refined supply. The expanded production losses at El Teniente add further pressure to a copper market already facing supply shortfalls from disruptions in Indonesia, Panama and the Democratic Republic of Congo as well as lower forecast output at operations including elsewhere in Chile.
The combined effect of these disruptions has pushed the copper market from a projected surplus into a structural deficit next year, analysts say. On Wednesday October 8, the International Copper Study Group (ICSG) revised its estimate for the 2026 refined copper market from a surplus of 209,000 tonnes to a deficit of 150,000 tonnes.
Codelco has launched a comprehensive internal and external investigation, with independent experts in geomechanics, geophysics and geoscience contributing to the review. Pacheco said the company’s focus remains on safety and understanding the root causes of the event before potentially making long-term adjustments to its mining plan.
“We believe that we need a couple more months, two to three months, to finalize all of the research we are doing and all of the studies that we are preparing,” he noted.
Despite the tragedy, Pacheco stressed that the company has met all its supply commitments so far.
“Production in the year to September 30 is 2% higher versus 2024,” he said. “So even though we have had a very dramatic accident with multiple impacts, the first of them being the fatalities of six miners, we have been able to run our business in a way that had no impact to our customers,” Pacheco noted.
“Obviously, without this accident, our production increase would have been much higher than 2%. We need to be very careful and very responsible in the way we develop our underground operations and that’s what we’re doing,” he added.
The El Teniente incident, Pacheco said, has become a stark reminder of how complex and fragile underground mining operations can be.
“In the latest report prepared by EY on the risks of our industry, the number one risk is operational continuity,” he said, adding that in 2024, the main risk was geopolitics. “We know that we are in a difficult, complex business,” he noted.
The event also underscores the growing geotechnical challenges miners face while they pursue copper deposits at ever greater depths.
“It’s clear for everybody what the challenges of underground mining are,” Pacheco said. “The deeper we go into the earth’s crust to extract the critical minerals that drive the economy, the greater the geotechnical challenges we face. And among these, one strikes us with particular force, which is the rock bursts,” he added.
A rock burst, he explained, is “the abrupt and instantaneous rupture of rock mass in tunnels, releasing energy in the form of seismic waves and projecting fragments.” While it is an inherent risk of deep mining, it “can be managed, anticipated and mitigated with knowledge, technology and operational discipline,” he noted.
Preliminary findings from an external investigation have pointed to structural changes deep within the deposit.
“The most probable cause of the rock burst, as precisely stated in the external preliminary investigation, is a process of vertical unloading due to geometric changes and cavity interaction in the northwest of the deposit,” Pacheco said.
“In simpler terms, this means that the deposit’s shape has changed, affecting how the material is supported,” he told Fastmarkets.
El Teniente, located about 80km south of Santiago, comprises more than 4,500 km of tunnels, multiple mining districts and an open-pit section.
While Codelco continues to invest in expanding and modernizing its underground operations, Pacheco said that over time, “cavities, or empty spaces, have formed and are now connecting, weakening the structure and facilitating downward movement of material.”
“This means that at depth, rock layers are shifting over one another,” he added.
Despite decades of experience managing such risks, Codelco is using the incident as a moment for re-evaluation.
“We’ve learned a lot and in this specific case, there are significant additional learnings that will allow us to improve all of the ways we manage rock bursts and the way we develop the mines,” Pacheco said.
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