Deep-level tunnel infrastructure at an El Teniente-style underground copper operation.
By Charles Pitts
Codelco has temporarily suspended development and construction work at the Andes Norte project inside El Teniente after identifying a possible new form of deep seismicity, adding another layer of uncertainty to Chile’s effort to restore production at the world’s largest underground copper mine.
The preventive decision, announced on August 4, follows six months of technical analysis and comes one year after a rock burst and collapse killed six workers in the mine. Codelco said the seismic behavior detected at the greater depths of Andes Norte appears different from the risks historically understood and managed at El Teniente.
The immediate effect is not a shutdown of the entire mine. Existing productive areas remain in operation. The larger concern is whether the suspension delays the expansion needed to sustain El Teniente’s production profile as older sections mature.
For operators, investors and copper consumers, the issue now extends beyond a project timetable. It combines worker safety, deep-mine engineering, Codelco’s declining output and the supply implications of delaying a major Chilean copper development.
What Codelco has suspended
The suspension applies to development and construction activities at Andes Norte, part of El Teniente’s broader New Mine Level program. Codelco has not announced a fixed date for resuming the work.
In its official statement, the company said technical information gathered during the previous six months was consistent with a possible emerging risk associated with the project’s greater depth.
Codelco said the company will use the suspension to:
- Expand seismic and geotechnical monitoring.
- Improve its understanding of deep seismic behavior.
- Reinforce instrumentation and technical analysis.
- Design and implement additional control measures.
- Coordinate an orderly process with contractors and their workers.
The company also said seismic monitoring systems and preventive protocols remain active across El Teniente, including productive areas.
That distinction is important. Andes Norte is a future production and mine-life project, while existing levels continue to supply ore. The suspension therefore creates limited immediate production disruption but raises a more significant medium-term question: how quickly can Codelco safely develop replacement capacity at depth?
Seismic monitoring and geotechnical control are central to the next phase of Andes Norte’s development.
Why the July collapse still matters
The Andes Norte decision follows the July 31, 2025 collapse in the Andesita and Teniente 7 areas of El Teniente. A rock burst triggered a seismic event estimated at magnitude 4.2 and killed six workers, making it Chile’s deadliest mining accident in decades.
The incident halted activity in affected areas and led to rescue operations, regulatory reviews and further scrutiny of ground-control conditions across the mine. Chilean authorities later allowed unaffected areas to reopen under enhanced monitoring and safety requirements, as reported by Reuters.
The criminal, regulatory and technical investigations into the accident remain underway. Their conclusions could influence how Codelco, regulators and contractors assess the relationship between the 2025 collapse and the newly identified deep-seismic phenomenon.
Codelco has not said the Andes Norte suspension is a direct finding of fault from the earlier accident. Instead, the company has described the current measure as precautionary and based on a different, potentially emerging risk at greater depth.
That leaves several questions unresolved:
- Whether the seismic behavior is localized to Andes Norte or represents a broader condition at depth.
- Whether new engineering controls can adequately reduce the risk.
- Whether the project design, sequencing or mine plan will need to change.
- Whether the suspension will last months or extend into a multi-year delay.
Timeline of the El Teniente disruption
| Period | Development | Operational significance |
|---|---|---|
| July 31, 2025 | Rock burst and collapse in the Andesita/Teniente 7 area kills six workers | Production and access are disrupted while rescue and investigations begin |
| August 2025 | Unaffected areas receive approval to reopen under enhanced controls | Current operations progressively resume outside the accident zone |
| 2025–2026 | Codelco and technical teams collect and analyze seismic data | Greater attention is placed on ground behavior at depth |
| August 4, 2026 | Codelco suspends Andes Norte development and construction | Future capacity is delayed while the company investigates new seismic risk |
| Beyond 2026 | Resumption timing remains uncertain | Project schedule, capital deployment and production replacement plans remain exposed |
The proximity of Andes Norte to the Andesita and Teniente 7 sections makes the new suspension particularly consequential, even though Codelco has not characterized the two events as identical.
The production question
El Teniente extends across more than 4,500 kilometers of tunnels and has historically been a critical contributor to Codelco’s copper output. Current annual production is around 300,000 tonnes, below pre-incident levels.
The mine’s challenge is not simply to maintain today’s output. It must also replace production from mature areas and develop deeper levels under increasingly complex rock conditions.
Codelco has warned that it is unlikely to meet its former 1.7 million-tonne annual group production target as it prioritizes profitability and operational discipline. Current group guidance is approximately 1.33 million to 1.36 million tonnes for 2026, according to market reporting summarized by Mining.com.
The Andes Norte suspension does not, by itself, change near-term group guidance because the affected work concerns future development rather than all current production. However, a prolonged pause could reduce the company’s ability to sustain output beyond the immediate planning period.
That matters in a copper market already facing long development timelines, declining grades at mature mines and rising demand from grids, electrification and data-center construction. Skillings’ copper outlook coverage provides broader context on the market’s exposure to project delays and supply constraints.
Ground support systems illustrate the engineering demands of deeper underground development.
Base, bull and bear scenarios
The main variable is not whether Andes Norte is important. It is how long the suspension lasts and what technical changes are required before work can resume.
| Scenario | Key assumptions | Likely implications |
|---|---|---|
| Bull case | Monitoring identifies a manageable, localized risk; additional controls are designed quickly; construction resumes after a limited pause | Andes Norte experiences a schedule delay but retains most of its production value and capital plan |
| Base case | Work remains suspended for an extended period while Codelco expands monitoring, redesigns controls and reassesses sequencing | Future production is deferred, contractor activity is reduced and El Teniente’s sustaining-capacity risk increases |
| Bear case | The seismic phenomenon proves broader or more difficult to control; suspension approaches the two-year duration suggested by union representatives | Major schedule slippage, higher development costs, lower medium-term production and further pressure on Codelco’s group output |
The bull case would require more than a favorable technical report. Codelco would also need regulatory confidence, contractor readiness and evidence that workers can operate under a revised risk-management system.
The base case is more operationally plausible. Deep underground projects often require extended monitoring because seismic behavior can change as excavation advances and stresses redistribute through the rock mass. A pause that initially appears temporary can therefore become a redesign and rescheduling exercise.
The bear case would affect more than Codelco. It could remove or delay a meaningful source of future Chilean copper supply at a time when new projects are difficult to permit, finance and build.
What decision-makers should monitor
The next signals will come from technical and regulatory processes rather than from production reports alone.
First, watch for a defined resumption framework. Codelco has not provided a formal end date. A credible restart plan should explain what measurements, thresholds and controls must be achieved before construction restarts.
Second, monitor the scope of the risk. If new seismic activity remains concentrated around the deepest Andes Norte works, the response may be manageable. If similar behavior appears elsewhere in El Teniente, the implications would be broader.
Third, track contractor and workforce impacts. The suspension includes companies involved in construction and development. A prolonged pause could affect specialist crews, equipment mobilization and the continuity of underground engineering expertise.
Fourth, separate current output from future capacity. El Teniente can continue producing while its expansion is paused, but that does not remove the mine-life risk. Investors and customers should distinguish quarterly production stability from the longer-term replacement of mature production areas.
Finally, follow the investigations into the 2025 fatal accident. Criminal, regulatory and technical findings may shape future standards for deep mining, worker access, ground support and seismic response across Chile’s underground sector.
Outlook
Codelco’s decision is a clear safety-first response to incomplete technical information. It also exposes the strategic difficulty of operating one of the world’s largest underground mines as activity moves deeper into more complex rock.
For now, the suspension is a development setback rather than a full operational shutdown. Existing production continues, but at levels below El Teniente’s pre-incident performance. The long-term risk is that a project designed to sustain the mine becomes delayed precisely when Codelco has fewer options for replacing lost capacity elsewhere.
The next phase will depend on whether the company can convert seismic data into controls that regulators, workers and contractors consider credible. Until then, Andes Norte remains a critical copper project with an uncertain timeline: and a reminder that the energy transition’s supply chain depends not only on metal prices, but also on the safety and geology of the mines producing them.
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Codelco has suspended Andes Norte development at El Teniente after identifying a possible new deep-seismic risk. The pause follows the 2025 rock burst that killed six workers and raises fresh questions about Chile’s future copper supply, mine safety and Codelco’s ability to restore output. Read the full base/bull/bear analysis.