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13 February 2026
Above: The new Guadalupe shaft exhaust fans at the Candelaria mine
Industry Partner Spotlight
This story was provided by Pan American Silver, a CIM Industry Partner, and appears in the February 2026 issue of CIM Magazine (view it in flip format here).
New life for Candelaria
A new shaft and ventilation system has many benefits for Pan American Silver’s La Colorada mining operation
In October 2019, Vancouver-based Pan American Silver’s La Colorada mining operation in Zacatecas, Mexico, found itself between weak rock and a hard place when the central exhaust raise at the Candelaria mine—one of the site’s three underground mines and its deepest, most geotechnically challenging deposit—collapsed. With restricted ventilation, mining activity at Candelaria’s East Zone was reduced.
The raise’s collapse, caused by an overlying layer of dacitic rock, was not the first major challenge at Candelaria. The first occurred in 2013, when the mine was attempting to bore a 540-metre-long raise to extend the ventilation circuit as the mining advanced. It collapsed before reaming could be completed. A year later, an attempt to replace the collapsed raise also failed. In 2017, an attempt to bore a 561-metre raise was completed but failed while being shotcreted. In 2020, the application of the best available engineering and technology, including multi-year pre-grouting and robotic shotcreting, did not result in successful raises through the dacite layer.
While 2021 mitigation efforts did boost airflow by more than 50 per cent, miners still faced restricted access to the Candalaria East Zone for their safety. That year, Pan American decided it had had enough. The company switched gears from trying to fix problems to reinventing the operation’s entire ventilation system for a holistic long-term solution. It was a bold plan that would cost approximately US$60 million, but it would also restore full production and secure the mine’s long-term future.
Getting to the Root Cause
The major shift in approach was the result of the company accepting that attempting to raise bore through the weak dacitic rock was unreliable and had a low probability of success even with extensive pre-consolidation using grouting. The inability to construct exhaust raises on a timely basis to meet the mine’s ventilation needs simply led to a vicious circle. “At the end of the day, the inability to maintain raises or to replace those that collapsed caused the ventilation system to degrade, as increasingly hot and humid air was forced through the remaining raises and resulted in instability and ultimately failures,” said Martin Wafforn, senior vice-president of technical services and process optimization at Pan American.
In August 2021, Pan American approved a US8 million investment in mid-2023 to install twin 2,000-horsepower surface fans that were connected to exhaust air through the Guadalupe shaft once it was completed. In June 2022, the company also invested in a refrigeration plant.
Completed in 2024, the results of the new Guadalupe shaft and ventilation system were almost immediate and nothing short of transformative. The ventilation flow rate at the mine increased by 37 per cent, reaching more than 1.2 million cubic feet per minute with additional fan capacity available for further mine expansion. The increase in air flow significantly reduced the temperature and humidity in the critical East Zone of the mine, allowing increased development and production from that area. The project also reconfigured several existing raises at the mine that were exhausting hot, humid air into lower-risk air intake raises.
Big Wins
“One of the biggest wins of the new ventilation system has been the improvement in conditions in the mine for workers,” said Wafforn. “They are working in safer and more comfortable and productive conditions now, even in the deepest, hottest areas of Candelaria.”
The improvement in ventilation resulted in increased production with throughput returning to approximately 2,000 tonnes per day and a decrease in cash costs per ounce. Another win was in energy cost savings. The large Guadalupe shaft allows air to move with less friction and turbulence, which means that the fans require less power to push or pull the same volume of air.
“The project proved that despite the higher cost to construct, you can do a lot of things with a conventionally sunk shaft that maybe you can’t do with raise boring,” said Wafforn. “What we have now is a very efficient system; the ventilation shaft is an absolutely fantastic installation that is generating value and provides enhanced understanding of how to adapt future ventilation infrastructure according to the ground conditions encountered as the vein mine continues to develop.”
While the project was a steep learning curve for Pan American, its lessons will continue to benefit the company for many years to come, especially when it comes to its plans to develop the even deeper Skarn deposit at La Colorada, which extends to at least 1,600 metres below surface. “The project has given us the capacity, confidence and know-how to tackle the next chapter in the life of the mine,” said Wafforn.
