Engineers discovered that falling rainwater can unexpectedly reverse airflow deep underground, solving a mystery with important implications for mine safety.
Operating a facility deep underground means constantly managing two essential challenges: air and water.
Fresh air must circulate through tunnels and shafts to keep people safe, while groundwater from rainfall and underground aquifers has to be collected and pumped back to the surface. At large underground sites, including mines and research facilities, entire engineering teams are dedicated to maintaining both systems.
One such facility is the Sanford Underground Research Facility (SURF). Although mining operations no longer take place there, mining engineers remain critical to safely operating the vast network of underground tunnels and shafts.
Heavy Rain Triggered a Strange Airflow Mystery
Jason Connot, a mining engineer who has worked at SURF since 2019, oversees the facility’s ventilation system. Not long after joining the team, he and his colleagues began noticing an unusual pattern during major rainstorms.
“We noticed our fan would go haywire at 5 Shaft. Some areas would show reduced or even reversed airflow during large rain events,” Connot said.
Under normal conditions, fresh air enters SURF through two main shafts before exiting through two separate exhaust shafts. One of those, known as 5 Shaft, typically carries air out of the underground facility. During periods of heavy rainfall, however, the shaft also serves another purpose. Excess water is diverted down 5 Shaft into a deep underground pool before being pumped back to the surface later.
“At first, we didn’t know what was going on with the airflow in large rain events,” Connot said. “We could all see these airflow changes occurring throughout the underground, and we were like, why is this happening?”
New Sensors Helped Reveal the Cause
Finding the answer required better measurements.
Engineers rely on data, but the team lacked enough information until Maestro airflow sensors were installed on the 2000 Level to operate an automated ventilation regulator.
Earlier clues had already begun to emerge thanks to Steve Gabriel, a Spearfish High School science teacher, and his students. They designed and installed a series of airflow monitors at SURF that captured an unusual event during a test of the shaft deluge system on the 4850 Level.
“We felt that airflow increase on the 4850 Level during that test. That’s what made the correlation and triggered everything,” Connot said.
Gabriel later joined SURF as a full-time ventilation technician.
Falling Water Was Pushing the Air
During especially heavy rain, water entering the facility can exceed the capacity of the underground pumping system. To prevent flooding, engineers send the extra water down 5 Shaft into the deep pool, much like an overflow spillway protects an overfilled dam.
The team suspected that this rushing column of water behaved like a giant syringe, forcing air through the underground ventilation network.
It was a compelling idea, but they needed evidence.
Connot searched the scientific literature and found reports describing the same effect in large municipal sewer systems. Those studies included fluid dynamics equations that explained the phenomenon.
Working with colleagues from South Dakota Mines, the team adapted those equations to match SURF’s underground layout. The calculations closely matched the airflow changes they had observed.
“When we added our numbers and parameters to the model, everything came out spot on,” Connot said. “You would not think the weight of water droplets could move so much air.”
Discovery Could Improve Underground Safety
The findings extend beyond heavy rainstorms and could benefit underground facilities around the world.
“If there’s ever a fire, mining engineers will sometimes turn a valve on up top and just dump water down the shaft. Knowing this can change the air flow is critical information for everyone. We tested this, we’ve seen it occur,” Connot said.
Because SURF serves as a science and engineering research facility, the engineering team had the time and resources to investigate a problem that might have gone unexplored at an active mine.
“This is not the kind of study you’d always have time to do in an operational mine,” Connot noted.
Bryce Pietzyk, SURF’s director of underground operations, said that level of investigation made all the difference.
“One thing I really like about working with Jason is he really wants to dive into the kind of details needed to understand complex operations systems such as this. No one had previously taken the time to grasp this issue—but it’s absolutely critical, and that’s why the whole team supported this study,” Pietzyk said. “Thanks to this work, we’re able to be way ahead of airflow issues, predict what will happen, and configure ventilation controls in the right manner.”
Connot’s research paper, “Effects of Water Inflows on a Mine Ventilation System: A Case Study,” was published in Mining, Metallurgy & Exploration.
Research Earns Praise From Colleagues
Dr. Andrea Brickey, Connot’s advisor and a professor in the Department of Mining Engineering and Management at South Dakota Mines, praised both the work and the curiosity behind it.
“As an advisor, one couldn’t ask for a better graduate student than Jason,” Brickey said. “He identified a phenomenon impacting ventilation systems, and his curiosity drove him to want to determine how to predict that behavior. He succeeded, and his work is helping SURF and an entire industry.”
Pietzyk also highlighted the effort required to complete the research while balancing work and family responsibilities.
“Jason is an engineer who goes above and beyond,” Pietzyk said. “The work he did to complete this research shows he really cares about this facility. He kept it all together while doing his full-time engineering job, commuting from Rapid City, completing his Master’s Degree, and raising a family. He deserves credit for this, it’s really an amazing effort.”
Reference: “Effects of Water Inflows on a Mine Ventilation System: A Case Study” by Jason Connot, Andrea Brickey, Purushotham Tukkaraja and Srivatsan Jayaraman Sridharan, 29 May 2026, Mining, Metallurgy & Exploration.
DOI: 10.1007/s42461-026-01586-0
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