Running a facility deep beneath Earth’s surface requires constant control of two essential elements: air and water.
Workers in underground tunnels and shafts depend on reliable ventilation to survive and work safely. At the same time, groundwater and rainwater that seep underground must be collected and pumped back to the surface.
That challenge is familiar at large mining operations, where specialized teams manage ventilation and water systems. It is also a critical part of operating the Sanford Underground Research Facility (SURF), a massive underground science laboratory in South Dakota. Although mining no longer takes place there, mining engineers remain responsible for maintaining the extensive network of tunnels and shafts safely.
Heavy Rain Triggered Unexpected Airflow Changes
Since joining SURF in 2019, mining engineer Jason Connot has overseen the facility’s ventilation system. During periods of intense rainfall, he and his colleagues began noticing something unusual. Airflow patterns underground sometimes weakened or even reversed direction.
“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 the facility through two primary shafts and exits through two separate shafts. One of those exhaust routes is 5 Shaft. During heavy rain, however, excess water is directed down 5 Shaft into a deep underground pool where it can later be pumped out.
“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?”
Sensors Reveal a Clue
Finding the answer required data.
The breakthrough came after Maestro airflow sensors were installed on the 2000 Level as part of an automated ventilation control system. Those measurements gave engineers a much clearer picture of how air was moving through the facility.
Earlier evidence had already hinted at a connection. During a test of the shaft deluge system, airflow sensors on the 4850 Level recorded an unexpected increase in air movement.
Those sensors had been built and installed by Steve Gabriel, a Spearfish High School science teacher, and his students. Gabriel later joined SURF as a full-time ventilation technician.
“We felt that airflow increase on the 4850 Level during that test. That’s what made the correlation and triggered everything,” Connot said.
The Surprising Effect of Falling Water
During major storms, incoming water can exceed the capacity of the underground pumping system. To handle the extra volume, engineers send surplus water down 5 Shaft into the deep pool below, much like an overflow spillway helps relieve pressure at a full reservoir.
The team suspected that the falling water itself might be affecting airflow.
Their theory was that the descending column of water acted somewhat like a syringe, pushing air through the shaft as it fell.
The idea was intriguing, but it needed scientific confirmation.
Connot searched the scientific literature and found reports describing a similar phenomenon in large municipal sewer systems. Those studies included fluid dynamics equations that explained how moving water could influence air movement in confined spaces.
Working with colleagues at South Dakota Mines, Connot adapted those equations to match the conditions at SURF. The results closely matched what engineers had observed underground.
“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.”
Implications for Mine Ventilation and Safety
The findings extend beyond heavy rainstorms and could have implications for underground operations 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 functions as a research facility, engineers had the opportunity to investigate the phenomenon in detail.
“This is not the kind of study you’d always have time to do in an operational mine,” Connot noted.
Bryce Pietzyk, director of underground operations at SURF, said the effort reflects Connot’s commitment to understanding the facility’s complex systems.
“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.”
Research Published in Mining Journal
Connot’s paper, Effects of Water Inflows on a Mine Ventilation System: A Case Study, was published in Mining, Metallurgy & Exploration.
Dr. Andrea Brickey, Connot’s advisor and a professor in the Department of Mining Engineering and Management at South Dakota Mines, praised both the research and the persistence 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 professional and personal 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.”