Far below Lead, South Dakota, air has to move exactly where engineers expect it to. At the Sanford Underground Research Facility (SURF), researchers depend on ventilation to keep fresh air moving through tunnels and shafts nearly a mile underground.
That is why Jason Connot noticed when the air began moving the wrong way.
Connot, a mining engineer who leads ventilation work at SURF, had seen the pattern during heavy rainstorms. At 5 Shaft, one of the facility’s vertical passages that normally helps exhaust air from underground, airflow sometimes dropped or appeared to reverse.
A new case study published in Mining, Metallurgy & Exploration traced the problem to heavy rainwater sent down 5 Shaft. As the water fell, it could drag air with it, disrupting the normal ventilation pattern and pushing air through parts of the underground facility in unexpected ways.
“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 in a press release.
Deciphering Why Heavy Rain Reversed Mine Ventilation Airflow
SURF no longer operates as a mine, but it still depends on mine-style systems to move air and control water. During heavy rain, the pumping system can become overwhelmed, so engineers send extra water down 5 Shaft into a deep pool, where it can be pumped out 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?”
An early clue came from airflow monitors built and deployed by Spearfish High School science teacher Steve Gabriel and his students. During a test of the shaft deluge system, the sensors captured an unusual airflow event. The timing helped connect the two things engineers had been seeing separately: water rushing down the shaft and air behaving strangely below.
“We felt that airflow increase on the 4850 Level during that test. That's what made the correlation and triggered everything,” Connot said.
Read More: Previously Unexplored Arctic Seamount Reveals Potential New Species in Deep-Sea Mining Zone
Falling Water Acted Like a Plunger
The team began to suspect that falling water was acting almost like a plunger, dragging air through the shaft and interrupting the usual ventilation pattern. Connot compared it to a syringe pushing fluid through a needle, but the team needed more than an analogy.
He searched the scientific literature and found similar effects in large municipal sewer systems. Those studies included equations for how water and air move together in enclosed spaces. Connot and collaborators from South Dakota Mines adapted that math to SURF’s conditions.
The model matched what they had seen underground.
“When we added our numbers and parameters to the model, everything came out spot on," Connot said in the release. “You would not think the weight of water droplets could move so much air.”
Reversed Airflow Could Matter During Mine Emergencies
Mines, tunnels, and other deep facilities rely on predictable airflow, especially during emergencies. Fire is one example. In some mine emergencies, engineers may send water down a shaft from the surface. If that water also changes airflow, it could affect where smoke, heat, or contaminated air travels.
“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.
SURF gave the team a unique chance to study the problem before it became a crisis. Bryce Pietzyk, SURF’s director of underground operations, said the work now helps the facility predict airflow issues and adjust ventilation controls.
For Connot, the strange readings at 5 Shaft became more than a maintenance problem. They showed that in an underground facility, even the systems built to solve one hazard can quietly create another.
Read More: Is Asteroid Mining the Next Gold Rush or Just Science Fiction? — Here's What We Know
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a case study published in Mining, Metallurgy & Exploration: Effects of Water Inflows on a Mine Ventilation System: A Case Study
