GREEN BAY, Wis. (WBAY) -- Sun Prairie's explosion may be rare according to statistics, but we're learning just how common gas leaks really are. Gas leaks can have many causes: like aging pipes, or contractor work, as we saw Tuesday.
So what does it take for excavators to dig safely without hitting a pipe?
Diggers Hotline is the well-advertised agency that wants you to call "811" before digging so they can investigate first.
"If you call that, they should come out, mark the utilities under the ground," explained Daniel Parsley, an NWTC Natural Gas Instructor. "Once they see the utilities, they should be hand digging to expose those utilities within the tolerance zone. Once they've exposed it, then they should be safely digging by it, but not too close to the pipe itself."
But pipeline accidents continue to happen. Last year, nearly 300 "significant" pipeline incidents were reported to the Pipeline and Hazardous Materials Safety Administration (PHMSA). Thirty-three people were injured, and eight people died across the U.S.
Gray-TV affiliate WBAY visited NWTC's outdoor classroom on Wednesday where right now, about 60 students are studying gas utility. They're learning how to safely excavate and move around pipelines. But the experts agree: sometimes, hitting one of these pipelines is unavoidable.
"I think everybody in the industry has hit one of these lines," said Mike Schoenwalder, NWTC Gas Utility Instructor. "We try to avoid it as much as possible, but there's a lot of stuff under the ground and eventually it's going to happen."
Schoenwalder said the explosion was a big moment for his students in the classroom the next day.
"Students: they don't really know the dangers of it yet, and that's what we try and teach them: that this stuff actually can happen and to avoid it as much as possible," said Schoenwalder. "You know, do as many of the safe practices that we teach them as possible, but a lot of it is just unavoidable."
The unsettling takeaway: a gas explosion could happen anywhere.