– It’s been a strange and scary few months for folks living near the Jefferson Quarry, a limestone and sand mining operation alongside the Minnesota River.

It started in April with an earsplitting explosion that shook dozens of homes. That was followed seconds later by what the company argued was the first earthquake in Mankato’s history, a massive tremor that originated near the quarry site.

Finally, last week, another quarry blast sent a barrage of rocks screaming through the Germania Park neighborhood on a quiet summer morning. Chunks of limestone bigger than bowling balls ripped limbs from trees and punched a hole in the wall of a house hundreds of feet from the explosion site.

Within hours, the city — for the second time — suspended the blasting permit of the quarry owner, Jordan Sands, while it investigates what happened. Meanwhile, neighborhood residents — many of whom have lived next to the quarry for years — are growing uneasy and wondering what’s next.

“I’m nervous,” said David Kreiselmeier, whose home was pierced by a rock that left a large, jagged hole just below his children’s bedroom window and next to their bikes. “Who’s to know whether you’ll come walking out the door one day and get blasted, or have a rock come through the window?”

An official of Jordan Sands said Monday that the company, whose primary produce is so-called frac sand for use in oil and gas extraction, is concerned about last week’s incident and that it is determined to find out what went wrong.

“I think we’d all like to get to the bottom of what transpired,” Scott Sustacek, the company’s chief executive officer, said. “Safety has always been our top priority. We’re conducting our own investigation and cooperating with the city’s investigation of this incident.

“Last week was not a great week for us.”

Tossing the evidence

Blasting has been a regular occurrence for years at the quarry, which is the last remaining quarry in the city of Mankato. In fact, many residents of the surrounding area said they’re accustomed to the explosions.

“The normal blasting — a good thunderstorm will shake the house as much,” said Ken Mead, 74, who has lived his entire life across the road from the quarry.

But last Tuesday was different.

Tim Slipy, who does handyman work in the area, said he was painting a building about 10:30 a.m. when he heard the three horn blasts that signal a coming explosion.

“Usually, they wait a minute and then blast,” he said. “This time, the blast went off 5 seconds after the last horn. That’s very unusual. That never happens.”

A hail of rock followed, with fragments ranging from the size of golf balls to bowling balls and larger. Within minutes of the blast, quarry workers in safety vests raced to the Germania Park neighborhood in a truck and started tossing rocks back into the strip of woods that separates the quarry from nearby houses. Slipy and Mike Sprenger, another resident, both said they saw workers chucking rocks into the woods.

“They were getting rid of the evidence,” Sprenger said.

But there were too many rocks to get rid of. Slipy said he collected a bunch of rocks the size of tennis balls and cantaloupes. Police soon arrived and hauled away a load of larger rocks, including one that took two men to lift it, Sprenger said.

Quarry could close

The neighborhood was shaken back in April after the quarry set off a charge of explosives weighing more than 4,500 pounds. The company later said the blast coincided with an earthquake measuring 2.8 on the Richter scale — which hit 7 seconds after the detonation, according to a consultant’s report commissioned by the company. If a quake indeed hit, it would be the first on record in Mankato, according to Barr Engineering Co., the consultant.

Scientists at the U.S. Geological Survey, however, have said they are virtually certain there was no earthquake.

For now, Jefferson Quarry is still shipping rock and sand, but its blasting permit remains suspended pending the results of the investigation into last week’s explosion.

The quarry has considered shutting down at the end of this year, according to city and company officials, although it’s not certain that that will happen. If the quarry does close, it would put an end to the city’s rich history of limestone mining, which goes back to the 1880s. The company, however, also could seek to renew its permit to operate in 2018.

If the quarry does shut down, its more than 50 acres could be redeveloped — perhaps as a park, perhaps for housing and commercial use, Sustacek said.

“It’s one of the last undeveloped pieces in Mankato on the river,” he said. “There are a lot of opportunities for that property.”

For some of the quarry’s neighbors, that can’t come soon enough.

“We want the quarry shut down,” Sprenger said.

Added Slipy: “They can’t be that hard up for rock that they would risk this.”