August 14, 2017
Jordan Sands, a Coughlan Companies-owned quarry in Mankato, Minn., had its blasting permit at Jefferson Quarry suspended following a 10:35 a.m. blast on August 8, 2017, that sent bowling ball-sized rocks flying into a nearby neighborhood, the Mankato Free Press reports. One rock reportedly knocked a hole in the siding of a home, another sheared off large tree branches, and a witness described the sound of dozens of rocks flying through treetops and bouncing off of roofs.
No one was injured, but the potential for harm was obvious, Jeff Bengtson, deputy director of the Public Safety Department, told the news agency. “Anything that could pose a safety hazard, I think, warrants suspension of the permit to ensure a thorough investigation… A 12-inch rock would be hazardous to people’s welfare.”
Jefferson Quarry is the same quarry that had its blasting permit suspended for 60 days following a blast on April 25 that was immediately followed by an earthquake-like tremor strong enough to rattle buildings. The city allowed blasting to resume after an investigation found no negligence by the quarry.
Tim Slipy, a Mankato resident who lives next door to the home that was struck by one of the large flying rocks, told the news agency that the blasts are frequent enough that he gave little thought to the quarry’s warning horn on August 8. “The horn blew. They do three blows before a blast, and about a minute later it goes off,” Slipy said. “This one, they did three blasts and, about five seconds later, there was a blast.” Then he noticed the sound of the rocks flying through the air.
According to the news agency, Jordan Sands Vice President Brett Skilbred said there was little he could say Tuesday night until more is learned about the cause of the flying debris. “We’re very concerned about the event today,” Skilbred said. “Safety continues to be our No. 1 priority. … We’ll continue to investigate this and bring forth more information as it becomes available.”
The blast was witnessed by a Department of Public Safety employee, as is the procedure for all explosions at the quarry. “Our community service officer was on site, as usual, to observe the blast, and she notified us that some rocks had left the quarry,” Bengtson told the news agency, adding that he had no idea why the explosion caused stones to fly into the neighborhood. “We’re still working on the cause right now.”
The quarry’s blasting permit will be suspended indefinitely while the investigation continues.