Cargill Shuts Down Lake Erie Salt Mine for the Week

Cleveland Plain Dealer:

The Cargill salt mine below Lake Erie has stopped mining because of concerns that the roof 1,800 feet below ground could collapse.
That's according to Cargill spokesman Mark Klein, who said the company stopped mining salt on Monday after its first shift, sending about 100 employees home for the week with pay.
"We don't want anybody in that area in case part of the roof comes down," Klein said.
The problem is called "convergence," Klein said. "Either the floor is coming up a little or the ceiling is coming down a little."
Klein said Cargill monitors measurements of the shaft and the room at the bottom of the mine on a regular basis.
"We're looking for movements of like one one-hundredths of an inch," he said.
The mine has been operating for more than 50 years and has been owned by Cargill since 1997. The salt is extracted from the face of the mine using ammonium nitrate explosives.
The company is still operating and shipping salt, it's just not mining any new salt, Klein said. About 75 people are still working above ground at the site.
"Over the past few weeks we've seen some data points that we need to do more study on," Klein said.
Asked if the company has had previous safety concerns with the mine, Klein said, "Nothing quite like this."

Yeah, if the roof is coming down, I don't want to be there.  Here's some video footage in the mine.  Here's what happens when a salt brine operation goes bad.