Kennecott slide registered magnitude 2.4 on seismograph

Published: Friday, April 12 2013 10:30 p.m. MDT

Motorists drive into Copperton Township Friday, April 12, 2013, with a view of Kennecott Utah Copper's Bingham Canyon Mine.

Jeffrey D. Allred, Deseret News

BINGHAM CANYON — Kennecott Utah Copper representatives said it is too early to know what caused a massive landslide to cripple its Bingham Canyon Mine and they don't know when workers will be back on the job.

The Mine Safety and Health Administration issued an order suspending work at the open-pit copper mine in southwestern Salt Lake County and dispatched personnel to the site, according to MSHA spokeswoman Amy Louviere.

Kennecott is waiting for clearance from MSHA to send its geotechnical experts into the pit to assess the scale of the slide and the damage it caused, said Kyle Bennett, spokesman for Rio Tinto's Kenecott Utah Copper.

"We have not cut corners. Nobody was hurt, so we don't want to start doing that now. We need to make sure the area is safe. We need to make sure the area is stable and then we're going to take our employees in," he said.

Bennett said the company doesn't know what caused the slide, which, after months of monitoring, turned out to be much larger than Kennecott anticipated. The University of Utah seismograph station recorded the slide as a magnitude 2.4 shake.

"There are a lot of factors that go into ground movement in a mining operation," he said, listing composition of the material, rain, thawing, runoff water and mine work itself. "It's kind of a combination of factors that make something like this happen."

The landslide occurred Wednesday night in the northeast section of the mine. No workers were injured, but roads, buildings and vehicles inside the pit were damaged.

Kennecott was aware of the impending slide and apprised employees of the situation as it developed, Bennett said. Company engineers detected movement in the ground as far back as February.

The U. seismograph station provides some insight into the enormity of the slide. It recorded two events in the mine at 9:30 p.m. and 11:05 p.m., with the first registering magnitude 2.4, said seismologist Katherine Whidden.

"It was a very big landslide," she said, adding the speed with which it came down likely caused it to registered on the seismograph.

Whidden said the slide also probably triggered several smaller events afterward that appear to be earthquakes. There was no seismic activity in the area preceding the slide, she said.

Ted Himebaugh, Kennecott's general manager of operation readiness, estimated about two-thirds of the bottom of the pit was buried.

Kennecott does not yet have a timeline for cleanup or resuming mining operations, Bennett said. It employs about 2,500 people, including 800 miners, he said.

Asked if the company has discussed the possibility of furloughs or layoffs, Bennett said, "We're not able to give mine employees access right now, but everybody at all our other plants are working right now just as they would every other day."

Wayne Holland, United Steelworkers International staff representative, said the unions met with workers at the mine met Friday to develop a plan moving forward. They have had some talks with Kennecott and MSHA and intend to meet more in the coming days.

"One of our questions will be if they expect any more movement. Obviously, right now the company is sending all the miners home as they report for work," he said.

"We're as concerned now about the process of repair and getting the mine back operable as we were when the slide happened because those little slides can be just as dangerous."

The company doesn't know if the slide disabled the mine's monitoring equipment, Bennett said.

Holland said he doubts Kennecott will have a plan for digging out and where to send crews until the middle of next week.

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