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Experts say shifting wall in Open Cut is slowing down

May 22, 2019

LEAD — Experts monitoring a horizontal crack in the eastern wall of the Open Cut in Lead can breath a little easier now that new data has been collected showing the rate at which the rock is shifting to be slowing.

“It has definitely slowed down in movement,” said Jeff Burich, closing manager with Barrick Gold Corporation, which owns the property.

Since 2009, erosion and shifting rock of the Open Cut has been closely monitored and experts have been focused on a particular crack in the eastern wall.

Mark Tieszen, an environmental manager with Homestake, said it is still likely that the 350-400 foot section of the wall will collapse; however, it would have no effect on residents or property owners around the pit.

“There’s no danger associated with it,” Tieszen said. “We expected this to fail some time ago. Probably with the right hydrological conditions, a big storm or something like that, (it) could go. … It’s just taking a lot longer than we originally anticipated.”

“It would just rubbelize that wall,” Burich said. (It would all be) within the pit boundary.”

Tieszen said the likely cause for the shift is the rock settling into place after the 126 years of disruption caused during the Homestake mining days.

“Anytime you have an open cut, or open pit, or any kind of a hole like that, there’s going to be some relaxation of the rock,” he said.

Recently Homestake has been using satellite based monitoring which has given them a better look into the shifting rock. The new data showed that the rate at which the rock is shifting has slowed down.

“If it gets to a situation where it’s going to fail, we will know that,” he said. “So when and if it does happen it’s not a big surprise.”

Burich also said that when excavation begins for the Long Baseline Neutrino Facility at the Sanford Underground research Facility, the estimated 875,000 tons of rock removed and deposited into the Open Cut could also help to reinforce the walls of the pit. “So that will also help with the stability of the wall,” he said.

Excavation work is anticipated to begin in November 2020.

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