Investigation continues at [Sudbury’s] Creighton Mine [seismic event] – by Carol Mulligan (Sudbury Star – November 28, 2011)

The Sudbury Star is the City of Greater Sudbury’s daily newspaper.

Vale officials are expected to continue assessing the damage to Creighton Mine this week after a 3.2-magnitude seismic event that occurred about noon Friday. No employees were injured and were all immediately accounted for in refuge stations shortly after the event, said Vale spokeswoman Angie Robson.

Before releasing personnel from those refuge stations, affected areas were cleared for seismicity, according to Vale’s emergency protocol, Robson said Saturday. Employees who were working at the 7,200-level or lower did not return to surface until about 11:30 p.m. Friday.

Activity is being restricted below the 7,200-foot level and activity at the mine’s 6,800- foot level and above is continuing as usual, said Robson. Creighton has been mined for 100 years or more, said retired health and safety activist Homer Seguin.

The former Inco, and now Vale, backfill areas when they are mined out, but that loose material can settle and contract leading to ground shifts that are essentially “minor earthquakes,” said Seguin, a former president of United Steelworkers Local 6500, which represents production and maintenance workers at Vale.

“Often (seismic events) take place in the areas that are no longer being mined and they’re less serious, but when they’re in the areas close to or at mining areas, they can cause serious collapses,” said Seguin.

There are “potentially serious consequences” to such ground shifts and Seguin speculated it could take some time and effort to “rehabilitate” the area of the mine affected by Friday’s seismic activity.

As with earthquakes above ground, there is always the danger of aftershocks after an underground seismic event, he said.

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