Environmental groups are urging the U.S. Forest Service and the state Department of Environmental Quality to rethink the permitting for the controversial Rock Creek mine in light of a 30-foot-wide, 50-foot-deep sinkhole that appeared in May at a mine that one forest supervisor has called “an excellent analogy for the proposed Rock Creek mining method and risks of subsidence.”
According to Cesar Hernandez, of the Cabinet Resource group, the Troy Mine sinkhole, or “subsidence” in geology speak, is a prime example of why the Rock Creek mine beneath the Cabinet Mountains Wilderness is a bad idea.
“[T]he subsidence happened in a fault zone. There are three fault zones that come together in the Cabinet Mountain Wilderness. They’ll find similar fault lines in Rock Creek Mines,” says Hernandez.
According to Butte-based engineer Jim Kuipers, a subsidence that causes a minor surface impact could have major impacts on surface hydrology, possibly including the draining of pristine mountain lakes.
“Scientific literature supports that in every case where you have underground mining you are going to have some subsidence,” says Kuipers.
“The one way to prevent it is to not mine it. A subsidence is certainly going to happen, it’s just a matter of when and where.”
Revette Minerals Inc., the mining company behind the controversial plan for the Rock Creek copper and silver mine, owns the Troy Mine. The Washington-based mining company has pointed to the Troy Mine as a model for the Rock Creek Mine in the past, and Kootenai National Forest supervisor Robert Castaneda has recently stated that in 20 years, the Troy Mine has not had a subsidence event.
In a letter to Castaneda dated June 20, Clark Fork Coalition staff attorney Matt Clifford urges the department to revisit the Rock Creek permits.
“Whatever our past difference over the risk of subsidence at Rock Creek, we hope you will agree with us that when the mine your experts consider an ‘excellent analogy’ for Rock Creek begins experiencing subsidence, it is time to reassess the conclusion that subsidence will likely not be a problem at Rock Creek.”