Federal Government Approves Central Idaho Mine Expansion on Public Land

Published September 22, 2016

A 500-acre expansion, mostly on public land in central Idaho for one of the largest molybdenum mines in the world was approved by federal land managers in August.

The separate decisions by both the U.S. Bureau of Land Management (BLM) and U.S. Forest Service, will allow expanded mining at Thompson Creek Mine, about 20 miles southwest of Challis, to continue for another 10 years. The agencies’ environmental reviews found no significant or permanent air or water damage would be caused by allowing the mine expansion.

Jim Kopp, site manager for Thompson Creek Mining Co., told the Associated Press (AP), “It’s been a long time coming.”

He noted work at the mine stopped in December 2014 as the company waited for approval of its 2008 request. “We’re happy that there’s a decision.”

Mine is Largest Employer in County

The mine has produced about 452 million pounds of molybdenum and the expansion will allow the mining of 93 million more pounds. The mine currently in a care and maintenance mode with about 50 workers and expansion won’t immediately begin because of low molybdenum prices.

At full production, the mine is rural Custer County’s largest employer with about 400 workers.

More than 90 percent of the mining operations are on private land, including the entirety of the open pit, which is about a mile long, nearly three-quarters of a mile wide and 2,000 feet deep. Mine owners needed federal approval to use additional public land for the expansion.

Deposits Will Be Richer

The mine, the fourth largest mine producing primarily molybdenum, began operations in 1981, but the discovery of more molybdenum deposits led mine owners to seek an expansion. The federal government’s decisions mean the open pit will be made slightly wider as more material is removed from the sides starting at the top and working down.

Ken Gardner, a geologist with the BLM, the project lead for the Thompson Creek Mine federal review, told the AP, “They found more ore they didn’t know about back then so they want to enlarge the pit.”

Molybdenum has a variety of uses, with over 85 percent produced being used in metallurgy and the rest in chemical applications. The alloy is used to make steel, cast iron, and other metals. It can withstand extreme temperatures without significantly expanding or softening, making it useful for military armor, aircraft parts, electrical contacts, industrial motors, and filaments.

Kenneth Artz ([email protected]) writes from Dallas, Texas.