After years of underground mining at a molybdenum deposit north of Taos, the mine owners are considering peeling back the earth and making it an open-pit mine, The Taos News reported this week.

Officials with Chevron Mining say they hope to decide soon on the future of the mine a few miles east of Questa. Molybdenum, which is used to strengthen steel, has been mined there since the 1920s, according to the environmental and social justice group Amigos Bravos. Open-pit mining was conducted from 1965 to 1983, when operations went underground. The mine’s owner, Molycorp, was purchased by Chevron Mining in 2005.

Amigos Bravos formed in 1988 to battle Molycorp over the 360 million tons of mine waste created by the previous open-pit operations. Precipitation washed heavy metals and acids out of tailings at the site, while a 10-mile pipeline carrying liquified mine waste to tailings ponds in the town of Questa ruptured more than 100 times, the group’s Web site says. The leaks and leaching have contaminated surface and groundwater in the area, including the Red River and domestic wells around Questa, Amigos Bravos contends. It sued Molycorp in 1995 over federal Clean Water Act violations. In 2000, the mine was declared a Superfund site by the U.S. Environmental Protection Agency.

Mine Manager Roy Torres told Taos County commissioners in late July that Chevron Mining was to decide in early August whether to open up a 150-million-ton deposit known as the Southwest Slice, according to the newspaper report. “We are very seriously looking at it,” Torres said.

Chevron expects the deposit to last about four years — if the company can find equipment to do the digging, Torres told the commission. Metals are commanding such high prices that mining equipment is scarce, he said. Molybdenum was selling for more than $33 an ounce in late July, compared with $3 an ounce in the mid-1980s, The Taos News reported.

Rachel Conn, policy analyst with Amigos Bravos, said that the group doesn’t know much about Chevron’s plans for the mine, but that it is concerned about issues such as stability of the ground at the mine itself and about the unexplained loss of water at the tailings pond in Questa. "We’ll definitely be watching," she said.