Drilling the ’Tooths: Stillwater Mining Co. calculates expansion by exploratory drilling

2014-07-14T00:00:00Z 2014-09-08T12:29:03Z Drilling the ’Tooths: Stillwater Mining Co. calculates expansion by exploratory drillingStory By BRETT FRENCH Photos By CASEY PAGE french@billingsgazette.com The Billings Gazette

DEAN — At 8,000 feet hidden among the pine trees overlooking Nye Creek, a three-man crew was busy Wednesday using a diesel-powered drill to bore deep into the 2.7-billion-year-old rock of the Beartooth Mountains.

Evan Martin, of Ruen Drilling out of Clark Fork, Idaho, said the work is “kinda nice. You get to ride in a helicopter, and you’re in your own space. There’s nobody to bug you,” except for the bugs, of course, hordes of mosquitoes and horseflies.

The work is occurring only about a mile east of the Absaroka-Beartooth Wilderness Area on the Custer National Forest in known bear habitat, as well as near whitebark pine trees, a species that has been declared warranted but precluded for protection under the Endangered Species Act.

Ruen is running two crews around the clock drilling into the Beartooth Mountains southwest of Dean to help the Stillwater Mining Co. understand what’s going on underground.

Stillwater Mining has permission for up to three drilling rigs at eight sites this year as well as a water injection test as part of its Blitz Ridge project.

“If we had X-ray vision, that would be great,” said Devin Dahlke, a geologist at Stillwater’s East Boulder Mine. “But we don’t, so we have to drill.”

The drilling, which is in its second year, is helping Stillwater Mining Co. target its planned expansion into the area, which is southeast across the Stillwater River from its headquarters.

“This will offer us sustainability and the opportunity for growth if successful,” said Brent LaMoure, director of planning and projects for Stillwater’s Montana operations.

“It’s a couple-hundred-million-dollar investment,” he added, which could pay off with another 20 years of operation.

Precious metals

Stillwater Mining Co. is the largest North American supplier of the precious metals platinum and palladium. Its Stillwater Mine is the largest hardrock underground mine in the United States, with more than 90 miles of active tunnels that are expanded each year by another 4 to 5 miles.

There is enough ore in the company’s two existing mines, at Nye and on the East Boulder River, to sustain operations for about five more years. That’s good news for rural Stillwater and Sweet Grass counties because the Stillwater Mine employs 900 workers while the East Boulder has 450, the most and highest paid employees in those areas.

Stillwater Mining Co. is tapping into a 28-mile-long, rare vein of rock known as the J-M Reef. If you think of rock laid down like layers of a cake, the J-M Reef has been tilted up and cracked and moved by faults over millions of years of mountain building. Southeast of the Stillwater River where drillers are now working, that vein of rock is even more jumbled than it is at the Stillwater and East Boulder mines.

The plan

Stillwater Mining Co.’s plan is to bore a drift, or nearly horizontal passageway, 3,000 feet underground and into the mountainside across the river from its headquarters. A large tunnel-boring machine will slowly chew the 18-foot diameter shaft as it travels about 20,000 to 25,000 feet from the existing mine.

In addition, the company is planning to drill and blast a 20-foot by 20-foot portal farther south, just above the concrete remains of an old chrome mill site that operated during World War II. The portal is almost perpendicular to the main shaft and would provide quicker access to the ore body to ensure production doesn’t lapse. Once the boring machine reaches the ore, the portal would only be used for ventilation and as an escape route, while all of the ore would be hauled out near the existing Stillwater Mine.

The portal would also help the company understand sooner what’s going on with the ore body underground.

“We need to understand early on in the project life what’s going on back here,” LaMoure said.

A draft plan outlining the company’s plans has already been reviewed by the Forest Service and Montana Department of Environmental Quality. Stillwater Mining Co. is in the process of responding to comments made by the two agencies, as well as from the public, before the document will go through a formal environmental assessment.

“When we say everything looks up to snuff, then we initiate the (National Environmental Policy Act) process,” said Dan Seifert, a geologist for the Beartooth Ranger District in Red Lodge. “The EA doesn’t start until the plan is complete.

Drill pad

The current drilling has been approved under a separate EA already completed by the Forest Service.

Drill sites like the one Martin and Dahlke were working at have a relatively small footprint, about 60 by 60 feet. All of the drilling equipment, pipe, lubricants, a bear-proof food storage cage and an outhouse were hauled in by helicopter, minimizing ground disturbance. Water is pumped uphill from a stream. Each day, the crew is helicoptered in to relieve the other to keep the drill running 24 hours a day.

“Our biggest concerns are fuel storage, compliance with the bear food storage order and that reclamation is done in a timely manner,” said Seifert, of the Beartooth Ranger District. So far, he said, Stillwater Mining Co. has been great to work with.

It used to be that to drill, a road had to be bulldozed into a site. In fact, the mountainside is already riddled with old roads from the chrome mining era. Many of those routes are now popular ATV and jeep trails for Billings-area recreationists. The main route into the area, the Benbow Road, is named after the first miner — T.C. Benbow — who sought chromite in the early 1900s.

“People talk about how pristine this area is, but it’s been mined for years,” Seifert said, evidenced by a massive I-beam headworks that is still standing. The headworks was the support for an elevator into the mine shaft.

Stillwater Mining Co. halted its exploratory drilling in the area in the mid-1990s, according to Sam Corson, chief project geologist. Like everything else, the technology of drilling operations has changed dramatically. Back in the 1970s and 1980s, a deep drill site would be 100 to 1,200 feet deep, he said. The latest holes are all more than 2,000 feet deep, with one last year ending at 3,600 feet.

Above ground

By Wednesday, and after only a few days of drilling, Martin’s crew had already bored 500 feet deep. How much farther they would go will depend on what the 10-foot long cores reveal as Dahlke and fellow geologist Sarah Jensen study, mark and measure the rock.

“I saw a lot of gabbro zone 2,” Dahlke said in geologist speak. Gabbro is a rock formed after molten magma has cooled. “We’re still a ways away from the reef and the ore zone.

“So the ultimate goal is to hit the ore zone and then we have a big party,” Dahlke joked. Last year he left just a day before the drillers hit the ore zone.

Despite last year’s disappointment, Dahlke and Jensen were reveling in the opportunity to be above ground for awhile, closely examining the boxed samples of round rock rods as they came fresh from the drill rig. Until they were assigned this job, they both worked underground to guide development of the other two mines. Bugs, heat and dirt be damned, Dahlke and Jensen were enjoying their duties.

“You’re going to have to drag me from this mountain,” Jensen said.

Copyright 2015 The Billings Gazette. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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