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Greens Creek Mine Looks For More Space

By | September 3, 2013 - 5:25 pm

The portal at Greens Creek Mine. Although the mine itself is underground, the surface footprint of the mill, camp, and roads is roughly 350 acres. (Hecla photo)

The portal at Greens Creek Mine. Although the mine itself is underground, the surface footprint of the mill, camp, and roads is roughly 350 acres. (Hecla photo)

The Greens Creek mine on Admiralty Island might have to shut down in 2016, unless it can find more room to dispose of its spent ore.

Mike Satre, the manager of government and community relations for the Hecla Mining Company, told the Sitka Chamber of Commerce last week that Greens Creek was undertaking an extensive permitting process to increase the area where it can put the spent ore, known in the industry as “tailings.”

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The best thing to do with mine tails, Satre says, is to put them back in the ground. And that’s what Greens Creek does with a little over half of the rock it extracts. It’s mixed with cement and used to fill shafts and leads, and provide solid support for the miners working other parts of the ore body.

But that leaves the rest on the surface. A large pile of material in a National Monument in the middle of the continent’s largest rainforest – material that can’t get wet. Satre described the pains Greens Creek takes to store tails.

“So what we do is de-water those tails. We truck them down to the Auke Inlet area. We have an engineered facility where we’ve cleared and grubbed everything off. We put down geotextile lining. We’ve isolated water from coming into that area, and we’ve placed those tails in a very engineered fashion, protect them from oxygen infiltration, and ultimately plan for closure.”

Water and oxygen plus mine tailings produces an acid, Satre says. Greens Creek collects runoff from the tailings area and sends it to its own water treatment plant. The trucks that deliver tailings are rinsed in a giant car wash.

“We’ve gone through one EIS (Environmental Impact Statement), one expansion that allowed us to come out this way to the east, and a little bit higher than originally planned and permitted. No we need even more room, so we want to come further to the south. We’ve gone through an EIS process that has multiple alternatives. There is a no action alternative – just like anything in a NEPA (National Environmental Policy Act) process. If we don’t expand our tails facility, probably the mine will be forced to shut down and go into reclamation and closure. We simply won’t have the place to put our tails.”

Satre made the case before the Sitka chamber that closure was not an attractive alternative. Greens Creek is on Admiralty Island, about 18 miles south of Juneau, and is one of the leading silver mines in the world, producing 2,200 tons a day of a fine sand concentrate containing silver, zinc, gold, or lead. The mine employs 390 people directly, and has a payroll of $54-million.

The Greens Creek ore deposit was discovered in 1975, three years before most of Admiralty Island became a National Monument. The federal legislation allowed for the development of a mine, in the event the deposit “proved up.”

The mine was closed for six years in the 1990s, because of low mineral prices. Hecla was part owner with Kennicott in those days. In 2008, Hecla bought out its partner for $750-million.

These numbers had the attention of the Sitka Chamber audience. In June, the assembly postponed consideration of spending $72,000 on a geotechnical survey along Green Lake Road.

Satre is also a professional geologist. He explained that although Greens Creek was on the next island, geologically it was a world apart. He said that the ore deposit was formed hundreds of millions of years ago, as black, sulfide-rich gases billowed from an ancient sea bed.

“Luckily, at the same time those sulfides were being ejected from these vents, some muddy, carbonate-rich sediments were being deposited on top, and they preserved that ore body over the years. And that formed many thousands of miles away from us, and – just like the rest of Southeast Alaska – through plate tectonics, was slammed up against the North American Craton, and that’s where it’s at today.”

Ironically, mining was one of Sitka’s largest industries following the Russian transfer in the 19th Century, with 40-percent of residents involved in the search for gold,according to a research paper by Matt Hunter, who currently holds a seat on Sitka’s assembly. None of the dozens of mines or claims in the area ever repaid the investment.

Nevertheless, Sitka Economic Development Director Garry White, who attended the presentation, asked Satre where he thought mineral prices were headed. Satre responded, as he has likely many times before: “If I knew that, I wouldn’t have to work in a mine.”

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