Digging into Kensington Gold Mine

At the Kensington Gold Mine, the work never stops. Miners are underground blasting, digging and hauling 24 hours a day. The end result is a gold concentrate that gets shipped around the world to refineries, which further process it into various products.

The concentrate itself looks basically like a very fine dirt, but with little flecks of gold shinning in it. To get that concentrate, thousands of tons of rock from inside the mine have to be crushed down and filtered through vats of water.

The mine has been running for 10 years now about 45 miles north of Juneau on a peninsula next to Berners Bay, and owners Coeur Alaska want to keep it going for at least another 10. The company has recently submitted a request to amend their Plan of Operations Amendment 1 (POA1) which would extend the life of the mine until 2033.

In order to do that the company would have to expand its existing infrastructure for waste water and rock, which has the potential for significant environmental impact, according to the National Forest Service.

The Forest Service has begun the process to draft a supplemental environmental impact statement (EIS) as required under the National Environmental Protection Act (NEPA).

Environmental impacts from mining have been a source of controversy over the years, especially given past environmental disasters in the region. In 2014, a dam collapsed at the Mount Polley mine in British Columbia, Canada sent over six billion gallons of waste water into lakes and rivers.

Before the Kensington Mine could even begin operations a decade ago, it was sued by a local environmental group in a case that went all the way to the Supreme Court.

The company maintains that it follows the strictest environmental standards and is committed to protecting the environment.

Kensington recently gave the Empire and other media a tour of the mine facilities to show how the mine works in practice and to demonstrate their commitment to environmental regulation.

Getting there

The tour started at 5 a.m. when miners go through security and get on buses at Engineers Cutoff in the Mendenhall Valley. Many of the miners live at the facility while they’re working, spending two weeks on and two weeks off. Others live in Juneau and make the daily commute. According to Coeur Alaska, about 45 people make the trip each day.

Buses then drive out the road to a dock at Yankee Cove where miners board a boat which takes them up to the mine about 45 miles north of Juneau next to Berners Bay.

The mine facility has dormitories, dining hall, rec room and gym for employees’ use. Since miners are working round the clock, those are open all the time to accommodate miners on various shifts.

There are only three entrances to the mine, and before entering everyone must have safety equipment including helmet with headlamp, steel-toed boots, reflective vest and emergency respirator that filters out smoke and other dangerous chemicals. The mine also has respirators, which can provide an hour’s worth of oxygen, placed strategically throughout the mine.

Outside the mine’s entrance is a checkpoint where everyone must “brass-in” or place a brass on a board which tells staff who’s in the mine and which section they’re in. Miners also sign in and out in a binder recording time and date.

Inside the mine

Inside the mine are long stretches of unlit roadway, pipes and wires bringing electricity, water and air run along the roof of the mine.

There are a number of facilities within the mine, such as processing plants and a workshop for maintenance on all the equipment used in the mine.

The mine has 28 miles of road underground over several levels. Roads spiral up or down to reach the various levels where mining occurs. Emergency hatches are installed to provide escape routes for miners in the event of an emergency.

Rock is extracted from the mine using a combination of drilling and blasting. It’s then hauled out of the mine in massive Caterpillar trucks which take the rock either to be processed, or to a rock dump if it has no economic value.

After being crushed, the ore containing gold is fed into the mill, which further crushes the rock down and feeds it through a series of vats.

The gold is put through a process making it “hydrophobic,” meaning it pushes away from water.

Gold concentrate floats to the top of those vats and then is further processed before being collected in massive bags which get shipped out.

Coeur is always looking for new ore veins, and there is a laboratory on site where rock can be tested for gold content. The laboratory is also used to test the quality of the gold concentrate before it gets shipped out.

Waste water and tailings

The process of extracting the concentrate from the rock requires a lot of water, and in turn produces a lot of waste water.

After being used in processing, water is then sent to a Tailings Treatment Facility (TTF) and water treatment plant. It’s the TTF that has been the biggest source of controversy in the past.

In 2005, after Coeur had obtained permits from the U.S. Army Corps of Engineers, the Southeast Alaska Conservation Council (SEACC), the Sierra Club, and Lynn Canal Conservation Inc. sued the company saying the permits violated provisions of the Clean Water Act.

That case was decided in the U.S. Supreme Court in 2009, which ruled in favor of Coeur. In 2013, Coeur paid for an independent audit of the Kensington Mine which found that, “Kensington is generally in compliance with operations and reporting for all authorizations with only a few exceptions.”

Environmentalist are concerned about “tailings,” which according to the Environmental Protection Agency are the “coarsely and finely ground waste portions of mined material.” Tailings are generally stored permanently in the storage lakes.

Coeur continually treats the water that goes into its TTF at a water treatment plant nearby. Once Coeur leaves the site, it will connect the TTF with the nearby Upper Slate Lake, but that will occur only once the water in the treatment facility meets state water quality standards.

“We would continue to treat until we reach those (water quality) levels,” Kensington General Manager Mark Kiessling said, “and if we weren’t able to reach those levels we continue to treat and treat and treat.”

Coeur wants to raise the height of the dam on the treatment facility by 36 feet to allow for another four million tons of tailings, according to the company’s documents.

Staff members at SEACC have voiced concern over Coeur’s plans, but have not yet made an official statement.

Acid rock drainage

One of the issues reported in the 2013 audit was the presence of “acid rock drainage,” or ARD. ARD is when acidic water forms when certain kinds of rock interact with surface water, according to the EPA. The audit reported that Coeur had been attempting to treat the issue using a concrete covering.

“The effectiveness of dental concrete in preventing ARD warrants further consideration and should be furthered addressed,” the audit said.

Earlier this year the EPA settled with Coeur over violations found at Kensington, including discharge of acid rock drainage.

In an opinion piece written for the Empire, Kiessling said those violations were “several years old and don’t reflect the current operating status of the mine.” Kiessling said the company submits monthly and annual reports to state and federal agencies, and that the mine is inspected routinely by those agencies.

Coeur Alaska is owned by Chicago-based Coeur Mining Inc. which has mines and projects throughout North America.

The Forest Service is currently accepting public comment on Coeur’s amendment plan. Comments will be accepted until Nov. 7, and can be made by phone, fax, post or online at the Forest Service website.

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• Contact reporter Peter Segall at 523-2228 or psegall@juneauempire.com.

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