A proposed expansion of the Greens Creek Mine's tailing disposal area could keep the mine running for 25 more years. But it might need the addition of carbon to keep metals from leaching into the ground and the water, according to a draft environmental impact statement released Friday.
Operators of Greens Creek, an underground polymetallic mine on Admiralty Island that employs about 260 people, want to expand its tailings disposal area to accommodate more ore reserves. Tailings are what's left of the material removed from the mine after the metal has been extracted.
The tailings site is about 23.2 acres, and is permitted to expand to 29 acres. Operators say that will allow them to operate for two more years. The mine has proposed to expand the site to 61.3 acres, which would allow enough room for 20 to 25 years' worth of tailings if the mine continues at its current pace, said Greens Creek Environmental Manager Bill Oelklaus.
The Greens Creek, which mines silver, zinc, gold and lead, was discovered in 1975, and the mine began operating in 1989. It was closed in 1993 after metal prices dropped, and reopened in 1996. The mine is within the Admiralty Island National Monument.
The draft EIS, which was prepared by engineering firm Michael Baker Jr. on contract from the U.S. Forest Service, recommended an alternative to the mine's proposal. The alternative would expand the tailings site to the requested size but require testing to determine whether a carbon additive is necessary.
A spokesman for the Utah-based company that owns about 70 percent of the mine said he was pleased that the draft EIS, which was about two years in the making, had been released, but said he doesn't think a carbon additive is necessary.
"We don't believe that it's required. If we need to prove that carbon addition is not needed, we would like to do that through a monitoring program," said Fred Fox, spokesman for the Kennecott Minerals Co.
Carbon addition facilitates the growth of sulfate-reducing bacteria, which feed on it. The bacteria turn sulfate into sulfide, reducing acid drain and rendering the metal immobile. Mobile metal can leach into the soil and water.
Fox said carbon is added to the tailings already, but the mine is willing to test the effect of more carbon on part of the tailings in order to determine whether more carbon should be added.
"It's a matter of going the extra mile to prove what's going to work and what's not going to work," he said.
The draft EIS does call for a test, but with the assumption that more carbon will be needed.
"Monitoring results would determine the amount of supplemental carbon needed to assure that post-closure water quality meets applicable effluent limits in the ... permit without supplemental water treatment," the statement reads.
Idaho-based Hecla Mining Co. owns the rest of Greens Creek.
Officials at the Forest Service did not return messages for comment.
Environmentalists said the mine already pollutes and the tailings site should not be expanded.
"The Forest Service's failure to protect Admiralty Island from the acid mine drainage and toxic metals that are leaking out of Greens Creek's waste piles sends a terrible message to the mining industry," said Shoren Brown of the Southeast Alaska Conservation Council.
The release of the draft EIS begins a 45-day public-comment period that ends June 9. Comments may be faxed to 586-8808, or mailed to: Pete Griffin, Juneau District Ranger, 8465 Old Dairy Road, Juneau, AK 99801.
Masha Herbst can be reached at email@example.com.