Greens Creek Mining Co. can expand its tailings disposal area to accommodate two more decades of mining, as long as mine operators also add carbon to the tailings to prevent metals from leaching into the ground, according to a record of decision issued by the U.S. Forest Service.
The Forest Service decision, announced Monday, alters the mine's original proposal, which did not include carbon addition.
Operators of Greens Creek, an underground polymetallic mine on Admiralty Island that employs about 260 people, proposed to expand the 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 covers 23.2 acres and is permitted to expand to 29 acres. Operators say that space will last two more years. The mine proposed to expand the site to 61.3 acres, allowing enough room for 22 years' worth of tailings if the mine continues at its current pace.
The Greens Creek mine, which mines silver, zinc, gold and lead, was discovered in 1975. It began operating in 1989. It closed in 1993 after metal prices dropped, and reopened in 1996. The mine is within the Admiralty Island National Monument.
The alternative approved by the Forest Service allows the 61.3-acre expansion, but shifts it to the east in order to minimize the impact on monument land. The approved alternative also requires a 30-month study to determine how much carbon should be added, what form of carbon would be most effective, and how to incorporate the carbon into the tailings, the Forest Service said.
"It addresses the long-range acid rock drainage and heavy metals leaching by providing for a continuous carbon addition to the tailings. We expect that that will improve the long-term water quality associated with the tailings pile," said Juneau District Ranger Pete Griffin.
Greens Creek General Manager Rich Heig said staff at the mine are pleased the decision has been issued.
"We'll be taking some time over the next few days to review the record of decision and develop our plan of operation around it," Heig said.
Kat Hall of the Southeast Alaska Conservation Council said the Forest Service is ignoring concerns about the mine's impacts on water quality and wildlife.
"They have failed to ensure the long-term protection of Admiralty Island and are ignoring the release of toxic wastes into surface waters," Hall said.
The record of decision will be published Nov. 14, which marks the start of a 45-day appeal period. Appeals must be submitted to the regional forester by Dec. 29.
They may be mailed to: Regional Forester, Alaska Region; USDA Forest Service; P.O. Box 21628; Juneau, AK 99802-1628.
Masha Herbst can be reached at email@example.com.