Coeur receives preliminary OK for Kensington expansion
If the draft record of decision remains substantively the same in its final version the underground mine’s life would be extended from 2023 out to 2033.
Chicago-based Coeur Mining Inc. applied for the first amendment to its operations plan in September 2019.
Extending the life of Kensington in this case involves increasing the mine’s tailings storage capacity by 4 million tons, or nearly 50 percent, to approximately 8.5 million tons, according to the draft decision. That would be done by raising the height of the tailings treatment facility from 88 feet to 124 feet and constructing another 40-foot “back dam” between the treatment facility and Upper Slate Lake, a natural lake.
The draft approval also allows Coeur to expand the mine’s existing Pit No. 4 and Comet waste rock storage facilities as well as construct a new waste rock facility for a total storage capacity increase of 6 million tons.
The work would also require 1.75 miles of new roads, according to the Forest Service.
The development growth would also allow Coeur to increase throughput at Kensington’s mill from approximately 2,000 tons to 3,000 tons per day.
Located about 45 miles north of Juneau on the edge of Lynn Canal, Kensington employs nearly 370 people.
“The Forest Service recognizes the importance of mineral resources and encourages safe, responsible mineral exploration and development as part of our multiple-use mandate,” Tongass National Forest Supervisor Earl Stewart said in a prepared statement. “We have worked closely with Coeur Alaska to mitigate potential impacts of their proposed extension of operations for the mine. Public engagement has been and continues to be an important part of the process.”
Forest Service officials opened a 45-day objection period along with publication of the draft decision that is open only to individuals who submitted “specific, timely comments” during any of the comment periods for the project, the July 9 announcement states.
In January, the Juneau-based Southeast Alaska Conservation Council requested the agency require dry-stack tailings to limit spill risk to nearby Berners Bay, an ecologically significant area, following the release of the draft EIS.
Southeast Alaska Fishermen’s Alliance Executive Director Kathy Hansen wrote in January comments on the project that the group supports Coeur’s plan because mining is an important part of the region’s economy, along with fishing, and the company’s operations have not harmed the surrounding marine environment.
Coeur is proposing to improve Dolly Varden habitat by constructing new stream channels and small stream deltas along with replacing three culverts to facilitate fish passage.
Forest Service officials state in the draft record of decision that there is a high likelihood that the tailings treatment facility — formerly Lower Slate Lake — will be restored to long-term fish habitat after closure of the mine.
The expansion project would result in the loss of approximately 52 acres of wetlands through water inundation or fill; however, Coeur’s reclamation plan calls for a net increase in wetlands in the area once the mine is closed, according to the Forest Service.
Coeur has operated the mine since startup in 2010, when Kensington represented about 5 percent of the company’s precious metal assets. Now, Kensington is nearly 30 percent of Coeur’s precious metal assets among its five operating mines, according to the company.
This year Coeur expects to produce between 115,000 to 130,000 ounces of gold at Kensington, very much in line with the 125,000 ounces produced last year. Kensington held an estimated 331,000 ounces of reserves at the end of 2020 and another 830,000 ounces worth of mineralized material, according to Coeur’s annual report. The mine also produced 28 percent of the company’s revenue last year.
Coeur expects to spend $23 million to $30 million on capital investments at Kensington this year that will be focused on pit development and equipment replacements, according to a corporate presentation.
Elwood Brehmer can be reached at [email protected].