Fort Knox gold mine has been exceeding expectations for years. Initially thought to contain 4 million ounces of gold and a mine life of about a decade when production began in 1996, Fort Knox poured its 8 millionth ounce of gold last October and has pushed its mine plan out to 2030.
That plan comes with some big changes on the horizon, however.
The mine, located 25 miles northeast of Fairbanks in the Fish Creek valley, is owned by Toronto-based Kinross Gold Corp. This year, the mine began preparing what it calls a legacy plan, according to Anna Atchison, external affairs manager. It is a comprehensive look at what is likely to happen in the next few years as the gold runs out, taking into account personnel needs, equipment and reclamation.
“Part of that is an eventual mill closure,” Atchison said. “That mill closure will be likely without ore coming in from somewhere and we’ll only be using the heap leach because of the lower grade of the ore.”
Even now, Fort Knox’s success is possible because it does things on a huge scale. You won’t find gold nuggets lying around — most of the gold is microscopic and it takes a ton of ore to produce 0.025 ounces of gold. Some areas have even lower grades where it doesn’t make economic sense to mill the gold, which is where the heap leach comes in.
The first heap leach stack was started in 2009. Ore is stacked on liners and chemicals are leached through it, dissolving the gold, which is recovered in carbon tanks. Under the current plan, the heap leach process is expected to be used through 2030.
Fort Knox has been sending out surveys to its 650 employees to find out if they’re interested in cross-training, moving to another Kinross facility, or possibly retire.
“They can take home these surveys and use them as conversation starters with their families,” Atchison said.
The 2021 date for the mill closure isn’t set in stone. Fort Knox has been trying out different scenarios such as new milling techniques, such as running only one or two of the three ball mills at a time. “That’s been an interesting year and a half of different trials,” she said.
The Gilmore area, immediately adjacent to the current pit, contains 2.1 million gold ounces in proven and probable reserves.
The heap leach itself has been upgraded so workers have quicker access and it takes less energy to get the gold out.
“We know there are more ounces (of gold) beyond the current phase of Gilmore,” Atchison said. “If we were able to develop it, then we would be looking at opportunities to supplement the ore in that mill.”
Fort Knox is also continuing to explore its Gil prospect, which is 5 miles east of the current mine.
“Do we get to the point that everything lines up?” Atchison asked. “What happens if gold prices go back up to $1,600 and stay there?”
So while the mine is planning for its eventual shutdown and reclamation, it’s also looking at ways to put that off as long as is feasible. The heap leach is currently permitted through 2030.
Fort Knox asks its employees for ideas on how to improve processes at the mine. It has set up whiteboards around the site where employees are encouraged to write down their ideas and challenge the ways “it’s always been done,” find ways to cut costs. It’s a way of thinking that has resulted in huge efficiencies at the mine over the years, she said.
“We’re still trucking along,” Atchison said. “If you were to talk to your average employee at the mine, it’s still an excellent place to work.”
Contact staff writer Julie Stricker at 459-7532.