GOLCONDA — Barrick Gold Corp. embarked on a more than $300 million shaft construction project at the Turquoise Ridge Mine to increase efficiency and production.
“This shaft is part of the foundation for TR’s future success,” said Joe Dase, Barrick Turquoise Ridge superintendent of projects management.
Development of Shaft No. 3 is the only known shaft project underway in the U.S., project leaders said, and it marks Barrick’s biggest capital investment in development in Nevada.
“It’s the largest capital spend on the books right now in terms of development projects,” Dase said. “Times have been tight for every mining outfit, so capital has been tight. It’s the right time to spend the money and move it toward completion.”
The project also coincides with the operator’s recent declaration of its 75 percent-owned Turquoise Ridge underground gold mine outside of Golconda as core producer. Newmont Mining Corp. owns the remaining quarter, and the companies recently renewed a contract to processes Turquoise Ridge ore at the Twin Creeks facility for another seven years.
“It’s part of the piece of the puzzle that’s driving Barrick to recognize the site as a core mine because without it,” Dase said, “you wouldn’t have the future production increases.”
Need and progress
From an overlook with a view of the shaft site, Dase described the need for additional mine access and pointed out progress. The company broke ground in August 2017 and contracted Thyssen Mining to sink the shaft.
“Our mining horizon has marched this way over the years,” Dase said, gesturing away from two existing shafts.
The third shaft will reach a depth of about 3,400 feet to where underground operations are advancing, cutting haul road distance and opening up potential.
“It puts us below almost all of our known and existing resources, so it puts us in a good position vertically to convey materials,” Dase said.
Earlier that day, Turquoise Ridge Operations Superintendent John McCurry put the value of the shaft in perspective from underground.
“Our mining front is getting so far away from these shafts,” he said. “We just keep finding more gold.”
Once Shaft No. 3 is completed in about 2022, trucks transporting ore will trade a 45-minute roundtrip drive for a five-to-10-minute trip, said Rory Howell, chief engineer of the Turquoise Ridge expansion project.
Today, only 20-ton haul trucks can fit in the southern zone, so Barrick plans to open up the drifts to allow 30-ton trucks, McCurry said.
Another benefit of the third shaft is that it allows for increased ventilation volume by about 35 percent. Increased ventilation means reduced heat exposure and reduced exposure to diesel particulate matter. Shaft No. 1, at the opposite end of the mine, will be used for ventilation only. At 1,830 feet deep, Shaft No. 2 will become a secondary escape.
As of early March, Layne — a water management, construction and drilling company — had just begun drilling two dewatering wells on the prepared grounds of an old copper pit operation on mine property. Removing water from sediment will continue through May and help ensure that shaft-sinking goes smoothly, as drills for the shaft can move through dry ground.
Sinking the shaft is expected to begin in about a year, with Canada-based Thyssen the winning bidder for the project after a rigorous review process. Thyssen’s other projects include the original Turquoise Ridge shaft and work for Newmont, said Ryan J. McHale, Thyssen chief operating officer.
“The big thing for us is partnership on this project,” Dase said, giving a nod to additional companies involved, including Newmont, Ames Construction and NewFields.
The new shaft requires building another substation; forming a new ore stockpile area; constructing separate roads for light and heavy equipment; and installing additional underground utilities. Three brand-new hoists are being designed by Hepburn Engineering Inc.
“Joe and I are excited,” Howell said. “We’ve never seen a brand-new hoist. All we’ve seen are used ones somewhere else.”
Thyssen expects to have a team of about 20 people, and Barrick plans to add a few more employees after shaft completion, as production increases over time.
As efficiency increases after Shaft No. 3 is finished, operations costs are expected to decrease. At first, mine life also decreases by four years after project completion. The life of mine is expected to reach 2035, said Turquoise Ridge Mine General Manager Henri Gonin.
Barrick’s share of production in 2017 totaled more than 210,000 ounces of gold with about 2,300 tons of ore extracted per day using an underhand cut-and-fill method. Turquoise Ridge has 5.9 million ounces of proven and probable gold, and the average grade is 0.55 ounces per ton, according to a Barrick statement designating Turquoise Ridge a core mine.
With the completion of Shaft No. 3 and processing ability at Twin Creeks, production is slated at 850,000 ore tons in 2018 and 2019, going up to 1.2 million tons a year between 2020-2024, according to Barrick’s 2017 year-end results.
Gonin said that Barrick is not yet at the limit of the ore body, which is still open in several directions, and that any additional tons would serve to further validate the decision to build the shaft.
“The mine has done a very good job of increasing their productivity to help justify the shaft,” Howell said. “So it’s a combination of the shaft making sense to start with, and then improvements on the other end increase the value of it even more.”