Homestake Mining plans a new conveyor system in downtown Lead, an official for state government’s minerals and mining program said Thursday.
The purpose? So the company can move 875,000 tons of rock, from the Sanford underground research facility, over to the company’s former mining site called the Open Cut.
Mike Cepak told the South Dakota Board of Minerals and Environment the rock would come from “nearly a mile deep” -- 4,850 feet -- in the Sanford lab.
He said Homestake intends to hoist the rock over to the Ross shaft inside the former underground mine, crush the rock to less than four inches in size, and then pipe it down the hill.
The rock would cross over Main Street, aka U.S. Highway 385, and spill into the Open Cut next to the basketball courts.
The new conveyor system would retrace part of the path of the old aerial tramway that, while now gone, had carried ore for decades o’er the streets of Lead.
The tramway ran from the Yates shaft at Homestake’s main underground mine to the company’s crusher at Terraville.
Homestake, in deciding there wasn’t much of a future left at Lead after more than a century of intensive mining, donated its massive underground operations to the South Dakota Science and Technology Authority about 15 years ago.
In turn, philanthropist T. Denny Sanford gave millions of dollars to the authority so the mine could be converted to a laboratory for research. His name consequently was attached to the lab.
One of those research projects is why the 875,000 tons of rock will become available.
Lab officials intend that enough space will be dug out for three large chambers that are part of the Sanford laboratory’s long-range search for neutrinos.
Fermilab, located near Chicago, Illinois, plans to fire an underground beam at the Sanford lab in Lead.
Two of the chambers will hold two tanks apiece of liquid argon. They are known as cryostats. “These would be the particle detectors,” Cepak told the minerals board.
A 2015 agreement between the authority and Homestake called for up to five million tons of rock to be put in the Open Cut.
Cepak said the rocks are mica schists and slate from the Poorman Foundation. It won’t affect the chemistry, he said.
The 875,000 tons will cover 8.3 acres in the Open Cut, according to Cepak. That’s less than 1 percent of the space in the giant hole left by the removal of 100 million, to 200 million, tons of rock.
The technical revisions to the permits received approval March 22, 2017, by the state Department of Environment and Natural Resources.
“A lot of people who grew up in town probably remember that conveyor,” Cepak said about the old system.
As for the rock, he said it’s not perfect. “Quartz would be better. But it will serve the purpose.”