PIERRE, S.D. (KELO) — The environmental manager overseeing the Homestake Open Cut at Lead has changed, somewhat, how he talks about the giant hole that remains after decades of mining.
Mark Tieszen used to say the eastside wall of the now-closed site would progress to failure.
Now he’s downgraded to could.
That is quite a change about a pit that reaches some 1,250 feet into the Earth.
“It’s been hanging on so long, I’ve changed that now,” Tieszen told the South Dakota Board of Minerals and Environment.
His presentation Wednesday didn’t trigger any alarmed questions from board members.
He’s still keeping watch on the east block and other specific areas of the mine, whose underground operations are being converted to a high-tech science laboratory.
For example, Tieszen said, the buttress installed at Bobtail Gulch nearly a decade ago has slowed rock movement.
He has some new tools to track what is — and isn’t — happening.
They began flying drones in 2017. Inclinometers installed in June showed one-tenth of an inch of movement last year.
This year they’ll be monitoring conditions via satellite, through a system equipped with historical data back to 2007, to study with what he called “millimeter precision.”
“We can look at whatever area we wanted to out there,” he said.
Aerial views of the Open Cut and the city of Lead are at https://www.123rf.com/photo_29734574_aerial-view-of-an-abandoned-open-pit-mine-and-the-town-of-lead-south-dakota.html and at https://www.blackhillsvacations.com/things-to-do/history-museums/supplier/651814-Sanford-Lab-Homestake-Visitor-Center-.