A roughly 25-foot diameter boulder crashed onto Highway 133 just before noon Saturday, closing the road in both directions for about three hours.
No one was injured when the massive rock crashed onto the highway at Nettle Creek, said Levi Borst, a sergeant with the Pitkin County Sheriff’s Office.
A geohazard team from the Colorado Department of Transportation assessed a second boulder on the hillside above the rockfall.
The first people on the scene, which is about 10 miles south of Carbondale, said they saw that rock shifting when they arrived, Borst said.
But CDOT engineers deemed it stable enough to reopen one lane around 2:30 p.m.
By late afternoon, rock scalers were drilling holes into the boulder to house explosives, said the agency’s regional communications manager, Tracy Trulove.
The debris will be cleared into the southbound ditch, and trucks are expected Monday to haul enough of it away to reopen the lane.
Temporary traffic lights will be installed for the lane closure, Trulove said. She said several people that encountered the slide were walking through the debris field before Borst arrived, which is dangerous.
“We don’t know if those slides are done yet, so it’s not a good idea to walk through debris fields,” Trulove said.