A “very, very large” boulder fell onto U.S. Highway 550 near Coal Bank Pass on Monday afternoon, and though no one was injured, the Colorado Department of Transportation says it is a good reminder to stay alert while driving mountain passes during the winter.

“It could have caused a lot of damage,” said CDOT spokeswoman Lisa Schwantes. “We need to be prepared driving through the Rocky Mountains at all times, but particularly during seasons of moisture.”

Around 1 p.m. Monday, a boulder fell into the southbound lane of Highway 550 around mile marker 57, just north of the top of Coal Bank Pass.

Schwantes said CDOT crews initially thought the road was going to be closed for an extended period of time.

“We didn’t know if we needed to blast it into smaller pieces,” she said. “We thought we were going to have major delays.”

Singer-songwriter Dave Mensch captured a video of the boulder after it fell on the highway. Mensch said he has seen a lot of potentially dangerous situations driving U.S. Highway 550 between Durango and Silverton over the years, but never a boulder covering an entire lane on the road.

As it turned out, a front loader was able to push the boulder and smaller debris pieces off the east side of the highway. By about 2 p.m., the road was open in both directions.

“We’re very happy it didn’t turn out to be too much (of a closure),” Schwantes said.

Schwantes said the boulder likely came loose as snow started to melt Monday morning, causing rocks to loosen and fall. Had someone been driving that stretch of road at the time the boulder came down, it could have been a bad situation, she said.

“We need to be prepared for anything we might encounter (driving in the mountains), which includes falling rocks,” she said.

jromeo@durangoherald.com