Planned blast’s massive rock slide — 20 times average — closes Boulder Canyon

Data pix.

BOULDER COUNTY, Colo. -- Colorado Highway 119 in Boulder Canyon will be closed for at least two days after a rockfall because of blasting on Wednesday, the Colorado Department of Transportation said.

The blasting was part of the highway's flood construction project. It is being done to move the road farther onto bedrock so it will survive another major flood.

Blasting typically brings down about 400 cubic yards of rock, but a blast Wednesday sent about 8,000 cubic yards of rock down the side of the mountain and onto the road.

A cubic yard is about the size of a washing machine, according to CDOT.

"You’re dealing with Mother Nature," CDOT's Jared Fiel said. "This is not an exact science."

Fiel said CDOT is now investigating what caused more rocks to fall than planned.

"There are some theories right now...that because of rain and everything, that water may have expanded and made this worse. We don’t really know yet."

Because some of the rock is too large to be moved, more blasting will be done before it's taken away.

The closure is expected to last two or three days, CDOT said.

No injuries were reported.

The canyon is very narrow where the slide happened. So, CDOT is limited in the number of people and amount of equipment it can use to clean up the rocks.

Crews are working from both the east and west side of the slide.

The Boulder Valley School District has made plans to get buses to students in the affected area, and local detours are available.

Colorado Highway 72 is the main road that can be used to bypass the area. Bus routes will also be changed based on the location of the blast.

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