John Scarffe, Boulder County. The Colorado Department of Transportation (CDOT) announced on Wednesday, September 11, 2019, that Colorado Highway 119 in Boulder Canyon would be closed indefinitely following a massive rockfall during regular blasting for the project. Usually a blast brings down about 400 cubic yards each time. 

The blast on September 11 sent about 8,000 cubic yards of rock down the side of the mountain and on to the roadway. A cubic yard is about the size of a normal washing machine, according to CDOT.

Some of the rock was too large to be moved and CDOT thought additional blasts would be needed to break it up before it could be taken away. No injuries were reported since the area was clear due to regular safety protocols during blasting.

In addition to this rockfall, CDOT officials found another area of rock that was loosened in this blast that will need to be blasted out to ensure the roadway is safe for regular traffic. The blasting that was happening was not to mitigate rockfall. 

This was part of the CO 119 flood construction project. “We are blasting into the mountain to move more of the road on to bedrock so it will survive during the next major flood,” according to CDOT.

Crews worked overnight through this process to clear the road as soon as possible. On September 12, CDOT announced that Highway 119 in Boulder Canyon was opened with one lane of alternating traffic around 4 a.m. that morning after Geotech experts determined the slope was stable and additional blasting was not needed on part of the rockface.

This assessment allowed crews to move safely and clear the one lane area. Included in that clearing was the need to blast several large boulders, estimated to be the size of a bus, into smaller pieces that could be hauled away. That additional blasting took place before dark which then gave time for crews to haul away and clear the one lane, according to CDOT.

After the rockfall from blasting on Wednesday sent 8,000 cubic yards of rock to the road, it was initially determined that another area of rock would need to be blasted, which is why CDOT said the road would be closed for two to three days.

After given the all-clear by the experts, crews worked through the night to clear about 4,000 cubic yards of rock to make room for the one lane. No closures were expected for Friday or over the weekend. Regular blasting closure started at 10 a.m. Monday.

As for the upcoming schedule, on Sunday, September 22, through Saturday, September 28, Boulder Canyon will have single and full lane closures. During working hours, up to five areas will be impacted concurrently, according to CDOT.

On Monday through Thursday, September 23 to September 26, rock blasting activities resulted in a full closure of Colorado Highway 119 from MP 39-40 between the hours of 10 a.m. to 2 p.m. Motorists entering the canyon from Nederland were stopped at 9:45 a.m.

Culvert installation will impact MP 36, and rock hauling will impact MP 40. Shouldering continues between MP 34 to 38, west of Magnolia and Sugarloaf roads. Motorists will be guided around the single lane closures with traffic control flaggers.

Three traffic signal zones will remain in place near MP 32, MP 38 and near MP 39, 24 hours a day, 7 days a week, to preserve the work areas. Up to 40 minute delays are expected through the canyon during work hours. Speed limits are reduced to 25 miles per hour in the construction zones. The work is weather-dependent, and the schedule may change.

For more information and updates, go to CDOT’s CO 119 Boulder Roadway Improvements for project details.

(Originally published in the September 26, 2019, print edition of The Mountain-Ear.)