Dangling from climbing ropes, rock scalers pried loose huge boulders above Colorado Highway 3 this week as part of the most extensive project ever done at the site.
The constant erosion of the sandstone and shale hillside has created a pressing safety hazard in the area of Highway 3 between the junction with U.S. 160 and Sawmill Road, said Jamie Jarrard, a rock scaler and foreman working the project.
“If you had a time lapse of this cliff over a long period of time, you would see a waterfall of rock,” he said.
Jarrard and his team of seven rock-scaling specialists, with TK Construction, are expected to remove between 500 to 1,000 tons of rock, much of it by hand suspended on climbing ropes, using pry bars, expanding grout, specialized air bags and small explosives, called boulder busters. Climbers are the only ones who can do the risky work.
Watching his team working about 300 feet above the ground, he said it seems rather insane.
“When you get this big storm of rock rushing past you and you swing out of the way, it’s exhilarating,” he said.
Once excess rock is removed along a seven-tenth of a mile stretch of road, cable netting will be hung from steel posts anchored in the rock. It will form a curtain, 1,600-foot-wide by 30-foot-long, that will catch falling rocks and protect vehicles, a Colorado Department of Transportation statement said.
CDOT began the work Aug. 21 and contracted with TK Construction to complete the project for about $1.56 million. This cost includes rock work that will be completed on Colorado Highway 145 south of Telluride.
It is the most extensive project CDOT has ever done along the old state highway, and as a result, crews will not have to do as much annual mitigation. But they will still have to clear out a culvert where rock will collect beneath the curtain regularly, said Ty Ortiz, CDOT’s geotechnical program manager.
The area was selected for mitigation because about 8,700 vehicles pass through the area every day. In addition, during the last 10 years, falling rocks have caused five accidents and resulted in injuries in two cases, a CDOT statement said.
Work has been progressing well. In the first five days, rock-mitigation crews completed half of the necessary rock removal, but progress was expected to slow as they began working with shale, said Tom Allen, project engineer from Yeh & Associates. Shale doesn’t break off in big boulders the way sandstone does, he said. For example, the team was able to bring down a 1-ton sandstone boulder. Any road damage caused by boulders will be patched.
Rain could also slow work because rock scalers are doing much of the work by hand and can’t work in adverse weather.
However, the project is moving much faster than it would have if the road had remained open. A similar project where rock had to be constantly cleared to allow for traffic recently lasted eight months, said Nancy Shanks, spokeswoman for CDOT. This one is scheduled to last for only three.
The project is also part of a statewide push to manage the more than 750 chronic rockfalls across the state in a more comprehensive way. CDOT had been managing immediate risks along small sections of rock faces, but not necessarily taking preventative steps to manage entire rock features known to pose risks. The large cable curtain planned for Highway 3 is an example of the new approach that is being rolled out this year.
CDOT now is trying to be proactive by starting preventative projects in areas with high-traffic flow, no alternative routes and previous incidents, Ortiz said.