Experts: Rockfalls in Glenwood Canyon all but impossible to prevent
The Denver Post
Geologists and engineers said Monday that preventing rocks from falling in Glenwood Canyon is all but impossible.
“That location is a bad spot with huge cliffs that go up thousands of feet,” said Ralph Trapani, the former project manager for designing and building the divided highway through Glenwood Canyon, which took from 1980 to 1992. “It’s literally impossible to control all those cliffs.
“Some rockfalls just can’t be prevented. If you do the math on rocks the size of cars falling 1,000 vertical feet, the energies are impossible to stop.”
Jerry Higgins, a geology professor at the Colorado School of Mines who surveyed the state’s highways for the most probable rockfall locations for the Colorado Department of Transportation, said the season for rockfalls has just begun, when daytime temperatures warm up enough to melt the snow. Water runs into cracks in the rocks,then freezes at night. A steady rain fell Sunday night in the canyon.
“When water freezes, it expands and widens the cracks. It’s called ice jacking. Eventually the rocks move enough to where they tumble down.”
To lessen the impact, engineers have long employed rockfall mitigation techniques in Glenwood Canyon, including fences, barriers, netting, rock bolting and covering rocks with concrete.
“We did extensive scaling; we rolled a lot of rocks off these slopes,” Trapani said. “But some of these cliffs are humanly impossible to scale.”
He said the rock face on Interstate 70 on the incline above Georgetown is a good example of scaling and netting done by CDOT. Much of that type of work in Glenwood Canyon can’t be seen from the roadway.