A cluster of boulders perched 300 feet above Colorado's main east-west highway will shut down the main route to many of the state's major ski resorts as officials plan to remove the unstable rocks.
Around 40 boulders, some as big as pickup trucks, pose a danger to the traffic below on Interstate 70, state transportation officials said. It is the most heavily traveled rock-fall area in the state.
Stacey Stegman, a Colorado Department of Transportation spokeswoman, said crews on Tuesday will use a device similar to a shotgun shell with high pressure to fracture the rocks and roll them down the slope.
If there's no room for the fragments on the road's shoulder, crews will haul away the pieces, she said.
Stegman said the pile over Georgetown Hill, about 45 miles west of Denver, had been monitored for about a month. Weathering and natural erosion have destabilized the slope.
"These rocks that looked fine years ago are not fine any longer," Stegman said.
Rocks contract in the winter but expand as the temperatures rise in the spring, Stegman said. Ice and moisture from snowmelt can freeze and fracture them further. The instability makes nearby highways susceptible to rock falls.
"We need to get to it now because it has the potential to come down now," Stegman said.
Five homes were asked to evacuate, officials said. Stegman said the homes are far away but officials took precautions due to the uncertainty of the work.
To pose a danger to homes, the boulders would have to roll down the slope over the highway, jump I-70 and trundle down another hill to Georgetown. Netting and fences were set up in potential paths to catch rocks.
The annual average daily traffic through the area is about 30,000 vehicles, Stegman said. Officials said a 25-mile stretch of I-70 between Silverthorne and Georgetown will be closed from 9 a.m. to 5 p.m. Tuesday, but could stretch into Wednesday.
The closure comes as many of Colorado's ski resorts make a last big push of the ski season. It has prompted many to offer incentives to keep up attendance.
The Loveland Ski Area planned to have a free pancake breakfast Tuesday morning for skiers willing to beat the lane closures, spokesman John Seller said.
"Of course we'd prefer if it didn't happen during ski season, but CDOT's been great in getting information out, and hopefully they'll have it wrapped up on Tuesday," Sellers said.
Officials at Vail Resorts said they were offering special lodging packages, and Keystone Ski Resort will stay open later Tuesday and Wednesday. Officials at Steamboat Springs said they're not worried because the resort is accessible through alternative routes.
During the closure, the major detour routes will be U.S. 40 at Empire Junction and U.S. 285 to Fairplay, both roughly 100 miles.
"The quicker they get it done the better," Sellers said.