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CDOT removes massive boulder from U.S. 160

A large boulder, estimated by Colorado Department of Transportation officials to be 10x20 feet and weighing about 40 tons, fell onto U.S. 160 on Yellowjacket Pass between Pagosa Springs and Bayfield at about 6 p.m. Thursday, March 18.

Despite its size, the boulder closed only the right westbound lane, leaving one lane of traffic open in each direction throughout the weekend and causing only minimal delays.

CDOT crews blasted the boulder into smaller pieces Friday about 12:30 p.m. in order to remove it from the highway. In addition, crews did rock scaling (manually pulling down rocks) in the area to eliminate other loose rocks, said Stacey Stegman, CDOT director of public relations.

A geologist and CDOT maintenance crews evaluated the site Monday in addition to completing additional scaling work.

“The geologist determined that, with scaling, no further mitigation is necessary,” said CDOT Regional PR Manager Nancy Shanks, adding that an eye would be kept on the area.

The hillside where the rock slide occurred, as well as much of the area, is sandstone sitting on top of shale and, if the shale erodes, it can undermine the sandstone, Shanks said.

“In the spring, you see more incidents of rock fall, especially when we have the weather warming up like it is right now,” Shanks said, explaining that the thaw and freeze pattern allows for water to seep into cracks and between rocks, at which point the water freezes and expands before melting again, thus loosening rocks.

Precautions that motorists can take to avoid damage from rock slides (as well as to avoid many other potential problems on the road) are to drive the speed limit, particularly in mountainous areas and around corners, Shanks said. Also, awareness is key, in order to give yourself time to react to any rocks in the road.

With a service launched in February, CDOT is also taking additional measures to inform travelers of road conditions and closures, travel alerts and other safety announcements from across the state (such as rock slides), broken down by specific corridors and regions of the state, via e-mail and text message.

Those interested can log on to and click on the “Sign up for Email and Wireless Alerts” icon in the upper right to sign up for the alerts, enter the needed information, then choose what transportation topics and areas to receive alerts regarding. Not all items are available as text alerts.

Subscribers can change their alerts or opt out of the service at any time by visiting the Web site.