Rockfall closes McClure Pass; detour over Grand Mesa might last all week

A large rockslide covers the road north of Paonia Reservoir at mile marker 29 on Colorado Highway 133. Motorists traveling between Paonia and the Roaring Fork Valley must make a detour of about 140 miles over Grand Mesa. Photo courtesy of Colorado Department of Transportation



Falling boulders including one as big as a dump truck have forced the closure of Colorado Highway 133 south of McClure Pass, and the closure will likely last throughout the week.

Sunday’s incident means motorists traveling between Paonia and the Roaring Fork Valley must take a detour of about 140 miles over Grand Mesa.

The Colorado Department of Transportation said the highway was closed about 9:30 a.m. Sunday at mile marker 29 about 13 miles south of the pass and just north of Paonia Reservoir after seven or eight rocks fell onto the road and into a ditch.

The largest rock was 30-feet by 15-feet by 10-feet in size, with another one about three-quarters of that size. The rocks’ cumulative volume was 120-feet by 50-feet by 20-feet, and one of the rocks left a 2-foot-deep depression in the roadway that’s about 12-feet by 10-feet in size.

The incident happened at the same location where a similar-sized rockfall incident closed the highway for several days starting April 27, 2007, CDOT said.

CDOT and rockfall contractor Yenter Companies blasted and removed rock from the hillside then, but Sunday’s incident involved rock from higher up the slope. Geology consisting of sandstone on layers of shale contributes to the size of rockfall incidents in the area.

Yenter began rock scaling operations at the site Monday. The work involves using pry bars to bring down threatening rocks and also employing air bags inflated behind rocks to break them free.

“Once it is determined that the hillside is stable, crews will blast rock on the roadway and haul it away. It is possible this could happen Wednesday or Thursday — all work is expected to last at least through this Friday,” CDOT said in Monday’s news release.

The detour makes use of state highway routes 92 and 65; Interstate 70; and Colorado Highway 82.

CDOT plans to post updates on the closure at http://www.cotrip.org (see “Travel Alerts”).

Meanwhile, CDOT is continuing an ongoing rock scaling project north of McClure Pass, between mile markers 44 and 49 near Marble. That work is requiring closures that sometimes will last 20 minutes or more, along with shorter delays and single-lane, alternating traffic during daylight hours Mondays through Fridays and some Saturdays.

“McClure … is ranked at the top of our Rockfall Hazard Rating System,” Ty Ortiz, CDOT’s rockfall specialist, said in the news release.

“The amount of rockfall we see here on an annual basis is quite a bit higher than what we see in many other sites around the state.”


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