Highway 82 near Aspen to see rockfall project
July 12, 2010
ASPEN – Highway 82 at Shale Bluffs, near Aspen, is slated for a $1.5 million project this year to reduce the danger of rocks falling on the roadway, according to the Colorado Department of Transportation.
The site is one of three in the greater Roaring Fork Valley that will see rockfall mitigation either this year or next, and one of six around the state that have been chosen for work, CDOT said. Highway 133 at McClure Pass is also slated for rockfall mitigation, as is a major problem area – Interstate 70 in Glenwood Canyon.
The agency typically receives about $3 million annually for rockfall mitigation projects, allowing for three to four projects each year around the state, but it has $4.3 million available this year, in part as a result of the FASTER bill signed into law by Gov. Bill Ritter in 2009. The Funding Advancements for Surface Transportation and Economic Recovery (FASTER) legislation increased vehicle registration fees to help improve the state’s transportation system.
The boost in funds allowed CDOT to accelerate certain projects, including the work at Shale Bluffs, where a project had been initially scheduled in 2013, according to CDOT. The agency now plans to drape steel netting on the bluffs above Highway 82 this summer or early in the fall.
The $1.5 million project is intended to help keep rocks that slough off the unstable bluffs from winding up in the roadway, according to Ty Ortiz, CDOT rockfall specialist.
Bolts were installed to help stabilize the bluffs when Highway 82 was widened to four lanes as it cuts through the bluffs, but rocks continue to fall. They tend to break apart behind the concrete barriers placed at the edge of the upvalley lanes when they hit the ditch alongside the highway. From there, the debris sometimes bounces over the barriers and onto the highway, Ortiz said.
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“Shale, when it’s exposed to air and water, really breaks down more quickly,” Ortiz said.
CDOT rates rockfall areas in order to prioritize projects; the ratings are based on the geology of the site, the steepness of the slope and the risk, a factor related to the volume of traffic on the affected roadway. Of 756 chronic rockfall areas around Colorado, Shale Bluffs is at No. 24 on the list, according to Ortiz.
The amount of traffic on Highway 82 pushed the project up on the list, he said.
Highway 133 at McClure Pass, south of Carbondale, is at No. 14, though both projects are roughly equal in terms of their hazard rating, Ortiz said.
CDOT is evaluating what should occur on Highway 133. Work could include rock scaling – breaking off hazardous rocks before they fall down, blasting and installation of rockfall netting. The work, at an estimated cost of $1.2 million, is likely to occur in the spring or summer of 2011.
At McClure Pass, shale mixed with sandstone results in instability, according to Ortiz. The shale erodes and sandstone rocks and boulders come loose as a result.
On the far side of McClure Pass, near Paonia Reservoir, another chronic rockfall site along Highway 133 is slated for work in 2012, Ortiz said.
Glenwood Canyon, the site of periodic slides, was shut down for three days last March after a massive slide brought multiple boulders down onto Interstate 70; no one was hurt. Repairs and installation of additional wire mesh cost roughly $1.2 million.
Another $600,000 has been allocated to repair and improve existing rockfall fencing in the canyon. There are between 25 and 30 different rockfall fences there, Ortiz said.
However, neither Glenwood Canyon nor Interstate 70 at Georgetown Hill are on the list of 756 problem sites.
“Glenwood Canyon and Georgetown Hill are kind of in their own separate category,” Ortiz explained.
CDOT is planning a $1.4 million project to continue installation of rockfall fencing and netting at Georgetown Hill, beginning in late fall.
Elsewhere around the state, a $1.7 million project on Highway 145 at Norwood Hill is planned this summer, as is work on US 285 in Turkey Creek Canyon, along with safety improvements on US 285 between Bailey and Richmond, at a cost of $150,000 to $300,000.
CDOT’s rockfall program began in 1996, with $750,000 for mitigation statewide. Since then, about 60 sites have seen work, and funding has quadrupled to about $3 million a year.
Since 1999, there have been nine deaths on Colorado interstates or state highways as a result of rocks hitting vehicles, and many instances of highway closures resulting from rockfall, according to CDOT.