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CDOT Maintenance to Conduct Rockfall Mitigation on US 550 South of Durango on Bondad Hill

April 9, 2012 - Southwestern Colorado/CDOT Region 5 - One lane open in each direction for much of Tuesday; traffic stopped midday in both directions – project could run through Thursday.

LA PLATA COUNTY – Tomorrow, April 10, the Colorado Department of Transportation will begin a several-day project to reduce the potential for rockfall on US 550 at Bondad Hill, about 10 miles south of Durango. This work, which is estimated to cost between $10,000 and $15,000, is expected to take several days to complete, depending upon results.

During the project, CDOT and rockfall contractor Yenter Companies will initially attempt to push a sandstone block off the slope with the use of air bags inserted into cracks behind the block and then inflated. Once the block is on the road, crews can break it apart and haul material away.

The following is a brief history of recent rockfall activity in this area, detailing the purpose and need for the current work (see also Rockfall Rating System, below):

  • In March 2008 a large sandstone block fell from this section of the slope on Bondad Hill; CDOT cleared the rock, geology staff assessed the hillside and conducted follow-up scaling (bringing any loose rock material down by hand;
  • In March 2010, during regular maintenance, several sandstone blocks were identified by CDOT’s local maintenance crews as appearing to be unstable. CDOT geologists concurred with R5 and in April 2010, three blocks were removed for approximately $24,000.
  • The 2010 recommendation also included monitor a fourth block, or “Block D,” until funds were available to remove it or until monitoring indicated movement of the block.
  • CDOT’s visual observations Block D have indicated movement; with the potential for wet spring weather, CDOT geologists have recommended prompt removal of the block.

“CDOT’s rockfall program allows us to be proactive in reducing the effects of this natural hazard,” Ty Ortiz, CDOT’s rockfall specialist, said.  “While our mitigation features vary among locations, each provides a method of protection and improved stabilization—our goal is reduce the potential for rockfall incidents.”

TRAVEL IMPACTS: The project is anticipated to take place from Tuesday, April 10, through Thursday, April 12. There will be a single-lane closure starting at 8 A.M.; but as this is a three-lane section, one lane will remain open in each direction until crews are ready to bring down the rock. Midday, motorists should expect a full traffic stop, in both directions, for 30 minutes or more. If work with the airbags is not successful in bringing Block D down, crews will continue work on Wednesday and possibly Thursday, and blasting operations may be necessary.

Thank you for going Slow for the Cone Zone. For information about other CDOT projects, log on to http://www.coloradodot.info/ or call 511 from anywhere in the state.

CDOT’s Rockfall Program

The Colorado Rockfall Hazard Rating System (CRHRS) divides this location on US 550 at Bondad Hill into two rockfall sites:  one between mile point 5.011 and MP 5.044, and one between MP 5.082 and MP 5.154.  Both sites rank 131 out of 756 identified rockfall sites statewide. The CRHRS sites are ordered in funding priority from 1, which has the highest combination of hazard and risk, to 756 which has the lowest. To determine which sites are of high priority, several factors are analyzed including slope profile, geological characteristics and traffic statistics.

The rockfall program, which started in 1996, was created to track rockfall information, implement a rating system and mitigate potential hazardous areas.  When the program first began, CDOT received just $750,000 for projects statewide. Since that time, funding for the Rockfall Program steadily increased to accommodate rising construction costs and allow for additional mitigation across the state. In recent years, the program was receiving $3 to $5 million per year; for the 2012-13 season, the program is receiving about $7 million—which includes $2 million in State Transportation Commission contingency funds, to help supplement projects statewide.

Since the program began, about 70 sites have been mitigated through CDOT’s Rockfall Program.  CDOT rockfall specialists also provide additional assistance at nearly 30-40 locations statewide each year in response to rockfall and other activity.

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