A large piece of the boulder remains, and crews will return Monday to blast it apart. The rubble will be hauled away.<\/p>\n
When the remaining piece is blown up Monday, traffic will be stopped a safe distance away.<\/p>\n
Larger pieces may need to broken up by a \u201cboulder buster,\u201d Jones said. The portable unit is placed over a drill hole filled with water. A small charge is set off, and the pressure of the charge and water breaks apart the rock without debris flying.<\/p>\n
CDOT geohazard crews will survey the area to determine whether rockfall mitigation work is needed, said Schwantes.<\/p>\n
Damage to the highway will not be known until the rest of the boulder broken apart and debri removed. CDOT officials said they have asphalt ready to repair the road.<\/p>\n
CDOT program engineer Kevin Curry said an initial survey of the hillside above the rockfall did not reveal other rocks or boulders that were in imminent danger of falling.<\/p>\n
He said the combination of erosion, moisture and freeze-thaw conditions likely caused the section of a sandstone cliff to break loose and slide onto the highway. The boulder broke off from an overhanging section about 30 feet above the highway. It did not tumble.<\/p>\n
Warm daytime weather melted snowpack in the area, and nighttime temperatures have been below freezing. The melting and freezing of water in the rock expands fractures, which triggered a piece of the cliff to calve off.<\/p>\n
The sandstone boulder is estimated to weigh 200 tons, CDOT officials said. It is 11 feet tall and 30-by-16-feet wide.<\/p>\n
The rockfall was reported by the Colorado State Patrol at 6:30 a.m. Friday. About 20 people from CDOT were on the scene, plus engineers from a geohazard consultant firm.<\/p>\n
No injuries were reported.<\/p>\n