GLENWOOD SPRINGS, Colorado — Interstate 70 through Glenwood Canyon remains closed to traffic Wednesday morning, and Colorado Department of Transportation officials are not sure how soon traffic will be able to resume.

Reopening the road to traffic hangs on the stability of a large 20-foot diameter rock, which geologists were concerned with on Tuesday. The large rock hangs above the damaged section of I-70.

According to CDOT spokeswoman Nancy Shanks, crews were formulating a plan of attack Tuesday night on how to bring down the boulder without causing more damage to the road surface. She said that bringing the boulder down would likely be the focus on Wednesday, and that CDOT would not guess as to how soon a traffic lane could be opened.

“Not until this rock comes down,” Shanks said. “Now that it's all been scaled above, I would guess that their efforts would be on this boulder [Wednesday].”

The interstate has been closed in both directions at Glenwood Canyon since about midnight on Sunday, after about 20 boulders, ranging in size from 3 to 20 feet, crashed down and punched holes along the elevated section of road. The largest boulder weighed an estimated 66 tons, according to CDOT engineers.

Crews hiked 900 feet up Glenwood Canyon early Tuesday morning and began rock mitigation work on the area above the damaged section of Interstate 70, Shanks said. The crew cleared loose rocks, using climbing ropes and pry bars, above the boulder of concern. They reached the large boulder at about 4:30 p.m. But by that point it was too late in the day to continue.

They need to decide whether to pry the boulder loose, or break it up so it falls in smaller pieces, according to CDOT spokeswoman Mindy Crane.

Shanks said that crews want to make sure that they can bring down the boulder without causing further damage to the road surface, which could delay the re-opening further.

“That would just set us back,” Shanks said.

It took crews less than two days to reopen the highway after the 2004 Thanksgiving Day rock fall closed I-70 in the same area. However, repairs took two months to complete at a cost of around $1.2 million, according to CDOT reports.

According to Shanks, CDOT met with contractors Tuesday to view the scope of repairs needed.

CDOT program engineer Joe Elsen estimated Monday that repairs this time around would be very similar to the 2004 slide. Elsen said Monday that CDOT would operate under emergency contract instructions in order to get a contractor signed on to begin repairs as soon as possible. And he was hopeful that they would have a contractor by the end of the week.

Two large holes, the largest measuring 10 feet by 20 feet, and at least a dozen smaller holes will need to be repaired. Along with at least one of the five steel support girders that were damaged by one of the falling boulders, about 120 feet of steel guard rail, about 100 feet of concrete median barrier, and two sections of precast retaining wall on the westbound lanes that were destroyed by the fall.

Governor Bill Ritter declared the 17-mile stretch of I-70 through Glenwood Canyon a disaster emergency Monday. The declaration will allow the state to seek funding from the Federal Highway Administration to help pay for repairs.

Elsen estimated that repair costs could be as much as $2 million.

The Associated Press contributed to this report.

Wed. morning update Workers breaking up boulder threatening Colo. road GLENWOOD SPRINGS, Colo. (AP) — Workers are breaking up a huge boulder threatening to tumble down a cliff onto Interstate 70 in western Colorado after a rock slide that closed the highway indefinitely. State officials say they hope to dislodge the boulder on Wednesday. After that, they'll decide how soon at least some lanes can reopen. The boulder is 20 feet in diameter and 900 feet above the highway. Workers will break it apart with compressor-powered drills hauled to the site by helicopter. A 17-mile stretch of I-70 has been closed since Monday after a rock slide rained boulders onto the road and punched gaping holes in an elevated section. No one was hurt and no vehicles were damaged. The shortest detour is more than 200 miles long. CDOT update: UPDATE: 10:40 AM, MARCH 10, 2010 The helicopter is on scene—ready to drop off drilling equipment and a generator for planned drilling/blasting operations. If all goes well, crews anticipate bringing the boulder down early afternoon. When the boulder is down, the hillside scaled and stabilized, and any resulting highway damage is assessed, we can begin to send information regarding estimated highway re-open times. We will send notice as soon as the boulder is down.