A massive rock slide that toppled onto Interstate 70 in Glenwood Canyon late Monday night will result in a lengthy detour for anyone headed to, or from, the Denver area until at least Thursday afternoon.

That’s the earliest Colorado Department of Transportation officials expect to be able to open a single lane of alternating traffic led by a pilot car, CDOT spokeswoman Tracy Trulove said — and that depends on the success of rock-scaling operations to make sure the canyon walls are stable and that the highway can be reopened, she said.

CDOT used a helicopter Tuesday to allow its geohazards team to view the damage from above, and engineers were inspecting the road for any structural damage.

“There is a lot of debris still up on the slope, which remains unstable,” Trulove said. “We had our geologists up there all day, and there’s just a lot of loose rock. The moisture we’ve had, followed by the warm temperatures isn’t helping.”

In the meantime, motorists heading east toward Denver must endure a 146-mile detour via state Highway 13 at Rifle to U.S. 40 from Craig to Steamboat Springs and Highway 131 back to I-70 at Wolcott. Travelers headed to and from the southeastern part of the state are advised to take U.S. 50.

The second rock slide of the day Monday happened just after 9 p.m. about three-quarters of a mile west of the Hanging Lake Tunnels and eight miles east of Glenwood Springs.

The slide involving more than a dozen car-sized boulders originated from high on the canyon wall in the same location as a smaller one that closed I-70 in both directions for about two hours early Monday morning.

After the earlier incident, crews determined it was safe to reopen one lane in both directions around 5 a.m. while the rocks were being removed throughout the day.

During the second slide, two westbound semis and at least one car were passing by and one of the semis was severely damaged by the falling boulders. No one was injured, however.

Trulove said that at least a dozen boulders fell onto the westbound lanes, “the largest about the size of my Dodge Durango,” she said.

Several boulders also crashed onto the eastbound lanes, while others tumbled all the way across the Colorado River.

I-70 was fully closed a little after 10 p.m. Monday, stranding dozens of motorists who had to be turned around toward either Eagle or Glenwood Springs.

Among those coming through the canyon to Glenwood Springs was Ron Milhorn, news and sports director for KMTS radio, who was headed home with his family after seeing his newborn granddaughter in Denver.

“We could see that the eastbound lanes were closed, and, when we got out of the tunnel, things just came to a stop,” he said from the Eagle Diner on Tuesday afternoon before making the trek up and over through Steamboat Springs and Craig.

Eventually able to turn around and find a safe spot to pull over, he said he walked up to take a look at the carnage and happened onto the truck driver who came away unscathed.

“The reporter in me said I had to go find the story when I stumbled onto the driver,” he said. “I asked if I could interview him. He was remarkably calm, cool and collected and described seeing a car in front of him. He said it just vanished in the snow and debris.”

damage uncertain

Trulove said it will take some time to determine the extent of the damage from the slide and the costs to repair it, but that several weeks of construction should be anticipated.

“We haven’t been able to move some of the larger boulders yet to delineate that,” she said, adding the westbound lanes are more heavily damaged. “We know there are some holes in the deck, and our engineers are out here taking a look at that.”

Once the single lane is opened, the pilot car could be in place for several days while the initial repairs and additional rock stabilization are completed, she said.

“As repairs progress, CDOT will move to open one lane in each direction,” according to a CDOT news release issued late Tuesday afternoon. “It could be several weeks before damage to the roadway walls and roadway are repaired, and the interstate is fully open to regular traffic operations.”

Rockfall contractors are already lined up to continue the rock scaling work, and, as a safety precaution, a rockfall mitigation fence will be erected on the westbound lanes.

The 12-mile stretch of I-70 through Glenwood Canyon — in particular the section just west of the Hanging Lake Tunnels — has had numerous major rock slides that have resulted in highway closures over the years.

In February 1995, three people were killed when a large rock tumbled onto the roadway, crushing their vehicle. One of the largest rock slides to occur was on Thanksgiving Day 2004, when I-70 through the canyon was closed for more than a day during the height of holiday traffic.

travel, delivery impacts

Several downtown businesses reported a surplus of customers Tuesday morning as people had begun making their way toward eastbound I-70 only to realize it was closed.

The Ramada Inn reported an unusually-high number of guests Monday night as motorists were stranded and didn’t want to make the nighttime drive over the winding, two-lane detour route.

“We had a lot of walk-ins last night and again today because of the closure,” Tammy Ott, front desk manager at the Ramada, said. “It’s great for business, sure, but it’s tough on the customers.”

Every time the highway through the canyon closes, it also forces delivery trucks, from grocery stores and major retail chains, to take the long detour.

The Napa Auto Parts store in Glenwood Springs was able to get its regular stock shipment in late Monday night but was told to expect delays until the interstate reopens, sales clerk Sara Bak said.

“When we order out of Salt Lake City, they still have to go through the Denver (distribution center) and then over here,” she explained. “So, we were told we will be held up a day. It will have a lasting effect until they get it open again.”

The interstate closure did not have an immediate impact on the Grand Avenue bridge construction in Glenwood, project spokesman Tom Newland said.

“They’re cranking away with the work down on Seventh Street,” he said Tuesday morning. “It’s not really impacting us at all, expect for maybe a little less traffic, which is good.”

Roaring Fork School District Superintendent Diana Sirko said she was not aware of any school activities that would have been impacted by the canyon being closed. However, high school wrestling teams headed to the state tournament in Denver on Thursday could be delayed.