Berm built on Grizzly Creek burn scar likely prevented major damage to Hanging Lake Tunnels
Work begins to clear debris and steer river back into channel, away from I-70
A major rock and debris flow down the Devil’s Hole drainage in Glenwood Canyon last week was largely unexpected in terms of its impact on Interstate 70, state transportation officials said Wednesday.
The massive debris flow caused by a rainstorm the evening of July 22 dumped piles of large rocks and trees into the Colorado River, damming the river and forcing it out of its channel up against the highway’s eastbound deck structure.
Concerns about the water and debris compromising the highway structure ultimately closed I-70 for the better part of two days as a result. Westbound lanes weren’t reopened until early Saturday morning, and the eastbound lanes remained closed until later that day.
“The reason we didn’t open up the highway on Friday is because we didn’t know what the river was doing underneath the road itself,” Colorado Department of Transportation Region 3 Director Mike Goolsby said Wednesday during a media tour of the impacted area.
“Until we were able to get our folks out there to evaluate it, we weren’t completely comfortable opening up the road,” he said.
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Goolsby called the threat to the highway in that particular location “totally unexpected.”
“We had been worried about the road surface and getting the traffic through, so this was something we were not completely prepared for planning-wise, in terms of the amount of debris that came down,” Goolsby said.
What was expected given rain event and debris flow modeling that was done after last summer’s Grizzly Creek Fire played out that same night just a few miles to the east in the Cinnamon Creek drainage above CDOT’s Hanging Lake Tunnel Command Center.
Largely out of sight from passing motorists, the command center was built in the natural drainage when I-70 was completed through Glenwood Canyon in the early 1990s. The building structure essentially connects two sections of eastbound and westbound tunnel bores to make one long tunnel.
It also serves as the central command system for the state highway system on the Western Slope of Colorado, with a staff of 35 people, a full fire response unit and camera eyes on virtually every section of I-70 in the canyon.
Last summer, during the height of the wildfire that started Aug. 10, 2020, and closed I-70 through Glenwood Canyon for nearly two weeks, a special Burned Area Emergency Response (BAER) team inspected the area and predicted exactly what happened July 22.
The recommendation at the time was to build a large earthen berm to the west of the creek drainage to protect the tunnel command center should a major debris flow occur.
During last week’s storm, upward of 100,000 cubic yards of material did in fact come rushing down Cinnamon Creek directly toward the tunnel structure, but was diverted by the berm and out of harm’s way.
“This berm basically stopped this complex from filling up with mud and debris,” said John Lorme, CDOT director of maintenance and operations.
“Had it not been here, we’d be trying to figure out how we’re going to clear all these tunnels out and rebuild this whole complex.”
Lorme called it a perfect example of an ounce of prevention being worth a pound of cure.
Damage was limited to a clogged and mildly damaged concrete culvert that normally channels the creek around the command center.
“It literally probably saved the state hundreds of millions of dollars,” Lorme said of the berm — not to mention what likely would have been an indefinite closure of I-70 through the canyon.
The berm was paid for out of just a small portion of the millions of dollars in emergency funds that were released to deal with the Grizzly Creek Fire impacts. Rather than bidding out what would have been about a $50,000 project, CDOT handled the work in house, saving even more dollars.
In any event, Hanging Lake Tunnels operational manager Trevor Allen said the command center had an evacuation plan in place and preparations to set up a temporary operations center in Glenwood Springs, if need be.
Back downstream at the Devil’s Hole debris flow site, heavy earthmoving equipment was brought in by train Wednesday to begin moving the tons of rock and other debris that’s now clogging the Colorado River.
The goal is to cut a pilot channel from the south side of the river and remove as much debris as possible to push the river back into its normal channel and away from the highway, where it now covers most of the recreation path that runs along the interstate.
The risk if the debris is not removed is that the flow of the river could undercut the highway deck structure and cause more severe damage.
“Right now we’re confident that it’s safe,” Goolsby said. “We just want to get the water away from the roadway so we can go in and make any repairs that we need to.”
As far as the highway itself goes, that’s not expected to be too extensive. The recreation path could be a different story, as several sections are believed to have been damaged by the recent mudslides, he said.
It’s likely to remain closed for the foreseeable future until that damage can be assessed and repairs made, Goolsby said. Similar extensive repairs have had to be made in high runoff years when the path has been damaged.
The focus now, and likely into the fall until the seasonal monsoonal weather subsides, is to keep the traveling public and recreational users safe, Goolsby said.
Any time there is a flash flood watch for the area including Glenwood Canyon, rest areas along the 16-mile stretch are closed and CDOT crews are put on alert to be prepared in the event of a flood.
If the watch is elevated to a flash flood warning, meaning heavy rains and flooding in areas are imminent, I-70 through the canyon is closed to traffic.
So far, about 80% of the time that has happened in recent weeks there has been a mud and debris flow at some location in the canyon, Goolsby said.
That, in turn, leads to a more lengthy closure, oftentimes overnight and into the next day, while crews remove the material from the road surface and make sure all is safe for traffic to flow again.
That process involves some 40 to 50 CDOT employees, many of whom are brought in from other districts in the state to help with the cleanup, he said.
Also joining the tour Wednesday was CDOT Executive Director Shoshana Lew. She also spoke to the forward-thinking mitigation that was done to protect the tunnel command center.
“It’s a little eerie being in this spot, after we were here last summer when this berm was being built,” she said. “What you are seeing now is the long tale of what we all sort of knew was coming.”
Glenwood Canyon remains one of the most challenging stretches of highway in the state system, she said, but last year’s fires and recent storms have had major impacts all across the state, including the deadly flash flood in Poudre Canyon recently below the Cameron Peak Fire burn scar.
Fortunately, no lives have been lost in Glenwood Canyon, and the CDOT response plan whenever there’s a threat of flooding is meant to keep it that way, Shoshana said.
“Our first priority is to keep people safe and keep them out of harm’s way,” she said. “We beg for people’s patience and caution in this.”
The dangers associated with Glenwood Canyon in particular are unique and require a lot of planning and financial investment, she added.
“As beautiful a gem of the interstate as it is to drive, it’s just extraordinarily complicated with risks,” Shoshana said. “We manage them, but they’re not going to go away.”