Workers drilled on the side of a steep slope, just over the edge of one of several chutes collectively known as the “Seven Sisters,” the most active avalanche area that crosses a Colorado highway. The site would connect a gas line to one of 11 devices known as “exploders” facing the east side of Loveland Pass, generating a burst at the push of a laptop button to mitigate large avalanches that often block U.S. Highway 6.
“The problems start right here. This is the big slide,” said John Crowder of Parsons Construction. “There are seven slides here.”
Since June, the Colorado Department of Transportation has worked to install a new avalanche system near Loveland Pass and Berthoud Pass, two avalanche-prone areas near major roadways. Crews hurried to install a remotely triggered avalanche system, Gazex, that uses a mixture of compressed gas and oxygen to start a controlled slide.
“CDOT’s desire is to move away from the use of explosives,” said Ray Mumford, a former avalanche control trainer for CDOT. “It’s safer.”
In previous years, CDOT would use a cannon to shoot mortars at the avalanche areas, which would detonate upon contact. However, the method had its risks, as a mortar detonated while still in the launcher last year, injuring two workers, not to mention the dangerous task of hiking up the pass in the winter to retrieve rounds that, for one reason or another, failed to detonate.
In addition, the method could take hundreds and hundreds of rounds, depending on the snow conditions that year. Two years ago, Crowder said, 1,500 rounds were shot at the avalanche chutes during a particularly brutal winter. On average, 40 to 50 avalanche missions are conducted in the area every year.
With the new system, Mumford said, a worker would be able to trigger the avalanches remotely from a laptop, combining a compressed mixture of propane and oxygen in a curved tube to create a fiery explosion resulting in a large shockwave, travelling at 1,750 meters per second.
“There’s a lot off power when those go off, so you have to have these huge concrete bases bolted into the bedrock,” said David Eller, CDOT Region Three transportation director.
The gas tanks are stored in control shelters, with four dotting the slope just east of the Loveland Ski Area. The plan is to store enough gas to last an entire winter, requiring no travelling to the top, which is nestled just above tree line. To form the concrete bases, the still-wet mixutre is transported by air, and then poured into a frame from the helicopter.
“We’ve been two years on this, if not more. It’s been quite a puzzle to put together,” said Grant Anderson, a project engineer with CDOT.
The new system would also allow workers to trigger slides regardless of the weather conditions. Mumford said the increased control should both reduce and shorten Loveland Pass closures, allowing trucks bearing hazardous material to pass through without holding up Interstate 70 traffic. When HAZMAT trucks have no choice but to travel through the Eisenhower-Johnson Memorial Tunnel, regular vehicular traffic is closed off an hour at a time.
The Loveland Pass project will cost $980,000 to install $1.5 million of equipment, including a total of four control shelters and 11 exploders. At Berthoud Pass, connecting Winter Park to I-70, instillation will cost $655,000 for two control shelters and five exploders, with the help of a $225,000 local partnership with Grand County.
Mumford said he hoped to see both systems working by mid-October, with plans to carry exploders near the top of Loveland Pass in the following week or two.