FRISCO — The Colorado Department of Transportation is quickly shifting the way that they perform avalanche mitigation efforts, hoping to create safer and more efficient alternatives to traditional mitigation missions.
There are about 400 known avalanche paths that potentially could impact highways in Colorado, and CDOT performs regular mitigation missions on about 180 of them. And while the number and frequency of missions varies considerably from year to year based on conditions, CDOT is constantly trying to improve its methods for keeping snow off the road and traffic moving smoothly through mountain corridors.
“There’s a few goals here for the program,” CDOT Winter Operations Manager Jamie Yount said. “Public safety and worker safety are the main categories, but we also want to provide a high level of service to the public. We want to go in there, do the work and get the roads back open.”
During a historic avalanche cycle, like Summit County and much of the state dealt with last winter, mitigation missions are frequent. Yount noted that during the 2018-19 winter, CDOT performed about 1,400 explosive detonations and triggered about 850 avalanches. But the techniques the department uses are beginning to change.
Traditionally, CDOT used military ordnance through a combination of avalaunchers — compressed-gas cannons that fire explosives into the sides of mountains — and helicopter missions. Those methods, which are still common, accounted for about two-thirds of all mitigation missions last year, Yount said. Safety concerns related to the explosives are typically the reason CDOT is unable to provide public notice before beginning mitigation efforts.
But the department is increasingly dedicated to the use of remote avalanche control systems. The systems — branded Gazex and O’bellx — are essentially gas chambers that CDOT installs on slide paths. Once activated, a central chamber fills with a mixture of oxygen and propane, or hydrogen gas, and fires an explosion directed toward the snow to create a controlled slide.
CDOT has been systematically installing the systems around the state for the past couple of years. There are currently 36 pods installed around mountain corridors, including around Eisenhower Tunnel and Berthoud Pass. Earlier this year, five new units were put in place on Monarch Pass and Wolf Creek Pass. The systems are already getting their work in, according to Yount, who noted that over the past five years, the number of projectile explosive missions have gone from about 3,000 annually to about 300.
Not only are the remote systems safer, in that they literally take explosives out of the hands of CDOT workers and help remove the possibility of hikers stumbling upon undetonated ordnance in the spring, they’re also helping to improve the efficiency of mitigation missions.
“One of the big advantages of gas exploders is we can do them at night,” Yount said. “So when we’re doing our road closures, we try to do those in off-peak hours. But when we’re using projectiles, we have to do daylight closures. With remote systems, instead of closing at 7 a.m., doing the mitigation work, the cleanup work and being open by 9, we’re doing the closure at 4 or 5 a.m., and we’re open by 7. The missions go a lot quicker and really help to improve our operational efficiency.”
Guessing at the avalanche cycle
Nobody really knows how often CDOT will be employing its remote avalanche control systems, or its traditional avalauncher or helicopter missions, this year because forecasting avalanche conditions more than a couple of days out can be incredibly difficult.
CDOT relies on a partnership with the Colorado Avalanche Information Center to help determine which areas of the state are at the most risk for slides and when mitigation efforts need to move forward. And while the area has had somewhat of a worrisome start to the season in regard to avalanche conditions, experts say it’s unlikely we’ll see a season as severe as last year.
“I think it’s pretty reasonable to say we’re probably not going to see this year what we saw last year,” Avalanche Information Center Director Ethan Greene said. “If you predict a 300-year avalanche cycle each year, you’re going to be wrong a lot.”
Greene emphasized that even though last winter was historic in regard to avalanches, much of the damage was done during a single week in March. Still, the conditions for the cycle were set early in the season.
Greene said there were three notable periods or events that lead up to the avalanche cycle earlier this year. The first was an even blanket of snow that built up above tree line in October, followed by a relatively dry November and early December, which allowed the snow to turn into what Greene called a “very weak layer of depth hoar” — essentially a weak crystal formation in the snowpack.
Second, the state saw small, but consistent, snowfall throughout January and February, which created a strong layer in the middle of the snowpack. Finally, the state had severe snowstorms “one after another” around March with very high precipitation rates that put a lot of weight on the existing snowpack in a short amount of time.
“It’s kind of a recipe for a big avalanche cycle,” Greene said. “Because when you have a really weak layer on the bottom, when something breaks, it’s going to take the whole snowpack with it. … It just started piling on weight, and when it broke, it broke catastrophically.”
Greene noted that this season started off somewhat similarly, with a weak layer of snow developing in October followed by a relatively dry November. Greene said it’s typically rare to have perfect avalanche conditions all line up together in the same season, but as avalanche forecasting is incredibly difficult more than a few days out, even experts will have to wait and see how conditions develop throughout the rest of the winter.
“We did have pretty good snowfall at the end of October, and then we had a fairly dry November,” Greene said. “That has created a nice, weak layer for us. That wasn’t a problem until around Thanksgiving, and we started to see avalanches on that layer pretty quickly. It gives you an idea of how weak and sensitive that layer is.
“What happens from now on really depends on what the rest of the winter brings. It’s pretty safe to say that we’ll continue to see elevated avalanche hazards with every new storm for the rest of December and maybe into January.”