Stationed in the Cascade Mountains of Washington, the avalanche control team has been hard at work this winter, ensuring the safety of public roads by triggering avalanches.
Consisting of seven regularly-scheduled employees and seven on-call staff members, the avalanche control team works on two of Washington's high mountain passes, the I-90 Snoqualmie Pass and the US-2 Stevens Pass.
Originally created back in the 1970s in response to avalanche accidents on the highway, the team is made up of forecast and control specialists.
"Our avalanche forecast and control specialists do assessments of the snowpack, measure new snowfall, snow temperatures and densities and look at any instabilities that may exist within the snow," Avalanche Control Forecast and Control Supervisor John Stimberis said.
Following the team's initial assessment, they get together and figure out the day's weather forecast to determine how the current snowpack will respond to that weather and what exactly the stability of the snow is going to do.
"If it looks like the trend will increase the instability of the snowpack, then we go ahead and schedule where and when avalanche control will be needed," Stimberis said. "The last thing you want is avalanches on the highway when traffic is there."
While avalanches can occur naturally, some type of disturbance is needed for this phenomenon. To provoke an avalanche, the team provides that disturbance.
Once it is determined that avalanche control is necessary, the team travels to the top of the avalanche path, while maintenance stops traffic on the highways below and the media warns people to expect travel delays.
When the roadways are cleared, one final sweep of the highway is done to ensure that no travelers still remain and then the avalanche control team detonates explosives to supply that instigative disturbance to the pass.
According to the Washington Department of Transportation, the team uses artillery or explosives to trigger these avalanches. These explosives are either placed by hand, cable-pulley bomb trams or with surplus military weapons.
"Most explosives are on a little cable but in a few areas artillery is needed," Stimberis said. "We've fired 18 rounds at slopes that aren't accessible by other means."
Causing a major snow slide, the amount of snow barreling down the mountain varies by location and snow type, but typically 8 to 10 feet of snow are knocked free during these detonations, according to Stimberis.
While the actual process of avalanche control is fairly quick, generally only 10 to 15 minutes, snow cleanup can take anywhere from 15 minutes up to two hours.
When cleanup is complete, roads are re-opened to public traffic and the team begins the process again.
Besides the avalanche control team, the Washington Department of Transportation also uses diversion dams and snow berms to help keep drivers safe and keep snow off the highway.
Outside of Washington, other states experience similar threats from avalanches. To combat these threats, typically roadways are closed ahead of the potential for an avalanche. Recently, 62 miles of U.S. 12 were closed on Wednesday, March 5, 2014, in Idaho due to the risk of an avalanche.