Washington transportation officials will no longer rely on artillery to dislodge accumulated snow on Snoqualmie Pass to safely trigger controlled avalanches above Interstate 90, concluding an era that saw World War II-era military equipment repurposed for mountain pass safety.
The roadway typically receives upward of 450 inches of snow annually, which could be dangerous for the 28,000 vehicles that depend on it on a typical day. The most common area for avalanches on the roadway is the west side of the pass.
Following a million-dollar appropriation from the Legislature, the Washington State Department of Transportation recently completed installation of a remote-controlled avalanche control system on the mountain pass.
According to the agency, Washington joins Colorado, Utah, Alaska, Wyoming and California in adopting the technology. A similar system is also in use on Stevens Pass.
“This is a safer, more effective system than what we were previously using to get the job done,” stated Tina Werner, a state transportation spokesperson, on Thursday.
The new system will replace methods previously used on the mountain pass for decades. Since the 1980s, transportation crews have used artillery including a recoilless rifle, an M-60 tank and a World War II-era howitzer that was lent from the United States Army to dislodge snow in the mountain.
The shots would trigger a controlled avalanche safely above the closed roadway.
According to the state, the process could include upward of six hours of preparation before the first artillery shot was fired. The roadway would also remain closed for hours following the artillery shot as crews cleared the roadway.
WSDOT discontinued the tank in 2018, after the agency stated it reached the “end of its useful life.” The US Army has since decommissioned the tank.
“That’s why for several years we’ve been working toward replacing our old, inefficient system that forces controlled avalanches on Snoqualmie Pass with safer, more reliable technology,” Werner stated.
The howitzer is currently the only artillery used for avalanche control in the United States, Werner indicated.
The new system includes six remote-controlled avalanche control towers and deployment boxes on the mountain pass that are powered by solar panels. The system, which detonates explosives that trigger controlled avalanches above the roadway, was funded through an appropriation included in the transportation budget approved by state legislators earlier this year.
According to WSDOT, the new system provides several benefits, including increased safety for crews clearing snow, a longer life span for the equipment and reduced setup times.
“Previously, my crew was less than a foot away from launching artillery systems,” stated John Stimberis, avalanche control supervisor for Snoqualmie Pass. “Now we’ll be able to force an avalanche in a controlled environment, potentially miles away.”
The avalanche system can be set up in minutes and could reduce road closures to between a half-hour and two hours. The system is expected to last at least 30 years.
The transition from artillery-based avalanche control to remote-controlled explosive systems on Snoqualmie Pass represents a significant technological upgrade that addresses safety concerns, operational efficiency, and the practical challenge of maintaining military equipment increasingly difficult to operate and support as original operators retire and spare parts become unavailable.
The use of World War II-era howitzers, M-60 tanks, and recoilless rifles for avalanche control emerged from practical necessity decades ago when transportation agencies needed effective tools for triggering controlled avalanches and surplus military equipment provided readily available solutions. These weapons could deliver explosive force at sufficient range to trigger avalanches from safe distances, creating functional if unconventional avalanche control systems.
However, the artillery approach carried significant operational burdens. The six hours of preparation time required before firing the first shot reflects the complexity of safely deploying military weapons, including positioning equipment, establishing safe zones, coordinating with law enforcement to close roadways, conducting safety briefings, and loading ammunition. This extensive preparation, combined with hours of post-avalanche road clearing, created extended closures affecting thousands of travellers and commercial freight operations dependent on I-90 as a critical trans-Cascade corridor.
