New technology improves avalanche safety and response times for Snoqualmie Pass winter closures

By: Tina Werner

If you’ve ever tried to travel between North Bend and Cle Elum during a winter storm, chances are you’ve been delayed by spinouts, crashes or heavy snowfall. You might have even been held up by our specialized crews forcing an avalanche in a secured location to reduce the risk to travelers below.

Interstate 90 over Snoqualmie Pass is one of Washington’s busiest mountain passes. An average of 34,000 vehicles use it each day, including thousands of trucks moving goods across the state.

When a mountain pass closes, it affects everyone - students, freight haulers, businesses and people taking medical trips. This photo shows I-90 Snoqualmie Pass a few years ago after a big crash that shut the highway. The closure lasted for hours while crews cleaned up and towed vehicles.

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. Thanks to one-time funding from the Washington State Legislature (senate bill 5161), this year we finally did.

Ending artillery use on Snoqualmie Pass

Artillery systems have been used to trigger avalanches on Snoqualmie Pass since the 1980s. Our avalanche specialists began operating them when the westbound lanes of I-90 first opened. Over the past 40 years, the team has used several types of artillery for this work, including

• A recoilless rifle
• An M60 tank
• A World War II-era Howitzer (loaned to us from the U.S. Army)

Each system works similarly. They fire a projectile into unstable snow to trigger an avalanche in a controlled manner. After that is complete, our maintenance crews clear the debris and safely reopen the highway to travelers.

While effective, artillery systems like the Howitzer are outdated. They are also costly to lease and near the end of their serviceable life. The older systems also require crews to work closer to explosives than today’s newer systems. Even with strict safety protocols, crews experience risks.

Launching artillery was no small task. Set up alone could close I-90 for up to six hours before firing the first shot. Preparing for extended closures requires significant time and staffing. Travelers must be cleared from the closure area to force the avalanche in a controlled manner. Then we secure the zone to keep people safe and clean up the fallen debris after each operation. Other states have encountered the same challenges and are also phasing out artillery systems in favor of safer, more efficient technologies.

Three team members fire a recoilless rifle along Snoqualmie Pass to force an avalanche. A recoilless rifle is one of several old artillery systems that have been used historically for forcing avalanches on Snoqualmie Pass and around the state.

Enter Remote Avalanche Control systems

This year, we installed a new Remote Avalanche Control system on Snoqualmie Pass. Powered by solar panels, the system allows crews to safely trigger avalanches from miles away from travelers.

Our first tower was installed this year just west of Snoqualmie Pass. Remote Avalanche Control systems are more efficient, reduce mobilization time and are safer for crews to operate than artillery systems.

The benefits are big:

• Faster mobilization : What once took four to six hours can now be ready at a moment’s notice.
• Potentially shorter closures : Avalanche work used to shut down the pass for many hours due to the labor and equipment set up needed. Now, crews may only need 30 minutes to two hours.
• Longer lifespan: The system is expected to last at least 30 years and is not on loan from another state or federal agency. We own it outright.
• Safer operations: Crews can work from a secure distance while still reducing avalanche risk.

We have already seen success with similar remote avalanche control systems on US 2 Stevens Pass. With eight total systems now operating in Washington, we’re joining states like Colorado, Utah, Alaska, Wyoming and California in adopting this modern technology. This is a safer, more effective system than what we were previously using to get the job done.

A worker opens a box that holds 12 explosives. The explosives can be triggered from far away to make a controlled avalanche. By bringing snow down in a calculated way, crews can clear slopes and reduce the risk of an unpredictable slide reaching the roadway.

Our Snoqualmie Pass avalanche team typically conducts several controlled avalanche missions every winter. Each operation requires closing a section of I-90.

“Previously, my crew was less than a foot away from launching artillery systems,” said John Stimberis, WSDOT Avalanche Control Supervisor for Snoqualmie Pass. “Now we’ll be able to force an avalanche in a controlled environment, potentially miles away.”

John has been with our agency for 25 years. He is nationally and globally recognized in the avalanche sector as one of the best and brightest. He graduated from the University of Washington and collaborates with other states, countries, ski resorts and universities on training and expertise. We are grateful to have him leading our program at Snoqualmie Pass.

Beyond remote systems

Avalanche work doesn’t stop with remote systems. Our avalanche team consists of three full-time and two on-call specialists. They rely on other tools to keep mountain highways safe. One method used are trams. These are like ski lifts and are used to place explosives in targeted snowfields. These complement our remote avalanche control systems and give crews options depending on conditions. When weather allows, we may also contract helicopters to drop explosives in hard-to-reach areas. All this work is done in closed locations where traffic is not present. During extreme storms however, helicopter services are often unavailable, so we must rely on other methods.

John holds a green pulley used on a tram to deliver explosives for triggering controlled avalanches.

Unmanaged avalanches can be deadly. While we can’t control the weather, we can reduce risk to travelers and our crews. Our specialists train extensively and follow strict safety protocols. We also partner with groups like the Northwest Avalanche Center, National Weather Service and WeatherNet to forecast storms. Forecast modeling helps inform our maintenance supervisors where to dedicate equipment and crews.

A truck moves salt from a maintenance storage shed during the winter.

When a storm hits, we shift people and equipment to where the need is greatest - a strategy we call “swarming the storm .” Crews work around the clock, even if you don’t always see them. If a plow isn’t on your route at a given moment, chances are it’s clearing another critical area or heading your way. Most snowplows cover anywhere from 40 to 100 miles of roadway per day.

Safer, smarter winters ahead

The new Remote Avalanche Control system is a major step forward in keeping Snoqualmie Pass safer. It allows us to prevent more uncontrolled avalanches. By combining modern technology with decades of expertise, our crew can respond more quickly and work in safer conditions.

That said, travelers should still expect long closures. Most winter highway closures are preventable. Most delays on cross-state routes like I-90, US 2, SR 14 and US 12 are caused by drivers going too fast for conditions, ignoring chain-up requirements or driving impaired or distracted. These behaviors put everyone at risk and lead to unnecessary closures.

How long it takes to open the road depends on many factors: weather patterns, avalanche activity, cleanup operations and sharing of equipment and staff across regions. We make every effort to provide timely, accurate updates, but conditions can change quickly. Follow chain up requirements, slow down on snow and ice and remain alert. Thank you for your patience and partnership in helping keep mountain passes open and safe.

A group of snowplows – what we call “tandem plowing” – clearing State Route 16 in Tacoma. This technique helps clear roadways of snow and ice in one pass.