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Utah Department of Transportation plans for more Wyssen Avalanche Towers in Little Cottonwood Canyon

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Mountain Technology,

In 2017, the Utah Department of Transportation (UDOT) was the first avalanche control team in the US to implement the use of the Wyssen Avalanche Tower for avalanche mitigation. This Swiss technology, though new to the US, is used widely in countries such as Austria and Switzerland and is a highly reliable and efficient tool for controlling avalanche hazard. These towers are used to protect roads and ski resorts as well as for other applications such as protecting railways.

In Little Cottonwood Canyon (LCC), Utah, where the ski resorts of Alta and Snowbird are located, traffic from eager skiers can be an issue and numerous avalanche paths endanger the highway. The UDOT avalanche safety team for LCC has their hands full every winter and employs the use of artillery and remote avalanche control systems (RACS) to mitigate avalanche hazards. UDOT has been using RACS for quite a few years, but was keen on trying out the Wyssen Tower, and the first tower in the US was installed in November 2017 in Cardiff Bowl, right across the canyon from Alta Ski Resort.

Figure 1. The first Wyssen Avalanche Tower in the US

After using the Cardiff tower for two winter seasons, UDOT is planning to install 12 more Wyssen Avalanche Towers to help protect the highway and town of Alta. After the installation, avalanche control that has historically taken upwards of an hour to complete by way of artillery is expected to be able to be carried out in only a handful of minutes. As avalanche control requires the closing of the road, clearing of adjacent backcountry areas and the securing of avalanche runout zones, traffic is often a major issue in the canyon. Decreasing the duration of road and backcountry closures can offer some much needed relief to the canyon’s recreational users, businesses and residents. Furthermore, because the systems have a relatively small footprint, are placed below ridgeline and have an unobtrusive tree-like shape, the visual impact on LCC is expected to be minimal compared to that of many other forms of avalanche control.

RACS are permanently installed structures, strategically placed to be able to trigger avalanches remotely. These systems detonate explosions to release an avalanche. Though there are already different types of RACS systems in the US, the Wyssen Tower in Utah is the first of its kind in the US. The Wyssen Tower consists of a steel tower supported by a small concrete foundation with a deployment box situated on the top of the tower. Charges are released from the deployment box via a web-based user interface. Once released, a charge will hang on a rope above the snowpack. Detonation above the snow allows the shock wave of the explosion to travel farther than if it had been buried in the snow and increases the effective range of the explosion.

Figure 2. The Wyssen Avalanche Tower

The tower is controlled remotely via an online platform and without the need for personnel in the field thus decreasing hazard to avalanche control teams. Avalanches can be released regularly to decrease the potential for large and destructive avalanches. For highway control, avalanches can be released at strategic times, such as very early in the day, and the road can be plowed in time for morning traffic.

The first Wyssen Avalanche Tower in the US promotes safer mountain conditions by protecting a section of highway in the LCC. Now that this technology in being used and expanded in Utah, in future years, there may be an increase of this technology in other avalanche prone states such as Colorado and California as well as in more locations around the world.

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Author: Roz Reynolds, US Project Manager, Wyssen Avalanche Control

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