Avalanche protection in Norway
In Norway, avalanche protection has traditionally been carried out with permanent measures such as tunnels, dams, snow sheds or snow fences. These measures are very effective, but the investment and running costs are often very high and the environmental impact is considerable. Active temporary measures, such as preventive avalanche control, have only been applied by the Norwegian Public Road Administration operationally in isolated locations, mainly with manual bombing ropeways. None of these locations have had a day-to-day operation, so the avalanche control has often been performed on fixed dates or after an avalanche has released in a nearby area.

Testing Wyssen Avalanche tower at Fv. 53 Tyin – Årdal
In 2010 the Norwegian Public Road Administration (NPRA) decided to test a Remote Avalanche Control System (RACS) at the county road 53 Tyin – Årdal in Oppland County. A Wyssen Avalanche Tower was installed in one of the many avalanche paths threatening the road to test out whether the system would perform in tough Norwegian winter conditions with strong winds, low temperatures and almost no daylight during the winter months.

Over the two years, all charges where successfully ignited, and a total of 12 avalanches was triggered. Yet, a very strong storm (Dagmar) in late December 2011 damaged the wind generator in the deployment-box, leaving the system unable to charge the batteries in the beginning of January in this period one natural avalanche released and covered the road. This event highlighted the need for preventive avalanche control in the area. At the end of January there was enough sunlight for the solar panels to sufficiently charge the system. A new and more robust wind generator has new been tested and will be installed on future installations.

The biggest challenge during the test-project was that the responsible person for the project was stationed in Bergen, about 250 km away from the test location. This made the task of monitoring the local conditions challenging. One of the main conclusions of the project was therefore that a local avalanche control operation is necessary if preventive avalanche control with RACS would be used to protect the road in the future.

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Wyssen Avalanche Tower at Fv. 53 Tyin - Årdal during the test project.

Economy and cost-benefit analysis
Fv. 53 has very low traffic numbers with about 300 cars per day. Even so, the road is very important for the community in Årdal and local businesses like Hydro Aluminum. The main road from Årdal, going west towards Lærdal, is exposed to many natural hazards such as avalanches and rock fall. If this road is closed, Fv. 53 is the only alternative traffic route. There are also many cabins in the area, which are used frequently during the winter season.

The original plans for avalanche protection by a tunnel and road alternation had an estimated cost of about 500 mill. NOK. NPRA calculated that by protecting the dangerous areas with RACS, the investment cost would be 95 % lower. The conclusion from the test project stated that a local avalanche control operation was necessary in addition to the investment of RACS.

Because of the low traffic numbers, a cost benefit analysis was carried out by SINTEF and NPRA in the summer 2014. The original project with tunnel and road alternation (Alt 1) was compared to the alternative solution with 13 RACS and a local avalanche control operation (Alt 2). The analysis showed that over a 40-year period, Alt 1 would have a negative cost-benefit of about 372 mill. NOK. Alt 2 would have a positive cost-benefit of about 70 mill. NOK over the same 40-year period.

Public tender for RACS at Fv. 53 Tyin – Årdal
In late January 2016 NPRA published a public tender for the purchase of 13 Remote Avalanche Control Systems, including 5-year service and delivery of explosive material. The suppliers were also asked to deliver a concept for operational avalanche control. The award criteria were 70 % price and 30 % quality.

For the quality part of the award criteria, the suppliers had to consider a variety of aspects, such as environmental impact, user interface, expected lifetime, access for repairs and re-loading, the need for external power supply and much more.

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Wyssen Avalanche Control Center, WAC.3: The web-based user interface used to control and monitor the Wyssen Avalanche Tower.

To document the effect of the system, Wyssen a viewshed analysis for each of the 13 locations has been carried out. This analysis was included in the offer and showed that all the expected release areas were covered by the effect of the system. In a couple of the locations it also became evident that the effective range would overlap between two or more towers. After signing the contract, the viewshed analysis was used to optimize the tower locations, and after an additional site inspection, some of the locations were changed to ensure the best possible effect of the system.

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Viewshed analysis of 4 avalanche tower positions (red stars) in three release areas. Red indicates terrain affected by the effective range and blue indicates overlapping effect from two or more towers.

Construction
The construction of the foundations started in July and were finished in August. The start-up was done in November so the whole system can be handed over to the Norvegian Road Authority on time by the 1st of December 2016.

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