Part of the ceiling of a road tunnel collapsed on Saturday evening between Riddes and La Tzoumaz (VS). There were no casualties, but the road will be closed for months, if not years. A diversion has been put in place, but heavy goods vehicles are excluded, which will significantly complicate life in La Tzoumaz.
“It was not a concrete ceiling that fell, because it was a tunnel dug into the rock,” a spokesperson for the Valais police said on Sunday. The event, which did not cause any injuries, occurred around 6:30 p.m. on Saturday. About ten cubic meters have subsided.
The tunnel was closed for a period that is still unknown, but the Mobility Department estimates that the closure could last several months, or even several years. Cantonal engineer and head of the Mobility Department Vincent Pelissier estimates that the cost of the work could run into several hundred thousand, or even millions, of francs.
The tunnel, at almost 1100 meters above sea level, allows you to reach the Tzoumaz station, above Mayens-de-Riddes. A diversion is in place through Fey and Isérables, but only for light vehicles. Coaches and trucks cannot use it.
A diversion is in place through Fey and Isérables, but only for light vehicles. [RTS]
Heavy consequences for La Tzoumaz
The consequences are serious for La Tzoumaz, because tourist buses can no longer access the resort. At the tourist office, the phone doesn’t stop ringing: in a week, more than 8,000 vacationers are expected. But fortunately, the majority of customers are families who travel with their own vehicle.
However, the issue of garbage disposal will have to be resolved and the ban on access to trucks will also pose problems for the construction sector, for example.
This twist of fate highlights the need for new access to the station, such as the cable link project from Riddes. But it would be planned at best for 2028, indicates Christel Duc, the president of the municipality of Riddes.
In the meantime, public transport is maintained, via Riddes station, the Riddes-Isérables cable car, then by the bus from Isérables to Tzoumaz and vice versa. To further improve access to the station, the Cantonal Mobility Service intends to intensify the pace and increase the amplitude of public transport.
>> See the 7:30 p.m. report: La Tzoumaz difficult to access for months, following the collapse of a tunnel / 7:30 p.m. / 2 min. / yesterday at 7:30 p.m.
Causes still unknown
The tunnel built in 1968 was under surveillance. In mid-December, a landslide had already occurred a little further down. The causes of the collapse are currently unknown. But according to natural hazards engineer Guillaume Favre-Bulle, interviewed in RTS 12:45, “we have signs that it could simply be fatigue of the rock”. This is “a first hypothesis”, he says.
The cantonal engineer, Vincent Pelissier, believes that the unprecedented bad weather in December combined with the mild weather of recent days could play a role in the collapse. And the tunnel, which is more than 50 years old, was dug “into a geologically complex cliff”.
This event raises the question of securing mountain roads. Geologists expect more landslides to occur and it seems impossible to make everything safe. In Valais alone, there are around a hundred “hot spots” along the road network.
>> How to ensure the safety of mountain roads? Claudine Gaillard Torrent’s analysis: How to ensure the safety of mountain roads? The analysis of Claudine Gaillard Torrent / 7:30 p.m. / 1 min. / yesterday at 7:30 p.m. >> Images of the collapse filmed by a witness: Images of the collapse between Riddes and La Tzoumaz filmed by a witness (Images: Jean-Daniel Lambiel) / News on video / 16 dry. / yesterday at 4:10 p.m.
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