The Grand Tunnel du Chambon re-opens

After two years of work, the connection between Isére and Hautes Alpes is open

Imprint: By Ian Huyton, Updated 2 January 2018

The tunnel is a vital link between the northern and southern French Alps. It allows visitors to reach Alpe d’Huez and Les Deux Alpes from Briançon or Italy, as well as connecting La Grave and Serre Chevalier to Grenoble and Lyon airports.

The road closed in April 2015 following significant movements being detected in the rock the tunnel was drilled through. The closure meant many people were unable to travel to work and children could not attend school. Initially, people had to walk for around 40 minutes on mountain paths to bypass the tunnel, and arrange for transport to meet them on the other side. Within a few weeks, a water taxi service had been put in place on Lac Chambon, the lake that the tunnel runs alongside.

In July 2015, geologists predicted that a large section of mountainside around the tunnel was due to slide into the lake. The water taxis were suspended due to fears of a resultant tidal wave and a helicopter shuttle was organised for essential workers. The huge landslide never materialised but several smaller rockfalls deposited significant amounts of rock into the lake.

By December, a relief road had been completed on the opposite side of the lake. This allowed light traffic to bypass the tunnel, providing the avalanche risk was not too great. At the same time, work began on re-routing the tunnel. The new section was drilled deeper into the mountain to pass behind the unstable rock and emerge further up the valley.

The tunnel opened temporarily from December 2016 to March 2017 and for a few weeks in summer of 2017. On each occasion, it closed after the holiday period finished to allow work to continue. These temporary openings were restricted to light traffic and coaches.

Earlier this week, the tunnel finally re-opened permanently. All works have been completed and the road is open to almost all traffic. Vehicles up to 26 tonnes can use the route unless carrying hazardous materials. Local residents on both sides will be relieved that the longstanding disruption to their lives and businesses is over.

Read more from our reporter Ian on his website.

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