Ambo and Caïros bridges installed in La Roya valley
Two imposing steel bridges have been installed over the Roya River, in the French commune of Breil-sur-Roya, two years after ‘Storm Alex’ destroyed the village’s original stone passages.
The two steel structures were supplied by the Italian civil engineering company BIT spa, in collaboration with Eiffage Génie Civil Méditerranée. The Ambo bridge is 75 metres long and made of 530 tonnes of steel, while the Caïros bridge is 55 metres long, and made of 350 tonnes of steel. The bridges were designed without any central pillars in the river bed, in a “bow-string” model. They will also be raised higher above the riverbed to increase resilience to inclement weather.
Built in Italy, the two prefabricated structures were brought to the site by road, while disassembled. They were then reassembled on a dedicated staging area on the edge of the RD 6204 road, to allow traffic to continue, in parallel with the foundation building. Once assembled, the bridges had to be positioned in the axis of their future location and slowly moved by means of self-propelled trolleys with temporary supports placed in the Roya to avoid parasitic stresses in the hangers. Each operation, conducted over two nights, took just over 12 hours, and approximately 50 workers.
Of the 200 million euros borrowed by the Alpes-Maritimes departmental council for the project, 100 million are provided by the French state, and 20 million euros by the Provence-Alpes-Côte d’Azur région. Several more months will be needed to rebuild the road. The bridge should be fully operational in January 2023. In the meantime, locals will continue to use a temporary wooden passage.
You can watch a simulation of the construction process here: