A variation of the final project was approved by the CIPE (Interministerial Committee for Economic Planning) in March 2018, following the Security Study conducted by the National Interuniversity Consortium for Transport and Logistics (NITEL), consisting of 20 Italian universities with over 500 researchers. According to this variation, and in order to ensure the safety of workers and citizens, the main activities for the construction of the base tunnel in Italy will start from the Chiomonte construction site (instead of from Susa as originally intended).

The site will expand by 4 hectares to a total of 12, extending under the viaduct of the A32 motorway to the municipalities of Chiomonte and Giaglione, in an area already used by SITAF during the construction of the motorway. At approximately 40 m from the first tunnel, a second one will be built parallel to the survey tunnel, having the same diameter as the base tunnel. During work, this will be the access point for the TBM which will begin boring towards Susa, while, once operational, the first section of the tunnel will be used for ventilation and smoke extraction for the base tunnel and as the Clarea safety site, and, in the second section, for the possible definitive storage of green rocks.

The construction of a safety site and of a ventilation centre for both the tunnel and this site is also planned. The centre is designed with a semi-underground solution, with terraces planted with greenery, and rows of vines and apple trees so as to integrate it seamlessly in the territory. It is foreseen to use materials such as weathering steel, wooden slats and local stone. The new configuration was deemed by the competent authorities to be the most suitable for ensuring safety while maintaining soil consumption to a minimum and limiting environmental impacts.