“Gaia” achieves its first kilometre of excavation on the Collettore Mediano of Turin

14 November 2025

On 13 November, the mechanical boring machine Gaia reached the milestone of its first kilometre of advance in the excavation of the main tunnel of the Collettore Mediano of Turin, a strategic infrastructure serving the Piedmontese capital and twenty municipalities of the Metropolitan City.
The TBM will excavate a total of 9.5 km of tunnel, crossing heterogeneous soil layers more than 10 metres below the water table.

A site visit to the excavation front was held in the presence of the Mayor of Turin and of the Metropolitan City, Stefano Lo Russo, together with SMAT’s top management  as well as representatives of the construction companies Itinera and Ghella, operating together within the COLMETO Consortium.

“It is fascinating to see the progress of a project that is barely visible from the surface yet so important for Turin and twenty metropolitan municipalities,” said the Mayor of the Metropolitan City and of Turin, Stefano Lo Russo. “The works are proceeding according to schedule and will provide the area with a more modern and safer infrastructure, helping to mitigate the impact of increasingly severe weather events.”

Gaia, a Mix Shield TBM with a diameter of 4.08 metres, installs a ring-shaped lining made of six reinforced-concrete segments. Its cutterhead is equipped with 18 disc cutters.
Commissioned on 3 June, the TBM is advancing at a depth of 20 metres. With a total length of 163 metres, it operates on three daily shifts and achieves an average excavation rate of 20 metres per day. The project involves more than 400 people including operators, technicians and associated services.

The Collettore Mediano will serve Turin and twenty municipalities in the southern and western metropolitan area—among them Beinasco, Moncalieri, Nichelino, Orbassano, Piossasco, Rivalta di Torino, Santena, Trofarello and Vinovo—improving hydraulic safety and enhancing the resilience of the metropolitan sewerage system.

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