First milestone of the Turin Median Collector: TBM “Gaia” reaches the intermediate shaft near city's Monumental Cemetery

One year after excavation began from Arrivore Park and after travelling 2.7 km beneath the city, TBM “Gaia” today reached its first intermediate milestone, completing its arrival at service shaft PZ030, located near Turin’s Monumental Cemetery.

The machine is constructing one of the most important strategic infrastructures for the Turin metropolitan area: the Turin Median Collector, a fundamental work for the territory’s hydraulic system.

Excavation activities are carried out by the highly specialised personnel of Colmeto Scarl, a consortium composed of Itinera S.p.A. (lead partner with 51%) and Ghella S.p.A. (49%), two leading companies in the construction sector.

The new collector, with a total length of 14 km, of which 9.5 km of tunnel will be excavated using a TBM, develops through heterogeneous ground conditions at a depth of approximately 20 m and more than 10 metres below the groundwater table. With the achievement of this first objective, progress on the main tunnel has reached approximately 30% of the total.

The mechanised excavation technique adopted for the Hydro-Metro involves the use of a Hydroshield (HS) TBM with a diameter of 4.08 metres. The machine installs a segmental lining consisting of rings, each composed of 6 reinforced concrete segments.

Commissioned on 3 June 2025, the TBM advances at an average speed of approximately 3 cm/min during excavation operations.

During the first 2,700 metres of excavation, the team encountered particularly complex geological conditions, characterised by the presence of extremely heterogeneous and highly abrasive materials. To date, these conditions have required more than 80 hyperbaric interventions for maintenance of the cutterhead, with operations carried out at a working pressure of 1.5 bar.

The arrival of the TBM at the intermediate shaft was attended, among others, by the senior management of SMAT and of the companies involved in the construction of the project.

The Median Collector, in addition to directly serving the City of Turin, will also serve 20 municipalities in the metropolitan area to the south and west of the Piedmont regional capital: Beinasco, Bruino, Cambiano, Candiolo, Chieri (Pessione), La Loggia, Moncalieri, Nichelino, Orbassano, Piobesi Torinese, Piossasco, Poirino, Riva presso Chieri, Rivalta di Torino, Sangano, Santena, Trana, Trofarello, Villastellone and Vinovo.