08/22/2025

Brenner Base Tunnel: First TBM breakthrough in a main tunnel tube in Austria

TBM Ida completes 8.4 kilometres of excavation in the Brenner Base Tunnel and reaches its target in the municipality of Navis (Wipp valley).

An important milestone for the cross-border railway infrastructure project, the Brenner Base Tunnel: After about 26 months of steady work, the tunnel boring machine (TBM) "Ida" has successfully achieved the first breakthrough of a main tunnel tube in the Austrian project section. The breakthrough point is located within the municipality of Navis (Wipptal), in the existing auxiliary drivage "Iris", which adjoins construction lot H53 Pfons-Brenner. In modern tunnelling, an auxiliary drivage is an important additional measure that supports the excavation of the main tunnel and secures the respective tunnel section in advance.

Since its launch in June 2023, Ida has cut through 8,400 metres of rock in the H41 Sill Gorge-Pfons construction lot. Ida is a tunnel boring machine (TBM) measuring approximately 160 metres in length, weighing 2,420 tonnes and with a cutter head diameter of 10.4 metres. The excavation started from the Ahrental project section near Innsbruck in the western main tunnel tube heading south and ran, in part, through geologically extremely challenging zones.

BBT CEOs Martin Gradnitzer and Gilberto Cardola are delighted: "Following the arrival of the last Italian TBM at the Brenner border a few months ago, Ida's breakthrough now marks another key project milestone on the Austrian side".

Several complex geological fault zones posed particular technical challenges - in particular the well-known Viggar valley and "Walzn" zones and the approximately 35 metres thick "Werner" zone, which were successfully traversed at the beginning of 2025.

Romed Insam, project manager for the Sill Gorge- Pfons construction lot, emphasises: "The successful overcoming of these challenges is thanks to a great team effort by the consortium, all service providers, suppliers, and BBT employees".

Harald Goldberger, Technical Managing Director of the construction company Implenia for the H41 construction lot, adds: "The team of the H41 consortium is delighted with Ida's successful breakthrough after around two years of hard work. We would like to thank BBT SE, the contracting authority, for placing their trust in us, and we wish everyone involved further success".

Judith Engel, patroness of the tunnel boring machine "Ida", member of BBT SE Supervisory Board and CEO of ÖBB-Infrastruktur AG: "Another step for one of Europe's most important transport axes has been successfully taken with the arrival of the TBM. Congratulations to the project team on their excellent work! With the Brenner Base Tunnel and its access routes, we are creating reliable and future-proof infrastructure for generations to come".

"Ida": A meaningful name
In 2023, the TBM was christened 'Ida' by children at Navis Elementary School - the machine was named after a calf on one of the students' farms. The name symbolises diligence and hard work. The children accompanied 'their Ida' throughout the entire project. At the end, they were even allowed to put their own designs on one of the last tubbing segments - precast concrete elements used to line the tunnel wall.

Looking ahead: TBM Lilia scheduled to arrive in autumn
Ida's twin sister, the TBM known as Lilia, is expected to break through in the eastern main tunnel tube in autumn 2025. This completes the TBM excavation in the H41 'Sill Gorge-Pfons' construction lot- another major step towards the completion of the Brenner Base Tunnel.

Excavation work is continuing southwards

The main focus is now on the exploratory tunnel. On 18 September 2025, the first cross-border underground connection between Italy and Austria will be celebrated: a historic milestone for European mobility.

Key data on TBM Ida