Hochstegen: after the Isarco River Underpass, another construction lot of the Brenner Base Tunnel is completed before Christmas 2023

Innsbruck/Bolzano, 15 December 2023

The construction work in the 'H52 Hochstegen' lot, near the Brenner border, was completed on schedule, just a few days after the end of construction in the 'H71 Isarco River Underpass' lot, in Italy.
Both the construction lot in Austria and the Isarco River Underpass were complex and challenging. This tunnel section crosses the so-called "Hochstegen" geological fault, characterized by strong water-bearing layers of carbonate rock.

For this reason, in addition to the excavation of the tunnel through the fault zone, consolidation and support measures had to be implemented during the 23 months of construction to allow the tunnel to be built safely.

"With a total of five kilometres of tunnels, the construction lot was not very large," explains project manager Michael Knapp. "However, it was very challenging to drive through the water-rich carbonate rock layers, where more than 900 metres of exploratory tunnel had to be dug in the direction of the Brenner Pass."

Project manager Michael Knapp sees the end of construction as another milestone for the BBT project: "Although the geological conditions were extremely challenging, we managed to complete the project on schedule. Our thanks go to the construction company responsible and especially to the miners, who did an excellent job under these difficult conditions. This result gives us confidence in view of the start of work on the H53 Pfons-Brenner construction lot."

The members of the Board of Directors of the project company BBT SE, Martin Gradnitzer and Gilberto Cardola, welcome the completion of a further tunnel section this year, after the Isarco River Underpass: "In this section, the exploratory tunnel came to just under two kilometres from the Brenner state border. With the continuation of the work, and after the breakthrough between the Italian and Austrian sections, there will for the first time be a seamless connection between the two countries".

Changeover from building plot H52 to building plot H53
At the end of 2023, the baton will immediately pass to the next construction company, responsible for the new 'H53 Pfons-Brenner' lot.

Project data for the H52 Hochstegen lot
Drill&Blast excavation of 5 km of tunnel:
Construction of approximately 3.2 km of main tunnels
Excavation of 0.9 km of interconnecting tunnels and cross passages
Excavation of 0.9 km of exploratory tunnel

Contract value: approximately EUR 102 million
Construction time: approx. 2 years

Scope of benefits

Cross-over point: construction of three secondary chambers and two interconnecting tunnels at the level of the main tunnel
Hochstegen Zone: crossing the transition zone from the Graubünden schist to the central gneiss (Triassic zone and Hochstegen marble at the level of the exploratory tunnel and at the level of the two main tunnels)
Excavation volume: approx. 400,000 m³
Total injection volume: 4,000 m³
Contractor: Swietelsky Tunnelbau