There was light at the Italian end of the world's longest railroad tunnel. An excavator recently broke through a wall separating two sections of the $9.6-billion Brenner Base Tunnel, creating a 24.1-km continuous bore from the south portal at Fortezza to the Austrian border at Brenner.

Since the machine driving the exploratory tunnel reached the border at Brenner in November, there is now a continuous bore in Italy. Both main Italian drives are due for completion by this year's end. Partly because of a contractual dispute, work in Austria is less advanced.

An excavator broke through the final portion of wall separating the two sections.
Photo courtesy Webuild

Excavating 5 km of both tubes southward from the Mules access tunnel took about 3.5 years, according to BBT SE, the project company jointly owned by Austria and Italy. Meanwhile, another team dug the final 500 m from the south portal, with the twin bores breaking through by May 19.

Work on the short southernmost Isarco River underpass contract is just over 80% complete, according to the consortium of Webuild S.p.A, Strabag A.G., Strabag S.p.A., Consorzio Integra and Collini Lavori S.p.A.. It won the $320-million contract in October 2014.

The longer twin drives on Mules contract to the border are due to break through around the end of this year, according to a BBT spokeswoman. The "Mules 2-3" contract covers the whole program’s most tunneling, totaling around 65 km, according to BBT. That includes 39.8 km of main drives and 14.8 km of exploratory tunnel.

Excavation took about 3.5 years on the Brenner Base Tunnel section where the breakthrough occurred.
Photo courtesy Webuild

BBT awarded in September 2016 the seven-year, $1.1-billion contract to a consortium including Astaldi S.p.A., which was since acquired by Webuild. Other consortium members originally included Ghella S.p.A., Oberosler Cav Pietro S.r.l., Cogeis S.p.A. and PAC S.p.A.

The consortium's tunneling machine Serena completed the exploratory drive to the border after 3.5 years' work in November. Two other TBMs have 4.4 km to complete on the west bore and 2.2 km on the east.

Once completed in 2032, the tunnel will run for 64 km between Innsbruck, Austria and Fortezza, Italy.
Photo courtesy Webuild

Austrian progress hit a major snag in late 2020 when BBT cancelled the contract covering about 25 km of tunnels on the Pfon-Brenner section in a dispute over the tunnel’s segment system.

Valued at $1 billion when signed in April 2019, the original 74-month contract went to a consortium of PORR Bau GmbH, G. Hinteregger & Söhne Baugesellschaft m.b.H., Società Italiana per Condotte d’Acqua S.p.A., Itinera S.p.A.

The owner called for new bids this January, aiming to award a 69-month contract by this year's end. Running for 64 km between Innsbruck, Austria and Fortezza, Italy, twin 8.1-m-dia tunnels, set 40-70 m apart, will form the world’s longest underground railroad that is set to open in 2032, according to BBT.