Lot KAT3 comprises the production of two tunnel tubes. While the conventional drill-and-blast and excavation methods were used to drive the south tunnel, the "KORA" tunnel boring machine was deployed for the north tunnel. The cross passages between the two tunnel tubes are being driven parallel to works on the south tunnel at intervals of 500m. The breakthrough of the south tunnel was achieved back in 2018.

Once fully operational, the Koralm Tunnel project part of a contract worth €297 million (US$333 million) will make it possible to travel from Graz to Klagenfurt by train in just 45 minutes.

With a length of around 33km, the Koralm Railway is Austria's longest rail tunnel and one of the most extensive tunnel constructions in the world.

"We are extremely proud to be part of this once-in-a-century project and to be able to demonstrate PORR's expertise in civil engineering, infrastructure and tunnelling. The tunnel breakthrough is a key milestone and a special moment for everyone involved in the project," said Karl-Heinz Strauss, CEO of PORR.

The Koralm Railway is a key project in the Baltic-Adriatic Corridor and links the up-and-coming economic areas on the Baltic Sea with the Adriatic region. The high-speed rail link will yield new capacities and significantly improve conditions for the transport of people and goods.