Semmering base tunnel (lots 1.1. and 2.1.)

The planned Semmering base tunnel (SBT) constitutes one of the most important major infrastructural projects currently being carried out in the heart of Europe. The tunnel forms part of the new Austrian southern railway line that runs from the Baltic Sea to the Adriatic coast, making it a key trans-European route. With a total length of 27.3 kilometres, the SBT connects Lower Austria with Styria.

In 2014, Implenia was co-contracted by site owner ÖBB-Infrastruktur AG to construct the 13-kilometre-long "Fröschnitzgraben" middle tunnel section (lot 2.1) together with Swietelsky in the ATF working group. Along with Hochtief and Thyssen Schachtbau, Implenia was also assigned lot 1.1, the approximately 7.5-km-long "Gloggnitz" tunnel section.

SBT lot 2.1, which requires TBM work (8.6 kilometres) and mining activities (4.3 kilometres), consists of 26 cross passages, an emergency stop bay and two ventilation shafts at over 400 metres deep that are designed to serve the entire construction site. The contract is valued at around EUR 623 million (approx. CHF 770 million; share of CHF 385 million for Implenia). Overcoming the geological conditions in the drilling region constitutes a major challenge of this large-scale project. The provision of building materials and the transportation of excavated rock away from the building sites are also complex undertakings. Work has been underway since summer 2014, with a planned completion date of 2024.

SBT lot 1.1 – the easternmost section of the three construction lots – consists of the construction of two single-track tunnels. These tunnels are being cyclically excavated from the entrance at Gloggnitz and the Göstritz access adit, and are connected via 16 cross passages, a machinery tunnel and two logistics galleries. The intermediate access adit consists of an entrance tunnel and two 450-metre-deep shafts. The work is highly complex: in addition to the construction of tunnels, shafts, superstructures and roads, the project comprises slope stabilisation, earthworks, asphalting, concrete ceilings, drainage channels and pipelines. Landscaping activities and maintenance are also required. The volume of work is valued at EUR 457 million (approx. CHF 480 million). As part of the working group with Hochtief and Thyssen Schachtbau, approximately 40% (CHF 192 million) has been allotted to Implenia, which is coordinating the technical and engineering work. Work started in summer 2015 and will continue until 2024.


Divisions performance

  • Contract value: CHF 1,250 million
  • Construction period: 2014 - 2024
  • Length: 28,000 m