Auerberg tunnel: Construction work with violent cost and time problems!

Auerberg tunnel: Construction work with violent cost and time problems!

The construction work on the Auerberg tunnel in Oberau are in default and will probably not be completed before 2030. Originally, an completion date was aimed for in the current decade, but now it turns out that the challenges in building in this alpine area are larger than expected. The project manager of Autobahn GmbH, Christian Schauer, described the current situation on a construction site tour.

A complex interplay of geology and unstable soil has ensured massive delays. The slope on which the Auerberg tunnel is to be created turned out to be problematic, which led to a conversion of the original plans. "We had up to 20 centimeters of movement in the field," said Schauer, which meant a high risk of the safety of the construction work. In order to counteract this problem, extensive slope protection measures had to be taken that use many resources.

Technical challenges and slope security measures

During the security work, hundreds of steel nails were driven up to 15 meters into the mountain, while anchors of up to 50 meters were used to stabilize the slope. These comprehensive measures not only cost time, but also significantly more money than originally planned. The total construction costs are now estimated at around 240 million euros, which represents an increase of over 30 percent compared to the original calculation of 2020. Originally, 167 million euros were planned.

Another central problem is the drainage bores that are necessary for pressure regulation in the building ground. As Schauer explained, they had applied for approval for this over a year ago at the district office, which has so far been long in coming. As a result, the construction work had to be stopped for four weeks last month. "The approval should come soon," the project manager hopes optimistically.

Planned construction progress and time frame

Work on the future southern portal of the tunnel now reaches the decisive phase, while there are currently little progress on the north end. The stabilization of the moss floor has not yet been fully completed, which slows down the construction work. "In April or May next year, things should continue there with strength," said Schauer. The preparatory work for the tunnel attack is currently taking place on the motorway side, the beginning of which is planned in autumn 2025.

The tunnel is built with two tubes and the propulsion is carried out in parallel but slightly offset. The entire completion of the project is expected to run over several years, with a complete degree between 2030 and 2031. Additional construction measures that affect the new state road and the connection to the existing B2 and the A95 are also part of the overall project.

These delays and the cost explosion are in a strong contrast to the initial assumptions and have already led to tense discussions about the financing strategy. The multitude of challenges also seems to be a lesson for future projects, especially in view of the problems that have occurred in the Kramert tunnel.

The Auerberg tunnel will not only be important for the traffic connection of the region, but also represent a sign of the challenges in tunnel construction under extreme geological conditions.