The south portal of the Hauenstein base tunnel near Trimbach around 1915 during tunnel construction

SBB to revamp century-old Hauenstein Base Tunnel

The south portal of the Hauenstein base tunnel near Trimbach around 1915 during tunnel construction SBB

Swiss railway manager SBB will renovate the Hauenstein base tunnel starting this summer after two postponements. Repairing the tunnel vault, renewing tracks and cables and improving drainage should guarantee safe, trouble-free rail operations in the tunnel over the next 25 years. The cost forecast for the project is currently around 140 million Swiss francs (142 million euros).

The Hauenstein Base Tunnel was built between 1912 and 1916. The tunnel is 8,134 kilometres long and is part of the Basel–Olten railway line, crossing the Jura mountain range between Tecknau and Olten. In 2019, an average of around 100 freight trains and 320 passenger trains used the two-lane tunnel every day.

The last extensive renovation work on the tunnel was carried out from 1980 to 1987. Since then, SBB has regularly carried out selective maintenance and renewal work. Now “major service” is necessary again, however.
SBB will start the works on the night of Sunday, September 3rd, to Monday, September 4th, 2023. From then on, SBB will renovate the tunnel vault and the technical systems at night. For this, closure of one lane in sections are necessary, which will happen from Sunday night to Friday morning and last from around 10:15 p.m. to 5:45 a.m. each night. This work will last until autumn 2026, with interruptions in the summer and at the end of the year.

The location of the Hauenstein base tunnel, © swisstopo © OpenStreetMap © SBB/CFF/FFS 08/2020

Next to repairing the tunnel vault, renewing tracks and cables and improving drainage, SBB will build a new emergency basin in Tecknau and Trimbach. These will enable more wastewater to be retained in the event of incidents in the tunnel than with the existing shaft solutions. SBB is also adapting various technical installations, including the ventilation shaft in Zeglingen.

Traffic impact

For the train traffic that relies on the tunnel, the renovation has its impact on the timetable. In long-distance traffic and on the S3 line (Olten–Basel SBB–Porrentruy), at times there will be earlier departure times and longer travel times. On the S9 line (Olten-Läufelfingen-Sissach), the last two pairs of trains (Olten from 9:37 p.m. and 10:37 p.m. / Sissach from 10:05 p.m. and 11:05 p.m.) will be replaced by buses from Sunday to Thursday.

The overhaul also includes renewing the tunnel tracks, for which a full tunnel closure is necessary. This will take place during five weeks in the summer vacation periods in 2024, 2026, 2027 and 2028. No summer closure is possible in 2025, partly because of the five-month total closure of the Laufental line.

During works in 2015, the Hauenstein base tunnel was also closed for the renewal of the points

On some weekends, a total tunnel closure is also planned, starting in autumn 2024. During these closures, both tunnel tracks will be closed day and night. SBB then carries out work on the switches or particularly exposed areas in the tunnel.

Delay of the works

SBB’s initial plan was to begin construction on the tunnel at the start of January 2023. However, on July 22, 2022, an unsuccessful bidder filed an appeal against the award of the construction contract with the Swiss Federal Administrative Court (FAC). In a first step, the court examined whether SBB had to wait with the start of construction until the court definitively decided on the appeal. Due to the pending decision, SBB had to postpone the start of construction twice – in December 2022 to January 30, 2023, and then at the end of January to the current starting date: September 2023.

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Author: Esther Geerts


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