Modernisation of the Saane Viaduct and dual-track expansion of the Mauss–Gümmenen section
Since 1901, the Saane Viaduct has straddled the River Saane and the wide valley plane. It is one of BLS’s most spectacular listed structures. The company wants to adapt the viaduct to modern-day requirements and preserve its history by comprehensively modernising it. In addition, BLS is planning to expand the entire section between Mauss and Gümmenen to two tracks.
The Saane Viaduct on the Bern–Neuchâtel line is over 115 years old. As one would expect of such a venerable structure, the brickwork shows signs of frost and joint damage that now needs repairing. The viaduct’s existing trackbed, which was installed between 1958 and 1980, also shows defects in its waterproofing, which is causing more water to permeate into the brickwork. The steel-frame bridge has also reached the end of its service life. To ensure that the viaduct continues to meet the standards of a high-performance infrastructure, BLS is completely modernising it whilst simultaneously expanding it to two tracks. The company is thereby completing the continuous dual track on the Bern–Gümmenen section. The project has projected costs of 45 million francs.
An architectural monument of national importance
The 400-metre-long structure comprises a viaduct made of natural stone and a steel-frame bridge that cross the valley floor and the River Saane. The Gümmenen side also features a 450-metre-long dam.
The viaduct stands as testimony to the developments in industry and transport technology at the close of the nineteenth century, and is catalogued as a listed structure in the canton of Bern’s architectural inventory. As a significant element in the landscape of Saanetal, the entire viaduct is a monument of national importance and great historical and cultural significance.
To ensure that, among other things, the dual-track expansion does not negatively impact the viaduct’s aesthetic value, BLS has worked with the Federal Commission for Monument Preservation (FCMP) and the Federal Commission for the Protection of Nature and Cultural Heritage (FCNC) to determine the framework conditions. The best version was then selected as part of a commissioned study.
The winning project was selected in 2013. BLS is very pleased with the selection, as the project ideally combines the character of the original structure with all the requirements for an innovative and modern infrastructure.
- The most distinctive change is the new steel-and-concrete bridge with framework struts of varying angles over the Saane. Otherwise, the character of the viaduct will be largely preserved. Because the existing steel-frame bridge has reached the end of its service life, it would have needed replacing by 2025 even without the dual-track expansion.
- The viaduct’s pillars and arches will be repaired and freshly waterproofed at the top.
- The 450-metre-long dam on the Gümmenen side (west) must be widened, and therefore have fresh rock added so that a second track can be installed.
- Five pillars on the Mauss side (east) will also be widened for the dual track.
- Also on the eastern side, the indent in the hillside must be enlarged to make room for the second track. To achieve this, part of the hillside must be removed.
- The concrete trackbed on which the track rests will be removed and replaced with a wider trackbed for the dual track. The new trackbed will lie across the entire 400 metres, i.e. across the 22 stone arches, the new steel bridge and the five additional stone arches on the eastern side of the River Saane.
BLS is utilising synergies with a neighbouring project
BLS operates not just commercially but also sustainably, and wants to make careful use of the available resources. That is why it is planning the work in such a way that important synergies with a neighbouring project can be utilised. To the east of the Saane Viaduct lies another major BLS construction site: the construction of the new dual-track Rosshäusern Tunnel, which will become operational in 2018.
For an environmentally friendly project, BLS is utilising the following synergies:
- A certain amount of gravel was already reserved at Mädersforst gravel pit during the “Rosshäusern Tunnel” project for the embankment work on the dam of the Saane Viaduct. The embankment work on the damn serves to prepare it for the construction of the second track.
- As soon as the construction installations surrounding the Rosshäusern Tunnel have been removed, this freed-up consignment of gravel can then also be used for the Saane Viaduct during the dismantling of the installation sites and construction-access trails on the Rosshäusern Tunnel project.
- The area around the old Rosshäusern Tunnel will be ecologically restored. Because the dual-track expansion on the Saane Viaduct also requires trees to be felled, BLS has already selected areas for reforestation in this ecological restoration area.
What will the project achieve?
An architectural monument of national importance will be preserved, whilst simultaneously being upgraded with cutting-edge technology.
For passengers, the dual-track expansion means more punctual trains on the Bern–Neuchâtel line; for BLS, it means an increase in operational flexibility. With a longer dual track, trains travelling in opposite directions no longer have to wait for one another to pass. Delays thus take longer to affect other trains. This is important for the future service at 30-minute intervals of the RegioExpress between Bern and Neuchâtel.
The travel time between Bern and Neuchâtel will be reduced, as trains will be able to travel this section at speeds of up to 160 km/h rather than 90 km/h.
The dual track enables BLS to offer any future expansions in its service along this line without any difficulties.