Refurbishing of the eastern bore of the Lötschberg Base Tunnel
No more sand in the Lötschberg Base Tunnel
Following an event of water and sand ingress in the eastern bore of the Lötschberg Base Tunnel, BLS is refurbishing the affected area. It is excavating a large cavity to the side of the bore so that sand can be deposited there in future.
In February and March 2020, water and sand were washed into the dual-track section of the Lötschberg Base Tunnel. As a result, the tunnel’s eastern bore had to be temporarily closed to trains three times in succession. As an immediate remedy, BLS installed a steel sedimentation tank in the affected area of the tunnel bore. As an additional measure, the company is now excavating a cavern outside the tunnel bore, into which the water can run off and the sand be deposited.
Why did sand enter the tunnel?
How BLS is refurbishing the affected area
In the affected area, BLS is excavating a cavern to the side of the eastern tunnel bore and installing a sedimentation tank there with a 2,000-cubic-metre capacity. The mountain runoff flows into this sedimentation tank; any sand is then deposited as sediment and the purified mountain runoff diverted to the Raron portal. The cavern and its tank are similar to an indoor swimming pool – there is therefore plenty of space for the sand to settle. As part of the regular maintenance work in the tunnel, the deposited sand can in future be removed from the tunnel in rail wagons. Based on current plans, the cost of the refurbishment will be around 15 million Swiss francs.
With the refurbishment project, BLS developed a good solution within a short period of time which can be implemented before the next snowmelt in the spring of 2021, thus significantly reducing the risk of more sand entering the tunnel. However, residual risks cannot be entirely eliminated because karst is unpredictable. If the situation inside the mountain changes and much more sand than expected is washed into the sedimentation tanks next to the eastern bore, BLS can expand the cavern.