Significant water ingress forces Lötschberg refurbishment

23 July 2020

Completed in 2007, the 34.6km Lötschberg Base Tunnel, Switzerland continues to see ‘unexpected’ water ingress which operator BLS is seeking to address as soon as possible to prevent deterioration. A mix of sand and water from mountain run-off have forced the company to submit construction plans to the Swiss Federal Office of Transport for approval.

In a bid to maintain long-term operational safety of trains passing through the tunnel, BLS plans a US$16.2m refurbishment in the eastern bore of the 14km twin-bore section. It wants to excavate a cavern adjacent to the tunnel which will house a 2,000m3-capacity sedimentation tank to intercept the inflows. Run-off will be diverted to the Raron portal while the sand deposited in the tank will be removed periodically by rail.

The new proposals follow the emergency measures instigated in February and March when sand was washed into the eastern bore, forcing its closure. BLS installed three steel sedimentation tanks which are currently emptied on a weekly basis. A similar but less significant incident in the western bore on March 13 has seen no further recurrence.

During the four-month construction period from September 2020 to December, the eastern bore will be closed with trains diverted to the western bore tunnel.

The Lötschberg Base Tunnel is one of the three key components of the New Rail Link through the Alps (NRLA). The Gotthard Base Tunnel and the Ceneri Base Tunnel (currently under construction) are the other two.