The twin-bore tunnel will be connected every 500m by transverse tunnels. Due to the geological and hydrological conditions and the shallow depth to a maximum of 20m, construction is considered technically challenging. DB says by using special materials and measures such as temporary embankments, soil stabilisation or soil freezing, "the most difficult sections are absolutely manageable."
Work will start in November to prepare for the arrival on site of tunnel boring machines in April 2015, which are expected to start drilling in October 2015. The tunnels should be bored though by the end of the first quarter of 2018.
DB plans to invite bids in March 2015 for a contract to fit out the tunnels. This work will be completed in 2020 followed by testing to allow trial running to start in 2022.