For Implenia, the Lückenschluss project has involved building two parallel tunnel bores, each 1.7 km in length, as well as a track-switching system and the shells of the Unter den Linden and Museumsinsel stations. Experts from various Implenia divisions have been working together on this extremely demanding major project since 2012 under the technical direction of Peter Hoppe. Implenia was able to hand over the Unter den Linden station, tunnel bores and track-switching system to the BVG at the end of 2017. Another key milestone followed in February 2020 with the shell construction of Museumsinsel station. One of the big challenges was the fact that this station lies directly below the Spree Canal, the historic Schlossbrücke bridge and the Bertelsmann Building. The solution was for Implenia’s special foundations experts to freeze 28,000 m³ of the subsoil – the largest ground-freezing ever undertaken in a European city centre. Only when the protective ice-shield was in place could the tunnelling commence for the creation of the platform area and station tunnels. Museumsinsel station is scheduled to open in summer 2021; until then, trains will pass through it without stopping. As a final major feat of engineering, the diaphragm wall that temporarily enclosed the building pit by the Spree Canal and facilitated the shell construction of Museumsinsel station, was broken up into individual pieces weighing up to 30 tonnes, gradually lifted out by a truck-mounted crane and taken away. This work finished in summer 2020.

“We at Implenia are extremely proud to have successfully completed a construction project of this magnitude. My thanks go to everyone involved in the project; their commitment and tireless effort made this success possible. We’d particularly like to thank BVG Projekt GmbH for their confidence and for their cooperation throughout the whole construction period,” said Henning Schrewe, Head of Civil Germany at Implenia.

The new east-west line between the Hönow terminus and Berlin Hauptbahnhof will provide an estimated 150,000 passengers a day with many additional direct and connecting routes. It will also help make mobility within the capital more sustainable by cutting the number of car journeys in the centre of Berlin by around 3,500 a day. “By closing this gap in the network we are creating an additional attractive public transport service in Berlin. We’re pleased that we were able to achieve this goal together with Implenia as our partner,” says Jörg Seegers, Director of Engineering, BVG Projekt GmbH.