To reduce congestion and increase the capacity on Stockholm’s local and regional rail network, a 6 km long underground railway line has been constructed beneath the city. Where the railway crosses the Söderström River, three 100 meter long, 20,000 tonne immersed tunnel sections complete the underground link between the islands Riddarholmen and Södermalm.

Prior to immersion of the tunnel elements, Proserve grout bags were fixed to pre-constructed piled and raft foundations by divers, some 20 meters below water level on the river bed. After the tunnel elements were leveled using temporary jack supports, the grout bags were pump filled with a highly fluid micro concrete to complete the permanent foundation bearings for the tunnel.