GERMAN FOUNDATION contractor Bauer Spezialtiefbau is playing a major part in the construction of the last of the new buildings around the Reichstag in Berlin.
Since autumn 1998, the firm has been working on the massive excavation for the new Elisabeth-Marie-Luders-Haus complex on the north bank of the River Spree, directly opposite the Reichstag the new seat of the German government.
Bauer is building the peripheral retaining wall, installing the horizontal grouted base slab and carrying out the 140,000m3 bulk excavation for the building's basement. Worth some £10M, the contract is due to finish early this summer.
Because of the very high water table and deep sand in Berlin (in places groundwater is just 1.5m below ground level), the excavation was designed to be watertight. The perimeter retaining structure comprises 4,800m2 of reinforced concrete diaphragm wall, 7,500m2 of single phase cutoff wall and 6,600m2 of sheet piling. These are supported by 417 ground anchors up to 42m long.
Below the base of the excavation, horizontal cutoff is provided by a 14,500m2 deep jet grouted base slab. Once these works are finished, the bulk excavation of the basement can start.
Intensive infrastructure and commercial construction has been carried out in the 1990s to rebuild the city after reunification. This project represents one of the last major Federal government contracts.