Costly tunnel construction in Mitte: BVG plans to drain Spree riverbed
The Waisentunnel, an 865-meter-long U-Bahn tunnel located under the Spree in Mitte, is in dire need of rebuilding due to its poor condition. This urgent need for renovation has been highlighted by the planners of the Ingenieurgemeinschaft ZPP/Amberg in their report.
The tunnel, originally opened in 1930, has faced numerous issues over the years. Seven years ago, the Water and Shipping Authority instructed the Berliner Verkehrsbetriebe (BVG) to repair the defects in the tunnel structure in the area of the Spreesole, as they posed a danger to the waterway and the Mühlendamm lock.
In 2018, divers found that the layer of gravel was mostly no longer present or very thin in the Waisentunnel, with cracks visible in the concrete and steel girders covered with mussels. This deterioration has led to the tunnel's closure five years ago.
The BVG plans to renovate the 180-meter-long Spree crossing as part of the Waisentunnel project. The dilapidated tunnel structure is to be dismantled underwater, and sheet pile walls will be driven into the bottom of the river to pump out the Spree water.
The planned new construction would be significantly smaller, as a second track would not be needed. Another advantage of the new construction would be the widening of the Märkisches Ufer, as it lost a lot of area during the beginning of the tunnel construction in 1914 and could be widened again in the context of the project.
However, the renovation project faces criticism from political parties such as the SPD and the Left. SPD member of parliament Sven Heinemann has raised doubts about the project's costs, suggesting that the BVG should examine alternatives to the Waisentunnel. Kristian Ronneburg from the Left party also demands an examination of alternatives, stating that if they do not work, a new construction of the Waisentunnel may be necessary.
The administration of Mobility Senator Bettina Jarasch (The Greens) finds the alternative less useful due to the need to cross private properties and a main traffic street, and the challenging construction tasks involved.
The BVG has applied for a plan-law procedure to obtain approval for the renovation project. If approved, the construction is expected to take about four years and cost around 52 million euros, with potential for cost increases.
It is important to note that if a new construction is not realized, the old tunnel must still be demolished due to the dilapidated condition of the structure, which could become a long-term danger to shipping traffic in the future. The U-Bahn trains of the U5 are currently separated from the main profile network due to the closure of the Waisentunnel, requiring almost 170 annual transports.
An alternative to the Waisentunnel project is to bring the U-Bahn on the U5 to Wuhletal and connect to the Deutsche Bahn network, then switch to the Neukölln-Mittenwalder Railway (NME). This alternative, while less favoured by the administration, could provide a solution to the current predicament if the renovation project faces insurmountable obstacles.
