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Cologne: Tunnel boring machine Henriette successfully recovered!
On August 14, 2025, the drilling machine “Henriette” was recovered in Cologne-Niehl, a crucial step in the expansion of the sewage system.
Cologne: Tunnel boring machine Henriette successfully recovered!
An exciting week for Cologne, as the large tunnel boring machine “Henriette” has begun its final journey. In Cologne-Niehl, the 20-ton cutting wheel and the impressive 100-ton drill were lifted from the target excavation pit today. “Henriette” has worked tirelessly under the Rhine since May 2025 and dug an important tunnel between Cologne-Stammheim and Niehl, which is crucial for the renewal of the over 100-year-old sewage pipes WDR reported.
The recovery of the machine was not entirely straightforward. Delays occurred due to a stubborn lump of clay and nuts that were difficult to remove. Ultimately, the rescue could only be completed around midnight. The construction of a second tunnel should now begin quickly in order to meet the city's increasing requirements.
The Rhine culvert as a future project
The new Rhine culvert is not only a technical masterpiece, but also a model project for urban development. Over 80 percent of Cologne's wastewater is treated in the Cologne-Stammheim sewage treatment plant, which serves around 800,000 residents and industrial wastewater from around 500,000 people. The new pipes are intended to make wastewater treatment much more efficient and enable the sewage treatment plant to utilize its full capacity. This modernization measure is a clear signal for the responsible use of resources and the response to the expected population growth, as it is STEB Cologne describes.
The sewage treatment plant, which was put into operation in 1953, has continuously developed since then and now fulfills both mechanical and biological cleaning processes. Modernizations in 1976 and 1992 ensured that legal requirements were met. With the new tunnels, the infrastructure is now fit for the future.
Insight into the technology
As part of the tunnel construction, which runs a total of 940 meters under the Rhine, the new tunneling machine with a diameter of 3.20 meters is being used. The Cologne City Drainage Company (StEB) has decided on this pipe jacking method in order to meet the existing requirements. The old pipes date back to 1928 and no longer meet modern standards; technology has developed significantly since then GFA News reported.
With an investment volume of around 110 million euros, the second tunnel construction is imminent. Completion is scheduled for November 2025, while commissioning of the new Rhine culvert is planned for 2028. Until then, pipes and cables still have to be laid and construction pits have to be expanded into shafts with platforms and control technology.
The progress in infrastructure is a good sign for all Cologne residents. Not only will wastewater disposal be improved, but also the quality of life in the city. It will be exciting to see how the construction work will develop in the coming period!