Paris 2024: Soletanche Bachy France and Bessac improve water quality in the Marne for swimming events

Through this project, Soletanche Bachy is helping to build infrastructure that preserves the environment by improving water quality: the XI structure project is part of the Marne and Seine sanitation programme to make those swimmable for events at the Paris 2024 Olympic and Paralympic Games. This programme, being carried out in Neuilly-sur-Marne and Noisy-le-Grand, particularly includes the creation of a depressed sewer structure and a tunnel under the Marne using a microtunnelling machine, which will eventually transport effluents between the XI structure and the RGM collector, thereby reducing discharges into the Marne.

For Soletanche Bachy, this involves building three structures, linked by two microtunnel sections 236m and 307m long (DN1200), in a dense urban environment:

• The Square de l’Eau structure, which will act as a depressed sewer, is a circular shaft with an internal diameter of 12.30m and a diaphragm wall, created using a hydrofraise and completed with ground injection. Jet-grouting plug work is also planned for the microtunnelling machine’s start point.

• The EcoQuartier structure involves a diaphragm wall constructed using a hydraulic grab and completed with ground injection and a jet-grouting plug (microtunnelling machine exit point).

• The Resistance structure involves secant piles completed with ground injection and a jet-grouting plug at the microtunnelling machine exit point.