The "Marne" pipe project implemented by Aéroports de Paris (ADP) consists in laying a stormwater discharge pipe between Paris-Charles-de-Gaulle airport and the river Marne. The pipe will be approximately 9 km long and pass through the municipalities of Gressy and Annet-sur-Marne. It will convey water by gravity flow from the Reneuse valley to the river Marne. The diameter of its standard sections will be 1400 mm, and that of the section bored by a micro tunnel-boring machine will be 1800 mm.
Most of the pipe will run through an alluvial valley. The investigations carried out in the context of the preliminary geotechnical design study show that the trench dug to lay the pipe sometimes overlaps with the aquifer. The structure hence interacts with groundwater, which has the following consequences:
- during the works phase: a need to implement aquifer drawdown operations (pumping/discharging) in order to lay the pipe on a dry bed,
- upon completion of the works: modification of the characteristics of land along the pipe, potentially modifying the level of the aquifer in some places.
In light of the environmental context, wetlands and watercourses are the features most likely to be affected from a hydrogeological viewpoint. ADP appointed Artelia to perform the technical study to assess the hydrogeological impact of the project.