The extension of the RER line E in the Paris region requires the digging of a tunnel with a length of about eight kilometers from the center of Paris, where the line currently ends, to La Defense business district in the west of Paris.
The difficulty and the specificity of this project lay in the fact that it is located in dense urban areas (e.g. the route is less than 200 meters from the Arc de Triomphe Roundabout and 400 meters from the Champs Elysees Avenue) and almost all of the works will take place within two groundwater aquifers.
The consortium responsible for the project management of the Eole extension instructed Antea Group to perform technical assistance services to study the feasibility of these works.
The technique of groundwater drawdown was chosen and validated by Antea Group teams through the development of a mathematical model, the scope of which extended to simulate the hydraulic impacts on these two water tables of a regional importance.
The model allowed for the sizing of a pumping device to locate and implement the pumping wells in the most relevant manner.
Thus, according to the drawdown objectives set by the geotechnical engineers and designers, the model concluded that it would be necessary to implement 47 wells equipped with pumps with operating flow rates between 40 and 120 m3/h. A network of 37 monitoring wells will also be installed to monitor the depth of the water table in real time.
In total, an average flow rate of about 2000 m3/h should continuously be pumped during a period of at least four years.
Another important challenge is the fate of groundwater. It will be redirected to the Seine River through the installation of pipes inside the sewerage network of the city of Paris or through the creation of new networks.
In addition, the question of the value of the groundwater has also been studied. It could supplement certain sectors such as the air conditioning network or used for the partial non-potable water supply to the City.