As part of the Grand Paris Express project, the consortium led by Bouygues Travaux Publics has been awarded the contract to carry out the civil engineering work for the project's very first station. The Fort d'Issy-Vanves-Clamart station, which is part of Line 15 South (batch T3B), is a complex engineering project, partly designed to be underneath Line N of the Transilien rail line linking Paris-Montparnasse to western Paris, without closing this line to traffic. The installation of the reinforced concrete slab covering the top of the structure - weighing 7,000 metric tons, i.e. the equivalent of the Eiffel Tower - was a high-precision operation. This roof, which is 80 metres long and 25 metres wide, was built separately from the rest of the construction and then slid into place. The station of batch T3B serves as an exit shaft for two of the TBMs from neighbouring batches: T3A to the west and T3C to the east.