Metro Line 16 covers a length of 13.5 km between infrastructure in Saint-Ouen and in Aulnay-sous-Bois, entirely underground, mainly through dense urban areas, crossing numerous existing infrastructures. The lot also includes interconnection works with other lines, such as the West connection serving line 16 and 17, which also performs the function of emergency and fire access, and the connection to the industrial site of Aulnay, in proximity of the homonymous station and that will also ensure the emergency functions, with ventilation, decompression and drain installations ; the Nord maintenance site welcomes personnel and equipment necessary for the maintenance of line 16 and 17. On the L16 for Eiffage Génie Civil, CIPA carried out two ventilation bypass, respectively 9.8 ml and 9.4 ml in axis, and both about 9m in diameter; the activities have been carried out accessing from the shafts with opening of the front of excavation by sawing of the opening walls according to the technique of sawing with diamond wire. The section of the bypass is about 60 m² each one, they are excavated in two half-sections, from the upper half-section, which made it necessary to assemble a modular platform, designed in particular for the geometry of the two wells, one circular and one rectangular. The temporary line are characterized by the installation of HEB ribs and spacers and by the application of dry concrete. At the end of the excavation of the entire section, the final lining is carried out, starting from the side of the future intersection with the existing tunnel, where the opening has not yet been created, backwards towards the access shaft, first realizing the invert along all the bypass and after the walls, also the central walls, and finally the vault.