During the first phase, advanced utility and traffic diversion works were completed. In particular, a viaduct was completely dismantled and rebuilt at a different location. In the second phase, the geotechnical works which comprised, an excavation of a 240,000 cu. metre “box” of 30 deep metre, was carried out. The third and last phase, currently under way, consists in building the permanent reinforced concrete underground structure and a building to accommodate the mechanical and electrical rooms.

The main technical difficulty of the project lies with the crossing of the existing metro line. This imposes a very specific sequence of works and limits the allowable settlement and displacements. The existing line being founded on barrettes socketed into the rock, BSGL has proposed to re-use them to support the newly built structure. The load transfer from the old to the new structure – a very delicate operation.