As part of the Monaco offshore extension project, Bouygues Travaux Publics is building maritime infrastructure as the first step of the six-hectare expansion of the city into the sea. This maritime infrastructure consists of a fill enclosed by a band of 18 trapezoid reinforced concrete caissons and will serve as base for construction of the new eco-neighbourhood in Monaco.

The caisson precasting area is located in Marseille-Fos, the large French seaport and consists of a 10,000 sq.m area working space at the dock, which will be used primarily for preparing the reinforcements and assembling formwork for the caissons. It also includes a 32,000 sq.m area of water, where three times the size of a football field, where a floating dock will be positioned. This 56-metre-long, 50- metre-wide and 27-meter-tall floating dock will make it possible to prefabricate the 18 caissons, a first in France.