Potains in land reclamation project

Started in 2016, Portier Cove is a €1.36bn plan that will see six hectares of land reclaimed from the sea, upon which 60,000 sqm of housing, an extension of the Grimaldi Forum and a coastal promenade will be built.

French company Bouygues Travaux Publics has been contracted to build the foundations of the offshore extension, including 18 reinforced concrete structures that will act as underwater struts. Known as caissons, these hollow, cylindrical chambers are being made in the Marseille-Fos Port in France before being towed to Monaco where they will be positioned and reinforced by infill.

To create the 10,000t, 26m-high structures, the contractor is renting a vast proportion of the French port, including a 10,000m2 caisson precasting zone, as well as a 32,000m2 area of water, where a floating dock is positioned. A first in France, this 56m-long, 50m-wide and 27m-tall floating dock will make it possible to assemble the caissons before they are delivered to Monaco.

It is here that three Potain top-slewing tower cranes are working over a period of 24 months: two brand new Potain MD 569s to help construct the caissons themselves and one MD 560 B for general supply of the shipyard from the harbour dock.

The two MD 569 tower cranes – erected at heights of 45m and 59m – are positioned on the water on floating platforms known as pilotis. This presented a challenge for Bouygues, as not only are the pilotis required to support the cranes when lifting heavy loads, such as 25t reinforcement cages, they also need to remain secure when battling the sea and the notoriously strong winds of the region.

The contractor worked with Manitowoc’s tower crane Lift Solutions team to find the answer. The team developed several pylon compositions specific to the site, combining different types of masts and chassis to increase the height and safety of the cranes. It also provided adapted load charts to account for piloti movement possibilities in all weather conditions.

Work on the caissons began in 2017 and is due for completion in 2019. Once complete, they will be towed to Monaco where they are run aground to form the foundations of the offshore extension. They will then be ballasted with sea water and weighted with quarry material. Each caisson façade has been specially designed to accommodate sea flora and fauna. Once the caisson belt has been finished, construction of the reclamation ground begins. The entire Portier Cove project is scheduled for completion in 2025.