How will the new Monaco extension maritime be built?
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caissons
Source: www.laprovence.com

How will the new Monaco extension maritime be built?

A press conference was held in Marseilles on the prefabrication of caissons which will constitute the maritime infrastructure of the extension at sea. The prefabrication of the 18 caissons will take place in Fos-sur-mer. It will last 2 years, starting in September 2017. The project will generate 700 direct and indirect jobs. Ultimately, more than 1.5 million tons of materials will be loaded and transported to Monaco.

The conference took place in Marseille City Hall in the presence of Jean-Claude Gaudin, Mayor of Marseille, President of the Metropole Aix-Marseille-Provence and Vice-President of the Senate, Philippe Bonnave, Chairman and CEO of Bouygues Construction and Christine Cabau-Woehrel, General Manager of the Grand Maritime Port of Marseille.

The prefabrication of the caissons will be carried out by means of a floating structure (caissonier) measuring 56 m long, 50 m wide and 27 m high. This is the first in France, qualifying the extension to sea as an “emblematic operation” says Bouygues TP.

The eighteen floats that will be used as a belt for the 6 hectares of land will be manufactured in the grounds of the Grand Maritime Port, said Philippe Bonnave, president of Bouygues Construction. The company was given the task of constructing the maritime infrastructure for 842 million euros to serve as the extensions foundation. Bouygues is installing a two-year factory for the prefabrication of these caissons in the port of Phocéen, including a “caissonnier”, a floating dock, which is a first in France, underlines Philippe Bonnave.

caissons
Source: gouv.mc

Jean-Claude Gaudin, senator of the LR neighbourhood in Marseille, obviously welcomed this project, which represents a 145 million investment and 700 direct and indirect jobs. Marseille was in competition with other ports like Toulon, Genoa and Barcelona.

Starting in September, the 27 m high and 10,000 ton caissons will be made in large part as a “continuous cast” at the floating dock. They will then be complemented by concrete poles to form a wave-breaking wall, then stored on a dike and finally transported by sea to Monaco from the end of March 2018. They will then be sunk to a depth of 20 metres, ballasted and assembled to form a dike, which will then be filled with sand.

Environmental constraints

Meanwhile, Bouygues Construction has begun preparatory work in Monaco to preserve the environment with the displacement of 140 large nacres, 500 m2 of posidonia meadows and lithophyllum.

“We had to integrate particularly heavy environmental constraints. It’s unique!” says Christophe Hinsinger, the Projects Manager.

caissons
Source: gouv.mc

In fact, the cove of Portier where the extension is to be built is located between two marine nature reserves, that of the Larvotto and Spélugues. Bouygues had to deploy a 5-meter high soundproofing wall along the site and an anti-turbidity screen underwater to avoid deposits in both reserves. The construction group have already began removing 110,000 tons of rock from the coast. Then they will dredge the sediments. The first polluted part will be sent to a treatment centre; the second will be released at sea. Once this is done, an embankment will be built at the bottom of the sea to serve as a base for the caissons.

The platform is to be delivered in November 2020. It will create a new district with 60,000 m2 of luxury housing and shops, an underground parking, an extension of the Grimaldi Forum whose surface will be doubled, a small marina and a one hectare park.

The construction of this new district, which will cost 2 billion euros, will be totally completed by 2025. This is not the first project for the Principality which has already reclaimed more than 40 hectares from the sea, equivalent to 20% of its territory.



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