Giant muscles and red corals

Next to the project site in Monaco, there are two nature reserves with red corals, giant muscles and sea grasses that cannot, be damaged or disturbed under any circumstances.  That is why, before the start of the project, a team of Jan De Nul’s environment department Mared has been permanently on site to closely monitor the strict environmental conditions.


“We have four persons of Mared permanently working here”, says Delphine Praet, who is a member of the team in Monaco herself. On one side of the project site, there is a nature reserve of sea grasses, and on the other side, we have protected red corals. Therefore, the department installed a total of six measuring buoys, three along each side, to measure the impact of the works on the reserves.

Delphine explains: “Prior to the start of the project, a number of thresholds in terms of turbidity, light and sedimentation were established. Turbidity refers to the cloudiness of the water and is caused by dredging works as during these works the seabed and the material to be dredged are stirred into the sea water. Sedimentation is a direct consequence of this turbidity as the stirred material swirls down onto the sea grasses. For these sea grasses, it is very important that their leaves are able to absorb sufficient light to ensure that the photosynthesis process can take place. As soon as certain turbidity tresholds are exceeded, we enter an alarm phase and adjust the working method or even suspend the works should this be neccessary."

"All data measured can be consulted continuously on a special website."

Delphine continues: “The elaborate early study phase was mainly used to simulate the impact of the works on the environment. Obviously, we always have the intention to work without interruptions. Additionally, we include a test period prior to the start of every activity, during which we sit together with all teams and the client on a daily basis. In this way, everyone knows exactly what to do and not to do, so we can achieve acceptable production levels without causing negative effects on the environment.”

All data measured by the measuring buoys can be consulted continuously and in real time on a special website that is accessible to all parties concerned, including the Principality. Delphine: “We go the extra mile to protect the environment. For instance, in the work area we found grands nacres, a protected species of giant muscles that can measure up to 1 metre. Before we started working, divers manually moved them as well as 500 m² of sea grasses to an area outside the project site. We also have divers working all the time to manually clean corals and remove sediments.”

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