In July 2019, the caisson belt installation has been completed, and the perimeter of the new Portier Cove eco-district is officially served as the new coastline of the Principality. The construction of solid land begins, extending through to the end of 2019.
The closure of the caisson belt creates a salt water basin between the existing coastline and the developing coastline.
To create the land, sand is gradually deposited in the ‘lake’ between mid October and mid December.
For this new operation, 2 vessels ensure four deliveries of sand per week, two per ship. 24,000 tonnes are deposited at each passing. In total, 31 deliveries will be required to transport the 750,000 tons.
Each ship is equipped with a 75-metre long unloading facility. The device called ‘the grasshopper’ is a mobile and tilting elevator, equipped with a conveyor belt (or buckets depending on the use), which allows the deposit of materials. Each ship is placed parallel to the caissons in a predetermined area. The grasshopper passes over the concrete structure to unload its cargo at the rear.
An unloading takes about 14 hours.
Photos © SAM L’Anse du Portier
While the quarry sand is deposited, the body of water is emptied by percolation. Sea water slowly escapes through the underwater backfill and flows out to the open sea outside of the caisson belt, at the same time as the sand is deposited. The advantage of this process is that the backfill acts as a filter. It retains the fine particles, the natural dusts contained in the sand, limiting turbidity outside of the caisson belt
The ground gradually emerge, as the volume of sand in the enclosure increases the water level will decrease.
The land is done on December 14, 2019.