Project

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Scope of work

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General Information

Lac Sud is located between the city of Tunis and the Gulf of Tunis

It was currently a shallow water area (mean water depth 60 cm) of about 1600 ha containing dead water. Since years, the lake has been used as an open sewer for all wastewater, coming from Tunis and from the adjacent industrial area. The water and the bottom of the lake were seriously polluted. Moreover and due to the pollution the lake contained huge amounts of algae, which spread an unbearable smell in the surrounding villages, especially during the summer season.

The project has been defined as ‘the project of the century’ in Tunis, aiming at a significant amelioration of the environment in one of the major cities of Northern Africa.

Description of the works

The project was basically an environmental project and is for its size and kind one of the major one ever realised in the southern Mediterranean.

The main aim was the sanitation of the lake. This objective has been achieved by creating a circulation of water between the sea and the lake, so that the water of the lake will be renewed every 6.4 days. The circulation will be generated by the natural tide (20 cm).

Scope of Works :

In order to rehabilitate the lake and to facilitate the water circulation, following works have been performed:

• evacuation of polluted silt
• deepening of the lake to -2.2m
• construction of locks, letting in the sea water at high tide and evacuating it at low tide
• rehabilitation of an existing access channel between the sea and the lake area
• transformation of the outline of the lake into a more hydrodynamic shape, thus facilitating water circulation. This also implied the construction of 15 km new dikes.
• transformation of the lake has been achieved by land reclamation : some 900 ha of land have been reclaimed. The transformed lake has been limited to an area of 700 ha.

In volumes the above-mentioned scope represent the dredging of 5,000,000 m3 of fine sands and 10,000,000 m³ of silt and soft clay. These dredging works will be realised by 2 cutter suction dredgers, which will be specially adapted to the particular environmental requirements and the dredging in shallow areas.

Main Equipment

Cutter suction dredgers : TIDEWAY 2 and VLAANDEREN XV