Construction
The construction of the project has been executed in a number of different phases in order to limit the environmental impact.
First, an inner basin was created, which was designed in a way that the surrounding flood currents where not altered in a mayor way. This basin was used to temporarily store sand and gravel from the newly dredged access channel. The next phase was the creation of the base of the western part of the island. Construction was only under-water, preventing obstruction of the flood currents. This provided time for the estuary system to adapt to the new situation. Finally, the dikes above water were constructed. And the last phase was opening the temporary dike en simultaneously the permanent (inner) dike was closed.
Material dredged from the port channel was used to construct the bird island. After construction of a dike along the future perimeter of the island, hopper dredgers discharged the sand during high-tide, while earth-moving equipment shaped the island during low tide. This method was favoured over the hydraulic transport of dredged material, which in this case would have resulted in higher turbidity. Finally, a rock revetment was placed around the island for protection against wave attack and at the same time as a new substrate.
The environmental factor has been of great influence on the construction process. During construction multiple measures were taken to mitigate the environmental impact. Moreover, the creation of underwater basins before closing off the harbour area provided time for the ecosystem to adapt to the new situation. Furthermore, dredged material was used to create environmental value in terms of bird habitat, mudflats and beaches.