Over a length of 16.5 kilometers, we reinforced the Wadden Sea dike on Ameland in combination with Jansma Drachten. We also raised the dike by an average of 35 centimeters. This extensive project is part of the High Water Protection Program (HWBP), a partnership between the national government and the water boards.
Work
At the bottom of the dike, the toe construction was excavated on the sea side. Here a canvas was applied with a layer of raw crushed stone on top. Next, the top layer of the dike was excavated and filled with clay. On top of this, geotextile with a layer of asphalt was applied. The top layer consisted of crushed rubble and a clay package. The turf was reused and returned to the dike after the work was completed.
Logistical challenge
A total of 800,000 tons of material was brought in. We had to take into account the limited draught around the Wadden Island, we were dependent on the tide, and (pleasure) shipping was not allowed to be hindered by the work. A logistical challenge!
The choice was made to use two coasters that brought material from the mainland towards Ameland. To distribute the inconvenience, the material was brought to 3 different unloading locations on the island.
Respect for nature
Ameland has high-tide refuges around the island. These are areas that remain dry at high tide where many species of birds gather at high tide. The execution of the work did not pose any nuisance or danger to the birds around the island.
Besides the birds, the Wadden area is also known for the presence of seals and Ameland specifically also of sheep on the dike and the Brent Goose. The sailing route of the two coasters naturally took into account the seals in the area, they were disturbed as little as possible. On the dike itself, the sods were reused and put back in place so there was no need to re-sow and the sheep and Brent Geese could quickly use the grass again.
Safe Ameland
Now that the work has been completed, the Wadden Sea dike on Ameland once again meets the national safety standard.