In the north gully a threshold made of stones and rocks was created 8 meters below sea level. The north part of the dam is 800 meters and it was calculated that this part only needed a height of 10 meters. In 1986 the construction of 12 caissons started. One caisson was 68 meters long, 18 meters wide and 16.2 meters high. Each caisson has 12 holes for tidal movements. These holes were closed with wooden gates during transport. To place the caissons above the final place they have to float and are tugged in the exact position. Then several holes in the wall of the caisson were opened so that it sank controllably. When the caisson was filled with water and sank on it’s right position the wooden gates were removed to prevent the current giving problems. It was impossible to put all the caissons tight together so the spaces between the caissons had to be filled also, When all the caissons were placed they waited for the tide to change. Only at that moment there is no water flow and the caissons were filled and covered with sand.