The two functions of the dam can be traced right back to the design of the dam. The Haringvliet dam consists of a closed part and a lock part. The locks were made in a polder, which was made in the middle of the Haringvliet. The water was pumped from a building excavation 1400 metres long, 600 metres wide and 10 metres deep. 22,000 concrete posts were driven into the bed to prevent it from sinking under the heavy weight of the locks.
The posts, which would sometimes exceed 20 metres, were topped with a 3-metre thick concrete layer. The first piers for the dam were finished four years after the completion of the building excavation. The 18 piers were placed next to one another over the length of the building excavation. Between each pier, joists were placed by a special crane.
Under these joists, large steel arms were placed, which could move the joists in case of high water levels.
In the meantime, the slides were constructed on land. These measured 56 metres long and 6 metres high. The first slide was placed in 1963, and over the next few years 33 more slides were placed. Two slides were hung in each of the 17 openings: one on the side of the North Sea and one on the side of the Haringvliet. In 1966, when all the slides had been placed, the water level was gradually raised back to normal.
After that, the dikes were removed entirely. Consequently, the left-over closing gaps on the north and south side had to be filled.