The dam from Hellegatsplein to Goeree-Overflakkee
The construction of the dam was a very complex operation, which comprised of both closing of the Volkerak dam and bridging the Haringvliet. The dam crosses a vast bare area, situated on the intersection of the Hollandsch Diep, the Haringvliet and the Volkerak. The dam from Goeree to the Hellegats square had to fill a gap 4.5 kilometres wide. This section consisted of two parts. The first part was 4 kilometres long and covered with asphalt. The second formed the other 450 metres and consisted of sand only. It was raised to +4.5 metres NAP (Normal Amsterdam Water Level) and was later included in the Hellegats square. As long as the Haringvliet was not closed (which would not happen until 1971), the surroundings of the Volkerak dam were faced with a water level of 4 metres NAP every fifty years. To be prepared for this situation, the dam had a height of 6.75 metres NAP.