Lock and bridge

Lock

The drainage sluice near Flakkee. Clearly visible is the current near the siphon.
Flakkeese spuisluis
When the dam was finished, a lock was built. The shipping through this lock primarily consisted of fishery ships, inland vessels, coasters, and recreational ships. Special contractors' materials also used the lock during the closure of the lake of Brouwershaven (‘Brouwershavensche Gat’), to the west of the Grevelingen dam. The materials that were used for the construction of the Brouwers dam were often so large, that an extra large lock had to be built. The largest ship that would pass would have a maximum length of one hundred metres; the largest towboat would have a maximum length of twenty metres. The widest ship that could pass was a sand suction dredger, with a width of fourteen metres. Consequently, the dimensions of the lock had to be 135 by 16 metres. The required depth of the lock was harder to determine, because the water level in the Grevelingen lake could change because of the construction of the Brouwers dam. After extensive research, it was concluded that a depth of 5.5 metres below sea level would be sufficient. Ships with a draught of more than 3.8 metres would not pass and a water level lower than one metre below sea level was not to be expected.

The lock itself was built of reinforced concrete. The doors were made of steel, because of their large surface area. Lock doors are normally made of granite, but for financial reasons, long delivery times, and complex placing procedures, steel was chosen over granite. The slides in the lock doors were regular lock slides. The only difference was that larger slides were necessary to regulate the shipping, as well as the water balance of the Grevelingen lake. The slides were divided into nine sections by eight joints. The 'three by nine' concrete plates were fixed to each other, and as a result a large tank was created, in which the doors were placed.

Bridge

A bridge was built on top of the dam, as it also functioned as the main connection between Schouwen-Duiveland and Goerree-Overflakkee. The bridge had a width of just over eleven metres: eight metres for the motorway and 3.25 metres for the cycle path (including verge). The underside of the bridge was placed at 6.5 metres above sea level, reducing the chance that the bridge would need to be opened to let shipping through.