The IJmuiden sea lock: three years late, and still the biggest

Amsterdam is not on the coast, yet it is a seaport. That is thanks to the North Sea Canal, which has linked the city to the North Sea since 1876. At its end, at IJmuiden, are the locks that separate the canal from the sea. Every ship heading for the port of Amsterdam has to pass through them.

Too small for modern ships

For a long time the biggest lock was the Noordersluis of 1929: 400 metres long, 50 metres wide and 15 metres deep. For today's ships that is too tight. So the state, the province and Amsterdam decided on a new lock. In 2015 the contract went to OpenIJ, a combination of BAM and VolkerWessels. That year the Bosatlas van Amsterdam wrote: 500 by 65 metres, ready in 2019.

Things went differently. Construction only started in July 2016, and the lock became 70 metres wide instead of 65. Amsterdam and North Holland wanted a bigger lock than Rijkswaterstaat had planned, and paid a good share of the cost.

Gates from South Korea

The most striking parts are the gates. They are rolling gates 72 metres long, 11 metres wide and 24 metres high; the one in use weighs 3,000 tonnes. They were built in South Korea and took 44 days to make the journey. In December 2018 they arrived at the Maasvlakte, where the transport ship was partly sunk so the gates could float off.

Meanwhile things had gone wrong with the concrete chambers the gates slide into. During sinking they could twist and crack, and they had to be redesigned. In July 2018 the builders announced a 27-month delay. Costs rose too: NH Nieuws later estimated the total at about a billion euros, not counting the losses the builders had to absorb themselves.

The biggest? Not according to Antwerp

On 26 January 2022 King Willem-Alexander opened the lock, without an audience, with a click and a sentence over the marine radio. The lock works independently of the tide, so large ships no longer have to wait for high water. Rijkswaterstaat called it the biggest sea lock in the world. The same day Antwerp came back with a calculation: its Kieldrecht lock is deeper and holds more water. Flemish broadcaster VRT headlined that the Dutch cannot count. In length and width IJmuiden is the biggest, in depth it is not.

The old Noordersluis has not been retired, by the way. At the end of 2025 it even got a new gate, and it is still in use, although Rijkswaterstaat expects its technical life to end around 2029.

More about water and transport? Read about the free ferries across the IJ.