An out-of-control cargo ship hit a substation foundation at the construction site for one of the world’s largest offshore wind farms, Hollandse Kust South in the Dutch North Sea.

The Julietta D was left rudderless in heavy seas after colliding with a chemical tanker on Monday, leaving it drifting at the site of the 1.5GW Hollandse Kust South.

The cargo ship hit a foundation in place to support one of two giant substation platforms being installed by TenneT for the project’s grid connection, the network operator said. TenneT said there were no employees working at the site of the Beta platform at the time, while the other Alpha platform, where 100 staff were working, was unaffected.

The Dutch coastguard said early on Tuesday that the situation was under control, with salvage vessels present and the Maltese-flagged Julietta D’s crew safely evacuated by helicopters (see video at foot).

TenneT said: “As soon as the weather permits, the situation at the jacket can be examined more closely. At the moment we cannot make any statements about possible damage or what consequences this will have for the completion of the transformer platform Hollandse Kust Zuid Beta.”

Hollandse Kust South is being built by Vattenfall ahead of scheduled entry to service in 2023, when it will briefly become the world’s largest offshore wind farm in operation before being overtaken by other North Sea projects within a few years.

The wind farm is being built without subsidies from the Dutch government and has attracted investment from chemicals giant BASF and insurer Allianz in deals that valued the project at more than €3bn ($3.4bn).