Vattenfall Blasts WWII Sea Mines at German Offshore Wind Project Sites

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Swedish energy company Vattenfall has removed three unexploded sea mines dating from World War II in the area where it will build its Nordlicht offshore wind cluster in the German North Sea.

The mines, each with an explosive force comparable to 200-300 kilogrammes of TNT, were first located as anomalies during prior geophysical surveys of the seabed at the Nordlicht 1 and Nordlicht 2 sites, located 85 kilometres north of the island of Borkum.

Using a remotely operated vehicle (ROV), Vattenfall’s geoscience team confirmed the objects and, after regulatory clearance, carried out controlled detonations on site in September.

To mitigate underwater acoustic impact, the company deployed a 90-metre bubble curtain system via a dedicated vessel to reduce shockwave transmission and protect marine life.

Vattenfall said that seven vessels, including support ships, the bubble curtain vessel and ROV carriers, were coordinated during the campaign. Because regulations prohibit two simultaneous noise events in the German Bight, the campaign was also timed around other marine construction activities, in particular pile driving carried out by RWE.

Vattenfall made the final investment decision on the Nordlicht 1 and 2 offshore wind farms at the beginning of this year and performed the unexploded ordnance (UXO) removal ahead of construction activities, which are scheduled to start in 2026.

Offshore construction will first get underway at Nordlicht 1, with the wind turbines expected to be installed in 2027 and the first wind farm fully operational in 2028.

Nordlicht 1 and Nordlicht 2 will comprise 112 Vestas V236-15.0 MW wind turbines, 68 of which will be installed in the first phase.

Once operational, the 1.6 GW Nordlicht cluster, comprising the 980 MW Nordlicht 1 and the 630 MW Nordlicht 2, is expected to generate approximately 6 TWh of electricity annually.

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