Vattenfall has completed the removal of three Second World War sea mines from the 1600MW Nordlicht offshore wind farm site after geophysical surveys identified magnetic anomalies interpreted as possible unexploded ordnance.
The geoscience team said each object was examined by remotely operated vehicle in spring and found to contain the equivalent of 200–300kg of TNT.
The mines were disposed of in September through controlled detonations following a complex permitting process.
“Clearing the seabed of wartime ordnance is one of those invisible but vital steps in developing offshore wind,” said Tobias Kulgemeyer, senior UXO engineer at Vattenfall Business Area Wind and technical lead for the campaign.
“It takes meticulous planning, coordination and care for the marine environment. With this campaign successfully completed, we’ve laid the foundation for a safe and sustainable start to Nordlicht’s construction,” added Kulgemeyer.
A 90-metre bubble curtain vessel was used to dampen sound around the detonation site, while coordination with other projects, including RWE pile-driving, was required to avoid simultaneous noise events.
Vattenfall said seven vessels were involved in the disposal campaign, which clears the way for installation activities.