Explosive ordnance disposal specialist Ramora UK carried out a controlled explosion on the 680kg mine, which had been laid by a German ship in World War 2.
Currently under construction, RWE and SSE’s Greater Gabbard wind farm will comprise 140 Siemens 3.6MW turbines. It is due to be the world’s largest offshore wind farm when it is completed next year.
The ground mine was detected in 35m of water at the Greater Gabbard site, 33km off the port of Harwich in Eastern England.
It had been assessed as high risk, due to damage previously sustained to it, and the remote-controlled explosion of the mine using a countermining charge left an underwater crater 20m wide by 4m deep.
This is not the first time a North Sea wind project has been delayed by an unexploded device from the second world war.
In May last year, an unexploded bomb was found during a survey of the Sheringham Shoal offshore wind farm.
The bomb was found by divers from underwater specialist Red7Marine and detonated by disposal expert MACC International.