More than unexploded 40 Second World War bombs have been detonated on the seabed off the Linconshire and Norfolk coast.
Contractors for Dong Energy discovered the 41 items while conducting surveys for the seabed ahead of work to install a cable route for the Race Bank offshore wind farm.
Up to 91 turbines are being built approximately 16.8 miles off Blakeney Point on the North Norfolk coast and 17.4 miles off the Lincolnshire coast at Chapel St Leonards.
A German Luftmine B ground mine containing a net explosive quantity of 698kg of hexanite was the most notable find along with small rockets to a larger 1,000lb high explosive bomb.
Specialist contractors detonated 36 live and high explosive-filled items at sea while five pieces, which were certified as free from explosives were recovered to shore and have been scraped.
Eleftheria Melekou, Site Investigations Project Manager at DONG Energy, said: “The number of items discovered was a surprise and the most we have seen on a DONG Energy project to date.
“We used the help of specialist and highly-skilled companies to ensure all of the 41 items of unexploded ordnance discovered at Race Bank were safely detonated or removed without risk to the local community.”
Contractors monitored the detonation areas for the presence of marine mammals using a dedicated marine mitigation vessel.
A post detonation search found a very low fish kill while no cetaceans or other marine mammals were observed
Klaus Skoust Møller, programme director for Race Bank at DONG Energy, said: “We have closely cooperated with the Marine Management Organisation and Natural England to ensure the least possible impact on the environment during this work.
“This has been a big and important task due to the number of UXOs involved, and we are very happy that the authorities have supported us in progressing the project.”
UK-based firms MMT, Ramora, Dynasafe Bactec and Ordtek were involved in the operation.
Race Bank, when operational, will have a capacity of up to 580MW providing enough energy to power over 400,000 UK homes
To watch the detonation go to www.youtube.com/watch?v=pYyu9l1gMkI