Vattenfall Unearths Mines at Windfarm Site

Vattenfall has shared two videos of a World War II mine with a 700kg explosive charge being unearthed from the seabed at the site of Denmark’s Horns Rev 3 offshore wind farm.

The mine had been identified from a geophysical survey of the area, which was conducted in 2015. The data collected was then analyzed and compared with the site where Vattenfall planned to install its turbines to determine whether or not the mine could pose a risk to the workforce and the equipment to be used.

"I understand that people are fascinated by the explosion, but 99.9 percent of the work actually takes place before the explosion," says Vattenfall's Senior Geophysicist Arne Rød Lauridsen, who came to Vattenfall a year ago to work on locating mines which were known to lie on the seabed in the vicinity of Horns Rev 3.

"We already knew the minefield existed because it was recorded on nautical charts but in order to obtain more precise information we found the mines' coordinates in German logs from 1944. Using old German nautical charts converted into modern-day GPS coordinates, we established that there were three mines in total. But this is not without challenges, and special equipment is needed to locate them," says Lauridsen.

Two of the mines in the vicinity of Horns Rev 3 were from World War I and were quite small. They were removed safely. However, the third mine was a so-called LMB mine - a naval mine dropped from an aircraft by parachute - from World War II, and it had an explosive charge of 700 kg. This required further action. 

The historical mine was handled by the Naval Staff division of Danish Defence Command (DDC). They sail out in a rubber dinghy from a larger vessel which is leased from Vattenfall. A DDC-diver placed the explosive in position and then returned to the boat, and the mine is blown up in a controlled way using a wire and a detonator.

It is estimated that there are around 5,000 to 6,000 mines left in Danish waters, some 70 of the World War II mines being located in the waters around Horns Rev. Three mines have already been detonated, and Vattenfall has now removed one, leaving 66 which are outside the area where Vattenfall plans to work on the seabed.