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Vattenfall's explosive plans for the summer

4C Offshore | Matthew White
By: Matthew White 22/05/2018 Vattenfall
VattenfallVattenfall is preparing to investigate the seabed at three of its wind farms locations.

In late summer, Vattenfall plans to send a ship to investigate the sea floor in the North Sea and Baltic Sea areas where
Vesterhav Syd and Nord and Kriegers Flak offshore wind farms are due to be built.

The aim of the survey is to find unexploded mines or bombs, before Vattenfall employees start building foundations for its wind turbines. It is believed there may be unexploded bombs or mines from the First and Second World Wars at the bottom of the sea in the very area in which Denmark's three next offshore wind farms are planned.

"The work to find potential mines is currently out to tender, and we're hoping to be in a position to get going in August"
, explains Vattenfall's senior geophysicist, Dorthe Reng Erbs. She also explains that most of the items likely to come to light will be metal waste.

"At Horns Rev 3 offshore wind farm in the North Sea, we found three unexploded mines, one of which had to be blown up. Members of the Royal Danish Navy EOD Services (explosive ordinance disposal) will also this time be on board to determine whether we were dealing with so-called UXO - unexploded ordinance – or simply waste. During a similar investigation at Kriegers Flak, Royal Navy engineers found an old, rusty anti-submarine net from the Cold War".
She continued.

Transitioning the area, a vessel will take measurements using devices such as magnetometers, sonar and multi-beam echosounders, which identify variations in the magnetic field of the sea floor. The technology relies on the difference between the magnetic field emanated by man-made materials such as iron and steel and the magnetic field of the sea floor and rock.

"We found 22 points at Vesterhav Syd, the same at Vesterhav Nord and 170 points at Kriegers Flak. Additionally there were some large areas where the changes in the magnetic field gave rise to measurements that were unclear. Generally, you can expect one to five per cent of fields which have been highlighted to contain dangerous objects. But we often find other interesting things such as old anchors and perhaps old wrecks"
, Dorthe explains.

From earlier surveys, Dorthe and her colleagues know that there are three wrecks at
Vesterhav Nord. They may be more than 100 years old, which would mean they are protected by the Danish Consolidated Act on Museums due to their potential cultural and historical value. These will be investigated in more detail, but are thought not to be in conflict with the offshore wind farm.

Dorthe anticipates that the investigation will begin in the North Sea. She hopes that the areas in question can be declared free of mines by the end of October.

For more information follow the links provided.

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