Vattenfall will begin investigating the seafloor of the Vesterhav Syd and Vesterhav Nord offshore wind project in the Danish North Sea and Kriegers Flak in the Baltic Sea in late summer, with an aim of finding old mines or bombs.
According to the Swedish energy group, experience has shown that unexploded bombs or mines from the First and Second World Wars might be found under the mud and seaweed in the exact area of the North and Baltic Seas where the three offshore wind projects will be built.
The work to find potential mines is currently out to tender, with the surveys expected to commence in August in the North Sea, which represents a bigger challenge than the Baltic Sea due to weather conditions, Vattenfall's Senior Geophysicist, Dorthe Reng Erbs, said.
Last year, a geophysical survey was conducted at the Vesterhav Syd and Nord sites, while explorations are still underway at Kriegers Flak.
"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," Erbs said.
It is familiar from previous investigations that there are three wrecks at Vesterhav Nord, potentially more than 100 years old and protected by the Danish Consolidated Act on Museums, however, they most likely will not be an impediment to the offshore wind farm.
Vattenfall plans to have the three offshore sites cleared of mines by the end of October.
The construction of Vesterhav Syd and Vesterhav Nord is scheduled to begin next year off the west coast of Jutland. The two wind farms will comprise a total of 41 Siemens Gamesa 8MW turbines scheduled for commissioning in 2020.
The 605MW Kriegers Flak wind farm will consist of 72 Siemens Gamesa 8MW turbines and is expected to be fully operational by 2021.