Innovative methods behind the environmental assessment of Denmark's largest offshore wind farm

Published: 12-10-2015

Birds and seals have got GPS transmitters on them, and the birds are monitored with radar in preparation for the establishment of Kriegers Flak offshore wind farm

It is a requirement for large construction projects such as ports, bridges and wind farms, that they must not affect the nature significantly. This requirement is particularly important when it comes to specially protected species. It has been NIRAS' task to ensure that this requirement is met when building Denmark's largest offshore wind farm in the Danish part of the shallow area Kriegers Flak in the middle of the sea between Denmark and Germany.

Therefore, NIRAS together with its sub-consultants developed new innovative methods to investigate occurrence of different species and predict the environmental impact of the 600 MW offshore wind farm, which will be one of the world's largest when completed in 2020. The result can be seen today at, that has just released a significant part of the so-called EIA of Krieger Flak, which NIRAS is close to complete of the on behalf of An EIA – Environmental Impact Assessment – procedure will examine the environmental impact of a construction project and establish specific environmental requirements that developers must comply in the assessed project.

Challenges encourages to innovate

"For every EIA, we do, there are new challenges, and that encourages us to constantly innovate and adopt new methods," says Mette Jeppesen from NIRAS, project manager of the EIA of Kriegers Flak offshore wind farm.

"Kriegers Flak is on the migration route of cranes, that passes from Sweden to central Europe on their way from north to south and back again," explains Mette Jeppesen.

The crane is a protected species, and its journey is as a new method among others things monitored by attaching GPS transmitters to the birds while also monitoring them by radars placed on a platform on the German part of Kriegers Flak.

"It has given us a much more detailed picture of the activities of the animals than we would otherwise have been able to achieve," says Mette Jeppesen.

The investigations of the cranes have been conducted by DHI which Niras has hired as sub-consultant.

No significant effect on the cranes

The conclusion of the detailed studies using new methods such as monitoring with GPS and radar is that an offshore wind farm at Kriegers Flak will not have any significant effect on the population of cranes. But are all the known planned offshore wind farms in Northern and Central Europe realised, it will probably affect the population of cranes significantly.

NIRAS together with our UK office have developed a special stepwise approach to assess whether or not the project may affect different Natura 2000 sites which the cranes are attached to cross borders. A Natura 2000 site is a natural resort that is selected to conserve species and habitat types subject to EU regulation. There are 252 Natura 2000 sites in Denmark. Together the sites cover 8.3 percent of the Danish land area and 17.7 percent of the Danish sea. Sites in other countries comes in addition to this.

It is this method from NIRAS' UK office and that there has been put GPS on cranes that are the new.

Seals and porpoises can communicate

A part of the EIA study has been to demonstrate that the project cannot harm cranes with their protection through Natura 2000 as the underlying basis. At the same time, the construction of a large project with the right countermeasures will not threaten the seals and porpoises in the area. NIRAS together with helped to develop a method to assess and manage underwater noise in relation to marine mammals. The seals in the area have also been monitored with GPS transmitters.

Mitigation measures are construction measures designed to neutralize undesirable environmental effects of a construction project – in this case the wind farm, where mitigation measures will ensure that the wind farm does not create underwater noise that disturbs communication of the marine mammals.

The preparation of the EIA report Kriegers Flak offshore wind farm has so far taken three years, which is a long time because it is a very large project with many field studies. Many EIAs can be completed in a year's time. The report will now be submitted to a public hearing after the autumn break.

20 GW in 25 years

NIRAS is in the top three in the world as one of the most experienced consultants in the establishment of wind turbines. NIRAS has been involved in projects totaling 20 GW in the last 25 years in Europe and Asia, in recent years the focus has been on offshore wind farms.

Read more: NIRAS knowledge behind the coastal wind farms.

Contact info

Betina Haugaard HeronBusiness Unit DirectorEnvironmentAarhusDenmarkT: +45 8732 3356E: Send E-mail
Further contact info
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