Germany: Offshore Wind Noise Reduction Test for Marine Mammals off Travemünde

Eight builders and operators of German offshore wind farms will test various noise reduction methods for the construction of offshore wind farms as from 13 August of this year. This series of tests will be conducted on the so-called “Brodtener Pfahl” near Brodten off Travemünde.

Every 2 days a tug boat with work pontoon and crew boat will sail to Brodtener Pfahl from Neustadt. From a present planning perspective, the tests will take 6 to 11 days depending on the weather. The test rigs for pile-driving noise reduction will be tested under identical conditions during short pile-driving operations. The local population does not have to expect any noise emissions because the test pile is situated about 2.3 km from the coast. Depending on the wind direction, dull thuds at the most may be heard on the cliff coast. Given the short daily pile-driving periods, however, there are not going to be any major adverse effects.

Offshore wind power plays a significant role in the federal government’s energy scheme. At present, nearly 30 wind farms have been approved with many more at the planning stage. Unlike other European countries, the plants are being erected in Germany a long way off the coast in extremely deep water. The offshore windmills rest on large foundations because they have to withstand the inclemencies of nature for many decades. The foundation structures are anchored with steel piles in the seabed to achieve maximum stability. This creates underwater noise (hydro-sound) which may disturb the orientation of the marine mammals. Five different methods to mitigate the underwater noise are to be tested.

One special feature of this project is the inclusion of the greatest possible number of German offshore wind farm designers and operators to make the benefits accessible to the entire German offshore industry. Following the evaluation of the results, the cooperation partners will provide all project partners with the final report, including their recommendations for particular technologies. Numerous workshops will be held to discuss the results with the licensing authorities and the manufacturers of noise reduction systems as well as to outline the way forward.

As this is a specific German issue, there are currently no effective measures for the reduction of impact noise that might be integrated into the complex installation logistics. In other European countries, where large numbers of offshore wind farms have already been built, the relevant licensing authorities simply require applicants to ensure that sea mammals are kept temporarily at a distance by various measures: using sonar buoys – so-called pingers and seal scarers – acoustic signals are emitted before the installation of the foundation, ensuring that sea mammals are kept at bay. Whale watchers then monitor the sea around the construction project and provide feedback on the effectiveness of the pingers. Moreover, a “soft start” of the piling process (pile driving with reduced energy) is to ensure that fish and porpoises are clearly kept at a distance from the construction site.

Source: rwe, August 08, 2011; Image: energia