Construction of the Deutsche Bucht offshore wind farm is subject to strict regulations and laws. The aim is to make it as environmentally friendly as possible. Sophisticated technology is therefore used to erect the turbines. Possible effects on the environment are continuously measured and monitored throughout development, construction and operations.
Protection of the marine environment plays a major role throughout the project’s lifecycle, beginning with site selection. For example, the Deutsche Bucht wind farm is located at a distance of over 100 kilometres from the coast, in an area which is designated for economic development and far removed from the Wadden Sea National Park.
The environmental impact assessment (EIA) plays a major role in the approval process, i.e. before permission is granted to build a wind farm. The EIA includes a detailed survey of the fauna and flora in the area of the wind farm. In carrying out this initial survey, the wind farm developers have to determine exactly which species among the so-called “protected assets of the marine environment” are to be found on the site, and their populations. This includes birds, fish, marine mammals such as porpoises and grey seals, as well as life on the ocean floor. Based on the survey data, a forecast of the possible impact of the wind farm is produced. Approval of the project is only granted if the EIA leads to a positive result, meaning that the wind farm can be built in an environmentally-friendly manner.
The approval authority for the German Exclusive Economic Zone, the Federal Maritime and Hydrographic Agency of Germany (BSH), has defined the scope of the examination in its standard examination concept “Investigation of the Impacts of Offshore Wind Turbines on the Marine Environment (StUK 4)”. The survey also serves as the basis for monitoring the environment. During the construction and operating phase of the wind farm, the fauna and flora are examined in detail several times at defined intervals to enable any potential impact to be identified.
In addition to studies on the environmental impact, detailed concepts on soundproofing while the foundations are laid must be presented and implemented. Among marine mammals, porpoises, which are a protected species, are considered to be particularly sensitive to noise. As they use their hearing to take their bearings, special rules apply for their protection in German waters: during the noise-intensive work to install the monopiles, the noise level must not exceed 160 decibels within a radius of 750 metres from the building site. A combination of two proven technologies was therefore used as part of the noise mitigation concept on the Deutsche Bucht wind farm: a hydro sound damper and a double Big Bubble Curtain.
The hydro sound damper (HSD) is a net which is placed around the monopile and lowered to the sea floor. Various foam elements (HSD elements) are fitted to the net; they dampen the underwater noise at different frequencies during the noise-intensive work. A double Big Bubble Curtain was also deployed. For this, two long hoses with holes several hundred metres in length are laid in a circle around the entire monopile building site and the installation vessel. Compressors pump air into both hoses with the result that air bubbles are released and travel upwards. This double bubble curtain stops the sound from propagating. The combination of these two systems, HSD and bubble curtain, is ideal, as a wide frequency range of sound waves can be absorbed due to their different effects. The efficacy of the soundproofing systems was reviewed as part of efficiency checks.