The use of renewable energy sources at sea is growing rapidly in Europe, including Germany, accelerated by the Renewable-Energy-Process after 2011. However, the demand for renewable energies must go along with an awareness of sustainability aspects, especially for the protection of marine ecosystems. Among other ecological issues, the underwater noise emissions have moved into focus, since the most offshore foundations are anchored in the seabed with the impact piledriving procedure. This noise-intensive installation method leads to impulsive noise emissions (so-called pile-driving noise), which could harm the marine life (e. g. Lucke et al., 2009). For the environmentally sustainable use of renewable energy sources at sea, it is therefore necessary to reduce this sound input into the water.
There are currently 18 offshore wind farms (OWF) in operation in the German Exclusive Economic Zone (EEZ), five more OWFs are under construction, with the noise-intensive installation phase of the foundations for the Offshore Wind Energy Turbines (OWET) already completed, and some OWFs are in the planning stage to achieve the expansion targets. Furthermore, re 35 substations, converter platforms and measurement platforms, like FINO 1 to FINO 3 have been installed by now.
Based on the Marine Strategy Framework Directive (MSFD, 2008), the „Good Environmental Status" (GES) must be defined and guaranteed for European waters on a national, as well as on a regional basis for the respective indicator species. Other, non-European countries are also striving for a environmentally sustainable expansion of renewable energy sources, so that the handling and the reduction of impulsive noise input has long since become an international issue.
The harbour porpoise (phocoena phocoena) is the only whale species regularly occuring in German waters of the North- and Baltic Sea. For orientation under water, search for food resources and communication, the harbour porpoise uses an echo sounding system and therefore reacts sensitively to the increase of ocean noise. For these reasons, this species is considered a key species in the German North- and Baltic Sea in the context of the evaluation of anthropogenic noise input into the water.
The Federal Maritime and Hydrographic Agency (BSH) is the regulatory and monitoring authority for offshore projects in the German EEZ. Following the precautionary principle BSH established in 2008 for the first time worldwide a dual noise mitigation value criterion of 160 dBSEL (to be met by the Sound Exposure Level) and 190 dBLp,pk (to be met by the zero-to-peak Sound Pressure Level). The noise mitigation values at activity level were based on scientific advice given by the Federal Environment Agency (UBA) and on results from research projects. These noise mitigation values must comply at a distance of 750 m from the point of emission during pile-driving works. In 2013, the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) has issued the noise mitigation concept for the harbour porpoise in the German North Sea, in which compliance with the noise mitigation values and a habitat approach to avoid and minimize cumulative effects are pursued.
This technical report documents the cross-project analysis of all 21 pcs OWF construction projects including Offshore Supply Stations (OSS) and converter platforms of the years 2012 to 2019 from the German Exclusive Economic Zone (EEZ) of the North- and Baltic Sea. This report focuses on the technical Noise Abatement Systems and Noise Mitigation Measures, which have already been used throughout (series application) the construction of at least one complete OWF and have proven to be offshore-suitable and robust.
The aim of the report is to give an overview of site-specific and technical-constructional characteristics of noise generation and transmission due to percussive pile-driving as well as the necessary technical solutions by means of Noise Mitigation Measures to comply with the noise mitigation values.
On the one hand, the cross-project state of knowledge shall be made accessible for the environmental assessments carried out by authorities. On the other hand, it provides a crossproject, comprehensive and up-to-date knowledge data basis to enhance planning reliability with regard to the development of noise mitigation concepts for future construction projects by the industry.