Abstract
The Dutch national Energy Agreement, which was signed in 2013, provided for the development of wind farms in the wind energy areas of Borssele, Hollandse Kust (south) and Hollandse Kust (north) in the period leading up to 2023. With the publication of the 2030 Offshore Wind Energy Roadmap on 27 March 2018, the government presented the planned roll-out for the further realisation of offshore wind energy for the period 2024 through to 2030. This roadmap also included the timetable and the selection of certain designated wind energy areas for the period leading up to 2030.
The North Sea policy document (2016 - 2021) stipulates that site decisions for offshore wind energy must be assessed using the Framework for Assessing Ecological and Cumulative Effects (KEC). In the case of impulsive underwater sound, the main focus here is on the assessment of possible effects on harbour porpoises on the Dutch section of the Continental Shelf. The guiding principle for the assessment of the effects on the harbour porpoise population is that it must be possible to establish, with a high degree of certainty (95%), that the harbour porpoise population will not decline by more than 5% as a result of the construction of offshore wind farms. To ensure that this objective is met, the government sets sound standards for each site that may not be exceeded during the construction of a wind farm. The KEC (update 2016) does not yet take into account the construction of wind farms provided for in the 2030 Offshore Wind Energy Roadmap in the wind energy areas Ten Noorden van de Waddeneilanden, Hollandse Kust (west) and IJmuiden Ver. The effects of the construction of wind farms must be assessed to facilitate the development of wind energy in these areas. A new KEC including these wind energy areas is therefore required (including sound standards).
This report sets out the results of research into the cumulative effects of the construction of offshore wind farms in the period 2016 - 2030, both for the Dutch section of the North Sea and the entire North Sea. That research included first updating, on the basis of the most recent knowledge and insights, the stages in the staged procedure adopted in the 2015 KEC/2016 to determine the effects of the realisation of offshore wind energy on the harbour porpoise population. On the basis of the updated stages, the effects of the realisation of offshore wind energy on the harbour porpoise population for the period 2016 - 2030 were then calculated and sound standards were derived for various ecological standards, that is to say values for the maximum permissible decline in the harbour porpoise population due to the construction of offshore wind farms in the period prior to 2030 that were not included in the Energy Agreement.
It emerges from the results of the calculations that the sound standards for the construction of the wind farms after 2023 may be higher than those for the wind farms in the Energy Agreement. This is partly due to the fact that a new version of the Interim PCoD model was used to calculate the effects on the harbour porpoise population that included the results of an expert elicitation workshop organised in June 2018. Calculations used in this model result in a population reduction that is 3 to 6 times less than the reduction calculated with the earlier version – version 2.1 – of the Interim PCoD model. If a single universal sound standard is assumed of SELss (750 m) = 168 dB re 1 Pa2s for the construction of the wind farms after 2023 using wind turbines with a maximum of 10 MW and the sound standards set out in the site decisions for the wind farms planned in the Energy Agreement, it has been calculated for the scenarios described in this report that, for the entire period up to and including 2030, the probability is higher than 95% that the harbour porpoise population on the DCS will decline by no more than 865 animals (= approx. 1.7% of the DCS population). This means that, as a result of the construction of offshore wind farms in the period 2016 - 2030, there is a high degree of certainty that the harbour porpoise population will remain at a level of at least 98% of the current average population.