The use of acoustic deterrent devices (ADDs) has been suggested as an alternate means to mitigate the risk of lethal and physical direct injury to marine mammals during pile driving (e.g. Gordon et al., 2007). There are, however, stakeholder concerns with the proposed use of ADDs as a blanket alternative to adoption of the JNCC protocol and the use of MMOs and PAM at offshore wind farms (OWFs), these concerns primarily relate to the evidence base for ADD effectiveness and uncertainties surrounding the extrapolation of this evidence to a range of different sites and conditions. As a result of these concerns and discussions within the Offshore Renewables Joint Industry Programme (ORJIP), a review was commissioned in 2013 and published by the Department for Energy and Climate Change (Herschel et al., 2013). This review investigated these issues and presented evidence on the effectiveness of available ADD technology for deterring UK marine mammal species at the ranges likely to be required for mitigating physical and auditory injury.
This report is intended to provide an update to the ORJIP Project 4, Phase 1 report (Herschel et al., 2013), highlighting any advances relevant to the use of ADDs for mitigation since its publication, in 12 | P a g e terms of evidence for effectiveness in offshore wind farm mitigation, advances in available ADD technology and advances in methodologies for field tests to improve our understanding of effectiveness. Note that the use of ‘Phase 1’ throughout this report refers to the previous review. This report also provides recommendations to improve the current evidence base for ADD effectiveness and provides a detailed evaluation of methods and field sites for future experimental trials.
The structure of the report is as follows:
- Section 3: An introduction to a general framework for assessing the potential for ADD based mitigation on a site by site basis;
- Section 4: ADD effectiveness review: an update to the evidence base presented in Herschel et al., (2013) to document research that has been carried out on ADDs for the marine mammal species of concern in relation to injury from pile driving noise during UK OWF construction;
- Section 5: Methodology review: A review of the techniques employed to date to measure ADD responses as a high level evaluation of to the various options for field trials. These options are further evaluated in Section 9 in light of the gaps identified in Section 4;
- Section 6: A detailed appraisal of the technological status, commercial availability and practicality of use of ADDs in relation to their potential application in the mitigation of the risk of injury from pile driving noise during UK OWF construction;
- Section 7: A review of the factors influencing sound propagation with a view to informing how results from a range of trial sites (past and future) would translate to OWF sites with a range of different characteristics;
- Section 8: A comparison of the potential costs between different mitigation approaches. To understand the potential value of ADD’s to the UK offshore wind sector by comparing the cost of using ADDs vs other current mitigation techniques such as MMO and PAM;
- Section 9: Detailed discussion and evaluation of methodology for field trials as well as a comparison and evaluation of a number of potential field sites for carrying out further ADD trials. This evaluation also includes a power analysis to determine the sample sizes required to allow a robust assessment of ADD effectiveness. This section concludes with recommendations for methods and sites based on this evaluation;
- Section 10: Overall conclusions and summary of recommendations.