9.3 Scope – Underwater Noise
9.3.1 Study Area 5.
The study area is defined by the area within which noise could potentially propagate to the extent that it may no longer be deemed to have an adverse impact on marine fauna. Thus, an area encompassing approximately 180 by 180km around the modelled foundations was adopted for single piling to ensure sufficiently large ranges were considered for the assessment.
9.3.2 Worst Case 6.
The worst case noise source modelled is pile driving using a 3,500kJ (Chapter 5 Description of the Development) hammer energy, this representing the highest hammer blow energy that is proposed for use at the East Anglia THREE site. Whilst this provides the potential worst case scenario, the maximum energy required to complete pile installation is likely to be less than 3,500kJ.
9.3.3 Embedded Mitigation 7.
To minimise any impacts resulting from underwater noise, mitigation strategies would be used during construction, primarily to reduce the risk of injury to marine mammals, in-line with JNCC guidance (JNCC 2010). In terms of the resulting underwater noise levels this includes the use of soft-start at the onset of piling to ensure a gradual increase in noise for every piling event. Receptor specific mitigation is provided in the fish and marine mammal impact assessments (Chapter 11 Fish and Shellfish Ecology and Chapter 12 Marine Mammal Ecology respectively).
9.4 Assessment Methodology – Underwater Noise
9.4.1 Legislation, Policy and Guidance 8.
Specific consideration has been given to the relevant NPS’, the principal decision making documents for Nationally Significant Infrastructure Projects (NSIP). The NPS relevant to the underwater noise assessment for these projects include; Overarching NPS for Energy (EN-1) (National Policy Statement (NPS) EN-1 2011); and NPS for Renewable Energy Infrastructure (EN-3) (National Policy Statement (NPS) EN-3 2011).
9.
Guidance is also provided by the Joint Nature Conservation Committee (JNCC) protocol for minimising the risk of injury to marine mammals from piling noise, (JNCC 2010), which has been used to inform the minimum requirements for mitigation relating to soft-start.
10.
The Marine Strategy Framework Directive (MSFD) 2008/56/EC (European Commission 2008) Descriptor No. 11, Criterion 11.1, Indicator 11.1.1 (Van der Graaf
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 9 Underwater Noise Page 3
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