The methodology set out in section 4 will be followed when preparing the marine mammal chapter of the Array EIA Report. The following guidance documents will also be considered with regard to marine mammals:

CIEEM guidelines for marine and coastal ecological impact assessment in Britain and Ireland (CIEEM, 2019);
European Union Guidance on wind energy developments and Natura 2000 and EU Nature legislation (European Commission (EC), 2010, 2021);
Oslo Paris Convention (OSPAR) guidance on environmental considerations for offshore wind farm development (OSPAR, 2008); and
The marine mammal noise exposure criteria recommended in Southall et al., (2019); and
JNCC guidelines for minimising the risk of injury to marine mammals from piling noise (JNCC, 2010a).

A detailed quantitative subsea noise assessment will be used to inform the impact assessment. The subsea noise assessment will include UXO clearance, pile driving, rock placement and vessel noise. This assessment will include PTS and behavioural disturbance with the risk of injury based on a dual metric approach: SELcum and peak SPLpeak. In order to assess the SELcum criterion, the predictions of received sound level over 24 hours are frequency weighted, to reflect the hearing sensitivity of each functional hearing group. The SPLpeak criterion will be used for unweighted received sound level. Good practice methodology will be followed during the assessment of disturbance, which, where possible, will include consideration of species-specific dose-response curves. Noise contours at appropriate intervals will be generated by the noise modelling. These contours will be overlain on species density surfaces to predict the number of animals potentially affected.
At this stage, the species densities surfaces and agreement of correction factors for availability bias will be discussed with relevant stakeholders as part of consultation process.

The key cumulative effect is likely to come from subsea noise produced by piling during the construction phase. A range of realistic cumulative subsea noise scenarios will be assessed in the CEA. This will be based on desk-based resources, communication with other developers (where possible), and consultation and agreement with stakeholders and regulators.
The approach to the CEA for marine mammal receptors will be holistic and combine all potential subsea noise sources:

piling;
UXO clearance;
disturbance from vessels; and
any other offshore construction that is planned within the relevant MUs for each species (such as rock placement).

Realistic scenarios for the CEA for subsea noise will be based on impacts that do not already occur throughout the baseline environment. For example, the impacts of commercial fishing and shipping will not be considered in the CEA as they already occur throughout the baseline environment and are therefore accounted for in the abundance and density estimates of the target marine mammal species.
The CEA will follow the approach outlined in section 4.3.7.

Appendix 3 presents the transboundary impacts screening which has been carried out for the Array. This screening exercise identified that there is no potential for significant transboundary impacts upon marine mammals from construction, operational and maintenance, and decommissioning impacts of the Array.

Do you agree with the study areas defined for marine mammal ecology?
Do you agree that the existing data available to describe the marine mammal baseline remains sufficient to describe the physical environment in relation to the Array? Are there any further desktop datasets which you would recommend are included?
Do you agree that the designed in measures described provides a suitable means for managing and mitigating the potential effects of the Array on the marine mammal receptors?
Do you agree that the impacts listed in Table 6.13 Open ▸ should be scoped in to the impact assessment for marine mammal receptors?
Do you agree that the impacts listed in Table 6.14 Open ▸ should be scoped out of the Array EIA Report for marine mammals?

This section provides a summary of suggested topic specific next steps that will be undertaken throughout the EIA process:

develop the approach and parameters to be used in subsea noise modelling with stakeholders, including:

– modelling locations;

– pile types;

– maximum hammer energy and duration;

– duration of soft start and ramp up energies;

– number of piles installed per day;

– occurrence of concurrent piling (i.e. more than one piling operation in the same day); and

– number of, size of and associated clearance charges of UXO.

Additionally, the durations and requirements of additional mitigation measures, such as soft-start and ramp-up measures, and the use of MMOs, PAM and ADDs, will be discussed with stakeholders and informed by the relevant guidance (JNCC, 2010a, 2010b, 2017).
The approach to these will be discussed as part of the post-Scoping consultation process as described in the dSEP (Appendix 1).