Significance of the Effect

443. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be low. Given that marine mammals can exploit a wide range of prey species but travelling longer distances may be associated with higher rate of energy expenditure, the effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Secondary Mitigation and Residual Effect

444. No secondary marine mammal mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 10.10) is not significant in EIA terms. Therefore the residual effect is considered to be of minor adverse significance, which is not significant in EIA terms.

Operation and Maintenance Phase

Magnitude of Impact

445. Potential impacts on marine mammal prey species during the operation and maintenance phase have been assessed in volume 2, chapter 9 using the appropriate maximum design scenarios for these receptors. These impacts include temporary subtidal habitat loss/disturbance, long term subtidal habitat loss, increased SSC and associated sediment deposition, EMF from subsea electrical cabling and colonisation of foundations, scour protection and cable protection.
446. There is the potential for up to 989,000 m2 of temporary habitat loss/disturbance during the operation and maintenance phase as a result of the use of jack-up vessels during any component replacement activities and during any inter-array, OSPs/Offshore convertor station platform interconnector and offshore export cable repair activities. Given that these impacts will be similar to those identified for temporary habitat loss/disturbance the construction phase (as discussed in paragraph 432) and will be highly restricted to the immediate vicinity of these operations, the magnitude was assessed as negligible. The sensitivity of fish and shellfish receptors ranged from low to medium with the majority of fish receptors deemed to be of low vulnerability and high recoverability. Consequently, the effects of temporary habitat loss/disturbance on fish and shellfish IEFs during the operation and maintenance phase were assessed as being of negligible to minor adverse significance.
447. As described in paragraph 434, the presence of infrastructure within the Proposed Development, will result in long term habitat loss of up to 7,798,856 m2 during the operation and maintenance phase (0.7% of the Proposed Development fish and shellfish ecology study area). An overview of potential impacts to fish and shellfish receptors and sensitivity conclusions were previously presented in paragraph 434 for construction phase and will not be reiterated here for operation and maintenance phase. The effect of temporary long-term habitat loss was assessed as being of minor adverse significance.
448. Increased SSC could occur as a result of repair or remedial burial activities during the operation and maintenance phase. The maximum design scenario assessed in volume 2, chapter 9 for increased SSC and associated deposition is for the repair of cables of up to 30,000 m in length and reburial of cables of up to 10,000 m in length for inter-array cables; and repair of cables of up to 4,000 m in length and reburial of cables of up to 4,000 m in length for offshore export cables, using similar methods as those for cable installation activities (e.g. jet-trenching) undertaken at intervals over the 35 years operation and maintenance phase. The assessment in volume 2, chapter 9 considered that any suspended sediments and associated deposition will be of the same magnitude, or lower as for construction, with the sensitivity of the receptors similar to that assessed for the construction phase (see paragraph 434). The overall significance of the effect was therefore deemed to be of negligible to minor adverse significance.
449. The presence and operation of inter-array, interconnector and offshore export cables will result in emissions of localised electrical and magnetic fields, which could potentially affect the sensory mechanisms of some species of fish and shellfish. Species for which there is evidence of a response to electrical and/or magnetic fields include elasmobranchs (sharks, skates and rays), river lamprey Lampetra fluviatilis, sea lamprey Petromyzon marinus, European eel Anguilla ecommis, plaice and Atlantic salmon Salmo salar (Gill et al., 2005, CSA, 2019). A range of their life functions is supported by either electric or magnetic sense, including detection of prey, predator avoidance, social or reproductive behaviours, orientation, homing, and navigation (Gill et al., 2005; Normandeau et al., 2011). Given that the range over which species can detect EMF will be very localised to within a few centimetres of the buried cable, with rapid decay of the EMF with increasing distance, the magnitude of the impact was assessed as low. Most fish and shellfish species were considered to be of low sensitivity, with the exception of elasmobranchs and decapod crustaceans, which were of medium sensitivity. The significance of the effect was considered to be negligible to minor adverse.
450. Artificial structures introduced to the marine environment, such as wind turbine foundations and scour/cable protection, provide hard substrate for settlement of various organisms, including small crustaceans and polychaete worms. These communities can provide a valuable food source for fish species and therefore, hard substrate habitat is likely to be colonised within days after construction by demersal and semi-pelagic species. The maximum design scenario assessed in volume 2, chapter 9 assumes up to 10,198,971 m2 of habitat created due to the installation of jacket foundations, associated scour protection and cable protection associated with inter-array cables, OSPs/Offshore convertor station platform interconnector cables and offshore export cables. The dominant natural substrate character (e.g. soft sediment or hard rocky seabed) will determine the number of new species found on the introduced vertical hard surface and associated scour protection. When placed on a soft seabed, most of the colonising fish tend to be associated with hard bottom habitats, thus the overall diversity of the area is expected to increase. If infrastructure is introduced to the area of rocky substrates, few species will be added to the area, but the increase in total hard substrate could sustain higher abundance (Andersson et al., 2009). The magnitude of the impact was assessed as low. Most fish and shellfish species are deemed to be of low to medium vulnerability and high recoverability, therefore the sensitivity of the receptor was assessed as low. The effect is expected to be of negligible to minor adverse significance.
451. The impact on marine mammals is predicted to be of local spatial extent, long-term duration, continuous and the effect on marine mammals is of high reversibility. The magnitude is therefore, considered to be low.

Sensitivity of the Receptor

452. Following placement on the seabed, submerged parts of the wind turbines provide hard substrate for the colonisation by high diversity and biomass in the flora and fauna. Faecal deposits of dominant communities of suspension feeders are likely to alter the surrounding seafloor communities by locally increasing food availability (Degraer et al., 2020). Higher trophic levels, such as fish and marine mammals, are likely to profit from locally increased food availability and/or shelter and therefore have the potential to be attracted to forage within offshore wind farm array area. However, still relatively little is known about the distribution and diversity of marine mammals around offshore anthropogenic structures. Species such as harbour porpoise, minke whale, white-beaked dolphin, harbour seal and grey seal were frequently recorded around offshore oil and gas structures (Todd et al., 2016; Delefosse et al., 2018; Lindeboom et al., 2011). Acoustic results from a T-POD measurement within a Dutch wind farm found that relatively more harbour porpoises are found in the wind farm area compared to the two reference areas (Scheidat et al., 2011; Lindeboom et al., 2011). Authors of this study concluded that this effect is directly linked to the presence of the wind farm due to increased food availability as well as the exclusion of fisheries and reduced vessel traffic in the wind farm (shelter effect). Russell et al. (2014) monitored the movements of tagged harbour seals within two active wind farms in the North Sea and demonstrated that animals commonly showed grid-like movement patterns which strongly suggested that the structures were used for foraging. During research on a Danish wind farm, no statistical differences were detected in the presence of harbour porpoises between inside and outside the wind farm (Diederichs et al., 2008). Diederichs et al. (2008) suggested, however, that a small increase in detections during the night at hydrophones deployed in close proximity to single wind turbines may indicate increased foraging behaviour near the monopiles. Whilst there is some mounting evidence of potential benefits of man-made structures in marine environment (Birchenough and Degrae, 2020), the statistical significance of such benefits and details about trophic interactions in the vicinity of artificial structures and their influence on ecological connectivity remain largely unknown (Petersen and Malm, 2007; Inger et al., 2009; Rouse et al., 2020, McLean et al., 2022; Elliott and Birchenough, 2022). Additional details about inter-related effects on marine organisms are provided in section 10.14
453. Overall, the sensitivity of marine mammals during the operation and maintenance phase is not expected to differ from the sensitivity of the receptors during the construction phase described in paragraph 440et seq. The sensitivity of the receptor is therefore, considered to be low.

Significance of the Effect

454. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be low. Given that marine mammals can exploit a wide range of prey species but travelling longer distances may be associated with higher rate of energy expenditure, the effect will, therefore, be of minor adverse significance, which is not significant in EIA terms. This is likely to be a conservative prediction as there is some evidence (although with uncertainties) that marine mammal populations are likely to benefit from introduction of hard substrates and associated fauna during the operation and maintenance phase.

Secondary Mitigation and Residual Effect

455. No secondary marine mammal mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 10.10) is not significant in EIA terms. Therefore the residual effect is considered to be of minor adverse significance, which is not significant in EIA terms.

Decommissioning Phase

Magnitude of Impact

456. Potential impacts on marine mammal prey species during the decommissioning phase have been assessed in volume 2, chapter 9 using the appropriate maximum design scenarios for these receptors. These impacts include temporary subtidal habitat loss/disturbance, long term subtidal habitat loss and increased SSCs and associated sediment deposition.
457. Decommissioning activities such as use of jack-up vessels during foundation removal, removal of inter-array, interconnector and offshore export cables, and associated anchor placements may result in temporary habitat loss/disturbance of up to 34,571,200 m2. The impact is predicted to be of localised extent and affect only a small proportion of this total area at any one time during the decommissioning phase, therefore the magnitude of the impact was assessed as low. The sensitivity of fish and shellfish receptors was considered to be negligible to minor. The significance of effect on marine mammal prey species was therefore deemed to be of negligible to minor adverse significance.
458. Decommissioning of infrastructure will lead to increases in SSC and associated sediment deposition. The maximum design scenario is represented by the cutting and removal of piled jacket foundations at seabed level and removal of inter-array, OSPs/Offshore convertor station platform interconnector and offshore export cables by jet dredging mobilising material from a 0.5 m deep and 2 m wide trench. Increases in SSC and associated deposition are assumed to be of a similar magnitude to the construction phase (i.e. low magnitude). The sensitivity of fish and shellfish receptors was considered to be low to medium and overall significance of the impact was deemed to be of negligible to minor adverse significance.
459. Leaving infrastructure, such as the scour protection associated with wind turbine and OSPs/Offshore convertor station platform foundations and cable protection associated with array, OSPs/Offshore convertor station platform interconnector and offshore export cables, in situ after decommissioning will result in permanent habitat loss with a maximum design scenario of up to 7,562,609 m2. An overview of potential impacts to fish and shellfish receptors and sensitivity conclusions were previously presented in paragraph 10.11.2.434 et seq. The significance of effect was deemed to be of minor adverse.
460. The impact on marine mammals is therefore predicted to be of local spatial extent, medium term duration, intermittent and of high reversibility. The magnitude is therefore, considered to be low.

Sensitivity of the Receptor

461. The sensitivity of marine mammals during the decommissioning phase is not expected to differ from the sensitivity of the receptors during the construction phase described in paragraph 440 et seq. The sensitivity of the receptor is therefore, considered to be low.

Significance of the Effect

462. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be low. Given that marine mammals can exploit a wide range of prey species but travelling longer distances may be associated with higher rate of energy expenditure, the effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Secondary Mitigation and Residual Effect

463. No secondary marine mammal mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond designed in measures outlined in section 10.10) is not significant in EIA terms. Therefore, the residual effect is considered to be of minor adverse significance, which is not significant in EIA terms.

10.11.3.         Proposed Monitoring

464. No residual significant effect on marine mammals has been identified in the assessment provided above (paragraphs 114 et seq.). There are a small residual number of harbour porpoise individuals that could potentially experience auditory injury during UXO clearance activities, and the Applicant will apply for an EPS licence post-consent along with EPS supporting information and UXO specific MMP for these works.  
465. Noise monitoring will be carried out during UXO clearance to provide empirical data on the measured received levels as predicted in the noise model. In addition, in-field noise monitoring has been suggested by stakeholders at increasing distances from the piling location to enhance the understanding of noise characteristics from piling activities and allow comparisons between modelled predictions and real-world data (Table 10.9). Any requirement for monitoring will be approved by MS-LOT.

10.12. Cumulative Effects Assessment

10.12.1.         Methodology

466. The Cumulative Effects Assessment (CEA) takes into account the impact associated with the Proposed Development together with other relevant plans, projects and activities. Cumulative effects are therefore the combined effect of the Proposed Development in combination with the effects from a number of different projects, on the same receptor or resource. Please see volume 1, chapter 6 for detail on CEA methodology.
467. The projects and plans selected as relevant to the CEA presented within this chapter are based upon the results of a screening exercise (see volume 3, appendix 6.4 of the Offshore EIA Report). Volume 3, appendix 6.4 further provides information regarding how information pertaining to other plans and projects is gained and applied to the assessment.  Each project or plan has been considered on a case by case basis for screening in or out of this chapter’s assessment based upon data confidence, effect-receptor pathways and the spatial/temporal scales involved.
468. In undertaking the CEA for the Proposed Development, it is important to bear in mind that other projects and plans under consideration will have differing potential for proceeding to an operational stage and hence a differing potential to ultimately contribute to a cumulative impact alongside the Proposed Development. Therefore, a tiered approach has be adopted. This provides a framework for placing relative weight upon the potential for each project/plan to be included in the CEA to ultimately be realised, based upon the project/plan’s current stage of maturity and certainty in the projects’ parameters. The tiered approach which will be utilised within the Proposed Development CEA employs the following tiers:

• tier 1 assessment – Proposed Development (Berwick Bank Wind Farm offshore) with Berwick Bank Wind Farm onshore;
• tier 2 assessment – All plans/projects assessed under Tier 1, plus projects which became operational since baseline characterisation, those under construction, those with consent and submitted but not yet determined;
• tier 3 assessment – All plans/projects assessed under Tier 2, plus those projects with a Scoping Report; and
• tier 4 assessment – All plans/projects assessed under Tier 3, which are reasonably foreseeable, plus those projects likely to come forward where an Agreement for Lease (AfL) has been granted.
  469. The specific projects scoped into the CEA for marine mammals, are outlined in Table 10.54   Open ▸ . There will be no cumulative effects with onshore elements of Berwick Bank Proposed Development.
  470. The range of potential cumulative impacts that are identified and included in Table 10.54   Open ▸ .
  471. Some of the potential impacts considered within the Proposed Development alone assessment are specific to a particular phase of development (e.g. construction, operation and maintenance or decommissioning). Where the potential for cumulative effects with other plans or projects only have potential to occur where there is spatial or temporal overlap with the Proposed Development during certain phases of development, impacts associated with a certain phase may be omitted from further consideration where no plans or projects have been identified that have the potential for cumulative effects during this period.
  472. As described in volume 1, chapter 3, the Applicant is developing an additional export cable grid connection to Blyth, Northumberland (the Cambois connection). Therefore, applications for necessary consents (including marine licenses) will be applied for separately. The CEA for the Cambois connection is based on information presented in the Cambois connection Scoping Report (SSER, 2022e), submitted in October 2022. The Cambois connection has been scoped into the CEA for marine mammals on the basis that Cambois connection will overlap spatially and temporally with the Proposed Development and the project will engage in activities such as cable burial and installation of cable protection which will impact marine mammal receptors.

Table 10.54: List of Other Developments and Plans Considered within the CEA for Marine Mammals

Figure 10.27: Other Projects/Plans Screened into the Cumulative Effects Assessment for Marine Mammals

473. The maximum design scenarios identified in Table 10.55   Open ▸ have been selected as those having the potential to result in the greatest effect on an identified receptor or receptor group. The cumulative effects presented and assessed in this section have been selected from the details provided in volume 1, chapter 3 of the Offshore EIA Report as well as the information available on other projects and plans (see volume 3, appendix 6.4), to inform a ‘maximum design scenario’. Effects of greater adverse significance are not predicted to arise should any other development scenario, based on details within the Project Design Envelope (e.g. different wind turbine layout), to that assessed here, be taken forward in the final design scheme.
474. As already mentioned in paragraph 472, where there is no spatial or temporal overlap with the activities during certain phases of the Proposed Development, impacts associated with other projects listed in Table 10.54   Open ▸ , may be excluded from further consideration. For the purposes of the marine mammal assessment of effects, cumulative effects have been screened in/out on the following basis:

• Injury/disturbance to marine mammals from elevated underwater noise during pile driving (construction phase) – the ZoI for pile driving can extend beyond the boundaries of proposed offshore wind farms and therefore, adopting a precautionary approach, the assessment has screened in projects within the regional marine mammal study area (harbour porpoise, white-beaked dolphin and minke whale) and within the north-east of Scotland (bottlenose dolphin, grey seal and harbour seal) whose construction phases overlap with the construction phase for the Proposed Development. Projects whose construction phase finishes in a year preceding the commencement of construction phase at the Proposed Development (2024) were screened in as the sequential piling at respective projects could lead to a longer duration of effect.
• Injury/disturbance to marine mammals from elevated underwater noise during site investigation surveys (pre-construction phase, operation and maintenance phase) – it is anticipated that the magnitude of the impacts will be of a similar scale to that described for the Proposed Development with the potential to experience disturbance by marine mammal receptors expected to be localised to within the boundaries of the respective projects. Therefore, the cumulative assessment has focussed only on site investigation surveys for those projects within the Firth of Forth and Tay region (see Figure 10.27   Open ▸ ). Of these, very few projects have considered serious injury surveys within the EIA. For pre-construction phase, where surveys are known to have been completed, this impact has been screened out of the CEA.
• Injury/disturbance to marine mammals from elevated underwater noise during UXO clearance (pre-construction phase) - the ZoI for UXO clearance can extend beyond the boundaries of other proposed offshore wind farms. Therefore, adopting a precautionary approach, the assessment has screened in projects within the regional marine mammal study area (harbour porpoise, white-beaked dolphin and minke whale) and within the north-east of Scotland (bottlenose dolphin, grey seal and harbour seal) whose construction phases (which would include pre-construction UXO clearance) overlap with the construction phase for the Proposed Development. Note, projects with completed UXO clearance campaigns are screened out of the assessment (e.g. Seagreen 1A Project). Projects whose construction phase finishes in a year preceding the commencement of construction phase at the Proposed Development (2024) were screened in as the sequential UXO clearance at respective projects could lead to a longer duration of effect.
• Injury and disturbance to marine mammals from elevated underwater noise due to vessel use and other activities (all phases) – it is expected that each project will contribute to the increase of vessel traffic and hence to the amount of vessel noise in the environment during the construction, operation and maintenance and decommissioning phases. However the potential to experience disturbance by marine mammal receptors would be expected to be localised to within the close vicinity of the respective projects and as such the assessment has focussed only on projects within the Firth of Forth and Tay region (see Figure 10.27   Open ▸ ).
• Injury of marine mammals due to collision with vessels (all phases) – it is expected that each project will contribute to the increase of vessel traffic and hence to the potential risk of collision during the construction, operation and maintenance and decommissioning phases. However the potential to experience disturbance by marine mammal receptors would be expected to be localised to within the close vicinity of the respective projects and as such the assessment has focussed only on projects within the Firth of Forth and Tay region (see Figure 10.27   Open ▸ ).
• Changes in fish and shellfish communities affecting prey availability (all phases) – potential cumulative effects on fish and shellfish assemblages, as identified in volume 2, chapter 9, may have indirect effects on marine mammals. For the purposes of the fish and shellfish ecology assessment of effects, cumulative effects have been assessed within a representative 20 km buffer of the Proposed Development fish and shellfish ecology study area. This 20 km buffer applies to all impacts considered in the assessment, except underwater noise, where a larger buffer of 100 km has been used to account for the larger ZoI of impacts. Therefore, only the projects considered in volume 2, chapter 9 are considered in the assessment of cumulative indirect impacts due to changes in fish and shellfish communities affecting prey availability.
  475. The assessment of cumulative effects with relevant projects has focussed on information available in the public domain (e.g. where the impact has been identified in the scoping study (Tier 3 projects) or the environmental statement (Tier 2 projects)). In this regard, where an impact has been identified and screened in, there is considered to be a potential for cumulative effects. Therefore, the impact will be considered further in section 10.12.2. Impacts scoped out from individual assessments of respective projects are not considered further.

Table 10.55: Maximum Design Scenario Considered for Each Impact as Part of the Assessment of Likely Significant Cumulative Effects on Marine Mammals

10.12.2.         Cumulative Effects Assessment

476. An assessment of the likely significance of the cumulative effects of the Proposed Development upon marine mammal receptors arising from each identified impact is given in paragraph 478 et seq.

Injury and disturbance from elevated underwater noise during piling

Tier 2

Construction phase

477. The construction of the Proposed Development, together with the construction of the Tier 2 projects identified in Table 10.55   Open ▸ , may lead to injury and/or disturbance to marine mammals from underwater noise during piling. Other projects screened into the assessment within the regional marine mammal study area include construction of Inch Cape Offshore Wind Farm, Seagreen 1A Project, Moray West and Blyth Demo 2 for bottlenose dolphin, harbour seal and grey seal and following additional projects Dogger Bank Creyke Beck A, Dogger Back Creyke Beck B, Dogger Bank Teesside A, Sofia Offshore Wind Farm, Hornsea Project Three and Hornsea Project Four for harbour porpoise, white-beaked dolphin and minke whale.
478. The potential to experience injury in terms of PTS by marine mammal receptors as a result of underwater noise due to piling would be expected to be localised to within the boundaries of the respective projects (assuming similar ranges of effect as presented for the Proposed Development). It is also anticipated that standard offshore wind industry construction methods (which include soft starts and visual and acoustic monitoring of marine mammals as standard) will be applied, thereby reducing the magnitude of the impact with respect to auditory injury occurring in marine mammals. Therefore, there is no potential for significant cumulative impacts for injury from elevated underwater noise during pilling and the cumulative assessment focuses on disturbance only.
479. Behavioural disturbance is expected to occur during piling at all offshore wind farms. Of all projects listed in paragraph 478, only construction of Dogger Bank Teesside A, Sofia Offshore Wind Farm, Hornsea Project Three and Hornsea Project Four will overlap with the piling phase for Proposed Development. Although there is an overlap of construction of Inch Cape and Seagreen 1A Project and construction of Proposed Development, the construction of both projects will be completed prior to commencement of piling at the Proposed Development and therefore could lead to a longer duration of piling operations (i.e. sequential rather than concurrent piling). The construction phases of Moray West, Blyth Demo 2, Dogger Bank Creyke Beck A and Dogger Back Creyke Beck B finish in the year following commencement of construction works at Proposed Development (i.e. two years before the commencement of the piling phase at Proposed Development). However, these projects are included in the assessment to consider temporal scenario to take account for potential disturbance to marine mammals caused by subsequent piling at Proposed Development. Where project piling phases overlap, the assessment is, conservatively, based on a maximum design scenario of all projects potentially piling at exactly the same time, however, in practice this is considered to be unlikely. For example, in order to reduce impacts on harbour porpoise within the Southern North Sea SCI, as a part of Site Integrity Plan, Hornsea Project Three have committed to schedule piling having regard to previous, ongoing and future piling associated with other offshore developments and other activities likely to act in-combination (GoBe, 2018b).
480. The cumulative assessment for Dogger Bank Creyke A (Forewind, 2013), Dogger Bank Creyke B (Forewind, 2013), Hornsea Project Three (GoBe, 2018a) and Hornsea Project Four (SMRU Consulting, 2021) is based on the original EIAs submitted alongside applications for Development Consent Orders to the Planning Inspectorate. The assessment for Moray West is based on the original EIA as submitted to Scottish Ministers under Section 36 of the Electricity Act 1989 (Moray West, 2018). Remaining projects listed in paragraph 10.12.1.472 (Blyth Demo 2, Dogger Bank Teesside A, Sofia Offshore Wind Farm and Seagreen 1A Project) had subsequent revisions of the project design. Paragraph 482 et seq. provide for more details about project-specific appraisals taken forward to the cumulative assessment.
481. The original Blyth Offshore Demonstration Project assessed the potential for lethality, injury and behavioural responses to anthropogenic noise based on a maximum design scenario of percussive piling of 15 monopiles (NAREC, 2012). Potential effects of anthropogenic noise impacts were concluded as probable but low in magnitude (NAREC, 2012). A review of the assessments of effects for marine mammals was undertaken as part of the 2013 Supporting Environmental Information (SEI) but this did not lead to any change in the conclusions of the original (NAREC, 2012) EIA (NAREC, 2013). Construction of Blyth Demo 2 will not require piling, as floating platforms with moorings and drag embedment will be used. Subsequently, the magnitude of the impact from subsea noise during piling as a result of the Blyth Demo 2 are considered to be less or equivalent when compared to existing consent (EDF, 2020) where the magnitude was assessed as low.
482. The assessment of underwater noise for Dogger Bank Teeside A was undertaken in the original EIA Report (Forewind, 2014), however, a non-material change application was made to increase maximum hammer energy from 3,000 kJ to 4,000 kJ (Royal HaskoningDHV, 2020). The EIA report concluded that for all marine mammal species there was no difference in the significance of the impacts for the revised application (4,000 kJ hammer) compared to the original EIA Report (3,000 kJ hammer) (Forewind, 2014). Impact ranges and number of animals potentially disturbed were, however, predicted to be larger and therefore this CEA is based on the revised application (Royal HaskoningDHV, 2020).
483. Similarly, for Sofia Offshore Wind Farm, the assessment of underwater noise was undertaken in the original EIA Report for a maximum hammer energy of 3,000 kJ (Forewind, 2014), however, Sofia Offshore Wind Farm Ltd identified that there may be a technical requirement to increase this maximum hammer energy to 4,000 kJ for monopole installation only (Innogy, 2020). The number of disturbed animals during construction of Sofia Offshore Wind Farm is based on the numbers presented as a part of the Environmental Appraisal of Increased Hammer Energy (Innogy, 2020).
484. In 2012, Seagreen submitted an original EIA Report (Seagreen Wind Energy Ltd, 2012) as a part of the application for development consent for Seagreen Offshore Wind Farm consisting of 150 wind turbines and the consent was awarded in October 2014. In 2018, Seagreen Wind Energy Ltd submitted an optimised application to Scottish Ministers for revised designs of the 2014 consented wind farms in the same area based on fewer, larger, higher capacity wind turbines including a monopile foundation option (Seagreen Wind Energy Ltd, 2018). As described in the 2020 PS, due to favourable ground conditions, locations of 114 of the 150 consented wind turbines were considered suitable for suction caisson foundations and these wind turbines are currently under construction (commenced September 2021; Seagreen Wind Energy Ltd, 2020; Seagreen Wind Energy Ltd, 2022a). Installation of the 114 suction caisson foundations does not require pile driving and this part of project is hereinafter referred to as “Seagreen 1”. The remaining 36 locations were, however, identified as requiring use of driven piles. With respect to these 36 locations, in April 2022, Seagreen Wind Energy Ltd. Applied for a variation of 2014 consent to allow for an increased size of wind turbine generators and increased weight of seabed steel deposits associated with the OSPs/Offshore convertor station platforms (Seagreen Wind Energy Ltd, 2022a). This project is hereinafter referred to as “Seagreen 1A Project”. Given that this 2022 variation does not result in a clear impact pathway to marine mammals, the Seagreen S36C Application Screening Report (Seagreen Wind Energy Ltd, 2022b) concluded that potential effects to marine mammals remain as previously assessed in the 2012 EIA Report (Seagreen Wind Energy Ltd, 2012) and 2020 PS (Seagreen Wind Energy Ltd, 2020). The cumulative assessment is based on the maximum design scenario (i.e. whichever is considered would result in the greater potential for cumulative effects between the original and optimised designs). It is, however, worth noting that as a part of the 2020 PS, the revised project design and programme demonstrates that piling for the wind turbines at Seagreen 1A Project is currently planned for April to July 2023 and therefore overlap with the piling programme for the Proposed Development is unlikely (Seagreen Wind Energy Ltd, 2020).
485. The original EIA for Inch Cape Offshore Wind Farm was submitted in 2014 (Inch Cape Offshore Ltd, 2014). However, as advised in the latest MS-LOT scoping opinion (February 2022), the revised EIA Report (Inch Cape Offshore Ltd, 2018) has been used to inform this CEA assessment.
486. Each project screened into cumulative assessment has a slightly different approach to assessing behavioural disturbance of cetaceans and pinnipeds. For many years since it was published, Southall et al. (2007), along with Lucke et al. (2009), has been the source of the most widely used criteria to assess the effects of noise on marine mammals, and was the main criteria used in the assessment of disturbance for Dogger Bank Creyke Beck A, Dogger Bank Creyke Beck B (Forewind, 2013). This represents a fixed threshold value approach, where it is assumed that all animals within the predicted impact area are to display a behavioural reaction, while none of the animals outside this area will react. Since then a dose-response curve derived using received noise level and harbour porpoise presence data (Graham et al., 2017) was used to determine the proportion of animals present likely to be displaced in assessments for projects such as Inch Cape (Inch Cape, 2018), Moray West (Moray West, 2018), Hornsea Project Three (GoBe, 2018a), Hornsea Project Four (SMRU Consulting, 2021) and Proposed Development (cetaceans only, see paragraph 97 et seq.). Given that respective projects used different criteria and noise thresholds modelled for marine mammal receptors in their assessments, it is necessary to exercise considerable caution if attempting any comparison between results of these appraisals. There are also variations between projects in the way results are presented. Using harbour porpoise as an example, some projects, such as Dogger Bank Teesside A and Sofia Offshore Wind Farms provided the range or area from which animals are expected to be excluded along with number of animals potentially disturbed, whilst other projects, such as Inch Cape, provide only number of animals predicted to be displaced due to underwater noise from pile driving. Various densities were used to assess these numbers (e.g. data from the integrated cetacean analysis (Mackenzie et al., 2012) and combined site-specific density surface and SCANS III block data at Hornsea Project Three). As these values come from different sources, density details may reflect various densities of respective species throughout the year (i.e. seasonal versus average across the year). Respective projects also used different reference populations (i.e. Dogger Bank Teesside A used the SCANS III harbour porpoise population, while others such as Inch Cape and Hornsea Project Three used NS MU harbour porpoise population). Furthermore, some projects presented number of animals predicted to be disturbed during concurrent piling events (Hornsea Project Three), while for others only an assessment for single piling was available (i.e. Dogger Bank Teesside A, updated EIA does not indicate whether concurrent piling is considered). Therefore, assessment of the potential effects on marine mammals predicted by other wind farms is not always directly comparable to those presented for Proposed Development due to different approaches to assessment taken by other offshore developers, different noise criteria and thresholds used, and differing levels of detail presented in associated EIAs.
487. Each of the projects screened in for the cumulative assessment also have different construction timeline (i.e. there will be just a year of overlap in the construction phases of the Proposed Development and Seagreen 1A Project and Inch Cape but two or more years of overlap with projects such as Dogger Bank Teesside A/Sofia, Hornsea Project Three and Hornsea Project Four Offshore Wind Farms). However, these timelines are indicative and subject to change. Piling at each of these projects will occur as a discrete element within the overall construction phase and therefore the periods of piling may not coincide.

Magnitude of impact

Harbour porpoise

488. The number of harbour porpoise individuals predicted to be exposed to noise levels that could result in behavioural disturbance at any one time during piling at Seagreen 1A Project ( Table 10.56   Open ▸ ) was based on a SCANS III Block R densities (0.599 animals/km2). The North Sea (ICES Assessment Unit) reference population was used for this assessment (345,373 individuals; Seagreen Wind Energy Ltd, 2020). The original EIA (Seagreen Wind Energy Ltd, 2012) indicated that there is no evidence to show that the impacted area for this species represents important breeding or foraging habitat that would not be available elsewhere within the species home range over the North Sea. An updated assessment provided in the 2020 PS represents no change in impact significance compared to the 2012 EIA assessment. The residual effect of disturbance of harbour porpoise from piling at Seagreen 1A Project was predicted to be of minor adverse significance.
489. The number of harbour porpoise individuals predicted to be exposed to noise levels that could result in a behavioural disturbance at any one time during piling at Inch Cape ( Table 10.56   Open ▸ ) was assessed using densities from SCANS III Block R data. The NS MU harbour porpoise population was taken forward as the reference population to inform the assessment (227,298 individuals: Inch Cape, 2018). The residual effect of behavioural disturbance on harbour porpoise from piling was predicted to be of minor adverse significance due to a medium-term duration and low magnitude (0.1% of NS MU population disturbed) effect.
490. Moray West assessed the number of harbour porpoise predicted to be affected by disturbance based on grid specific surface from MORL (2012) (Moray West, 2018; Table 10.56   Open ▸ ). The NS MU harbour porpoise population has been taken forward as reference population to inform the assessment (345,373 individuals; Moray West, 2018). It has been concluded that due to high mobility of this species and the availability of alternative foraging areas at the scale of the wider management unit, the survival of individuals is unlikely to be affected. However, a maximum of 0.4% of the population is expected to fail to breed over duration of piling (44 days). The residual effect of behavioural disturbance on harbour porpoise from piling was predicted to be of minor adverse significance.
491. The number of harbour porpoise individuals predicted to be exposed to a behavioural disturbance from concurrent piling events at Dogger Bank Creyke Beck A and B ( Table 10.56   Open ▸ ) was assessed using precautionary approach based on densities estimated from site specific surveys and harbour porpoise and potential harbour porpoise sightings combined (Forewind, 2013). The NS MU harbour porpoise population has been taken forward as reference population to inform the assessment (232,450 individuals; Forewind, 2013). The assessment for both, Dogger Bank Creyke Beck A and B, predicted that it is unlikely that a significant effect would occur at the population level. The residual effect of behavioural disturbance on harbour porpoise as a result of piling was predicted to be of minor adverse significance.
492. The number of harbour porpoise individuals predicted to be exposed to a behavioural disturbance at any one time during piling during the construction of Dogger bank Teesside A ( Table 10.56   Open ▸ ) was based on SCANS III Block N harbour porpoise densities. The SCANS III harbour porpoise reference population was used for this assessment (345,373 individuals; Royal Haskoning DHV, 2020). At any one time during piling, harbour porpoise is expected to be disturbed within approximately 34 km from the source. The residual effect of disturbance of harbour porpoise from piling was predicted to be of negligible adverse significance.
493. The revised environmental appraisal for Sofia Offshore Wind Farm (Innogy, 2020) used site-specific survey data to predict the number of harbour porpoise individuals with the potential to be exposed to noise levels that could result in a behavioural disturbance at any one time during piling ( Table 10.56   Open ▸ ). The NS MU harbour porpoise reference population was used for this assessment (227,298 individuals: Innogy, 2020). At any one-time during piling, harbour porpoise was expected to be disturbed within approximately 3,160 km2 from the source. The residual effect of disturbance of harbour porpoise from piling was predicted to be of negligible adverse significance.
494. The assessment for Hornsea Project Three predicted 7,330 porpoises to be exposed to behavioural disturbance during concurrent piling events, by combining the site-specific density surface estimates and the SCANS III density data (where impact areas extended beyond the mapped survey area) ). The NS MU harbour porpoise reference population was used for this assessment (227,298 individuals: GoBe, 2018a). The effect of disturbance of harbour porpoise from piling was predicted to be of minor adverse significance. A cumulative assessment on the North Sea harbour porpoise population as a result of a number of scenarios of offshore wind farm construction in the North Sea has been carried out by Booth et al. (2017) and presented in Hornsea Project Three EIA (GoBe, 2018a). Based on current best evidence and expert judgement on how disturbance will affect individual porpoises, the assessment found that even with 15% of the population potentially disturbed, there was only a small (6%) increase in the risk of an annual population decline of 1% per year and that overall, impacted population trajectories were not significantly different from baseline population trajectories.
495. Hornsea Project Four assessed the number of minke whales predicted to be affected by disturbance based on SCANS III block O[9] (0.888 animals/km2; SMRU Consulting, 2021; Table 10.56   Open ▸ ). The NS MU harbour porpoise population has been taken forward as reference population to inform the assessment (345,373 individuals). Based on findings of Benhemma-Le Gall et al. (2021), it was concluded that harbour porpoise can compensate for any resulting loss in energy intake by increasing foraging activities beyond impact zone and therefore the EIA considered it unlikely that there would be any significant effect on survival and reproductive rates, and thus no long-term effect on population trajectory (SMRU Consulting, 2021). The residual effect of behavioural disturbance on harbour porpoise from piling was predicted to be slight, which is not significant in EIA terms.

Table 10.56: Harbour Porpoise Cumulative Assessment – Numbers Predicted to be Disturbed as a Result of Underwater Noise During Piling for Tier 2 Projects

496. Most projects refer to the North Sea reference population, which, as presented in the original Seagreen EIA (Seagreen Wind Energy Ltd, 2012), stretches across an area of 750,000 km2. The number of harbour porpoise potentially disturbed has been considered for projects located more than 300 km from the Proposed Development array area ( Table 10.54   Open ▸ ). Delineating the spatial extent of cumulative effects is commonly acknowledged as a challenge. Although harbour porpoise is generally rare in waters >200 m depth, the fact that this species utilises such a vast area further complicates a choice of appropriate spatial scale (Murray et al., 2014). Given the vast extent of available habitat, the fact that harbour porpoise is a wide ranging species and the low percentage of the NS MU population disturbed as a result of piling at respective projects ( Table 10.57   Open ▸ ), the likelihood of cumulative effects with projects located at large distances (e.g. >100 km) from the Proposed Development is considered to be low.
497. Due to the short-term, intermittent occurrence of piling within the wider construction phases (paragraph 488) and the conservative nature of each assessment, a cumulative assessment of the potential effects on marine mammals has been carried out by combining numbers of animals potentially disturbed across regional marine mammal study area. This is likely to represent an over precautionary assessment. Nevertheless, population modelling was carried out to explore the potential for cumulative effects as a result of disturbance during piling to affect the population trajectory over time (discussed with consultees during the Road Map meetings; Table 10.9   Open ▸ ). Population modelling considered all projects listed in Table 10.56   Open ▸ and respective numbers of animals potentially impacted against the MU population (see volume 3, appendix 10.4 for methods applied in the model). Results of the cumulative iPCoD modelling for harbour porpoise showed that the median ratio of size of the impacted to unimpacted population at a time point of 25 years after commencement of piling at cumulative projects was 99.2%. Small differences in the population size over time (e.g. 345,311 for the impacted population vs 349,064 for the unimpacted population at 25 years) fall within the natural variance of the population trajectory as can be seen in Figure 10.28   Open ▸ . Therefore, it was considered that there is no potential for a long-term effect on this species as a result of cumulative piling at the Proposed Development and respective projects (see volume 3, appendix 10.4 for more details).

Figure 10.28: Simulated Harbour Porpoise Population Sizes for Both the Baseline and the Impacted Populations Under the Cumulative Scenario and no Vulnerable Subpopulation.

498. The cumulative impact of behavioural disturbance with respect to harbour porpoise is predicted to be of regional spatial extent, medium term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be low.

Figure 10.29: Unweighted Single Pulse SEL Contours Due to Concurrent Impact Piling of Piles at Wind Turbines at Maximum Hammer Energy (4,000 kJ) Overlaid with Projects within a Footprint of Behavioural Disturbance.

Bottlenose dolphin

499. The number of bottlenose dolphin individuals predicted to be exposed to noise levels that could result in a behavioural disturbance at any one time during piling in Seagreen Project 1A ( Table 10.57   Open ▸ ) was based on a precautionary scenario. Densities were calculated on the assumption that half of the total MU population (98) is spread evenly across the area inside the 20 m depth contour between Aberdeen and south of Firth of Forth. The CES MU population was taken forward as reference population to inform the assessment (195 individuals, Seagreen Wind Energy Ltd, 2020). The residual effects of disturbance of bottlenose dolphin from piling at Seagreen 1A Project were predicted to be of minor adverse significance. To provide context for this assessment it is worth noting that the revised EIA used iPCoD population modelling to investigate effects of disturbance from the construction of 150 wind turbines when built sequentially (Seagreen Wind Energy Ltd, 2018). The results of iPCoD model predicted that the mean impacted baseline population would experience an initial slight decline in the growth rate. However, the population would continue to increase at the same rate as the baseline population for the remainder of the stimulations. There was no significant difference between the predicted baseline (unimpacted) and impacted population sizes as a result of predicted levels of disturbance.
500. The number of bottlenose dolphin individuals predicted to be exposed to noise levels that could result in behavioural disturbance at any one time during piling at Inch Cape ( Table 10.57   Open ▸ ) was assessed using densities calculated based on the assumption that half of the total CES MU population (98) is spread evenly across the area inside the 20 m depth contour from Rattray Head south. The CES MU bottlenose dolphin population was taken forward as the reference population to inform the assessment (195 individuals; Inch Cape, 2018). Population level modelling predicted that displacement from pile driving at Inch Cape is unlikely to affect the size or growth of the bottlenose dolphin population off the east coast of Scotland. The residual effect of behavioural disturbance of bottlenose dolphin from piling was predicted to be of minor adverse significance due to a medium term duration and low magnitude (< 10% of CES MU population disturbed).
501. Moray West assessed the number of bottlenose dolphin predicted to be affected by disturbance based on grid specific surface densities from revised MORL (2012) (Moray West, 2018). The CES MU bottlenose dolphin population was taken forward as reference population to inform the assessment (195 individuals; Moray West, 2018). It was concluded that the highest bottlenose dolphin abundance areas were relatively distant from the piling locations and due to the high mobility of bottlenose dolphins and the availability of alternative known foraging areas and other areas of high usage within the Moray Firth, short-term displacement was unlikely to result in any effect on the survival of individuals. Population modelling results indicated that none of the bottlenose impact scenarios discussed in the EIA resulted in a significant long term population effects (Moray West, 2018). The residual effects of behavioural disturbance of bottlenose dolphin from piling was predicted to be of minor adverse significance.

Table 10.57: Bottlenose Dolphin Cumulative Assessment – Numbers Predicted to be Disturbed as a Result of Underwater Noise During Piling for Tier 2 Projects

502. All projects screened in for the cumulative assessment for bottlenose dolphin ( Table 10.57   Open ▸ ) are located within the main distributional range of the population, restricted to the Moray Firth and coastal waters of the eastern Scotland ( Figure 10.31   Open ▸ ).
503. Population modelling considered all projects listed in Table 10.57   Open ▸ Table 10.56   Open ▸ and respective numbers of animals potentially impacted against the MU population (see volume 3, appendix 10.4 for methods applied in the model). Results of the cumulative iPCoD modelling for bottlenose dolphin showed that the median ratio in population size between the impacted and unimpacted population was 100% at a time point 25 after commencement of piling at cumulative projects. Very small differences in population size (i.e. 513 for the impacted population and 532 for the unimpacted population at 25 years) fall within the natural variance of the population ( Figure 10.30   Open ▸ ). Therefore, it was considered that there is no potential for a long-term effect on this species as a result of cumulative piling at the Proposed Development and respective projects (see volume 3, appendix 10.4 for more details).

Figure 10.30: Simulated Bottlenose Dolphin Population Sizes for Both the Baseline and the Impacted Populations Under the Cumulative Scenario and no Vulnerable Subpopulation.

504. The cumulative impact of behavioural disturbance with respect to bottlenose dolphin is predicted to be of regional spatial extent, medium term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore, considered to be low.

Figure 10.31: Unweighted Single Pulse SEL Contours Due to Concurrent Impact Piling at Maximum Hammer Energy (4,000 kJ) Overlaid with Projects within a Distributional Range of Bottlenose Dolphin Population

White-beaked dolphin

505. The number of white-beaked dolphin individuals predicted to be exposed to noise levels that could result in behavioural disturbance at any one time during piling at Seagreen Project 1A ( Table 10.58   Open ▸ ) was based on a precautionary scenario using densities from SCANS III Block R (0.243 dolphins/km2). The CGNS MU white-beaked dolphin abundance estimate was taken forward as a reference population to inform the assessment (36,287 individuals; Seagreen Wind Energy Ltd, 2020). The residual effect of disturbance of white-beaked dolphin from piling at Seagreen 1A Project, was predicted to be of minor adverse significance
506. The number of white-beaked dolphin individuals predicted to be exposed to noise levels that could result in a behavioural disturbance at any one time during piling at Inch Cape ( Table 10.58   Open ▸ ) was assessed using densities from SCANS III Block R data. The CGNS MU white-beaked dolphin population has been taken forward as the reference population to inform the assessment (15,895 individuals: Inch Cape, 2018). The residual effect of behavioural disturbance of white-beaked dolphin from piling was predicted to be of minor adverse significance due to a medium-term duration and low magnitude of effect (0.3% of CGNS MU population disturbed).
507. The number of white-beaked dolphin individuals predicted to be exposed to noise levels that could result in behavioural disturbance from concurrent piling events at Dogger Bank Creyke Beck A and B ( Table 10.58   Open ▸ ) was assessed using average densities estimated from site-specific surveys (Forewind, 2013). Updated analysis of the SCANS-II white-beaked dolphin population has been taken forward as the European reference population to inform the assessment (16,536 individuals; Forewind, 2013). The assessment for both Dogger Bank Creyke Beck A and B predicted that it is unlikely that a significant effect would occur at the population level. The residual effect of behavioural disturbance of white-beaked dolphin a result of piling was predicted to be of minor adverse significance.
508. The number of white-beaked dolphin individuals predicted to be exposed to a behavioural disturbance at any one time during piling at Dogger bank Teesside A ( Table 10.58   Open ▸ ) was based on SCANS-III Block O white-beaked dolphin densities. The CGNS MU white-beaked dolphin reference population was used for this assessment (15,895 individuals: Royal Haskoning DHV, 2020). At any one time during piling, white-beaked dolphin was expected to be disturbed within approximately 11 km from the source. The residual effect of disturbance of white-beaked dolphin from piling was predicted to be of negligible adverse significance.
509. The revised environmental appraisal for Sofia Offshore Wind Farm (Innogy, 2020) predicted the number of white-beaked dolphin individuals with potential to be exposed to a behavioural disturbance at any one time during piling ( Table 10.58   Open ▸ ) based on densities from site specific surveys. The British Irish MU white-beaked dolphin reference population (IAMMWG (2013) based on SCANS II) was used for this assessment (15,895 individuals: Innogy, 2020). At any one time during piling, white-beaked dolphin was expected to be disturbed within approximately 390 km2 from the source. The residual effect of disturbance of white-beaked dolphin from piling was predicted to be of negligible adverse significance.
510. The assessment for Hornsea Project Three predicted 12 white-beaked dolphins to be exposed to behavioural disturbance during concurrent piling events, by combining the site-specific density surface and the SCANS-III density data ( Table 10.58   Open ▸ ). The CGNS MU white-beaked dolphin reference population was used for this assessment (15,895 individuals: GoBe, 2018a). The residual effect of disturbance of white-beaked dolphin from piling was predicted to be of negligible adverse significance.
511. Hornsea Project Four assessed the number of white-beaked dolphins predicted to be disturbed based on SCANS III block O (0.002 animals/km2; SMRU Consulting, 2021; Table 10.58   Open ▸ ). The CGNS MU white-beaked dolphin population has been taken forward as reference population to inform the assessment (43,951 individuals). The assessment for Hornsea Project Four EIA considered it unlikely for animals to remain in the impacted area on repeated days of impact, and thus unlikely that they would receive the repeated levels of disturbance that would result in changes to vital rates (SMRU Consulting, 2021). The residual effect of behavioural disturbance on white-beaked from piling was predicted to be slight, which is not significant in EIA terms.

Table 10.58: White-Beaked Dolphin Cumulative Assessment – Numbers Predicted to be Disturbed as a Result of Underwater Noise During Piling for Tier 2 Projects

512. The cumulative assessment of the potential effects on marine mammals carried out by combining numbers of animals potentially disturbed based on estimated by various wind farms is likely to be over precautionary due to the short-term, intermittent occurrence of piling within the wider construction phases (paragraph 488) and the conservative nature of each assessment. Since iPCoD did not facilitate modelling for white-beaked dolphin, as agreed with consultees ( Table 10.9   Open ▸ ) no population modelling was carried out for this species.
513. Given the vast extent of available habitat, the fact that white-beaked dolphin is a wide ranging species and the low percentage of the CGNS MU population potentially disturbed as a result of piling at respective projects ( Table 10.58   Open ▸ ), the likelihood of cumulative effects with projects located at very large distances (e.g. >100 km) from the Proposed Development is considered to be low.
514. There is, however, the potential for cumulative effects with projects within the behavioural disturbance footprint of the Proposed Development. Figure 10.10   Open ▸ displays unweighted noise contours with SELss values decreasing in 5 dB steps from the source. The outermost contour of 120 dB represents the edge of the area within which white-beaked dolphins may experience noise levels which could result in behavioural disturbance during concurrent piling (at a 4,000 kJ hammer energy) at the Proposed Development.
515. Only Inch Cape and Seagreen Project 1A are located within these disturbance contours ( Figure 10.29   Open ▸ ). The assessment presented in the Inch Cape EIA (Inch Cape Offshore Ltd, 2018) and Seagreen 1A Project PS (Seagreen Wind Energy Ltd, 2020) estimated that 48 and 764 white-beaked dolphins could experience disturbance during piling at respective projects ( Table 10.58   Open ▸ ). The construction of Inch Cape and Seagreen 1A Project will be completed prior to commencement of piling at the Proposed Development so the potential for simultaneous piling, and therefore additive cumulative effects, with Proposed Development is highly unlikely. However, there is a potential that animals in the vicinity of the Firth of Forth will experience disturbance consecutively as piling at different projects progresses.
516. The cumulative impact of behavioural disturbance with respect to white-beaked dolphin is predicted to be of regional spatial extent, medium term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore, considered to be low.

Minke whale

517. The number of minke whale individuals predicted to be exposed to noise levels that could result in a behavioural disturbance at any one time during piling at Seagreen Project 1A ( Table 10.59   Open ▸ ) was based on a precautionary scenario using integrated cetacean analysis. The European reference population was used for this assessment combining estimates from SCANS-II and CODA (25,379 individuals: Seagreen Wind Energy Ltd, 2012). The original EIA reported that as a result of piling, minke whale is expected to show a behavioural response to piling across an area of up to 18,195 km2 in extent (Seagreen Wind Energy Ltd, 2012). The effects are considered in context of the North Sea as a minimum range for this species (approximately 750,000 km2) and therefore the area of exclusion represents approximately 2.4% of the wider available habitat (Seagreen Wind Energy Ltd, 2012).
518. The number of minke whale individuals predicted to be exposed to noise levels that could result in behavioural disturbance at any one time during piling at Inch Cape ( Table 10.59   Open ▸ ) was assessed using densities from SCANS III Block R data. The CGNS MU minke whale population has been taken forward as reference population to inform the assessment (23,528 individuals: Inch Cape, 2018). The residual effect of behavioural disturbance of minke whale from piling was predicted to be of minor adverse significance due to its medium-term duration and low magnitude (0.7% of the CGNS MU population disturbed).
519. Moray West assessed the number of minke whales predicted to be affected by disturbance based on grid specific densities from Paxton et al. (2014) (Moray West, 2018). The CGNS MU minke whale population has been taken forward as reference population to inform the assessment (23,528 individuals; Moray West, 2018). The residual effects of behavioural disturbance on minke whale from piling was predicted to be of minor adverse significance.
520. The number of minke whale individuals predicted to be exposed to noise levels that could result in behavioural disturbance from concurrent piling events at Dogger Bank Creyke Beck A and B ( Table 10.58   Open ▸ ) is assessed using average densities estimated from site specific surveys (Forewind, 2013). The updated analysis of the SCANS II minke whale population has been taken forward as reference European population to inform the assessment (25,723 individuals; Forewind, 2013). The assessment for both, Dogger Bank Creyke Beck A and B, predicted that it is unlikely that a significant effect would occur at the population level. The residual effect of behavioural disturbance of minke whale as a result of piling was predicted to be of minor adverse significance.
521. The number of minke whale individuals predicted to be exposed to noise levels that could result in behavioural disturbance at any one time during piling at Dogger bank Teesside A ( Table 10.59   Open ▸ ) was based on SCANS III block N minke whale densities. The CGNS MU minke whale reference population was used for this assessment (23,528; Royal Haskoning DHV, 2020). During piling, minke whale was expected to be disturbed within approximately 41 km from the source. The residual effect of disturbance of minke whale from piling was predicted to be of negligible adverse significance.
522. The revised environmental appraisal for Sofia Offshore Wind Farm (Innogy, 2020) predicted the number of minke whale individuals with potential to be exposed to noise levels that could result in behavioural disturbance at any one time during piling ( Table 10.59   Open ▸ ) based on densities from site specific surveys. The British Irish Management Unit minke whale reference population (IAMMWG, 2013 based on SCANS II and CODA (Hammond et al. 2009)) was used for this assessment (23,528 individuals: Innogy, 2020). During piling, minke whale was expected to be disturbed within approximately 4,370 km2 from the source. The residual effect of disturbance of minke whale from piling was predicted to be of negligible adverse significance.
523. The assessment for Hornsea Project Three predicted 51 minke whales could be exposed to noise levels that could result in behavioural disturbance during concurrent piling events, by using SCANS III density data (GoBe, 2018a; Table 10.59   Open ▸ ). The CGNS MU minke whale reference population was used for this assessment (23,528 individuals: GoBe, 2018a). The effect of disturbance on minke whale from piling was predicted to be of minor adverse significance.
524. Hornsea Project Four assessed the number of minke whales predicted to be affected by disturbance based on SCANS III block O (0.010 animals/km2; SMRU Consulting, 2021; Table 10.59   Open ▸ ). The CGNS MU minke whale population has been taken forward as reference population to inform the assessment (20,118 individuals). Based on findings of expert elicitation and most conservating approach, individuals could be repeatedly disturbed and in the year of disturbance a small proportion of the MU could potentially fail to breed (SMRU Consulting, 2021). However, since animals are likely to move away from the area and therefore not be subject to repeated disturbance, this scenario was considered unlikely. The residual effect of behavioural disturbance on minke whale from piling was predicted to be slight, which is not significant in EIA terms.

Table 10.59: Minke Whale Cumulative Assessment – Numbers Predicted to be Disturbed as a Result of Underwater Noise During Piling for Tier 2 Projects

525. Given the extent of available habitat, the fact that minke whale is a wide ranging species and low percentage of the CGNS MU population potentially disturbed as a result of piling at respective projects ( Table 10.58   Open ▸ ), the likelihood of cumulative effects with projects located at very large distances (e.g. >100 km) from the Proposed Development is considered to be low.
526. Population modelling considered all projects listed in Table 10.59   Open ▸ and respective numbers of animals potentially impacted against the MU population (see volume 3, appendix 10.4 for methods applied in the model). Results of the cumulative iPCoD modelling for minke whale suggested a very slight decrease in the mean ratio size of the impacted population after the first two piling campaigns at Berwick Bank. However, the median of the ratio of impacted to unimpacted population size was predicted as 100% at all time points and growth rate remains constant suggesting that such declines would not be discernible in the context of natural population stochasticity, as can be seen in Figure 10.32   Open ▸ .

Figure 10.32: Simulated Minke Whale Population Sizes for Both the Baseline and the Impacted Populations Under the Cumulative Scenario and no Vulnerable Subpopulation

527. Therefore, it was considered that there is no potential for a long-term effects on this species as a result of cumulative piling at proposed Development and respective projects (see volume 3, appendix 10.4 for more details).

Figure 10.32: Simulated Minke Whale Population Sizes for Both the Baseline and the Impacted Populations Under the Cumulative Scenario and no Vulnerable Subpopulation

528. The cumulative impact of behavioural disturbance with respect to minke whale is predicted to be of regional spatial extent, medium term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore, considered to be low.

Harbour seal

529. The number of harbour seal individuals predicted to be exposed to noise levels that could result in behavioural disturbance at any one time during piling at Seagreen Project 1A ( Table 10.60   Open ▸ ) was based on a precautionary scenario using regional density estimates (at-sea densities as presented in Sparling et al., 2012). The East Coast Management Area (ECMA), which extends from Fraserburgh to the Scotland-England border was used as reference population for the assessment (540 individuals: Seagreen Wind Energy Ltd, 2012). The original EIA reported that as a result of piling, harbour seal is expected to show behavioural response to piling across an area of up to 885 km2 in extent (Seagreen Wind Energy Ltd, 2012). Due to a high level of uncertainty regarding harbour seal behavioural response to piling as well as biological consequences of the disturbance, the 100% of reduction in fecundity for up to 9% of the population was conservatively assumed for the duration of piling (two years). However, it needs to be noted, that although the original EIA represents the maximum design scenario when compared to the 2020 PS in terms of numbers of harbour seals potentially affected, the revised project design envelope represents a 76% reduction in terms of the number of piled wind turbines compared to the maximum design scenario assessed in the original 2012 EIA. Additionally, 2020 PS assumes 36 days of piling and therefore, the duration of any disturbance will be relatively short in comparison to the duration of 300 days originally assessed (Seagreen Wind Energy Ltd, 2020).
530. The number of harbour seal individuals predicted to be exposed to noise levels that could result in behavioural disturbance at any one time during piling at Inch Cape ( Table 10.60   Open ▸ ) was assessed using densities from seal usage maps produced by SMRU (Inch Cape, 2018). The ES MU harbour seal population was taken forward as reference population to inform the assessment (511 individuals: Inch Cape, 2018). The residual effect of behavioural disturbance of harbour seal from piling was predicted to be of minor adverse significance due to a medium-term duration and a low magnitude of effect (< 10% of the ES MU population disturbed).

Table 10.60: Harbour Seal Cumulative Assessment – Numbers Predicted to be Disturbed as a Result of Underwater Noise During Piling for Tier 2 Projects

531. Population modelling considered all projects listed in Table 10.60   Open ▸ and respective numbers of animals potentially impacted against the MU population (see volume 3, appendix 10.4 for methods applied in the model). Results of the cumulative iPCoD modelling for harbour seal showed that no impacts are predicted on the population resulting from disturbance due to cumulative piling events, with the median of the ratio of impacted population to unimpacted population 100% at all modelled time points. Therefore, it was considered that there is no potential for a long-term effect on this species as a result of cumulative piling at the Proposed Development and respective projects ( Figure 10.33   Open ▸ ; see volume 3, appendix 10.4 for more details).

Figure 10.33:  Simulated Harbour Seal Population Sizes for Both the Baseline and the Impacted Populations Under the Cumulative Scenario and no Vulnerable Subpopulation.

532. The cumulative impact of behavioural disturbance with respect to harbour seal is predicted to be of regional spatial extent, medium term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore, considered to be low.

Grey seal

533. The number of grey seal individuals predicted to be exposed to noise levels that could result in behavioural disturbance at any one time during piling at Seagreen Project 1A ( Table 10.61   Open ▸ ) was based on a precautionary scenario using regional density estimates (at-sea densities as presented in Sparling et al., 2012). The ECMA was used as reference population for the assessment (5,657 to 12,011 individuals; Seagreen Wind Energy Ltd, 2012). The original EIA reported that as a result of piling, grey seal is expected to show a behavioural response to piling across an area of up to 885 km2 in extent (Seagreen Wind Energy Ltd, 2012). It was assumed that repeated exposure may lead to habituation or seals may be sufficiently motivated to carry on their normal behaviour despite the noise. As reported in the original Seagreen EIA and supported by most recent studies (SCOS,2020), the population of the east coast is increasing and therefore is likely to be robust to the degree of perturbation caused by behavioural response to pile driving. The residual effect of disturbance of grey seal from piling was predicted to be of minor adverse significance. Moreover, as previously presented for harbour seal in paragraph 530, although the original EIA represents the maximum design scenario when compared to the 2020 PS in terms of numbers of grey seals potentially affected, 2020 PS assumes 36 days of piling and therefore, the duration of any disturbance will be relatively short in comparison to the duration of 300 days originally assessed (Seagreen Wind Energy Ltd, 2020).
534. The number of grey seal individuals predicted to be exposed to a behavioural disturbance at any one time during piling at Inch Cape ( Table 10.61   Open ▸ ) was assessed using densities from seal usage maps produced by SMRU (Inch Cape, 2018). The ES MU grey seal population has been taken forward as reference population to inform the assessment (15,950 individuals: Inch Cape, 2018). The residual effect of behavioural disturbance of grey seal from piling was predicted to be of minor adverse significance due to medium term duration and low in magnitude (< 10% of the ES population disturbed).

Table 10.61: Grey Seal Cumulative Assessment – Numbers Predicted to be Disturbed as a Result of Underwater Noise During Piling for Tier 2 Projects

535. Population modelling considered all projects listed in Table 10.56   Open ▸ and respective numbers of animals potentially impacted against the MU population (see volume 3, appendix 10.4 for methods applied in the model). Results of the cumulative iPCoD modelling for grey seal showed that no impacts are predicted on the population resulting from disturbance due to cumulative piling events, with the median of the ratio of impacted population to unimpacted population 100% at all modelled time points. Therefore, it was considered that there is no potential for a long-term effect on this species as a result of cumulative piling at the Proposed Development and respective projects ( Figure 10.34   Open ▸ , see volume 3, appendix 10.4 for more details).

Figure 10.34:  Simulated Grey Seal Population Sizes for Both the Baseline and the Impacted Populations Under the Cumulative Scenario and no Vulnerable Subpopulation

536. The cumulative impact of behavioural disturbance with respect to grey seal is predicted to be of regional spatial extent, medium term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore, considered to be low.

Sensitivity of receptor

537. The sensitivity of marine mammal IEFs to disturbance from elevated underwater noise due to piling activities is as described in section 10.11, paragraph 207 et seq. Behavioural disturbance may lead to the interruption of normal behaviours (such as feeding or breeding) and avoidance, leading to displacement from the area and exclusion from potentially critical habitats, making it difficult for an animal to perform its regular functions (Goold, 1996; Weller et al., 2002; Castellote et al., 2010, 2012). Some exposures may be loud enough to trigger stress responses, which in turn can lead to a depressed immune function and reduced reproductive success (Anderson et al., 2011; De Soto et al., 2013). The extent to which an animal will be behaviourally affected, however, is very much context-dependant and varies both inter- and intra-specifically.
538. All marine mammals, which are IEFs of international value, are deemed to be of medium vulnerability and high recoverability. The sensitivity of the receptors to behavioural disturbance is therefore considered to be medium.

Significance of effect

539. Overall, the magnitude of the cumulative effect is deemed to be low and the sensitivity of the receptor is considered to be medium. The cumulative effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Further mitigation and residual effect

540. No secondary marine mammal mitigation, other than that proposed for the Proposed Development alone (described in detail in paragraph 244 et seq.) is considered necessary because the predicted effect in the absence of mitigation is not significant in EIA terms.