6.3. Assessment of the Adverse Efects of the Array Alone

6.3.1. Underwater Noise Generated During Piling

  1. The LSE2 assessment during the HRA Stage One process identified that during the construction phase, LSE2 could not be ruled out for underwater noise generated during piling. This relates to the following sites and relevant Annex II marine mammal features:
  • Berwickshire and North Northumberland Coast SAC;

–           grey seal.

  • Southern North Sea SAC; and

–           harbour porpoise.

  • Moray Firth SAC;

–           bottlenose dolphin.

  1. The MDS and designed in measures considered for the assessment of underwater noise generated during piling are shown in Table 6.7   Open ▸ and Table 6.8   Open ▸ , respectively. Underwater noise modelling was undertaken using the MDS as outlined in Table 6.7   Open ▸ , with the detail of the assessment provided in volume 3, appendix 10.1 of the Array EIA Report.
Table 6.7:
MDS Considered for the Assessment of Potential Impacts to Annex II Marine Mammals due to Underwater Noise Generated During Piling in the Construction Phase

Table 6.7: MDS Considered for the Assessment of Potential Impacts to Annex II Marine Mammals due to Underwater Noise Generated During Piling in the Construction Phase

Table 6.8:
Designed In Measures Considered for the Assessment of Potential Impacts to Annex II Marine Underwater Noise Generated During Piling in the Construction Phase

Table 6.8: Designed In Measures Considered for the Assessment of Potential Impacts to Annex II Marine Underwater Noise Generated During Piling in the Construction Phase

                        Information to support the assessment

                        Overview of underwater noise modelling conducted for the Array
  1. Pile driving during the construction phase of the Array has the potential to result in higher levels of underwater noise when compared to background levels and could result in auditory injury and/or potential behavioural effects on Annex II marine mammal features of the three SACs identified for Appropriate Assessment. A detailed underwater noise modelling assessment was carried out to investigate the potential for such effects to occur, using the latest assessment criteria (see volume 3, appendix 10.1 of the Array EIA Report).
  2. As recommended by stakeholders during the pre-Scoping workshop, only the SPLpk has been used to inform the appropriate mitigation zone, although both metrics (SPLpk and SELcum) are presented in the assessment of PTS for the Array. During piling, with respect to the SPLpk metric, the soft start initiation is the most relevant period, as this is when animals may potentially experience injury from underwater noise emitted by the initial strike of the hammer, after which point it is assumed that they will move away from the noise source. However, to ensure a precautionary approach, the injury ranges for SPLpk are based on the noise from the maximum hammer energy over the entire installation.
  3. The scenarios modelled were based on the maximum hammer energies (of 3,000 kJ or 4,400 kJ, see Table 6.7   Open ▸ ) over the longest possible duration, noting that piling is unlikely to reach and maintain the absolute maximum hammer energy at all locations. The assessment of potential effects on Annex II marine mammals from piling considered a maximum spatial and maximum temporal scenario ( Table 6.7   Open ▸ ).
  4. Maximum spatial scenarios assume concurrent piling of piles at OSPs and wind turbine (anchors), leading to the largest area of effect at any one time. Maximum temporal scenarios, leading to the greatest number of days of piling, is based on single piling of piles at wind turbines (anchors) and OSPs (jackets) ( Table 6.7   Open ▸ ).
  5. Underwater noise modelling modelled concurrent piling at:
  • wind turbines (anchors) with a maximum hammer energy of 3,000 kJ; and
  • wind turbine and OSP with a maximum hammer energy of 3,000 kJ and 4,400 kJ, respectively.
  1. For the concurrent piling scenario, the following assumptions were identified:
  • minimum separation distance of 950 m between concurrent piling events as a maximum design scenario for potential injury; and
  • maximum separation distance of up to 30 km as a maximum design scenario for potential disturbance based on the PDE and site bathymetry ( Table 6.7   Open ▸ ).
  1. The modelled locations were species-specific, e.g. those that were likely to generate noise contours with the highest potential to overlap with sensitive areas for a given species (e.g. density hotspots). The modelling locations were as follows:
  • a point at the northern end of the site boundary (single piling) as well as at the northern end and the central point of the site boundary (concurrent piling) to capture potential overlap with the coastal distribution of bottlenose dolphin; and
  • a point at the southern end of the site boundary (single piling) as well as the southern end and the central point of the site boundary (concurrent piling) to assess potential effects on grey seal density hotspots within the Berwickshire and North Northumberland Coast SAC and the Southern North Sea SAC designated for harbour porpoise.
  1. For the maximum temporal scenario the assessment focused on the longest duration of piling and the greatest number of days over which piling could occur. The longest duration of piling per pile for wind turbines (anchors) or OSPs (jackets) is eight hours per pile. Therefore, conservatively, the assessment assumes that piling activities can take place over a maximum of 602 days (530 days at wind turbines and 72 days at OSPs) ( Table 6.7   Open ▸ ).
                        Injury
  1. The maximum spatial effect was predicted for concurrent piling at wind turbines and OSPs with a hammer energy of 3,000 kJ and 4,400 kJ, respectively ( Table 6.9   Open ▸ ). Whilst the effect of PTS is considered to result in permanent injury to animals, the risk of animals being exposed to noise levels leading to auditory injury would occur during piling only. As shown in Table 6.7   Open ▸ , piling will be intermittent over an eight-year construction piling phase and will occur up to a maximum of 602 days.
  2. The instantaneous injury (based on SPLpk metric with no ADD) could occur out to a maximum range of 1,600 m across all species during single pile installation at OSPs, with the maximum range predicted for harbour porpoise ( Table 6.9   Open ▸ ). Considering cumulative exposure using the SELcum metric, the risk of PTS was not exceeded for bottlenose dolphin or grey seal, but extended to 10 m and 70 m for harbour porpoise ( Table 6.9   Open ▸ ).
  3. The maximum spatial effect was estimated using two different concurrent piling scenarios, at wind turbines with a hammer energy of 3,000 kJ with either another wind turbine with a hammer energy of 3,000 kJ or with an OSP with hammer energy of 4,400 kJ ( Table 6.10   Open ▸ ). Given that the potential injury range for the concurrent scenarios based on the SPLpk metric remain the same as the injury ranges for the single installation scenario (as detailed in volume 3, appendix 10.1 of the Array EIA Report) ( Table 6.9   Open ▸ ), these were omitted from the results presented in Table 6.10   Open ▸ and are as presented in paragraph 500. Considering cumulative exposure using the SELcum metric, the risk of PTS was not exceeded for bottlenose dolphin or grey seal and was estimated to occur out to a maximum range of 203 m for harbour porpoise during concurrent pile installation at wind turbine and OSP ( Table 6.10   Open ▸ ).

 

Table 6.9:
Summary of PTS Ranges for Single Pile Installation at Wind Turbines (3,000 kJ) and OSPs (4,400 kJ) Using Both Metrics – SPLpk and SELcum (N/E = threshold not exceeded)

Table 6.9: Summary of PTS Ranges for Single Pile Installation at Wind Turbines (3,000 kJ) and OSPs (4,400 kJ) Using Both Metrics – SPLpk and SELcum (N/E = threshold not exceeded)

 

Table 6.10:
Summary of PTS Ranges for Concurrent Pile Installation at Wind Turbines (3,000 kJ) and at Wind Turbines (3,000 kJ) and OSPs (4,400 kJ) Using SELcum (N/E = threshold not exceeded)

Table 6.10: Summary of PTS Ranges for Concurrent Pile Installation at Wind Turbines (3,000 kJ) and at Wind Turbines (3,000 kJ) and OSPs (4,400 kJ) Using SELcum (N/E = threshold not exceeded)

 

  1. An MMMP will be implemented to reduce the likelihood of PTS. Such mitigation will include deployment of an ADD as recommended in the guidelines (JNCC, 2010c). The efficacy of ADDs as a mitigation tool was subsequently undertaken as part of this assessment with respect to both SPLpk and SELcum ranges applying a 30-minute deployment time prior to hammer initiation. The exact duration of ADD activation will, however, be discussed and agreed with consultees post-consent and in respect of any refinements in the Project Description that may be available at a later stage and included within the outline MMMP (volume 4, appendix 22 of the Array EIA Report).
  2. Based on the underwater noise modelling, ranges at which marine mammals could experience potential injury extend to up to 1,600 m (SPLpk metric for harbour porpoise). As such, tertiary mitigation will be required in the form of an ADD to deter animals from the area of impact. The type of ADD and approach to mitigation (including activation time and procedure) is included in the outline MMMP and will be further discussed and agreed with relevant stakeholders post-consent.
  3. ADDs have commonly been used in marine mammal mitigation at UK offshore wind farms to deter animals from potential injury zones prior to the start of piling. The JNCC (2010c) draft guidance for piling mitigation recommends their use, particularly in respect of periods of low visibility or at night to allow 24-hour working. It is considered to be more effective at reducing the potential for injury to marine mammals compared to actions informed by standard monitoring measures (MMO2 and PAM) which have limitations with respect to effective detection over distance (Parsons et al., 2009, Wright et al., 2015).
  4. There are various ADDs available with different noise source characteristics (McGarry et al., 2022) and a suitable device will be selected based on the key species requiring mitigation for the Array. The selected device will typically be deployed from the piling vessel and activated for a pre-determined duration to allow animals sufficient time to move away from the noise source whilst also minimising the additional noise introduced into the marine environment.
  5. Therefore, underwater noise modelling was carried out to determine the efficacy of using ADDs for a duration of 30 minutes to reduce the risk of injury (see volume 3, appendix 10.1 of the Array EIA Report).
  6. The maximum injury ranges using SPLpk metric were predicted for single pile installation at OSPs with a hammer energy of 4,400 kJ ( Table 6.9   Open ▸ ). Assuming conservative swim speeds listed in Table 6.11   Open ▸ , it was demonstrated that activation of an ADD for 30 minutes would deter all animals beyond the maximum injury zones.

 

Table 6.11:
Summary of Maximum PTS Ranges due to Single Pile Installation (at OSPs, Hammer Energy 4,400 kJ) Using SPLpk Metric, Indicating Whether the Individual Can Move Beyond the Injury Range During the 30 minutes of ADD Activation

Table 6.11: Summary of Maximum PTS Ranges due to Single Pile Installation (at OSPs, Hammer Energy 4,400 kJ) Using SPLpk Metric, Indicating Whether the Individual Can Move Beyond the Injury Range During the 30 minutes of ADD Activation

 

  1. The maximum injury ranges using SELcum metric were predicted for concurrent pile installation at wind turbine and OSP with hammer energies of 3,000 kJ and 4,400 kJ respectively ( Table 6.10   Open ▸ ). Activation of an ADD 30 minutes prior to commencement of piling reduced injury ranges to a level which does not exceed injury thresholds for all species ( Table 6.12   Open ▸ ).

 

Table 6.12:
Summary of Maximum PTS Ranges due to Concurrent Pile Installation (at Wind Turbine and OSP, Hammer Energies of 3,000 kJ and 4,400 kJ) Using SELcum Metric With and Without 30 Minutes of ADD Activation (N/E = Threshold Note Exceeded)

Table 6.12: Summary of Maximum PTS Ranges due to Concurrent Pile Installation (at Wind Turbine and OSP, Hammer Energies of 3,000 kJ and 4,400 kJ) Using SELcum Metric With and Without 30 Minutes of ADD Activation (N/E = Threshold Note Exceeded)

 

                        Behavioural disturbance
  1. Disturbance during piling was predicted to have far-reaching potential effects across the northern North Sea. It should be noted that the extent of the contours is likely to be an overestimate as it assumes that the noise from piling maintains its impulsive characteristics at large distances, which is considered unlikely to be the case. Since there is no agreed approach to modelling the cross-over point from impulsive to continuous noise and this is an ongoing active area of research (see volume 3, appendix 10.1 for more details), it was not possible to account for it in the underwater noise modelling. Applying associated impulsive noise thresholds for the whole contour range is likely to overestimate predicted impact distances and therefore leads to a potentially over-precautionary assessment. Considering the above as well as caveats highlighted by Southall et al. (2021) (see paragraph 454 et seq. for more details), quantitative assessment of disturbance based on SELss metric should be interpreted with caution.
  2. The estimated numbers of animals predicted to experience potential disturbance as a result of different piling scenarios are presented in Table 6.13   Open ▸ . It should be noted that these are derived from information presented in the assessment of significance in the Array EIA Report, which are derived from relevant dose-responses for each species, rather than an area-based assessment. The estimated numbers of animals potentially disturbed are based on the MDS which describes the maximum potential effect for each species. This has been defined with reference to either the extent of the effect, or spatial overlap with abundance hotspots (e.g. areas near the coast).
  3. For grey seal the quantitative assessment (which used the dose-response) was undertaken by overlaying the unweighted SELss contours for the piling location that would result in the highest overlap with the density hotspots based on at-sea density maps produced by Carter et al. (2022) ( Table 6.3   Open ▸ ). The number of animals in each 5 km x 5 km grid cell was summed for each isopleth and corrected using the proportional dose response as per Whyte et al. (2020).
  4. For harbour porpoise, a quantitative assessment of the number of animals predicted to experience disturbance was undertaken by multiplying the density values ( Table 6.3   Open ▸ ) with the areas within each 5 dB isopleth for the piling location that would result in the highest number of animals potentially disturbed and correcting the value using the relevant proportional dose response from Graham et al. (2019).
  5. For the bottlenose dolphin Coastal East Scotland MU population, given its coastal distribution, a piling location taken forward to the assessment was chosen based on the highest overlap of noise disturbance contours with the MU boundaries. The calculations of the number of animals predicted to experience disturbance (which used the dose-response) were undertaken by multiplying the density values from Lacey et al. (2022) ( Table 6.3   Open ▸ ) with the areas within each 5 dB isopleth that overlap with the MU boundaries and correcting the value using the relevant proportional response from Graham et al. (2019) for the unweighted SELss level.
  6. To facilitate an area-based assessment for HRA purposes for harbour porpoise, the unweighted noise threshold value of 143 dB re 1µPa2s SELss have been presented (paragraph 448). This threshold is relevant to the HRA process as it is an area-based approach and is therefore similar to the JNCC guidance on the use of EDRs to assess noise disturbance at harbour porpoise SACs (JNCC, 2020). Although the JNCC (2020) guidance applies to England, Wales, and Northern Ireland, it is still relevant to this assessment as the Southern North Sea SAC lies within English waters. An EDR of 26 km has also been considered in the assessment on the harbour porpoise feature of the Southern North Sea SAC as per the recommendation presented in JNCC (2020).
  7. For bottlenose dolphin and grey seal, the NMFS (2005) unweighted thresholds of 160 dB re 1 μPa (rms) (strong disturbance) and 140 dB re 1 μPa (rms) (mild disturbance) have also been presented and discussed for their respective SACs (as described in paragraphs 446 to 453).
  8. For all species, figures showing the modelled SELss and SPLrms noise disturbance contours (and EDR for harbour porpoise) and a discussion of the modelling are provided below for their relevant SACs.

 

Table 6.13:
Potential Number of Annex II Marine Mammals Predicted to be Disturbed Within Weighted SELss Noise Contours Based On Relevant Dose-Responses (Graham et al., 2019, Whyte et al., 2020) as a Result of Different Piling Scenarios. The Bold Numbers Represent Scenarios for Modelling Location With the Highest Number of Animals Potentially Impacted

Table 6.13: Potential Number of Annex II Marine Mammals Predicted to be Disturbed Within Weighted SELss Noise Contours Based On Relevant Dose-Responses (Graham et al., 2019, Whyte et al., 2020) as a Result of Different Piling Scenarios. The Bold Numbers Represent Scenarios for Modelling Location With the Highest Number of Animals Potentially Impacted

 

                        Summary of iPCoD modelling
  1. To aid with the assessment of magnitude, the potential for population-level consequences of behavioural disturbance has been considered using the iPCoD approach for harbour porpoise, bottlenose dolphin, and grey seal. There is limited understanding of how behavioural disturbance and auditory injury affect survival and reproduction in individual marine mammals and consequently how this translates into potential effects at the population-level. The iPCoD framework was developed using a process of expert elicitation to determine how physiological and behavioural changes affect individual vital rates (i.e. the components of individual fitness that affect the probability of survival, production of offspring, growth rate and offspring survival). The iPCoD framework applies simulated changes in vital rates to infer the number of animals that may be affected by disturbance as a means to iteratively project the size of the population.
  2. For bottlenose dolphin, the Coastal East Scotland MU was used as the relevant reference population. Given the importance of the Moray Firth SAC for bottlenose dolphin in this area, the sensitivity of this population and its known ranging behaviour further south towards St Andrews Bay and the Tay Estuary, and inshore in north-east English waters, it is important to capture the potential impact on this important coastal ecotype which may experience potential barrier effects.
  3. Whilst there is an abundance estimate for the Greater North Sea MU (2,022 animals (IAMMWG, 2023)) this large MU extends the entire length of the east coast of the UK and east to Scandinavia, so apportioning numbers of the offshore ecotype to the east coast of Scotland is not possible. It is also unlikely that the Array will create significant barrier effects for this offshore ecotype. Therefore, the assessment has focused on the impacts for bottlenose dolphin within the Coastal East Scotland MU and Moray Firth SAC.
  4. For harbour porpoise, only the North Sea MU for occurs in the vicinity of the Array marine mammal study area (IAMMWG, 2023), and the population estimates for it have been used for iPCoD modelling. The site boundary coincides with the boundary between two SMUs, so for grey seal the reference population comprises the sum of the East Scotland SMU and the Northeast England SMU (SCOS, 2023) (see section 6.2.4).
  5. The population estimates used to parameterised iPCoD models were taken from IAMMWG (2023) for cetacean species and from SCOS (2023) and Stevens (2023) and for grey seal, (summarised in Table 6.3   Open ▸ ), alongside vital rates taken from Sinclair et al. (2020), presented in Table 6.14   Open ▸ .

 

Table 6.14:
Vital Rates Used to Parameterise iPCoD Models (from Sinclair et al. (2020))

Table 6.14: Vital Rates Used to Parameterise iPCoD Models (from Sinclair et al. (2020))

 

  1. The dual metric approach has been used to inform the PTS assessment, but SPLpk used to define the appropriate mitigation range following advice from NatureScot (received as a result of Marine Mammal Consultation Note 1; Table 2.1   Open ▸ ). The number of animals that may experience PTS to be inputted into the iPCoD models were derived from calculations based upon the most animals effected from the dual metric approach (paragraph 445) using numbers of animals from dose-response approach. Furthermore, calculation of the number of animals that may experience PTS assumed a 30-minute implementation of ADD, as per standard industry practice and was agreed with NatureScot (following Marine Mammal Consultation Note 1).
  2. Both the maximum temporal scenario (e.g. the single piling scenario with fewer animals impacted per day, but over more days) and the maximum spatial scenario (e.g. the concurrent piling scenario with more animals impacted per day, but for fewer days) were modelled in iPCoD. It should be noted that for the RIAA, that the populations of the MUs and SMUs used in the iPCoD modelling cannot be directly attributed or allocated to the specific populations within the SACs being assessed. However, the results of the iPCoD modelling still provide important context at a population level which aids the overall assessment.
  3. Results of population modelling are discussed for each SAC below, with further detail provided in volume 2, chapter 10 of the Array EIA Report.

                        Construction phase

                        Berwickshire and North Northumberland Coast SAC
Grey seal

                        Injury

  1. Based  on SPLpk metric, the maximum range for injury to grey seal was estimated as 379 m during pile installation at OSPs ( Table 6.9   Open ▸ ). Applying a density value of 0.180 animals per km2, no more than one animal would be at risk of experiencing PTS (based on the dose response approach). However, with designed-in measures applied, it is predicted that no animals would be affected by peak pressure (SPLpk) as they would be able to flee the potential injury range (379 m) during the period of ADD activation ( Table 6.11   Open ▸ ).
  2. Given that the injury range is within hundreds of metres, it will be localised to within the Array marine mammal study area and therefore there is no potential for spatial overlap with the Berwickshire and North Northumberland Coast SAC (which is a minimum of 113.95 km away).
  3. Grey seal typically live between 20 to 30 years with gestation lasting between ten to 11 months (SCOS, 2023). The duration of piling is up to 602 days, within an eight-year piling programme, and therefore could potentially overlap with a maximum of eight breeding cycles. It should be noted that piling at OSPs with the hammer energy of 4,400 kJ resulting in maximum injury range of 379 m would take place over only a fraction of the total piling days (72 days). The total duration of the impact in the context of the life cycle of grey seal is classified as medium term, as animals will be at the risk of potential injury (albeit very small) over a meaningful proportion of their lifespan.
  4. As stated in paragraph 523, whilst the populations of the SMUs cannot be directly attributed or allocated to the specific population within the Berwickshire and North Northumberland Coast SAC, the results of the iPCoD modelling still provide important context at a population level to help inform the overall assessment.
  5. Simulated trajectories for both the unimpacted and the impacted grey seal populations (using the total population estimate for the East Scotland SMU (10,783) and Northeast England SMU (25,913)) were modelled using iPCoD for the maximum temporal and spatial scenario. The results of the iPCoD modelling for grey seal against these SMU populations showed that the median ratio of the impacted population to the unimpacted population was 1.000 at six years and 25 years, for both the maximum temporal scenario and the maximum spatial scenario. This indicates that there would be no significant difference between the population trajectories for the unimpacted (baseline) population and the impacted population. At 25 years after the start of piling there was no difference in the number of animals in the impacted population when compared to the unimpacted population, for both the maximum temporal and maximum spatial scenario. It is therefore considered that there would be no potential long-term effects on the grey seal population of these SMUs resulting from elevated underwater noise arising during piling.

                        Behavioural disturbance

  1. There was no overlap of the unweighted SELss 145 dB re 1 μPa2s contour for grey seal (Whyte et al., 2020) with the Berwickshire and North Northumberland Coast SAC ( Figure 6.3   Open ▸ and Figure 6.4   Open ▸ ). The Array EIA Report (which used dose response) found that up to 436 animals were predicted to potentially be disturbed within weighted SELss noise disturbance contours, which equates 1.19% of the total East Scotland SMU and Northeast England SMU population ( Table 6.13   Open ▸ ). However, it is important to note that for the Appropriate Assessment, numbers of animals potentially disturbed cannot be accurately attributed or apportioned to an individual SAC using an area based approach (such as the NMFS (2005) thresholds of 160 and 140 dB (rms) for strong and mild disturbance). An area-based approach assumes 100% disturbance of all animals within the area rather than a continuum, and therefore would lead to a vast over-estimate of numbers of animals if simply multiplied by a conservative density value. Furthermore, loss of habitat area (as is the case for area-based assessment) is a binary event, with an area is either ensonified by a sound at a given level or not (NRW, 2023).
  2. There was no overlap of the 160 dB (rms) or 140 dB (rms) contours for strong and mild disturbance, respectively, (based on NMFS (2005)) with the Berwickshire and North Northumberland Coast SAC ( Figure 6.5   Open ▸ and Figure 6.6   Open ▸ ). The areas of the strong disturbance contours were 1,698.50 km2 at the northern piling scenario and 1,515.87 km2 at the southern piling scenario. The areas of the mild disturbance contours were 45,638.41 km2 at the northern piling scenario and 45,888.84 km2 at the southern piling scenario. However, no estimates of the number of grey seal with the potential to be disturbed within these areas has been provided, given the inaccuracies associated with doing so using an area-based approach in contrast to a dose-response (see paragraphs 446 et seq.). It is acknowledged that grey seal foraging trips can be wide ranging (i.e. <100 km; (SCOS, 2022)), however during the breeding season, they are typically within 20 km of the haul out sites (pers. comm., with NatureScot). Therefore, no overlap with any of the contours presented in Figure 6.3   Open ▸ to Figure 6.6   Open ▸ is likely to occur during this key stage of the species’ life history.

                        Conclusion

  1. Adverse effects on the qualifying Annex II grey seal feature of the Berwickshire and North Northumberland Coast SAC which undermine the conservation objectives of the SAC will not occur as a result of underwater noise generated during piling in the construction phase for the Array alone. Potential effects from this activity on the relevant conservation objectives (as presented in section 6.2.1) are discussed in turn below in Table 6.15   Open ▸ .

Figure 6.3:
Unweighted SELss Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Northern Limit of the Site Boundary overlaid with Carter et al. (2022) At-sea Density Maps and Berwickshire and North Northumberland Coast SAC

Figure 6.3: Unweighted SELss Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Northern Limit of the Site Boundary overlaid with Carter et al. (2022) At-sea Density Maps and Berwickshire and North Northumberland Coast SAC

Figure 6.4:
Unweighted SELss Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Southern Limit of the Site Boundary overlaid with Carter et al. (2022) At-sea Density Maps and Berwickshire and North Northumberland SAC

Figure 6.4: Unweighted SELss Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Southern Limit of the Site Boundary overlaid with Carter et al. (2022) At-sea Density Maps and Berwickshire and North Northumberland SAC


Figure 6.5:
Unweighted 140 and 160 dB re 1 µPa (SPLrms) Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Northern Limit of the Site Boundary overlaid with Carter et al. (2022) At-sea Density Maps

Figure 6.5: Unweighted 140 and 160 dB re 1 µPa (SPLrms) Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Northern Limit of the Site Boundary overlaid with Carter et al. (2022) At-sea Density Maps


Figure 6.6:
Unweighted 140 and 160 dB re 1 µPa (SPLrms) Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Southern Limit of the Site Boundary overlaid with Carter et al. (2022) At-sea Density Maps

Figure 6.6: Unweighted 140 and 160 dB re 1 µPa (SPLrms) Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Southern Limit of the Site Boundary overlaid with Carter et al. (2022) At-sea Density Maps


Table 6.15:
Conclusions Against the Conservation Objectives of the Berwickshire and North Northumberland Coast SAC from Underwater Noise Generated During Piling in the Construction Phase of the Array Alone

Table 6.15: Conclusions Against the Conservation Objectives of the Berwickshire and North Northumberland Coast SAC from Underwater Noise Generated During Piling in the Construction Phase of the Array Alone

 

  1. It can be concluded, beyond reasonable scientific doubt, that there is no risk of an adverse effect on the integrity of the Berwickshire and North Northumberland Coast SAC as a result of underwater noise generated during piling in the construction phase of the Array alone.
                        Southern North Sea SAC
Harbour porpoise

                        Injury

  1. Based on SPLpk metric, the maximum range for injury to harbour porpoise was estimated as 1,600 m during pile installation at OSPs ( Table 6.9   Open ▸ ). Based on the density value of 0.651 animals per km2, up to six animals would be at risk of experiencing PTS. However, with designed-in measures applied, it is predicted that no animals would be affected by peak pressure (SPLpk) as they would be able to flee the potential injury range (1,600 m) during the period of ADD activation ( Table 6.11   Open ▸ ).
  2. The injury range is predicted to be localised to within the Array marine mammal study area and therefore there is no potential for spatial overlap with the Southern North Sea SAC (which is a minimum of 129.86 km away).
  3. Harbour porpoise typically live between 12 and 24 years and give birth once a year (Lockyer, 2013). The duration of piling is up to 602 days, within an eight-year piling programme, and therefore could potentially overlap with a maximum of eight breeding cycles. It should be noted that piling at OSPs with the hammer energy of 4,400 kJ resulting in maximum injury range of 1,600 m would take place over only a fraction of the total piling days (72 days). The total duration of the impact in the context of the life cycle of harbour porpoise is classified as long term, as animals will be at the risk of potential injury (albeit very small) over a meaningful proportion of their lifespan.
  4. Simulated trajectories for both the unimpacted and the impacted harbour porpoise populations (using the total population estimate for the North Sea MU) were modelled using iPCoD for the maximum temporal and spatial scenario. The results of the iPCoD modelling of the maximum temporal scenario for harbour porpoise showed that the median ratio of the impacted population to the unimpacted population at six years was 0.9986 and at 25 years was 0.9985. For the maximum spatial scenario these ratios were 0.9995 at six years and 0.9994 at 25 years. For both scenarios, results indicated no significant difference between the population trajectories for an unimpacted population and the impacted population. 25 years after the start of piling, the simulated impacted population was estimated to be 1,878 animals smaller than the unimpacted population for the maximum temporal scenario, equating to 0.005% of the North Sea MU population. For the maximum spatial scenario, there were estimated to be 1,302 fewer animals in the impacted versus unimpacted population, equating to 0.004% of the MU population. Given these results, it is expected that there would be no potential long-term effects on the harbour porpoise population of the North Sea MU resulting from elevated underwater noise arising during piling. As stated in paragraph 523, the population of the North Sea MU cannot be accurately attributed or allocated to the specific population within the Southern North Sea SAC. However, the results of the iPCoD modelling still provide relevant context at a population level to inform the overall assessment.

                        Behavioural disturbance

  1. The Array EIA Report (which used dose response) found that at the most conservative scenario for concurrent piling of the wind turbine (3,000 kJ) in the centre and OSPs (4,400 kJ) at the Northern limit of the site boundary, up to 8,309 harbour porpoise could experience potential disturbance ( Table 6.13   Open ▸ ; Figure 6.7   Open ▸ ). This equates to 2.4% of the North Sea MU population ( Table 6.13   Open ▸ ). The estimated number of individuals potentially impacted was based on conservative densities and the assumption that the peak seasonal site-specific density of 0.651 animals per km2 is uniformly distributed within all noise contours. Additionally, the underwater noise modelling assumed that the maximum hammer energies are reached at all piling locations (see volume 3, appendix 10.1 of the Array EIA Report for more details), which is highly conservative.
  2. Given the far-reaching extent of the outer noise contours, there is potential for overlap with the Southern North Sea SAC. Based on the dose-response curve presented in Graham et al. (2019), from 1% to 4% of animals are likely to respond within noise contours that overlap with this SAC (120 to 130 dB SELss) which is also below the NMFS (2005) threshold for strong disturbance (=160 dB rms). Moreover, there is a possibility that a small number of individuals from this SAC population may be occasionally present within the mapped disturbance contours outside the site. Therefore, using the area-based approach (as described in paragraphs 446 to 453) for the unweighted noise threshold of 143 dB re 1µPa2s disturbance contours were presented for the maximum design scenario concurrent piling at wind turbines (3,000 kJ) in the centre and OSPs (4,400 kJ) at the southern limit of the site boundary (i.e. the closest to the SAC) ( Figure 6.8   Open ▸ ). This approach, which focuses on a threshold associated with the onset of avoidance behaviour, showed that the 143 dB re 1µPa2s disturbance contour does not extend to the Southern North Sea SAC and therefore animals are unlikely to experience significant disturbance within the site. Additionally, at these distances it is unlikely that noise contours would result in barrier effects restricting harbour porpoise from reaching key habitats within the SAC.
  3. The different approaches described above suggest that close to the piling the disturbance response is likely to be measurable and the probability of such a response is high such that individuals could change their baseline behaviour or in some cases actively avoid disturbed areas. Moving further away from the piling source, behavioural responses are likely to decrease with some individuals (proportional to the distance from the source) tolerating the increase in elevated underwater noise. At ranges beyond the received level of 143 dB re 1 µPa2s (SELss) the disturbance is unlikely to be significant with less likelihood of active avoidance (Brandt et al., 2018, NRW, 2023).
  4. A 26 km EDR has also been presented on Figure 6.7   Open ▸ and Figure 6.8   Open ▸ , as per the JNCC guidance to assess noise disturbance at harbour porpoise SACs (JNCC, 2020). This is relevant to the Array, as although it lies within Scottish waters, the Southern North Sea SAC lies within English waters. As illustrated, there is no potential for overlap between the 26 km EDR and the Southern North Sea SAC ( Figure 6.7   Open ▸ and Figure 6.8   Open ▸ ).

                        Conclusion

  1. Adverse effects on the qualifying Annex II harbour porpoise feature of the Southern North Sea SAC which undermine the conservation objectives of the SAC will not occur as a result of underwater noise generated during piling in the construction phase for the Array alone. Potential effects from this activity on the relevant conservation objectives (as presented in section 6.2.2) are discussed in turn below in Table 6.16   Open ▸ .

Figure 6.7:
Unweighted SELss Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Northern Limit of the Site Boundary and 26 km EDR

Figure 6.7: Unweighted SELss Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Northern Limit of the Site Boundary and 26 km EDR


Figure 6.8:
Unweighted SELss Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Southern Limit of the Site Boundary and 26 km EDR

Figure 6.8: Unweighted SELss Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Southern Limit of the Site Boundary and 26 km EDR


Table 6.16:
Conclusions Against the Conservation Objectives of the Southern North Sea SAC from Underwater Noise Generated During Piling in the Construction Phase of the Array Alone

Table 6.16: Conclusions Against the Conservation Objectives of the Southern North Sea SAC from Underwater Noise Generated During Piling in the Construction Phase of the Array Alone

 

  1. It can be concluded, beyond reasonable scientific doubt, that there is no risk of an adverse effect on the integrity of the Southern North Sea SAC as a result of underwater noise generated during piling in the construction phase of the Array alone.
                        Moray Firth SAC
Bottlenose dolphin

                        Injury

  1. Based on SPLpk metric, the maximum range for injury to bottlenose dolphin was estimated as 171 m during pile installation at OSPs ( Table 6.9   Open ▸ ). Based on the density values of 0.003 animals per km2, no more than one animal would be at risk of experiencing PTS. However, with designed in measures applied, it is predicted that no animals would be affected by peak pressure (SPLpk) as they would be able to flee the potential injury range (171 m) during the period of ADD activation ( Table 6.11   Open ▸ ).
  2. The injury range is predicted to be localised to within the Array marine mammal study area and therefore there is no potential for spatial overlap with the Moray Firth SAC, the closest site designated for bottlenose dolphin (which is a minimum of 175.86 km north).
  3. Bottlenose dolphin typically live between 20 and 30 years. The gestation period is 12 months with calves suckling for 18 to 24 months with females reproducing every three to six years (Mitcheson, 2008). The duration of piling is up to 602 days, within an eight-year piling programme, and therefore could potentially overlap with a maximum of three bottlenose dolphin breeding cycles. It should be noted that piling at OSPs with the hammer energy of 4,400 kJ resulting in maximum injury range of 171 m would take place over only a fraction of the total piling days (72 days). The total duration of the potential impact in the context of the life cycle of bottlenose dolphin is classified as long term, as animals will be at the risk of potential injury (albeit very small) over a meaningful proportion of their lifespan.
  4. As stated in paragraph 523, the population of the Coastal East Scotland MU cannot be directly attributed or allocated to the specific population within the Moray Firth SAC. However, the results of the iPCoD modelling still provide important context at a population level to help inform the overall assessment. Simulated trajectories for both the unimpacted and the impacted bottlenose dolphin populations (using the total population estimate for the Coastal East Scotland MU) were modelled using iPCoD (using numbers from dose response) for the maximum temporal and spatial scenario. The results of iPCoD modelling for the Coastal East Scotland MU bottlenose dolphin population indicated that the median ratio of the impacted population to the unimpacted population was 1.000 at six years and at 25 years, for both the maximum temporal scenario and the maximum spatial scenario. A ratio of 1 corresponds to no significant difference between the population trajectories for an unimpacted population and the impacted population. 25 years after the start of piling, for the maximum temporal scenario the impacted population was predicted to be seven animals smaller than the unimpacted population, equating to 0.031% of the Coastal East Scotland MU. For the maximum spatial scenario, the impacted population was predicted to be four animals smaller than the unimpacted population, equating to 0.018% of the Coastal East Scotland MU. It is therefore considered that there would be no potential long-term effects upon the coastal bottlenose dolphin population resulting from elevated underwater noise arising during piling.

                        Behavioural disturbance

  1. The Array EIA Report (which used dose response) found that based on the most conservative scenario for concurrent piling of the wind turbine (3,000 kJ) in the centre and OSPs (4,400 kJ) at the northern limit of the site boundary, up to five bottlenose dolphin are predicted to experience potential behavioural disturbance ( Table 6.13   Open ▸ ; Figure 6.9   Open ▸ ). This equates to 2.23% of the Coastal East Scotland MU population ( Table 6.13   Open ▸ ).
  2. An area-based approach of the 140 dB and 160 dB (rms) contours for mild and strong disturbance, respectively, (based on NMFS (2005)) is presented in Figure 6.10   Open ▸ . There was no overlap with the Moray Firth SAC and the strong or mild disturbance contours ( Figure 6.10   Open ▸ ). The area of the strong disturbance contour was 1,698.50 km2 and 45,638.41 km2 for the mild disturbance contour. However, no estimates of the number of bottlenose dolphin with the potential to be disturbed within these areas has been provided, given the inaccuracies and likely vast over-estimation associated with doing so using an area-based approach in contrast to a dose-response (see paragraphs 446 et seq.). The following paragraphs provide a qualitative assessment, taking into account the known behaviour, ecology, and distribution of this species in the region.
  3. The assessment assumed precautionarily that bottlenose dolphins from the Coastal East Scotland MU can be present within the whole extent of the MU ( Figure 6.9   Open ▸ ), although it should be noted that empirical evidence from studies on this population suggest that they are mostly encountered 2 to 5 km from the shore (Palmer et al., 2019, Paxton et al., 2016, Quick et al., 2014, Thompson et al., 2015b). Animals from this MU are unlikely to be present in the offshore areas that may be exposed to high levels of noise from piling at the Array. However, bottlenose dolphins from the offshore populations may experience behavioural disturbance outside the Coastal East Scotland MU. Given that there is an estimate of 2,022 animals for the entire Greater North Sea MU, which extends across to Europe (IAMMWG, 2022) and no further information on offshore populations, the effect has not been quantified for behavioural disturbance during piling outside the Coastal East Scotland MU. Further, the Coastal East Scotland MU is most relevant for the assessment of the Moray Firth SAC.
  4. The Coastal East Scotland MU lies approximately 56 km west from the site boundary and at this distance the received level from piling will have lost much of the impulsive characteristics ( Figure 6.9   Open ▸ and Figure 6.10   Open ▸ ). The outermost SELss noise contours reach the coastal areas and therefore may overlap with the key inshore distribution of bottlenose dolphin in the MU ( Figure 6.9   Open ▸ ), potentially resulting in barrier effects (e.g. restricting animals from moving along the coast). Received noise levels within the Coastal East Scotland MU are predicted to reach maximum SPLrms levels of 140 dB ( Figure 6.10   Open ▸ ), which is below the NMFS (2005) threshold for strong disturbance (=160 dB rms) and therefore likely to elicit less severe disturbance reactions. However, the modelled noise contours that overlap with the Coastal East Scotland MU meet the threshold for mild disturbance (=140 dB rms) ( Figure 6.10   Open ▸ ). According to the behavioural response severity matrix suggested by Southall et al. (2021) such low level disturbance (scoring between 0 to 3 on a 0 to 9 scale) could lead to mild disruptions of normal behaviours, but prolonged or sustained behavioural effects, including displacement are unlikely to occur.
  5. There is no potential for overlap of the SELss or the SPLrms noise disturbance contours (mapped out to 120 dB) with the Moray Firth SAC ( Figure 6.9   Open ▸ and Figure 6.10   Open ▸ ). However, as noted in paragraph 550, there is a possibility that a small number of individuals from this SAC population may be occasionally present within the mapped disturbance contours outside the site (though, as discussed in paragraph 530, it is not possible to apportion numbers of animals disturbed to the Moray Firth SAC).

                        Conclusion

  1. Adverse effects on the qualifying Annex II bottlenose dolphin feature of the Moray Firth SAC which undermine the conservation objectives of the SAC will not occur as a result of underwater noise generated during piling in the construction phase for the Array alone. Potential effects from this activity on the relevant conservation objectives (as presented in section 6.2.3) are discussed in turn below in Table 6.17   Open ▸ .

Figure 6.9:
Unweighted SELss Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Northern Limit of the Site Boundary

Figure 6.9: Unweighted SELss Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Northern Limit of the Site Boundary


Figure 6.10:
Unweighted SPLrms Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Northern Limit of the Site Boundary

Figure 6.10: Unweighted SPLrms Contours Due to Concurrent Piling at Wind Turbine (3,000 kJ) at the Centre and OSP (4,400 kJ) at the Northern Limit of the Site Boundary


Table 6.17:
Conclusions Against the Conservation Objectives of the Moray Firth SAC from Underwater Noise Generated During Piling in the Construction Phase of the Array Alone

Table 6.17: Conclusions Against the Conservation Objectives of the Moray Firth SAC from Underwater Noise Generated During Piling in the Construction Phase of the Array Alone

 

  1. It can be concluded, beyond reasonable scientific doubt, that there is no risk of an adverse effect on the integrity of the Moray Firth SAC as a result of underwater noise generated during piling in the construction phase of the Array alone.