20.8.1. Assessment of Inter-Related Effects

For each of the receptor groups listed above, the scope for impact to these receptors to create Array lifetime effects over all phases and/or receptor-led effects through interacting together on a particular group has been explored and discussed in the following sections.
The sections have been subdivided into the categories listed in paragraph 21.

Physical environment

Physical processes

For physical processes, the following potential impacts have been considered within the inter-related effects assessment:

increase in SSCs and associated deposition and sediment transport due to operation and maintenance activities;
impacts to the wind field due to the presence of infrastructure; and
impacts to seasonal stratification due to the presence of infrastructure.

Table 20.4 Open ▸ lists the inter-related effects (Array lifetime effects) that are predicted to arise during the construction, operation and maintenance and decommissioning phase of the Array and also the inter-related effects (receptor-led effects) that are predicted to arise for physical processes receptors.
Physical processes receptors have the potential to have secondary effects on other receptors and these effects are fully considered in the topic specific chapters and elsewhere in this chapter. These receptors and effects are:

benthic subtidal ecology:

– increased SSCs; and

– increased sediment deposition; and

– changes to seasonal stratification.

fish and shellfish ecology:

– increased SSCs;

– increased sediment deposition; and

– changes to seasonal sediment deposition.

marine mammals:

– increased SSCs;

– sediment deposition; and

– changes to seasonal stratification.

infrastructure and other users:

– increased SSCs.

Table 20.4: Summary of Likely Significant Potential Inter-Related Effects for Physical Processes from Individual Effects Occurring across the Construction, Operation and Maintenance and Decommissioning Phases of the Array (Array Lifetime Effects) and from Multiple Effects Interacting Across all Phases (Receptor-led Effects)

Biological environment

Benthic subtidal ecology

For benthic subtidal ecology, the following potential impacts have been considered within the inter-related effects assessment:

temporary habitat loss and disturbance;
long term habitat loss and disturbance;
increased SSCs and associated deposition;
effects to benthic subtidal ecology from electromagnetic field (EMF) from subsea electrical cabling;
colonisation of hard substrates;
effects to benthic subtidal ecology due to removal of hard substrates; and
increased risk of invasive non-native species (INNS).

Table 20.5 Open ▸ lists the inter-related effects (Array lifetime effects) that are predicted to arise during the construction, operation and maintenance and decommissioning phase of the Array and also the inter-related effects (receptor-led effects) that are predicted to arise for benthic subtidal ecology receptors.
Benthic subtidal ecology receptors have the potential to have secondary effects on other receptors and these effects are fully considered in the topic specific chapters and elsewhere in this chapter. These receptors and effects are:

fish and shellfish ecology;

– temporary (during construction, operation and maintenance and decommissioning phases), long term (during operation and maintenance phase only) and permanent habitat alteration (post decommissioning) habitat loss and disturbance;

marine mammals;

– effects on marine mammals due to altered prey availability; and

offshore ornithology;

– – changes to prey availability.

Table 20.5 Summary of Likely Significant Potential Inter-Related Effects for Benthic Subtidal Ecology from Individual Effects Occurring across the Construction, Operation and Maintenance and Decommissioning Phases of the Array (Array Lifetime Effects) and from Multiple Effects Interacting Across all Phases (Receptor-led Effects)

Fish and shellfish ecology

For fish and shellfish ecology, the following potential impacts have been considered within the inter-related effects assessment:

temporary habitat loss and disturbance;
long-term habitat loss and disturbance;
effects to fish and shellfish receptors due to EMF from subsea electrical cabling;
colonisation of hard structures;
underwater noise impacting fish and shellfish receptors; and
underwater noise from the operation of floating wind turbines and anchor mooring lines impacting fish and shellfish receptors.

Table 20.6 Open ▸ lists the inter-related effects (Array lifetime effects) that are predicted to arise during the construction, operation and maintenance and decommissioning phase of the Array and also the inter-related effects (receptor-led effects) that are predicted to arise for fish and shellfish ecology receptors.
Fish and shellfish ecology also have the potential to have a secondary effect on other receptors and these effects are fully considered in the topic-specific chapters and elsewhere in this chapter. These receptors and effects are:

marine mammals;

– changes in the fish and shellfish community resulting from the impacts during construction, operation and maintenance, and decommissioning may lead to the loss of prey resources for marine mammals resulting in effects of negligible significance, which are not significant in EIA terms (volume 2, chapter 10);

offshore ornithology;

– changes in the fish and shellfish community resulting from the impacts during construction, operation and maintenance, and decommissioning may lead to the changes in prey availability for birds. However, as noted in volume 2, chapter 11, there are negligible to minor effects on fish and shellfish ecology and therefore negligible or minor effects are predicted for offshore ornithology, which are not significant in EIA terms.

commercial fisheries;

– changes in fish and shellfish community resulting from impacts during construction, operation and maintenance, and decommissioning may affect commercial fisheries receptors by effects on access to target species, however as noted in this chapter, there are negligible or minor effects on fish and shellfish receptors therefore negligible or minor effects are predicted for commercial fisheries, which are not significant in EIA terms.

Table 20.6: Summary of Likely Significant Inter-Related Effects for Fish and Shellfish Ecology from Individual Effects Occurring Across the Site Preparation and Construction, Operation and Maintenance and Decommissioning Phases of the Array (Array Lifetime Effects) and from Multiple Effects Interacting Across all Phases (Receptor-led Effects)

Marine mammals

For marine mammals, the following potential impacts have been considered within the inter-related effects assessment:

injury and disturbance from underwater noise generated during piling;
injury and disturbance from underwater noise generated during UXO clearance;
injury and disturbance due to site investigation surveys (including geophysical surveys);
Injury and disturbance to marine mammals from elevated underwater noise due to vessel use and other activities.
injury due to collision with vessels;
effects on marine mammals due to EMFs from subsea electrical cabling in the water column;
injury and disturbance from underwater noise generated during the operation of floating wind turbines and anchor mooring lines;
effects on marine mammals due to entanglement associated with the Array; and
effects on marine mammals due to altered prey availability.

Table 20.7 Open ▸ lists the inter-related effects (Array lifetime effects) that are predicted to arise during the construction, operation and maintenance, and decommissioning phases of the Array and also the inter-related effects (receptor-led effects) that are predicted to arise for marine mammal receptors.

Table 20.7: Summary of Likely Significant Inter-Related Effects for Marine Mammals from Individual Effects Occurring Across the Site Preparation and Construction, Operation and Maintenance and Decommissioning Phases of the Array (Array Lifetime Effects) and from Multiple Effects Interacting Across all Phases (Receptor-led Effects)

Stressor 1: injury or disturbance from elevated underwater noise (from piling, UXO clearance, site-investigation surveys, vessels, operational noise from turbines/mooring lines)

During the construction phase activities resulting in elevated underwater noise include piling, UXO clearance, site investigation surveys and vessel movements could occur. These activities are likely to result in disturbance to marine mammals which may be additive in nature if activities are synchronised, as it could lead to a larger area disturbed at any one time. Disturbance is likely to occur as short term, localised events for each activity within the construction phase. Prior to piling, for example, UXO clearance could result in no more than 15 single clearance events, and disturbance occurring mainly during secondary mitigation (ADDs and soft start) rather than the UXO clearance event itself which would be no more than seconds for each. There is also a small potential that animals could experience injury during UXO clearance (due to an accidental high order detonation). Site investigation surveys are likely to occur over a total duration of up to five months (over a three year period) whilst disturbance during vessel activity will occur intermittently throughout this phase with timings linked to the pre-construction activities (UXO and site-investigation surveys).
During the construction phase, activities resulting in elevated underwater noise include piling, other construction activities and vessel movements could occur. Since injury to marine mammals will be mitigated through the Marine Mammal Mitigation Protocol (MMMP) (volume 4, appendix 22), the key focus is on disturbance effects. Disturbance could occur intermittently on a total of 602 days over the construction phase of 96 months. Other construction activities (e.g. drilling and cable laying) and vessel movements would occur intermittently within the eight year construction phase. When piling occurs the disturbance effects are likely to be greater than for any of the other activities contributing to elevated underwater noise so there is less likely to be an additive or synergistic effect during piling. There may, however, be an additive effect spatially where two or more noise-producing activities occur in different parts of the Array, or temporally due to ongoing disturbance from activities throughout the construction phase (e.g. if they occur consecutively).
During the operation and maintenance phase, activities resulting in elevated underwater noise include vessel activity, geophysical surveys and operational noise from floating turbines and mooring lines. These activities have the potential to result in disturbance to marine mammals which may be additive if activities are synchronised, as it could lead to a larger area disturbed at any one time. Disturbance is likely to occur as short term, localised events for vessel activity and geophysical surveys and the disturbance from operational noise is expected to be minimal, but there may be an additive effect spatially where two or more noise-producing activities occur in different parts of the Array, or temporally due to ongoing disturbance from activities throughout the operation and maintenance phase (e.g. if they occur consecutively).
During decommissioning, vessel movements associated with decommissioning activities will result in elevated underwater noise which could lead to disturbance to marine mammals. Disturbance is likely to occur as short term, localised events and there may be an additive effect spatially where vessels are operating in different parts of the Array, or temporally due to ongoing disturbance throughout the decommissioning phase.
Therefore, marine mammal receptors have the potential to experience ongoing disturbance due to elevations in underwater noise from different sources at all phases of the Array. The sensitivity of key species will be linked to their ability to tolerate the stressor such that their ability to function normally (e.g. forage, reproduce, communicate, avoid predators) is not impeded. The assessment, which adopts a highly precautionary approach, demonstrated that for all impacts, considered in isolation, the residual effects will not be significant (after implementation of secondary mitigation) as either the spatial scale is very localised or where larger scale effects do occur (i.e. during piling or UXO) these will be highly reversible with animals returning to baseline levels rapidly. After implementation of secondary mitigation there is, however, potentially a small residual number of harbour porpoise Phocoena phocoena that could experience auditory injury during UXO clearance activities and would represent only a very small proportion of the NS MU population.
There are, however, uncertainties as to how all activities interact to contribute to an additive effect from underwater noise as a stressor. In a Before-After-Control-Impact design (BACI) study looking at foraging activity of harbour porpoise between baseline periods and different construction phases of the Beatrice and Moray East Offshore Wind Farms (Benhemma-Le Gall et al., 2021) an eight to 17% decline in harbour porpoise occurrence in the impacted area during pile-driving and other construction activities was observed, with probability of detection negatively related to levels of vessel intensity and background noise.
To some extent it is anticipated that animals will acclimatise to or compensate for such increases in underwater noise. Graham et al. (2019), for example, demonstrated acclimatisation in harbour porpoise. The study showed that the proportional response of harbour porpoise to piling noise decreased over the piling phase, with the proportion of animals disturbed at a received level of 160 dB re 1 µPa decreased from 91.5% to 49.2% from the first pile to the last pile. Kastelein et al. (2019) suggest that harbour porpoise (a species with high daily energy requirements) may be able to compensate for period of disturbance as they can dramatically increase their food intake in a period following fasting within out any detriment to their health. In the Moray Firth, harbour porpoises displaced during wind farm construction of Beatrice and Moray East Offshore Wind Farms increased their buzzing activity, potentially compensating for lost foraging opportunities (although there may be an additional energetic cost from the fleeing and distance travelled to compensate for) (Benhemma-Le Gall et al., 2021).
Therefore, as detailed in paragraphs 50 to 56 above, significance is considered to be minor adverse and therefore not significant in EIA terms.

Stressor 2: injury due to collisions with vessels

Injury due to collisions with vessels is associated with increased vessel movement, the impact of which was assessed from different types of vessels and at different phases of the Array. As described in paragraph 50 et seq., over the lifetime of the Array there will be a longer term risk to marine mammal receptors however, with designed in measures in place the potential of experiencing injury is likely to be reduced and therefore it is not anticipated that an additive effect will occur. Additionally, to some extent the noise from the vessels themselves (Stressor 2, paragraph 50 et seq.) would act antagonistically with this impact by deterring animals away from vessels and thereby further reducing the risk of injury due to collision. Furthermore, marine mammals in this area are already accustomed to high level of vessel activity. For example, Buckstaff (2004) demonstrated that bottlenose dolphins Tursiops truncastus increased their rate of whistle production at the onset of a vessel approach, and then decreased production during and after it had passed. This increased whistle production may be a tactic to reduce signal degradation to ensure that information is being communicated in elevated noisy environment, but it also demonstrates that animals are aware of approaching vessel from a distance. This corroborates previous research of Nowacek et al. (2001) found that bottlenose dolphins swim in tighter aggregated groups during vessel approaches, therefore if a vessel is loud enough to be detected by an animal for which it adjusts its behaviour, the likelihood of collision decreases.
Therefore, as detailed in paragraph 58, significance is considered to be minor adverse and therefore not significant in EIA terms.

Stressor 3: EMF

EMF is highly localised and there is limited information on the effect of EMF on marine mammal receptors. It is unlikely to be additive with other stressors, given it will be confined to very specific locations in close proximity to the cables. There may be some synergistic effects if animals moving away from other disturbance activities (such as vessels) dive down and therefore move closer to the inter-array cables. Therefore, significance is considered to be minor adverse and therefore not significant in EIA terms.

Stressor 4: entanglement

The risk of entanglement is highly localised. The possibility of primary entanglement is very unlikely given design factors such as the taut mooring lines with high bending stiffness (Statoil, 2015) and low weight of the cable systems (Synthesis of Environmental Effects Research (SEER), 2022). It is noted there is limited information to assess entanglement of marine mammal receptors in offshore wind development to date. Injury from entanglement is very different to other types of injury (e.g. injuries from collision, PTS) and therefore there is not considered to be any additive effects. As is the case for stressor 2, to some extent the noise (pinging or snapping) from operational noise from turbines/mooring lines and any vessels utilised during the operation and maintenance phase themselves may act antagonistically with this impact by deterring animals away from the mooring lines. Therefore, significance is considered to be minor adverse and therefore not significant in EIA terms.

Stressor 5: changes in prey communities.

The EIA considered overall effect on fish and shellfish communities from multiple stressors (i.e. habitat loss, SSC, underwater noise, EMF etc) (see volume 3, chapter 9) and therefore, in this respect, has taken an ecosystem-based approach. For some, stressors such as underwater noise effects on fish and shellfish, will be over the same timescales as marine mammals whilst for others, such as temporary habitat loss, timescales may be different to those assessed for marine mammals (e.g. low mobility or sessile species may recover slowly). The assessment of effects, however, demonstrated that due to the high mobility of marine mammals, generalist feeding strategy and ability to exploit different prey species, combined with the small scale of potential changes in context of wider available habitat, the changes to fish and shellfish communities are unlikely to have an effect even from multiple stressors. Therefore, significance is considered to be minor adverse and therefore not significant in EIA terms.

Multiple stressors: inter-related effect of all stressors

Arrigo et al. (2020) studied synergistic interactions among growing stressors to an Arctic ecosystem and found that synergistic interactions amplify adverse stressor effects, and the impact of synergy is predicted to increase with the magnitude of stressors. Arrigo et al. (2020) suggests that large organisms at higher trophic levels, such as marine mammals, tend to be generally negatively impacted by increasing stressor interaction strength but the variability in the response to stressor is small and therefore reduces the probability of population collapse.
For stressor 1 (elevated underwater noise), there is the potential for marine mammals to forage in different habitats and to compensate for reduced foraging time. As such the ability of displaced animals will depend on the availability of prey resources in the habitat to which the animals are displaced. Studies have shown that for small, localised marine mammal populations with high site fidelity, there may be biological risks posed by displacement (Forney et al., 2017). For example, due to the importance of the areas for survival (i.e. areas of high resource availability), animals may be highly motivated to remain in an area despite adverse impacts which may increase stress (Rolland et al., 2012). Thus, the inter-related effects of underwater noise and changes in fish and shellfish prey resources needs to be considered. Impacts on fish and shellfish prey resources (stressor 5) were predicted to be localised and short-term and therefore unlikely to contribute to an inter-related effect where animals are displaced beyond the site boundary. Within the site boundary however, there may be short term inter-related effects of noise disturbance and reduced fish and shellfish prey resources. For marine mammals remaining in proximity to the Array, a substantial disruption in foraging may not be easy to compensate for where there are shifts in the species composition or localised reductions of fish and shellfish communities. It has been suggested it may be possible that damaged or disoriented prey could attract marine mammals to an area of impact due to providing short term feeding opportunities but increasing levels of exposure (Gordon et al., 2003) however, there is currently little evidence available to investigate such indirect effects on marine mammals.
The assessment has largely described potential adverse effects but there is also potential for some beneficial effects on marine mammal receptors. Construction of offshore wind farms can lead to the introduction of hard substrates which can lead to the establishment of new species and new fauna communities, and this may in turn attract marine mammals (Fowler et al., 2018, Lindeboom et al., 2011, Raoux et al., 2017). Consequently, even where there is potential for an inter-related effect between ongoing vessel noise during the operation and maintenance phase this may be compensated for, to some extent, by an increase in available prey resources. Russell et al. (2014) and Russell and McConnell (2014) demonstrated that harbour seals Phoca vitulina and grey seals Halichoerus grypus moved between hard structures at two operational wind farms and used space-state models to predict where animals were remaining at these locations to actively forage and where they were travelling to the next foundation structure. Lindeboom et al. (2011) studied the ecological effects of the Egmond aan Zee Offshore Wind Farm and found that even though the fish community was highly dynamic in time and space, with only minor effects upon fish assemblages observed during the operation and maintenance phase, some fish species (e.g. cod Gadus morhua) benefited from the ‘shelter’ within the wind farm, although this effect may be reduced for floating wind turbines. This is likely due to reduced fishing activity and the new hard substratum with associated fauna which attracts predator species. Lindeboom et al. (2011) suggested the observed increase in echolocation activity of harbour porpoise within the wind farm may be correlated with presence of additional increased food sources compared to reference areas (Lindeboom et al., 2011).
The potential inter-related effects between underwater noise and collision risk have been discussed previously (in paragraph 58) and it is considered likely that marine mammals will move away from moving vessels in response to engine noise, therefore reducing the risk of collision (classed as an antagonistic interaction). Alternatively, marine mammals may tolerate and persist in a highly stressed state (as a result of injury caused by underwater noise) while the vessels are approaching (Muto et al., 2018). Animals could also become habituated to vessel noise and not move away from the vessel (McWhinnie et al., 2018) which would result in a synergistic interaction (Weilgart, 2011). Therefore, the outcome will depend on the degree of habituation and prior-experience and a number of acoustical properties that allow an approaching vessel to be detected by a marine mammal species (Gerstein et al., 2005). However, as described in the impact assessment, with measures adopted as part of the Array (e.g. the VMP) in place it is likely that any risk of injury from collision with vessels will be negligible.
Evidence for the potential long-term effects of offshore wind farms on marine mammals (related to all potential stressors) comes from monitoring programmes which baseline levels of abundance to construction and post-construction (operation and maintenance) phases. Few monitoring studies regarding impacts on marine mammals have been carried out to date.
Aerial survey haul-out counts were conducted before, during and after the construction phases at Scroby Sands Offshore Wind Farm, off the coast of Norfolk, to monitor harbour and grey seal counts at haul-out site, located less than two kilometres away from the offshore wind farm array (Skeate et al., 2012). The two studies reported a decline in harbour seal numbers during construction, with numbers remaining lower over several subsequent years. However, the numbers of grey seals increased dramatically year after year throughout the construction and early operational periods. It has been suggested that it is possible that changes in harbour seal numbers may be linked to rapid colonisation of competing grey seal (Skeate et al., 2012). It was noted regional changes in patterns of haul-outs of harbour seal in the Wash coincided with the construction of the Scroby Sands Offshore Wind Farm, but such changes in harbour seal number could have been part of wider regional dynamics (Verfuss et al., 2016). It should be noted that Scroby Sands Wind Farm is located 2.5 km off the coast of Great Yarmouth whereas the Array is located 80 km offshore and therefore a greater distance from haul-out sites. As a part of marine mammal monitoring at Robin Rigg Offshore Wind Farm, boat-based surveys for cetaceans were conducted before, during, and after construction (Canning et al., 2013). The monitoring data suggested that harbour porpoise were displaced from the wind farm site during the construction phase and operation period when compared to the pre-construction numbers. However, because there was only one year of pre-construction survey, natural variation cannot be ruled out as the reason for the observed change, especially since control survey locations outside of the wind farm also appeared to experience declines in harbour porpoise density.
With the rapid expansion of offshore wind farms, post-construction monitoring programmes are being implemented at various developments in Europe. Tougaard et al. (2003) studied short-term effects of the construction of wind turbines on harbour porpoises at Horns Rev Offshore Wind Farm. The study showed a decrease in porpoise acoustic activity within the wind farm at the onset of piling operations and subsequent recovery to higher levels a few hours after each piling operation was completed (Tougaard et al., 2003). (Tougaard et al., 2003) also showed that over the entire construction phase at Horns Reef there was no significant change in the abundance of harbour porpoise in the wind farm area compared to reference areas. Teilmann et al. (2008) also reported that during the operation and maintenance phase porpoise activity was higher in both the wind farm and reference area compared to baseline levels. As a result of monitoring at Nysted Offshore Wind Farm, it was demonstrated initially during construction and the first two years of operation that there were lower acoustic detections of harbour porpoises in the wind farm area, with recovery starting to occur within two years after the end of construction (Teilmann et al., 2006). Teilmann et al. (2006) suggested that animals were gradually habituating and returning to the wind farm area.(Teilmann et al., 2006).
Nabe-Nielsen et al. (2011) suggested, using simulations of the response of harbour porpoise to wind farm construction, that wind farms already existing off Danish coast do not have impact on harbour porpoise population dynamics and that the that construction of new wind farms is not expected to cause any changes in the long-term dynamics of the population. Likewise, Edrén et al. (2010) and McConnell et al. (2012) investigated possible interactions between seals and Danish offshore wind farms (Nysted Wind Farm and Rødsand II) and found that although there was a temporary reduction in the number of seals hauled out during construction operations (i.e. piling), there was no long-term effect on haul-out behaviour trends.(Edrén et al., 2010)
The examples of monitoring studies given in paragraphs 69 and 70 suggest marine mammal receptors can quickly recover and return to the impacted area, despite the potential effects from multiple stressors associated with offshore wind farms. Therefore, as detailed in paragraphs 63 to 70, significance is considered to be minor adverse and therefore not significant in EIA terms.

Offshore ornithology

For offshore ornithology, the following potential impacts have been considered within the inter-related effects assessment:

temporary habitat loss and disturbance;
indirect habitats from construction/decommissioning noise;
indirect impacts from UXO clearance;
disturbance and displacement from the physical presence of wind turbines and maintenance activities;
barrier to movement;
collision with wind turbines;
changes to prey availability; and
entanglement.

Table 20.8 Open ▸ lists the inter-related effects (Array lifetime effects) that are predicted to arise during the construction, operation and maintenance, and decommissioning phases of the Array and also the inter-related effects (receptor-led effects) that are predicted to arise for offshore ornithology receptors.
Effects on offshore ornithology receptors are not expected to have secondary effects on other receptors.

Table 20.8: Summary of Likely Significant Inter-Related Effects for Offshore Ornithology from Individual Effects Occurring Across the Site Preparation and Construction, Operation and Maintenance and Decommissioning Phases of the Array (Array Lifetime Effects) and from Multiple Effects Interacting Across all Phases (Receptor-led Effects)

Human environment

Commercial fisheries

For commercial fisheries, the following potential impacts have been considered within the inter-related effects assessment:

temporary loss or restricted access to fishing grounds;
long term loss or restricted access to fishing grounds;
displacement of fishing activity into other areas;
interference with fishing activity;
increased snagging risk, which could result in loss or damage to fishing gear;
increased steaming/vessel transit times; and
impacts to commercial exploited species populations.

Table 20.9 Open ▸ lists the inter-related effects (Array lifetime effects) that are predicted to arise during the construction, operation and maintenance, and decommissioning phases of the Array and also the inter-related effects (receptor-led effects) that are predicted to arise for commercial fisheries receptors.
Effects on commercial fishing also have the potential to have a secondary effect on other receptors and these effects are fully considered in the topic-specific chapters and elsewhere in this chapter. These receptors and effects are:

fish and shellfish ecology:

– displacement of fishing activities into other areas could increase fishing pressure in these areas and affect fish and shellfish receptors; and

benthic subtidal ecology:

– displacement of fishing activities into other areas could increase fishing pressure in these areas and affect benthic subtidal ecology receptors; and

socio-economics:

– reduced value of fish caught by commercial fisheries with potential downstream impacts, for example on fish processors.

Table 20.9: Summary of Likely Significant Inter-Related Effects for Commercial Fisheries from Individual Effects Occurring Across the Site Preparation and Construction, Operation and Maintenance and Decommissioning Phases of the Array (Array Lifetime Effects) and from Multiple Effects Interacting Across all Phases (Receptor-led Effects)

Shipping and navigation

For shipping and navigation, the following potential impacts have been considered within the inter-related effects assessment:

increased vessel to vessel collision risk resulting from displacement (third party to third party);
increased vessel to vessel collision risk resulting from displacement (third party to Array vessels);
vessel to structure allision risk; and
reduced access to local ports and harbours.

Table 20.10 Open ▸ lists the inter-related effects (receptor-led effects) that are predicted to arise for shipping and navigation receptors. No inter-related effects (Array lifetime effects) are predicted to arise during the construction, operation and maintenance and decommissioning phase of the Array since the potential impacts listed above in paragraph 78 will not be further exacerbated over the lifetime of the Array.
Shipping and navigation receptors also have the potential to have secondary effects on other receptors and these effects are fully considered in the topic-specific chapters and elsewhere in this chapter. These receptors and effects are:

commercial fisheries

– displacement from fishing grounds for commercial fishing vessels due to the presence of the buoyed construction and decommissioning areas during the construction and decommissioning phases, respectively; and

– displacement from fishing grounds for commercial fishing vessels due to the floating wind turbines and anchor mooring lines during the operation and maintenance phase.

Table 20.10: Summary of Likely Significant Potential Inter-Related Effects for Shipping and Navigation from Individual Effects Occurring across the Construction, Operation and Maintenance and Decommissioning Phases of the Array (Array Lifetime Effects) and from Multiple Effects Interacting Across all Phases (Receptor-led Effects)

Aviation, military and communications

For aviation, military and communications, the following potential impacts have been considered within the inter-related effects assessment:

creation of a physical obstruction to aircraft operations (including airborne SAR and low flying aircraft); and
wind turbines causing interference on aviation radar systems (including PSR and ADR).

Table 20.11 Open ▸ lists the inter-related effects (Array lifetime effects) that are predicted to arise during the construction, operation and maintenance, and decommissioning phases of the Array and also the inter-related effects (receptor-led effects) that are predicted to arise for aviation, military and communications receptors.
The Array alone impacts were assigned residual significance of impact of no greater than minor adverse once mitigation is applied. It is therefore anticipated that the significance of combined effects on airspace and radar users will not be of any greater significance than the effects when assessed in isolation.

Table 20.11: Summary of Likely Significant Potential Inter-Related Effects for Aviation, Military and Communications from Individual Effects Occurring across the Construction, Operation and Maintenance and Decommissioning Phases of the Array (Array Lifetime Effects) and from Multiple Effects Interacting Across all Phases (Receptor-led Effects)

Infrastructure and other users

For infrastructure and other users, the following potential impacts have been considered within the inter-related effects assessment:

physical restrictions on space for recreational craft/recreational fishing vessels; and
physical impact or loss of access to existing cables and pipelines.

Table 20.12 Open ▸ lists the inter-related effects (Array lifetime effects) that are predicted to arise during the construction, operation and maintenance, and decommissioning phases of the Array and also the inter-related effects (receptor-led effects) that are predicted to arise for infrastructure and other users.
As previously mentioned in paragraph 23, infrastructure and other users receptors are linked to physical processes and aviation, military and communication receptors. The inter-related effects have been fully in assessed in volume 2, chapter 7 and volume 2, chapter 14 of this Array EIA Report, respectively.
Effects on infrastructure and other users have the potential to lead to secondary effects on other receptors and these effects are fully considered in the topic specific chapters and elsewhere in this chapter. These receptors are as follows:

shipping and navigation

– displacement of recreational sailing and motor cruising, recreational fishing (boat angling) and other recreational activities (diving vessels); and

– physical impacts or loss of access to existing cables and pipelines.

Table 20.12: Summary of Likely Significant Potential Inter-Related Effects for Infrastructure and Other Users from Individual Effects Occurring across the Construction, Operation and Maintenance and Decommissioning Phases of the Array (Array Lifetime Effects) and from Multiple Effects Interacting Across all Phases (Receptor-led Effects)

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20.8. Part One: Receptor Based Inter-Related Effects Assessment