Publication - Strategy/plan

Sectoral marine plan: appropriate assessment

Assessment of the implications of the sectoral marine plan for offshore wind energy for designated special areas of conservation special protection areas, candidate special areas of conservation and proposed special protection areas in view of the sites' conservation objectives.

Sectoral marine plan: appropriate assessment
13. Appropriate assessment of the implications for the site in view of the site's conservation objectives.

13. Appropriate assessment of the implications for the site in view of the site's conservation objectives.

13.1.1 The following assessment is based upon the information contained in the HRA Report and the advice received from SNH, JNCC and MSS. Consideration has also been given to other consultation responses detailed above. Consideration of the effect on site integrity for each European site or European offshore marine site and qualifying interest(s) follows below.

13.1.2 For each of the qualifying interests identified, the worst-case scenario ("WCS") has been considered and details of the WCS for each receptor have been provided in the HRA Report. As detailed above, generic conservation objectives have been applied in this assessment.

13.2 Coastal and marine habitat features

13.2.1 The following generic conservation objectives ("GCO") ensure that for qualifying habitats the following are maintained in the long term;

  • Extent of the habitat within the site (GCO-CMH1);
  • Distribution of habitat within the site (GCO-CMH2);
  • Structure and function of the habitat (GCO-CMH3);
  • Processes supporting the habitat (GCO-CMH4);
  • Distribution of typical species of the habitat (GCO-CMH5);
  • Viability of typical species as components of the habitat (GCO-CMH6); and
  • No significant disturbance of the habitat (GCO-CMH7).

13.2.2 Intertidal, subtidal and supralittoral interest feature habitats are sensitive to physical loss or gain of habitat, where new structures are introduced to or removed from the seabed or coastal habitats. Development under the Plan may result in the introduction of permanent or temporary structures (either lying on the seabed or protruding from the seabed), causing a direct loss (either temporary or permanent) of habitat. The installation, presence and/or removal of WTG foundations could result in habitat loss or gain, where WTG foundations are located within the area of an interest feature habitat. It should be noted that no Plan Options overlap with these areas, although several POs do abut European/Ramsar sites.

13.2.3 In addition, works associated with the installation or removal of cables (or cable armouring) may also result in direct loss. At present, detail regarding cable routes to shore are not available and any European/Ramsar sites which support coastal or marine habitat features and lie within 100 km of the DPOs were screened into the assessment (except those located well seaward of the DPOs).

13.2.4 The sensitivity of habitats from direct effects and the magnitude of any effects are dependent on a range of factors, including; the habitat type impacted, the extent of the habitat impacted, the location and nature of the activities and the temporal nature of the activities. The potential for AEOSI on the qualifying marine and coastal habitat features from the generic impact pathways (Table 18) is considered below in Table 12.

Habitats - conclusion

13.2.5 Direct habitat loss or gain can be mitigated by avoiding habitat interest features within European/Ramsar sites at the project-planning stage (i.e. careful cable routing and landfall, as well as further spatial planning within POs). Standard licence conditions pertaining to toxic contamination and introduction of INNS may mitigate the risk of AEOSI.

13.2.6 Scottish Ministers consider that the Plan will not cause an adverse effect on the integrity on the coastal and marine habitat features of any SAC or cSAC, provided the mitigation measures set out in Section 4 of this AA are complied with (i.e. the completion of further project-level assessment which considers the timing, scale, nature and location of future activities).

Table 12 Coastal and marine habitat features - consideration of AEOSI

Qualifying and supporting feature

Impact pathway

Sensitivity and relevant generic conservation objectives (see above for reference)

Conclusion

  • Morphological features encompassing a range of habitats
  • Subtidal habitats (with typically soft-sediment habitat)
  • Subtidal habitats with typically hard-substratum habitat (reefs)
  • Intertidal habitats (including saltmarshes)
  • Supralittoral habitats

Physical loss/gain of habitat

Loss of coastal and offshore habitat - under footprint of devices, cables and cable armouring.

During the installation, operation and decommissioning phases of any works.

GCO-CMH1
GCO-CMH2
GCO-CMH3
GCO-CMH5
GCO-CMH6
GCO-CMH7

No direct overlap between POs and relevant sites, therefore, no direct habitat loss.

Cable alignment and landfall may cause LSE (physical loss/gain of qualifying habitat features).

Possibility of AEOSI due to inherent uncertainties at Plan-level.

Mitigation measures include further spatial planning at project-level to avoid habitats and minimise exposure/risk (e.g. cable routeing, installation methods such as HDD at landfall).

No AEOSI, provided mitigation measures set out in Section 4 of this AA are complied with.

  • Morphological features encompassing a range of habitats
  • Subtidal habitats (with typically soft-sediment habitat)
  • Subtidal habitats with typically hard-substratum habitat (reefs)
  • Intertidal habitats (including saltmarshes)
  • Supralittoral habitats

Physical damage to habitat

Damage from baseline surveys (e.g. boreholes/trawls), from equipment use causing abrasion, damage or smothering during installation, maintenance and removal of cables and devices (e.g. from jack-up legs, vessel anchors, mooring chains).

GCO-CMH2
GCO-CMH5
GCO-CMH6
GCO-CMH7

Survey phases likely to be of shorter duration - with localised changes. Impacts may be lessened due to small volume of material extracted and short duration of activity (when compared to construction).

Works during installation, maintenance and decommissioning phases may be more significant, but are likely to still result in short-term, localised impacts. E.g. increased suspended sediments and turbidity.

Disposal of construction material may damage habitats (e.g. sediment deposition on habitat features)

Possibility of AEOSI due to inherent uncertainties at Plan-level.

No AEOSI, provided mitigation measures set out in Section 4 of this AA are complied with.

Mitigation measures include further spatial planning at project-level to avoid habitats and minimise exposure/risk (e.g. cable routeing, installation methods such as HDD at landfall).

Effects of construction activity and cable routing likely to be localised and temporary. Careful alignment of cable routes to mitigate impacts.

  • Morphological features encompassing a range of habitats
  • Subtidal habitats (with typically soft-sediment habitat)
  • Subtidal habitats with typically hard-substratum habitat (reefs)
  • Intertidal habitats (including saltmarshes)

Physical damage to habitat

Changes to coastal and offshore habitat as a result of alterations to the wave climate or hydrodynamic regime, from the presence of devices or cable armouring causing physical changes (including changes to sediment transport and/or sediment scour).

GCO-CMH1
GCO-CMH2
GCO-CMH3
GCO-CMH4
GCO-CMH5
GCO-CMH6
GCO-CMH7

Extent will be influenced by type and location of devices.

Deposition of fine sediment may occur in areas of reduced tidal flow and scouring of benthic communities may result on the seabed around the base of WTG. Cumulative impacts of multiple devices likely to be additive.

Extent of effect defined in the HRA Report as being 1 tidal excursion distance from the DPO.

Effects of scour around devices and associated moorings considered to be of generally low significance and highly localised.

Resultant changes in coastal processes and, potentially, sediment transport are likely to have the greatest risks of impact in areas of medium to high energy. Consideration of impacts required at a project-level.

Possibility of AEOSI due to inherent uncertainties at Plan-level.

No AEOSI, provided mitigation measures set out in Section 4 of this AA are complied with.

  • Morphological features encompassing a range of habitats
  • Subtidal habitats (with typically soft-sediment habitat)
  • Subtidal habitats with typically hard-substratum habitat (reefs)
  • Intertidal habitats (including saltmarshes)
  • Supralittoral habitats

Toxic contamination (reduction in water quality)

Spillage of fluids and/or construction materials during installation, removal, survey or maintenance of structures

Release of contaminants associated with dispersion of suspended sediments during installation or removal of structures (devices and cables).

GCO-CMH5
GCO-CMH6
GCO-CMH7

Potential for accidental spillage during all phases of the works. Likelihood of spillage is comparatively low (due to standard safety measures deployed and licence/consent conditions). No direct overlap between DPOs and European/Ramsar sites - although may be overlap with cable routing and landfall activities.

Low likelihood of contaminated sediments within DPOs. The receiving waterbody will provide high levels of dilution.

Inshore cable routes and landfalls may be associated with areas of higher contaminants.

No AEOSI, provided mitigation measures set out at Section 4 of this AA are complied with.

Mitigation measures include further spatial planning at project-level to avoid habitats and minimise exposure/risk (e.g. cable routeing, environmental management procedures, vessel management plans).

Careful alignment of cable routes and landfalls (and selection of installation methods) to mitigate impacts.

  • Morphological features encompassing a range of habitats
  • Subtidal habitats (with typically soft-sediment habitat)
  • Subtidal habitats with typically hard-substratum habitat (reefs)
  • Intertidal habitats (including saltmarshes)

Non-Toxic contamination

Elevated turbidity

Increase in turbidity associated with release of suspended sediments during installation or removal of structures

GCO-CMH5
GCO-CMH6
GCO -CMH7

Excavation work has the potential to cause redistribution of sediment and potential adverse effects on surrounding habitats. Extent of effect defined in the HRA Report as being 1 tidal excursion distance from the DPO.

No direct overlap with DPO and European/Ramsar sites but cable routing/landfall activities may overlap.

Tidal excursions of several DPOs overlap with European/Ramsar sites. Disposal of construction material from installations and piled devices may have the potential increase turbidity levels.

Possibility of AEOSI due to inherent uncertainties at Plan-level.

No AEOSI, provided mitigation measures set out in Section 4 of this AA are complied with.

Effects are likely to be localised and temporary. Spatial planning with DPOs to mitigate potential impacts.

  • Morphological features encompassing a range of habitats
  • Subtidal habitats (with typically soft-sediment habitat)
  • Subtidal habitats with typically hard-substratum habitat (reefs)
  • Intertidal habitats (including saltmarshes)

Biological disturbance

Introduction of non-native species ("INNS")

Introduction of new substructures, providing new substratum, facilitates the colonisation and ingress of INNS.

Introduction and ingress of INNS as biofouling species on the surfaces of vessels/construction plant.

GCO-CMH5
GCO-CMH6
GCO -CMH7

No direct overlap with DPO and European/Ramsar sites but cable routing/landfall activities may overlap.

Placement of structures underwater introduces new, potentially barren, surfaces which have the potential to facilitate spread of INNS.

Difficult to quantify risk of INNS. Assumption that current spread of species limited by prevailing physical regime and lack of new colonizing substrate, the options which cause the greatest change in physical processes and provide the greatest amount of colonizing space would be expected to pose the greatest risk.

INNS may be introduced by plant/vessels used during the construction, operational and decommissioning phases. Likelihood considered low due to regular maintenance and cleaning regimes (provided these are undertaken).

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

Standard licence/consent conditions, including the requirement to prepare and adhere to a biosecurity plan to reduce risk of introduction and spread of INNS.

13.3 Marine Mammals

13.3.1 In its response, dated 25 March 2020, SNH advised that there would be no adverse effect on the integrity of any SAC or cSAC with marine mammal qualifying interests from the Plan alone or in-combination with other projects.

13.3.2 The HRA Report considers the potential for AEOSI from Section 7 (page 28) onwards. Potential effects were considered against the following generic conservation measures for the qualifying species;

  • Population of the species as a viable component of the site (GCO-MM-1);
  • Distribution of the species within site (GCO-MM-2);
  • Distribution and extent of habitats supporting the species (GCO-MM3);
  • Structure, function and supporting processes of habitats supporting the species (GCO-MM4); and
  • No significant disturbance of the species (GCO-MM5).

13.3.3 Marine mammals have extensive ranges and cover large distances to forage in the pelagic environment. Critical habitat areas are those which are essential for day-to-day well-being and survival, as well as maintaining population growth. These critical habitat areas will be the most sensitive parts of a marine mammal's range to any loss (or gain) of habitat.

13.3.4 Foraging areas are critical habitat for marine mammals and these may encompass large areas, however, marine mammals may aggregate in hotspots (where prey resources found in high densities). Spawning and nursery sites for prey species will be particularly sensitive to any environmental change and such spawning/nursery grounds may be impacted by activities such as piling/noise/vibration.

13.3.5 There is the potential for collision risk to occur with underwater structures, although as underwater structures are essentially static (for floating and fixed technologies), the risk is considered low. [22] Further, marine mammals have the potential to become entangled with rope and/or lines. The risk factors for entanglement are associated with the biological characteristics of the marine mammals and the physical features of the mooring lines. Current evidence suggests that entanglement in mooring lines is unlikely to be a significant issue and high visibility mooring lines may mitigate potential risks. As further deployment of floating offshore wind technologies take place, it is expected that understanding of the potential risks and impacts of entanglement and efficacy of mitigation measures will become available.

13.3.6 Marine mammals are sensitive to acoustic disturbance in the marine environment and the hearing sensitivity and frequency range of marine mammals varies between species and physiology. The impacts of noise on marine mammals can broadly be split into lethal and physical injury, auditory injury and behavioural response. Chronic stress related disorders can also occur with long-term, repeated exposure to a noise source. Very high exposure levels (e.g. associated with offshore impact piling, underwater explosive operations) it is possible for lethality and physical damage to occur. Permanent threshold shift ("PTS") can occur as a result of prolonged exposure to noise or very intensive noise, with temporary threshold shift - a temporary reduction in hearing capability - occurring as a result exposure to underwater noise. Levels of PTS and TTS will depend on the species and physiology.

13.3.7 The HRA Report considers marine mammals are at low sensitivity to all generic impact pathways during all phases of the works, with the exception of non-physical disturbance during the construction phase, i.e. as a result of pile driving, seismic survey, UXO clearance, vessel movements. The level of risk will be dependent on the level of exposure (i.e. exposure may be higher if development takes place closer to a designated site). As it is not possible to predict the level of exposure a WCS has been assumed in the HRA Report.

13.3.8 The HRA Report considered that there was the potential for AEOSI from certain activities, but these could be mitigated via appropriate and meaningful mitigation measures at a project-level. The potential for AEOSI from the generic impact pathways is summarised below in Table 13.

Conclusions - Marine Mammals

13.3.9 In the event that concurrent construction noise in a particular geographic region requires further consideration, then there is the potential to implement sequencing of developments within the same broad geographical region. This approach could, however, extend the duration of effects (depending on the nature and type of activity and receptors impacted). It is, therefore, considered appropriate that such risks are most appropriately and effectively managed at a project-level, once the necessary details are available and there is greater certainty regarding the nature and timings of potential impacts. As further deployment of floating offshore wind technologies takes place, it is anticipated that an increased understanding of the potential risks of entanglement with mooring lines will take place and the potential effects of this impact pathway will need to be considered within future project-level HRAs (as appropriate to the proposal).

13.3.10 Scottish Ministers concur with the view of SNH, that the Plan will not cause an adverse effect on the integrity on the marine mammal qualifying interests of any SAC or cSAC, provided the mitigation measures set out in Section 4 of this AA are complied with (i.e. the completion of further project-level assessment which considers the timing, scale, nature and location of future activities).

Table 13 Marine mammals - consideration of AEOSI

Qualifying and supporting feature

Impact pathway

Sensitivity and relevant generic conservation objectives (listed above)

Conclusion

  • Common seal
  • Grey seal
  • Bottlenose dolphin
  • Harbour porpoise

Physical loss/gain of habitat

Potential for loss of foraging areas from reduction in coastal and offshore habitat due to installation of devices and cable armouring (both at the development footprint and outside these areas from associated scour and indirectly from changes to the hydrodynamic regime, as well as from chains anchoring devices disturbing seabed habitat during operation.

GCO-MM4
GCO-MM3

Marine mammals are highly mobile and have large foraging ranges.

Any loss of habitat from development is likely to only constitute a small part of the available foraging range and, therefore, sufficient alternative habitat likely to be available.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with

  • Common seal
  • Grey seal
  • Bottlenose dolphin
  • Harbour porpoise

Physical loss/gain of habitat

Presence of structures on seabed for duration of project may result in changes to prey and species behaviour (e.g. acting as fish aggregating device ("FAD"), artificial reef or bird roost).

GCO-MM2
GCO-MM3
GCO-MM4

Turbine bases could act as artificial reefs and FADs for prey species (e.g. increase in biomass resulting in positive feeding opportunities).

The size of the array will be key consideration - and devices with the highest FAD potential are those with large elements, e.g. large mooring points or floating structures.

Devices with large moorings may provide additional shelter and food (habitat) for small demersal fish such as territorial biennies and gobles). Increases in demersal fish have been found around piles of OWF.

Empirical data regarding this impact is currently limited.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with

  • Common seal
  • Grey seal
  • Bottlenose dolphin
  • Harbour porpoise

Damage to habitat

Reduction in quality of foraging areas, as a result of damage to coastal and offshore habitat from survey activities (i.e. borehole and trawls) and equipment use causing abrasion, damage or smothering during installation, maintenance or removal of cables/devices or from scour, sediment transport and hydrodynamic change during operation.

GCO-MM3
GCO-MM4

Marine mammals are highly mobile and have large foraging ranges.

The extent of habitat reduced in quality is likely to constitute on a small proportion of the available foraging habitat and, therefore, sufficient alternative habitat likely to be available.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with

  • Common seal
  • Grey seal

Physical damage to habitat

Damage to seal haul out locations during installation, decommissioning and operation of cables and cable armouring

Seal haul-out sites are generally located in remote areas and are highly sensitive to damage and disturbance (particularly during the breeding season).

Cable routes most likely to make landfall near existing infrastructure. Most seal haul-outs are not located close to this infrastructure, therefore, impacts unlikely.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

Spatial planning of cable routes to avoid sensitive areas/mitigate potential impacts.

  • Common seal
  • Grey seal
  • Bottlenose dolphin
  • Harbour porpoise

Damage to species

Collision risk and possible mortality - due to presence of devices or vessels transiting to/from the development site (including above and below water) and the influence of lighting.

Risk of entanglement following a collision with power cables or mooring elements.

GCO-MM1
GCO-MM2
GCO-MM5

Pinnipeds and cetaceans may collide with construction vessel propellors and machinery (leading to physical injury/fatality). Juvenile grey seal pups most vulnerable to collision risks.

Ships travelling at >14 knots more likely to cause lethal/serious injuries. Vessels used during the construction phase are likely to be travelling at lower speeds or be stationary, thereby reducing risks.

Marine mammals have the potential to become entangled with ropes and/or lines. Risk factors are related to biological characteristics of marine mammals (body size, flexibility, ability to detect moorings and mode of feeding) and the physical features of the mooring lines.

Marine mammals may become entangled if the animal's ability to detect the object is compromised (e.g. particular environmental conditions such as low light or storm conditions) or when distracted while feeding on mobile prey species.

Entanglement risk may be mitigated by using high visibility mooring lines.

Ghost fishing gear (where abandoned or lost fishing gear becomes entangled in lines and cables), thereby creating a potential entanglement risk for marine mammals, fish and seabirds. Systemic inspection of mooring and anchor lines to check for the presence of ghost gear and removal of gear may mitigate this risk.

Behavioural responses to wind farm development may either be long-range avoidance or close-range evasion, depending upon the distance at which the threat is perceived and the subsequent behavioural response. Collision risk with WTG structures is considered to be low.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

Deployment of high visibility mooring lines to mitigate risk of entanglement. Systemic inspection of mooring and anchor lines to check for presence of ghost gear and arrangement for removal.

  • Common seal
  • Grey seal
  • Bottlenose dolphin
  • Harbour porpoise

Non-physical disturbance

Barrier to movement - presence of sub-surface structures and disturbance (noise or visual) which may block migratory pathways or access to feeding grounds

GCO-MM2
GCO-MM3

Potential for barrier effect will be dependent on the extent to which noise and visual cues from the device cause an avoidance response. Dependent on ability of marine mammal to navigate around devices.

Significance of obstruction will depend on spatial confines and size of array.

Marine mammals are highly manoeuvrable and offshore location of DPOs, sensitivity considered low.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with

  • Common seal
  • Grey seal
  • Bottlenose dolphin
  • Harbour porpoise

Non-physical disturbance

Visual disturbance and exclusion from areas as a result of surveying, cable and device installation, operation and decommissioning and vessel movements.

GCO-MM2
GCO-MM5

Visual disturbance during all phases of works considered to be short-term.

Level of impact dependent on distance from seal haul-out sites and key foraging areas.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with

  • Common seal
  • Grey seal
  • Bottlenose dolphin
  • Harbour porpoise

Non-physical disturbance

Noise/vibration disturbance and exclusion from areas as a result of vessels and other activities during survey work (e.g. seismic exploration and geophysical surveys), construction (e.g. piling, drilling, cable laying), operation (e.g. device noise), maintenance or decommissioning works.

GCO-MM2
GCO-MM5

Sensitivity during construction phase considered to be high (particularly if piling activity undertaken), but low/medium during other phases.

Geophysical surveys involving side scan sonar may cause acoustic disturbance.

Effects from vessel noise are not clear, with both attraction and avoidance reactions having been observed.

Key sources of noise during construction and installation include;

Shipping and machinery;
Dredging;
Pile-driving and drilling.

Cable burial may require use of trenching, jetting machinery or rock cutting machinery depending on habitat type (or laying of mattresses/rock protection).

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

Standard licence/consent conditions, including the requirement to prepare and adhere to a Piling Strategy, Construction Method Statement, Vessel Management Plan and the requirement to obtain and adhere to European Protected Species licenses (if appropriate) to mitigate potential impacts.

  • Bottlenose dolphin
  • Harbour porpoise

Non-physical disturbance

Impacts from EMF on electromagnetically sensitive fish and cetaceans, interfering with prey location and mate detection in some species and creating barriers to migration, during the operational phase.

GCO-MM2
GCO-MM5

It is assumed cetaceans may be sensitive to electromagnetic cables, but that anticipated magnetic fields from cables is likely to be very small. Sensitivity considered low.

Risk can be mitigated via cable armouring/protection/burial methods.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

Standard licence/consent conditions, including the requirement to prepare and adhere to a Cable Laying Strategy (and associated burial/protection/armouring) to mitigate potential impacts.

  • Common seal
  • Grey seal
  • Harbour porpoise
  • Bottlenose dolphin

Toxic contamination (reduction in water quality)

Spillage of fluids and/or construction materials during installation, removal, survey or maintenance of structures

Release of contaminants associated with dispersion of suspended sediments during installation or removal of structures (devices and cables).

GCO-MM1
GCO-MM2
GCO-MM5

Potential for accidental spillage during all phases of the works. Likelihood of spillage is comparatively low (due to standard safety measures deployed and licence/consent conditions). May include anti-fouling paints, accidental leakage of fluids and/or spillage fuels or cargo from vessels.

Quantities and toxicities associated with sacrificial anodes and antifouling coatings are considered to be extremely low, therefore impact considered negligible significance.

Low likelihood of contaminated sediments within DPOs. The receiving waterbody will provide high levels of dilution. Impacts likely to be extremely localised, thus minimising impact on water quality.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI, provided mitigation measures set out at Section 4 of this AA are complied with.

Mitigation measures include further spatial planning at project-level to avoid habitats and minimise exposure/risk (e.g. cable routeing, environmental management procedures, vessel management plans).

Careful alignment of cable routes and landfalls (and selection of installation methods) to mitigate impacts.

  • Common seal
  • Grey seal
  • Harbour porpoise
  • Bottlenose dolphin

Non-toxic contamination

Elevated turbidity

Increase in turbidity associated with release of suspended sediments during installation or removal of structures

Local suspended sediment concentrations may increase as a result of drilling activity, burial of power export cables and disposal of drill cuttings.

Increased turbidity could affect foraging, social and predator/prey interactions of marine mammals (although marine mammals around UK regularly recorded foraging in highly turbid environments). All features considered to have low sensitivity to this impact pathway.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

13.4 Diadromous fish and freshwater pearl mussel features

13.4.1 The HRA Report considers the potential for AEOSI at Section 8 (page 183 onwards). Potential effects were considered against the following generic conservation measures for the qualifying species and interests;

  • Population of the species, including range of genetic types for salmon, as a viable component of the site (GCO-FF1);
  • Distribution of the species within site (GCO-FF2);
  • Distribution and extent of habitats supporting the species (GCO-FF3);
  • Structure, function and supporting processes of habitats supporting the species (GCO-FF4);
  • No significant disturbance of the species (GCO-FF5);
  • Distribution and viability of the species' host species (e.g. freshwater pearl mussel) (GCO-FF6); and
  • Structure, function and supporting processes of habitats supporting the species' host species (GCO-FF7).

13.4.2 Although direct loss of freshwater habitats may occur as a result of cable installation or landside infrastructure works, potential effects from non-marine development are outwith the scope of the HRA Report and this AA. There is, however, the potential for loss of migratory fish foraging areas or pearl mussel habitat in marine and estuarine environments. It is anticipated that any sensitive habitats should be avoided where possible (e.g. via further spatial-planning at a project-level) and that during the construction period the WCS would involve temporary effects. Damage to the offshore habitats during the operational phase may influence the foraging area for migratory fish species, however, the high mobility and ranges of this group may enable them to utilise other foraging areas (if required).

13.4.3 There are several migratory diadromous fish species found within Scottish waters and which use Scottish rivers for spawning, including Atlantic salmon, sea trout, sea lamprey, river lamprey and shad, plus European eel which spawns at sea. Many migratory species are protected, generally through SAC in riverine environments. Scotland is a stronghold for Atlantic salmon with nearly all rivers which are accessible to upstream migrating salmon other than those with poor water quality containing salmon populations (see further, the Regional Locational Guidance). The largest salmon rivers with the largest populations of salmon are on the east coast. The sea feeding grounds are remote from Scottish marine waters which the outgoing smolts and returning adult fish must pass through

13.4.4 There is now some information on the migration paths of the outgoing salmon smolts from acoustic tagging and research trawling studies and the likely migration routes of the returning adult salmon, mainly from traditional tagging studies, particularly close to the coast. Outgoing smolts or returning adults are likely to migrate through all Plan Options but there remain uncertainties about the relative numbers passing through particular Plan Options. These impacts will need to be considered and assessed at a Project-level.

13.4.5 Potential impacts on salmon associated with offshore wind development include those which could arise from high impact piling and detonation of unexploded ordnance during construction, possible increased predator abundance at structures, and subtle changes to magnetic fields stemming from cables conducting electricity affecting the migratory behaviour of salmon using geomagnetic cues. The salmon populations associated with each river vary in their productivity and resilience to any impacts, with some populations, but not others, able to accommodate some losses.

13.4.6 A summary of the consideration of the for potential of AEOSI from the generic impact pathways on the fish and freshwater mussel features is provided at Table 14 below.

Fish and freshwater pearl mussel features - conclusion

13.4.7 There is the potential for AEOSI on fish and freshwater pearl mussel qualifying interests of SACs and cSACs as a result of development under this Plan. Non-physical disturbance presents the highest risk of effects (of all assessed impact pathways) for these qualifying interests. Mitigation measures relating to spatial planning within POs, array layout, restrictions on piling activities (including timing, duration and frequency) and cable routing will need further consideration at a project-level (as appropriate). Further, it is anticipated that further evidence regarding migratory routes will become available and can be used to inform future plan and project-level assessments.

13.4.8 Scottish Ministers consider that the Plan will not cause an adverse effect on the integrity of the fish and freshwater pearl mussel features of any SAC or cSAC, provided the mitigation measures set out in Section 4 of this AA are complied with (e.g. the completion of further project-level assessment which considers the timing, scale, location and nature of future activities).

Table 14 Fish and freshwater pearl mussel features - consideration of AEOSI

Qualifying and supporting feature

Impact pathway

Sensitivity and relevant generic conservation objectives (listed above)

Conclusion

  • Atlantic salmon
  • Sea lamprey
  • River lamprey
  • Allis shad
  • Twaite shad
  • Freshwater pearl mussel (indirectly)

Physical loss/gain of habitat

Potential for loss of foraging areas from reduction in coastal and offshore habitat due to installation of devices and cable armouring (both at the development footprint and outside these areas from associated scour and indirectly from changes to the hydrodynamic regime, as well as from chains anchoring devices disturbing seabed habitat during operation.

GCO-FF3
GCO-FF7

Atlantic salmon and shad are highly mobile, migratory species - undergo large shifts in distribution during the marine phase of their lifecycle, with a pelagic lifestyle at sea (little association with the seabed). Atlantic salmon and shad considered to be transient within DPOs - therefore, potential damage to seabed in deployment locations will be of negligible significance.

Sea lamprey are highly mobile migratory species which are widely distributed at sea - therefore, potential damage to seabed in deployment locations will be of negligible significance.

River lamprey adults live primarily in estuaries, before migrating upstream to spawn in freshwater. Therefore, no direct overlap of POs and river lamprey habitat/foraging areas.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

  • Atlantic salmon
  • Sea lamprey
  • River lamprey
  • Allis shad
  • Twaite shad
  • Freshwater pearl mussel (indirectly)

Physical loss/habitat gain

Direct change to habitat around the development footprint

Presence of structures on the seabed for the duration of the project, resulting in changes to local predator abundance and behaviour (e.g. acting as FAD, artificial reef or bird roost).

GCO-FF1
GCO-FF2
GCO-FF3
GCO-FF4
GCO-FF5
GCO-FF6
GCO-FF7

Empirical evidence has shown greater presence of fish around WTG foundations.

Wilhelmsson et al[23] investigated the potential for WTG to function as artificial reefs and FADs. Fish abundance was found to be greater in the vicinity of the WTG, whilst species richness and Shannon-Wiener diversity (H') were similar. On the monopiles of foundations, fish community structure was different and total fish abundance was greater, while species richness and diversity (H') were lower on the surrounding seabed. Blue mussels and barnacles covered most of the submerged parts of the WTG. On the seabed, more blue mussels and less red algae were recorded (compared to adjacent areas).

A gill netting survey at the Svante OWF (Sweden) found higher numbers of cod present within 200 metres of an operational WTG, compared to surrounding open waters, and higher numbers when the WTG was non-operational.

Diver-held video surveys of the North Hoyle OWF piles found extremely high densities of juvenile whiting, feeding on dense populations of amphipods amongst the fouling biota on the piles.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

  • Atlantic salmon
  • Sea lamprey
  • River lamprey
  • Allis shad
  • Twaite shad
  • Freshwater pearl mussel (indirectly)

Physical damage to habitat

Indirect and temporary damage

Reduction in quality of foraging areas, due to damage to coastal and offshore habitat from baseline surveys (e.g. boreholes and trawls), from equipment use causing abrasion, damage or smothering during installation, from maintenance and removal of cables/devices or from scour, sediment transport and hydrodynamic change and damage from chains anchoring devices during operation.

GCO-FF3
GCO-FF7

Atlantic salmon and shad are highly mobile, migratory species - undergo large shifts in distribution during the marine phase of their lifecycle, with a pelagic lifestyle at sea (little association with the seabed). Atlantic salmon and shad considered to be transient within DPOs - therefore, potential damage to seabed in deployment locations will be of negligible significance.

Sea lamprey are highly mobile migratory species which are widely distributed at sea - therefore, potential damage to seabed in deployment locations will be of negligible significance.

River lamprey adults live primarily in estuaries, before migrating upstream to spawn in freshwater. Therefore, no direct overlap of POs and river lamprey habitat/foraging areas.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

  • Atlantic salmon
  • Sea lamprey
  • River lamprey
  • Allis shad
  • Twaite shad
  • Freshwater pearl mussel (indirectly)

Physical damage

Direct damage to species from collision risk

Collision risk and possible mortality due to presence of devices or from vessels transiting to/from site (including above and below water collision risk and the influence of lighting), risk of entanglement following a collision with power cables or mooring elements.

GCO-FF1
GCO-FF2
GCO-FF5
GCO-FF6
GCO-FF7

Behavioural responses in fish to perceived threats may be demonstrated: Long range avoidance (i.e. avoiding the area within the vicinity of the device) or close-range evasion (dependent on distance at which device perceived and subsequent behavioural response). Fish which are actively migrating on a fixed heading may be less likely to be displaced.

Long range response is considered distances beyond which visual response can be undertaken (e.g. noise and vibration cues). Close range evasion would occur where primary stimulus is visual reaction to physical characteristics of the device.

The essentially static base of the WTG (regardless of technology type) means that collision risk is unlikely. Fish have been recorded colliding with anthropogenic structures, but generally in areas of poor visibility.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

  • Atlantic salmon
  • Sea lamprey
  • River lamprey
  • Allis shad
  • Twaite shad
  • Freshwater pearl mussel (indirectly)

Non-physical disturbance

Barrier to movement from presence of sub-surface structures and disturbance (noise or visual) which may block migratory pathways or access to feeding grounds depending on array design

GCO-FF1
GCO-FF2
GCO-FF5
GCO-FF6
GCO-FF7

It is considered WTG arrays will pose minimal barrier effects to the highly mobile migratory fish species.

Significance of obstructions dependent on spatial confines and size of devices/arrays (e.g. whether it spans the entire mouth of an estuary) and the functional use of the area by the fish species.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

  • Atlantic salmon
  • Sea lamprey
  • River lamprey
  • Allis shad
  • Twaite shad
  • Freshwater pearl mussel (indirectly)

Non-physical disturbance

Noise/vibration disturbance from vessels and other activities during survey work (e.g. seismic exploration and geophysical surveys), construction (e.g. piling, drilling, cable laying), operation (e.g. device noise), maintenance or decommissioning.

GCO-FF1
GCO-FF2
GCO-FF5
GCO-FF6
GCO-FF7

Noise from installation activities could arise from vessel traffic, possible requirements for bed levelling, driving and drilling of piles, installation of power export cables (i.e. ploughing sediment, rock cutting hard seabed areas, bolting to the seabed and/or directional drilling).

Understanding of source noise impacts and frequencies is increasing.

Impacts from pile driving and the use of explosives are of most concern to these qualifying interests. Some exposures can result in changes/damage to sensory structures or hearing capabilities, with the potential for mortality.

Behaviour changes may result in animals avoiding migratory routes or leaving feeding or reproduction grounds, with potential population-level consequences. Biologically important sounds can be masked where received levels are marginally above existing background levels.[24] The ability to detect and localise the source of sound is of considerable biological importance to these qualifying interests.

Disturbance effects on migratory fish from noise are most likely during the construction phase of works. The potential for activities such as impact piling means it is concluded that migratory fish are highly sensitive to construction noise.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

Project-level mitigation measures may include the requirement to prepare and adhere to a Piling Strategy and consideration of timing of activities and migratory patterns.

  • Atlantic salmon
  • Sea lamprey
  • River lamprey
  • Allis shad
  • Twaite shad
  • Freshwater pearl mussel (indirectly)

Non-physical disturbance

Impacts from EMF and thermal emissions on benthic invertebrates and electromagnetically sensitive fish and cetaceans interfering with prey location and mate detection in some species and creating barriers to migration.

GCO-FF1
GCO-FF2
GCO-FF5
GCO-FF6
GCO-FF7

The generated magnetic fields from OWF and associated cables are likely to be perceived by Atlantic salmon and other migratory species as a new localised addition to the heterogeneous pattern of geomagnetic anomalies already in existence.

The expected magnetic field from cables is expected to be very small (when compared to the Earth's own magnetic field). Although, very small differences in the earth's local magnetic field have been shown to be used as cues by geomagnetically navigating Pacific salmon, the modified fields only exist relatively close to OWF and associated cables.

The conclusion of most project-specific EIA to-date is that, whilst there could be an interaction between these species and subsea cables, the result is unlikely to be of significance at a population-level.[25]

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

  • Atlantic salmon
  • Sea lamprey
  • River lamprey
  • Allis shad
  • Twaite shad
  • Freshwater pearl mussel (indirectly)

Toxic contamination

Spillage of fluids and/or construction materials during installation or removal of structures (devices and cables) or during survey/maintenance works.

GCO-FF1
GCO-FF2
GCO-FF5
GCO-FF6
GCO-FF7

There is the potential for accidental discharge/spillages during all phases of works. Adoption of standard safety measures would reduce the likelihood of this occurrence.

Quantities and toxicities associated with sacrificial anodes and antifouling coatings are generally expected to be small, therefore, potential effects will likely be of negligible significance.

Should toxic contamination occur, it is not possible to make an estimation of the geographic extent of any impact, due to the large number of potential variables (e.g. metocean conditions, quantities leaked).

Accidental leakage of hydraulic fluids may be more significant, however, the probability of large quantities of oil or hydraulic fluids entering the environment is low.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

Project-level mitigation measures may include the need to prepare and adhere to the terms of a Vessel Management Plan and Environmental Management Plan to minimise and mitigate any risks associated with toxic contamination.

  • Atlantic salmon
  • Sea lamprey
  • River lamprey
  • Allis shad
  • Twaite shad
  • Freshwater pearl mussel (indirectly)

Toxic contamination

Release of contaminants associated with dispersion of suspended sediments during the installation or removal of structures (devices and cables).

GCO-FF1
GCO-FF2
GCO-FF5
GCO-FF6
GCO-FF7

Sediments within DPOs are generally expected to be low in contaminant concentrations, given the high-energy environments in which the WTG will be located.

Large volumes of water and highly dispersive and diluting nature of the surrounding environment will reduce potential effects on water qualify, should contaminants be re-suspended.

There is the potential for contaminated sediments to be re-suspended during cable routing and landfall works, depending on the contaminant levels of the sediment. Impacts are likely to be highly localised, thus minimising impact on water quality.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI, provided mitigation measures set out at Section 4 of this AA are complied with.

Careful alignment of cable routes and landfalls (and selection of installation methods) to mitigate impacts.

  • Atlantic salmon
  • Sea lamprey
  • River lamprey
  • Allis shad
  • Twaite shad
  • Freshwater pearl mussel (indirectly)

Non-toxic contamination

Increase in turbidity associated with the release of suspended sediments during the installation or removal of structures (devices and cables).

GCO-FF1
GCO-FF2
GCO-FF5
GCO-FF6
GCO-FF7

Migratory fish regularly transit through estuaries with high levels of suspended sediment and are relatively tolerant of turbid conditions (unless associated with reduced oxygen levels or the presence of toxic materials). The characteristically high-energy offshore environments in which the POs are located will assist in the dispersion of any localised increases in turbidity, thus minimising any impacts on water quality.

No AEOSI, provided mitigation measures set out at Section 4 of this AA are complied with.

Careful alignment of cable routes and landfalls (and selection of installation methods) to mitigate impacts.

13.5 Seabird SPAs and pSPAs

13.5.1 The HRA Report considers the potential for AEOSI for seabird qualifying interests of SPAs and pSPAs at Section 8 (page 183 onwards) Potential effects on the qualifying bird species listed in Table 10 were considered in light of the following generic conservation objectives;

13.5.2 To avoid deterioration of the habitats of the qualifying species, or significant disturbance to the qualifying species, thus ensuring that the integrity of the site is maintained; and

To ensure that for qualifying habitats the following are maintained in the long term;

  • Population of the species as a viable component of the site (GCO-ON1);
  • Distribution of the species within site (GCO-ON2);
  • Distribution and extent of habitats supporting the species (GCO-ON3);
  • Structure, function and supporting processes of habitats supporting the species (GCO-ON4); and
  • No significance disturbance of the species (GCO-ON5).

13.5.3 General characteristics and sensitivities of relevant bird features were presented and reviewed against OWF development activities. Different species will have different sensitivities to effects, according to several factors, including;

  • Their foraging strategy, e.g. pursuit divers or surface feeders;
  • Daily activity patterns across seasons, e.g. nocturnal, crepuscular or diurnal activity; and
  • Their life-history and breeding ecology, e.g. diving species such as auk species may incur increased energetic costs (individual fitness) and/or subsequent effects to breeding success via barrier or displacement effects.

13.5.4 For example, diving species may be at increased risk from the effects of increased turbidity, due to predator-prey interactions. Species with higher energy cost burdens of flight and foraging (such as auks) may find it harder to increase their foraging ranges in response to barrier effects resulting during the operational phase.

Collision risk and displacement are considered to be the key impact pathways for seabird qualifying interests, particularly as a result of in-combination effects with other consented/operational OWF in the Moray, Forth and Tay regions. All species scoped into the assessment are considered to be at collision risk during all phases of the works, although this will differ according to the nature of the environment and species foraging modes. The HRA Report concluded that large gulls, such as a great black-backed gull, herring gull, lesser black-backed gull, northern gannet and black-legged kittiwake are most sensitive to the risk of collision mortality, as these species tend to spend a comparatively higher proportion of their flying time at an altitude that overlaps with blade height.[26] The HRA Report presents a detailed consideration of the models used to assess and predict collision risk. The current predicted levels of in-combination collision risk arising from consented/operational development in the North East and East regions has resulted in the application of Plan-level mitigation measures, as discussed later in this AA.

13.5.5 Displacement and barrier effects may result in AEOSI for the seabird qualifying interests of designated sites during all phases of the works. Exclusion from habitats prevents access to prey sources (although such exclusion could reduce other effects, such as collision risk). Reductions in the availability of habitat and access to prey could lead to changes in seabird foraging behaviour, including increased individual stress levels and alterations to individual time budgets (owing to increased foraging distances), with consequent population-level impacts (i.e. decreases in breeding success and individual fitness).[27] The level of impact will be dependent on the project specifics (i.e. location, timing of activity, scale of development), the availability of areas of alternative habitat, the number of disturbance occurrences and the status of the conditions that are prevalent.

13.5.6 SNH advised that, at this stage, at the Plan-level, it would be unable to advise that there would be no AEOSI arising from development within DPOs E1 and E2, alongside existing consented OWF development in this region. SNH advised that considers it, "necessary for regional studies of seabird density and SPA connectivity to be undertaken within these DPOs to establish whether these species are present in sufficient numbers for some or all of the sea area within E1 and E2 to be subject to the same temporary restriction on development as applied at E3 and NE2-NE6 or whether and where they are sufficiently low as to enable leasing and consenting to proceed with no further Plan mitigation measures required."

13.5.7 Further, SNH advised that it strongly supported the need for temporary restriction on OWF development within DPOs E3 and NE2-NE6, until such time "that enough evidence on the environmental capacity for seabirds exists to reduce the risk to an acceptable level." SNH advised that, due to concerns regarding the predicted in-combination impacts of existing and consented OWF on specific east coast SPAs and seabird species, no development should be permitted until and unless research and post-consent monitoring of existing OWFs in eastern Scotland demonstrate that "capacity for further development, with respect to SPA impacts, exists." SNH strongly advised that the research and monitoring requirements outlined be completed, to improve understanding regarding the impacts of OWF development, and that derogations should be pursued only in circumstances where such research and monitoring effort has been undertaken and is unable to demonstrate further capacity of OWF development.

13.5.8 Potential applicants will be able to submit licence and consent applications for the POs covered by Plan-level mitigation before the removal of the mitigation at a Plan-level (via the iterative plan review process). Such applications, however, will be subject to further project-level assessment and consideration. A consent/licence will not be granted unless it can be concluded that the project will not have an AEOSI, or Scottish Ministers opt to pursue a derogation under the Habitats Regulations. Given the current predicted in-combination levels of collision and displacement impacts and level of uncertainty regarding the presence and distribution of key seabird species within certain DPOs, it is unlikely that Scottish Ministers would be able to conclude that development within these DPOs would not result in an AEOSI. Should applicants wish to pursue this consenting route, they are encouraged to undertake early and sustained engagement with Scottish Ministers and the SNCBs.

13.5.9 Developers who are successful in obtaining Option Agreements for POs E1 and E2 are expected to discuss the parameters of the necessary survey and assessment work with the Ornithology Working Group (to be established upon the adoption of the Plan, see Table 2 for further detail) prior to undertaking any such work. The outputs will need to be provided in the manner/format and timescales set out by Marine Scotland, before the submission of any licence or consent application(s). The continued application of these mitigation measures will be considered via the iterative plan review process.

13.5.10 The HRA Report highlights that there may, in some cases, be a lack of evidence regarding nocturnal activities and, therefore, "future project level HRAs should consider individual species behaviour and current research."[28] SNH stated that it considered that the information regarding nocturnal behaviour (provided at Table 8 of the HRA Report) was potentially misleading as the categorisation presented was too simplistic. ABPmer have considered this response and consider that, whilst future HRA Reports should include a more nuanced categorisation of impacts, this would not alter the conclusions regarding the significance of this impact.

Ornithology - conclusions

13.5.11 Scottish Ministers consider that the Plan, in-isolation, will not cause an adverse effect on the integrity of the seabird qualifying features of any SPA or pSPA, provided the mitigation measures set out in Section 4 of this AA are complied with (e.g. the completion of further project-level assessment which considers the timing, scale, location and nature of future activities). Further consideration of potential in-combination impacts follows at section 14.3 below.

Table 15 Seabird qualifying interests - consideration of AEOSI

Qualifying and supporting feature

Impact pathway

Sensitivity and relevant generic conservation objectives (listed above)

Conclusion

  • All seabird species

Physical loss/gain of habitat

Potential for loss of foraging areas from reduction in coastal and offshore habitat due to installation of devices and cable armouring (both at the development footprint and outside these areas from associated scour and indirectly from changes to the hydrodynamic regime, as well as from chains anchoring devices disturbing seabed habitat during operation.

GCO-ON3
GCO-ON4

All seabird species are considered sensitive to this effect during the operational phase of works.

Effects dependent on quality and location of habitat impacted, e.g. loss of sandy sediments within DPOs may have greatest impacts due to importance for sandeels (prey species). Loss of intertidal habitat due to cable installation works could potentially affect foraging areas for over-wintering birds.

Dependent on the array size, if the area lost represents a small proportion of the available habitat, there may be sufficient alternative habitat available thereby resulting in no AEOSI.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

  • All seabird species

Physical loss/gain of habitat

Presence of structures on seabed for duration of project may result in changes to prey and species behaviour (e.g. acting as FAD), artificial reef or bird roost).

GCO-ON3
GCO-ON4

Underwater structures may provide new foraging opportunities for diving species.

Construction of OWF and structures above water (with a stable platform) may serve as an additional resting and/or breeding habitat for gulls and terns.

Extent of this habitat creation effect and potential implications for increased collision risk (negative effect) are unknown at present. It is considered sensitivity is likely to be low.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with

  • All seabird species

Damage to habitat

Reduction in quality of foraging areas, as a result of damage to coastal and offshore habitat from survey activities (i.e. borehole and trawls) and equipment use causing abrasion, damage or smothering during installation, maintenance or removal of cables/devices or from scour, sediment transport and hydrodynamic change during operation.

GCO-ON3
GCO-ON4

HRA Report considered all species of low to medium sensitivity to this impact. Higher sensitivities occurring during the construction and decommissioning phases of works.

Effect dependent on quality and location of impacted habitat and its function.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with

  • All seabird species

Damage to species

Collision risk and possible mortality - due to presence of devices or vessels transiting to/from the development site (including above and below water) and the influence of lighting.

All conservation objectives relevant.

Deployment of WTG leading to creation of 'barrier effect' - deviation of flight routes to avoid structures.

Evidence of birds exhibiting avoidance behaviour by increasing flight height has been obtained via post consent monitoring at Robin Rigg and Barrow OWF.

Seabirds flying and foraging at night are considered to have medium sensitivity to collision risk. Diurnally foraging species considered to be of low sensitivity to risk of collision mortality.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

  • All seabird species

Non-physical disturbance

Barrier to movement - presence of sub-surface structures and disturbance (noise or visual) which may block migratory pathways or access to feeding grounds (depending on array design).

GCO-ON2
GCO-ON3
GCO-ON4

Empirical evidence regarding sensitivity of species to barrier effects and their ability to alter flight heights is limited.

Avoidance behaviour may lead to increased energy expenditure - potentially leading to disruption of linkages between distant feeding, breeding, moulting and roosting areas which otherwise would be unaffected.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

Anticipated further evidence and research regarding seabird behaviour at sea and energetics will come forward.

  • All seabird species

Non-physical disturbance

Visual disturbance and exclusion from areas as a result of surveying, cable and device installation, operation and decommissioning and vessel movements.

GCO-ON2
GCO-ON5

Potential to occur during survey, cable lay and device installation works. May occur during operation and decommissioning.

Greatest disturbance likely to be caused by human presence, which may lead to displacement of seabirds.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with

  • All seabird species

Non-physical disturbance

Noise/vibration disturbance and exclusion from areas as a result of vessels and other activities during survey work (e.g. seismic exploration and geophysical surveys), construction (e.g. piling, drilling, cable laying), operation (e.g. device noise), maintenance or decommissioning works.

GCO-ON1
GCO-ON2
GCO-ON4
GCO-ON5

Potential effects during cable and device installation, operation and decommissioning. Lesser effects anticipated during pre-construction survey phase.

Sensitivity of airborne birds to construction noise is considered to be low/medium (given their ability to habituate to continual noises such as piling).

Sensitivity of species to underwater noise is unknown, but likely to be greater for diving species and sea surface foragers. Potential for displacement impacts as a result of noise/vibration disturbance.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

  • All seabird species

Non-physical disturbance

Presence of structures resulting in an exclusion/displacement of a species from the area.

GCO-ON2
GCO-ON3
GCO-ON4

Exclusion or displacement from foraging areas may result in increased energy burdens for seabird species. HRA Report considers that surface feeding species will have a low sensitivity to this effect, compared to medium sensitivity for diving birds.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.

  • All seabird species

Toxic contamination (reduction in water quality)

Spillage of fluids and/or construction materials during installation, removal, survey or maintenance of structures

Release of contaminants associated with dispersion of suspended sediments during installation or removal of structures (devices and cables).

GCO-ON2
GCO-ON4
GCO-ON5

Potential for accidental spillage during all phases of the works. Likelihood of spillage is comparatively low (due to standard safety measures deployed and licence/consent conditions). May include anti-fouling paints, accidental leakage of fluids and/or spillage fuels or cargo from vessels.

Quantities and toxicities associated with sacrificial anodes and antifouling coatings are considered to be extremely low, therefore impact considered negligible significance.

Low likelihood of contaminated sediments within DPOs. The receiving waterbody will provide high levels of dilution. Impacts likely to be extremely localised, thus minimising impact on water quality.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI, provided mitigation measures set out at Section 4 of this AA are complied with.

Mitigation measures include further spatial planning at project-level to avoid habitats and minimise exposure/risk (e.g. cable routeing, environmental management procedures, vessel management plans).

Careful alignment of cable routes and landfalls (and selection of installation methods) to mitigate impacts.

  • All seabird species

Non-toxic contamination

Elevated turbidity

Increase in turbidity associated with release of suspended sediments during installation or removal of structures

GCO-ON2
GCO-ON4
GCO-ON5

Local suspended sediment concentrations may increase as a result of drilling activity, burial of power export cables and disposal of drill cuttings.

Impact may occur during construction or decommissioning phases.

Increased turbidity could affect foraging and predator-prey interactions.

Possibility of AEOSI due to inherent uncertainties at a Plan-level.

No AEOSI provided mitigation measures set out in Section 4 of this AA are complied with.


Contact

Email: sectoralmarineplanning@gov.scot