1.7 Potential environmental effects – Offshore ​

1.7.1 Physical processes ​

1.7.1.1 Physical Processes refer to the coastal and marine processes as well as tidal currents, wave climate and sediment transport . The physical processes receptors applicable to the Mona Offshore Wind Project were numerically modelled using datasets collected from a series of site-specific surveys, including geophysical and metocean data. This was coupled with a detailed desktop review of existing studies and datasets.

1.7.1.2 The site-specific geophysical surveys and habitat assessments indicated that seabed within the Mona Array Area is comprised of sandwaves, megaripples, sediment waveforms and outcrops. The site-specific geophysical survey within the Mona Offshore Cable Corridor indicated the north section of the Mona Offshore Cable Corridor was predominantly flat and featureless however sandwaves and megaripples were observed on the south section towards the intertidal area. The seabed sediments present in the Mona Array Area are classified as sand, sandy gravel, and gravelly sand. There was a transition travelling south from the Mona Array Area of coarse gravelly seabed to finer sand. The geophysical data highlights active sandwaves in the Mona Array Area and desktop studies have drawn attention to a sandbank crossing the Mona Offshore Cable Corridor known as Constable Bank classified under the Habitat’s Directive as an Annex 1 habitat although it is not within an SAC. Within the Mona Array Area, the water depth varies from 28.5m to 46.1m relative to the LAT.

1.7.1.3 Across the Mona Array Area, the tidal current floods to the east and ebbs to the west. The flows are relatively strong with tidal current speeds typically between 1.2 to 0.9m/s during peak flood, with ebb currents being slightly lower at 0.8 to 0.9m/s. Both the largest proportion and greatest magnitude of waves approach the Mona Offshore Wind Project from the southwest direction. Modelled currents (driven by tides and waves) within the Mona Array Area resulted in an increase of currents on the flood tide and corresponding reduction on the ebb tide during the dominant conditions.

1.7.1.4 Within the Mona Array Area, the residual current speeds are high resulting in high sediment transport rates, with sediment transport rates typically lower nearer the shore. During storms approaching from the west, sediment transport increases during flood tides in the Mona Array Area. The non-algal Suspended Particulate Matter (SPM) was estimated to be on average 0.9 to 3mg/l between 1998 to 2015 (Cefas, 2016) displaying typical seasonal patterns with an increase in concentration in winter months within the Mona Offshore Wind Project.

1.7.1.5 Five potential impacts on the physical processes receptors due to the construction, operations and maintenance, and decommissioning phases of the Mona Offshore Wind Project, were identified. These were noted as:

• Increase in suspended sediments due to construction, operations and maintenance and/or decommissioning related activities, and the potential impact to physical features
• Impacts to the tidal regime due to presence of infrastructure and the associated potential impacts along adjacent shorelines
• Impacts to the wave regime due to presence of infrastructure and the associated potential impacts along adjacent shorelines
• Impacts to sediment transport and sediment transport pathways due to presence of infrastructure and associated potential impacts to physical features and bathymetry
• Impacts to temperature and salinity stratification due to the presence of infrastructure.

1.7.1.6 The potential impacts of an increase in suspended sediments due to construction, operations and maintenance and decommissioning related activities, and the potential impact to physical features such as the sandbanks, reefs, mudflats and sandflats which are the qualifying features of the designated sites and the Constable Bank were either of negligible or minor significance (i.e. not significant in EIA terms). The sediment plumes arising during the construction phase are identified as localised and do not persist beyond the physical processes study area with limited deposition occurring at distance from the site of construction. Sedimentation during the construction phase comprises local material which is not expected to influence the bathymetry of receptors such as sandbanks, reefs, mudflats and sandflats within the Menai Strait and Conwy Bay SAC, Traeth Pensarn Site of Special Scientific Interest (SSSI) and Constable Bank (Annex 1 habitat). Hydrodynamic processes supporting Menai Strait and Conwy Bay SAC, Traeth Pensarn SSSI and Constable Bank characteristics are not altered by the low level of bathymetric change as a result of the construction phase sediment releases. The increased sedimentation from the offshore export cable installation causes a slight increase in sedimentation within the intertidal zone, however this would be insufficient to affect the beach profile.

1.7.1.7 During the operations and maintenance phase the effects are reduced in comparison to the construction phase, as works are limited to intermittent, discrete repair activities. Overall, for all receptors associated with Menai Strait and Conwy Bay SAC, Great Ormes Head SSSI, Little Ormes Head SSSI and Constable Bank, the effect will be negligible or minor significance (not significant in EIA terms). The effects during the decommissioning phase would be of lesser magnitude than both the construction phase and the operations and maintenance phase with scour and cable protection remaining in situ. Increases in suspended sediments may occur during decommissioning if suction caisson foundations are removed however the sediment plume would not interact with any designated areas.

1.7.1.8 The Mona Offshore Cable Corridor passes through Menai Strait and Conwy Bay SAC and sediment plumes associated with the Mona Offshore Wind Project may reach Constable Bank and the Traeth Pensarn SSSI. The landfall intersects the Traeth Pensarn SSSI. Horizontal Directional Drilling (HDD) is being considered as an option which would largely avoid impacts at the landfall, but the MDS is open trench technology with the application of coffer dams reducing the release of sediment in the intertidal zone. Any increase in sediment material would be from the sediment cell and will therefore not affect geodiversity. The increased sedimentation from the Mona Offshore Cable Corridor installation causes little or no sedimentation in the intertidal zone which would be insufficient to affect the beach profile. Overall, for all receptors in the intertidal zone, the effect will be negligible or minor (not significant in EIA terms).

1.7.1.9 The presence of infrastructure may potentially lead to changes in impacts to the tidal regime, wave regime and sediment transport and associated sediment transport pathways. However, the impacts on receptors within the Menai Strait and Conwy Bay SAC, Traeth Pensarn SSSI and Constable Bank was deemed to be of negligible or minor significance (not significant in EIA terms). These minor changes in hydrodynamics occur in close proximity to the location of the wind turbines and do not extend beyond the physical processes study area. The limited magnitude of changes observed would not alter the physical characteristics of sandbanks such as the Constable Bank.

1.7.1.1 During the decommissioning phase, the magnitude of the impact would be similar to the operations and maintenance phase as all structures above the seabed would be removed, however, scour protection and cable protection are to remain in situ. Increases in suspended sediment concentrations due to the removal of inter-array, interconnector and offshore export cables would be similar to those experienced during the construction phase, as retrieval would be undertaken using similar techniques to installation. Overall, for all receptors, the effect will be negligible or minor significance (not significant in EIA terms).

1.7.1.1 No further mitigation in addition to the measures adopted as part of the Mona Offshore Wind Project (e.g. scour protection) is considered necessary for physical processes because the predicted impacts in the absence of mitigation is not significant in EIA terms.

1.7.1.1 Cumulative effects are assessed in full in the PEIR. The magnitude of these cumulative effects is deemed to be low for all phases and effects to be of local spatial extent effecting receptors of low sensitivity for all assessed, therefore non were deemed to be significant in EIA terms.

1.7.1.1 No significant transboundary effects with regard to physical processes from the Mona Offshore Wind Project on the interests of other States were predicted.

1.7.2 Benthic subtidal and intertidal ecology ​

1.7.2.1 Benthic ecology refers to the communities of animals and plants which live on or in the seabed and the relationships that they have with each other and with the physical environment. The subtidal and intertidal benthic ecology of the Mona Offshore Wind Project was characterised via a series of site-specific surveys using grab sampling, underwater video and eDNA.

1.7.2.2 These surveys indicated that the subtidal seabed within the Mona Array Area supports a variety of plant and animal communities that are typical of this area. Key habitats recorded included habitat dominated by marine worms and bivalves in offshore mixed sediments, as well as more general coarse and mixed sediment habitats dominated by marine worms, molluscs and echinoderms. Additionally, some reef-based communities were also identified through these surveys within the Mona Array Area including low resemblance stony reefs as well as sponges that live on hard substrate.

1.7.2.3 An Intertidal survey was also conducted for the Mona landfall which identified a diverse range of plants and animals. The upper shore at the Mona landfall contained a wide band of barren shingle and rock with lichens. The middle shore contained boulders, cobbles and rock with barnacle-based communities. The lower shore was characterised by sandy habitats dominated by marine worms and molluscs. An extensive reef formed by the honeycomb worm Sabellaria alveolata was also identified at the Mona landfall.

1.7.2.4 A number of potential impacts on benthic subtidal and intertidal communities/species, associated with the construction, operations and maintenance, and decommissioning phases of the Mona Offshore Wind Project, were identified. These included:

• Temporary habitat disturbance/loss
• Increased suspended sediment concentrations and associated deposition (including smothering) Disturbance/remobilisation of sediment-bound contaminants
• Long-term habitat loss
• Colonisation of hard substrate
• Increased risk of introduction or spread of Invasive Non-native Species (INNS)
• Removal of hard substrate
• Changes in physical processes
• Electromagnetic fields and heat from subsea cabling.

1.7.2.5 With the measures adopted as part of the Mona Offshore Wind Project (e.g. cable burial where possible) in place, all of these impacts result in effects of either negligible or minor adverse significance which is not significant in EIA terms.

1.7.2.6 Temporary and long-term habitat loss/disturbance was deemed to be of negligible to minor adverse significance (not significant in EIA terms) for the subtidal, intertidal and Menai Strait and Conwy Bay SAC habitats. This conclusion was reached based on the small proportion of habitat loss predicted in the context of available habitats in the Mona Array Area and as most of the disturbed habitat is sedimentary the habitat is likely to recover following disturbance/loss. Additionally, no significant effects were predicted on protected potential reef habitats within the Mona Array Area, on the assumption that measures to avoid direct impacts to these features will be implemented.

1.7.2.7 Increases in suspended sediment concentrations and associated deposition were also deemed to be of negligible to minor adverse significance (not significant in EIA terms) for the subtidal, intertidal and Menai Strait and Conwy Bay SAC habitats. This conclusion was reached due to the short-term nature of the impact with sediments quickly dispersing and most of the important ecological features being of low sensitivity to this type of impact. Again, no significant effects were predicted on protected potential reef habitats within the Mona Array Area, on the assumption that measures to avoid direct impacts to these features will be implemented.

1.7.2.8 Long term habitat loss was deemed to be of negligible to minor adverse significance (not significant in EIA terms) for the subtidal and Menai Strait and Conwy Bay SAC habitats (no long-term habitat loss in the intertidal is predicted). This conclusion was reached due to the small area affected in relation to the Mona benthic subtidal and intertidal ecology study area. Again, no significant effects were predicted on protected potential reef habitats within the Mona Array Area, on the assumption that measures to avoid direct impacts to these features will be implemented.

1.7.2.9 Cumulative effects from aggregate extraction activities, dredging activities, cables and pipelines, remedial works and other offshore renewable developments were assessed for their impact in relation to:

1.7.2.1 Temporary habitat disturbance/loss, increased suspended sediment concentrations and associated deposition, long-term habitat loss, colonisation of hard substrate, increased risk of introduction or spread of INNS and changes in physical processes. The cumulative effects assessment predicted these impacts would result in effects of negligible to minor adverse significance (not significant in EIA terms) upon subtidal and intertidal benthic communities within the CEA benthic subtidal and intertidal ecology study area.

1.7.2.1 No transboundary effects with regard to benthic subtidal and intertidal ecology from the Mona Offshore Wind Project on the interests of other States were predicted.

1.7.3 Fish and shellfish ecology ​

1.7.3.1 Fish and shellfish ecology refers to the communities of animals (various commercially and ecologically important fish, crustacean, and mollusc species) which live in the water column or on and in the seabed, including fish which travel between marine and freshwater environments for spawning activity, and the relationships these organisms have with each other and the physical environment. The fish and shellfish ecology chapter of the Mona Offshore Wind Project was characterised primarily through desktop review due to the large amount of data publicly available to help increase the scope of the review.

1.7.3.2 The desktop review and incorporated survey results showed the presence of a range of fish, shellfish, and shark and ray species with spawning or feeding grounds in the vicinity of Mona Offshore Wind Project, and in the wider fish and shellfish ecology study area. Species of particular ecological and commercial interest included herring, which have high and low intensity spawning grounds to the north and northeast of the Mona Offshore Wind Project. Sandeel, which are a key prey species for many other marine predators, were also noted as having important populations and spawning grounds in this area. Consultation with stakeholders highlighted the importance of queen and king scallop to commercial fishing activities. Therefore, information from vessel position data and outputs from fisheries stakeholder consultation were incorporated into the fish and shellfish ecology chapter to show the distribution of key fishing and spawning grounds for these species, with overlap with the Mona Array Area noted. Basking shark and angel shark populations were also examined, with the potential for these passing through or occurring within the Mona Offshore Wind Project highlighted. The likelihood of angel shark being present within the area is low, with the most abundant local populations identified approximately 30km from the Mona Array Area, and only intermittently present. Whilst basking shark are known to migrate through the wider fish and shellfish ecology study area, none were recorded from the site-specific surveys for the Mona Offshore Wind Project.

1.7.3.3 A number of potential impacts on fish and shellfish species associated with the construction, operations and maintenance, and decommissioning phases of the Mona Offshore Wind Project were identified. These included:

• Temporary habitat loss or disturbance
• Underwater sound impacts
• Increased suspended sediment concentrations and associated sediment deposition Long term habitat loss
• Electromagnetic fields from subsea electrical cabling
• Colonisation of hard structures by new communities
• Injury to basking shark due to increased risk of collision with vessels.

1.7.3.4 With the measures adopted as part of the Mona Offshore Wind Project (e.g. implementation of piling soft-start and ramp-up measures), all of these impacts in all project phases result in effects of either negligible or minor adverse significance, which are not significant in EIA terms.

1.7.3.5 The impact of underwater sound was not considered to result in a significant impact to herring spawning at the known spawning grounds off the coast of the Isle of Man due to the distance from the Mona Offshore Wind Project to these grounds.

1.7.3.6 Temporary and long-term habitat loss/disturbance were both deemed to be of minor adverse significance (not significant in EIA terms) to fish and shellfish receptors, as the proportion of habitat lost within the Mona Offshore Wind Project was predicted to be small in the context of other similar available habitats in the wider fish and shellfish ecology study area.

1.7.3.7 Cumulative effects from nearby offshore wind farm construction, dredging and disposal, and other relevant projects were assessed within a 50km radius of the Mona Offshore Wind Project for direct impacts, and a 100km radius for underwater sound. These nearby projects were examined and predicted to result in negligible to minor adverse (non-significant) impacts on fish and shellfish species within the defined 50km study area. For underwater sound, the impact was assessed to still be minor adverse due to the very low level of cumulative noise impact from other projects.

1.7.3.8 No transboundary effects on the interests of other States are predicted for fish and shellfish ecology from the Mona Offshore Wind Project.

1.7.4 Marine mammals ​

1.7.4.1 The marine mammal chapter considers species of whales, dolphins and porpoises as well as seal species found in the vicinity of the Mona Array Area, in terms of their distribution, abundance and density. The chapter baseline was informed by a combination of site-specific surveys, in the form of digital aerial surveys, and a desk-top study.

1.7.4.2 The site-specific surveys indicated that the species found in the vicinity of the Mona Array Area include bottlenose dolphin, harbour porpoise, Risso’s dolphin, grey seal and harbour seal. Other species known to occur regularly in the region include short-beaked common dolphin and minke whale. Harbour porpoise occur throughout the Mona marine mammal study area, whilst short-beaked common dolphin and Risso’s dolphin are largely restricted to the south of the Irish sea. Sightings of bottlenose dolphin are highest in coastal waters of Cardigan Bay in west Wales. Harbour porpoise and bottlenose dolphin occur year-round, whereas common-dolphin, Risso's dolphin and minke whale occur in highest numbers during summer months, moving further offshore in winter months. Grey seal occur extensively throughout the southern Irish Sea, whereas harbour seal are concentrated along the northeast coast of Ireland, east coast of Northern Ireland and the Firth of Clyde.

1.7.4.3 A number of potential impacts on marine mammals, associated with the construction, operations and maintenance, and decommissioning phases of the Mona Offshore Wind Project, were identified. These included:

• Injury and disturbance from elevated underwater sound during piling
• Injury and disturbance to marine mammals from elevated underwater sound during UXO clearance
• Injury and disturbance to marine mammals from elevated underwater sound due to vessel use and other activities
• Increased risk of injury to marine mammals due to collision with vessels
• Injury and disturbance to marine mammals from elevated underwater sound during site investigation surveys Underwater sound from wind turbine operation
• Changes in fish and shellfish communities affecting prey availability.

1.7.4.4 With the measures adopted as part of the Mona Offshore Wind Project (e.g. the inclusion of low order techniques as a UXO clearance option) in place, these impacts result in effects of either negligible or minor adverse significance which is not significant in EIA terms.

1.7.4.5 Injury and disturbance from elevated underwater sound during piling was deemed to be of minor adverse significance (not significant in EIA terms) to marine mammals in the Mona marine mammal study area; whilst underwater sound modelling predicted ranges of impact which had the potential to result in injury and disturbance to a small number of animals. For the assessment of injury, with measures adopted as part of the Mona Offshore Wind Project in place in the form of a draft Marine Mammal Mitigation Protocol (MMMP), the impact would result in a very small risk of injury, as animals will be deterred beyond the predicted injury range. For the assessment of disturbance, it was considered that whilst a small number of animals could experience mild disturbance, this was unlikely to lead to population level effects. In addition, population modelling was carried out to explore the potential of disturbance during piling to affect the population trajectory over time for harbour porpoise, bottlenose dolphin, minke whale and grey seal, which confirmed the assessment that this impact was unlikely to lead to population level effects.

1.7.4.6 Increased risk of injury of marine mammals due to collision with vessels was deemed to be of minor adverse significance (not significant in EIA terms). An increase in vessel movements could lead to an increase in interactions between marine mammals and vessels, resulting in fatal and non-fatal injuries. Vessels travelling at 7m/s or faster are those most likely to cause death or serious injury to marine mammals. Largely, vessels involved in the construction phase are likely to be travelling considerably slower than this, and all vessels will be required to follow the provisions set out in the offshore Environmental Management Plan (EMP). With the adherence of this EMP, in combination with the likelihood that animals will be deterred by the noise of moving vessels, the risk of collision is reduced.

1.7.4.7 Cumulative effects were assessed for injury and disturbance from elevated underwater sound during piling, injury and disturbance to marine mammals from elevated underwater sound during site investigation surveys, injury and disturbance to marine mammals from elevated underwater sound during UXO clearance, injury and disturbance to marine mammals from elevated underwater sound due to vessel use and other activities, increased risk of injury of marine mammals due to collision with vessels, and changes in fish and shellfish communities affecting prey availability (section 1.7.3). These were predicted to result in effects of negligible or minor adverse significance (not significant in EIA terms) upon harbour porpoise, short-beaked common dolphin, Risso’s dolphin, minke whale, grey seal and harbour seal within the Celtic and Irish Seas. For bottlenose dolphin, a moderate adverse effect (significant in EIA terms) resulted when considering the impact in the context of the Irish Sea Management Unit population, however when considered in the context of the wider combined population of the Offshore Channel and Southwest England MU plus the Irish Sea MU, there is no significant effect.

1.7.4.8 No transboundary effects with regard to marine mammals from the Mona Offshore Wind Project on the interests of other States were predicted.

1.7.5 Offshore ornithology ​

1.7.5.1 Seabirds refer to species that depend on the marine environment for survival at some point in their life cycle. In addition to the true seabirds, seaducks, divers and grebes are also considered because of their additional reliance on marine areas, especially in the non-breeding season. Information on seabirds within the Mona offshore ornithology array area study area and the Mona offshore ornithology offshore cable corridor study area was collected through a detailed desktop review of existing studies and datasets and site-specific surveys (digital aerial surveys).

1.7.5.2 The site-specific digital aerial surveys indicated that the Mona Array Area supported a seabird assemblage that is the typical of the Irish Sea, and dominated by common guillemot, razorbill, black-legged kittiwake, Manx shearwater and northern gannet. For most seabirds, distribution was varied depending on year and month.

1.7.5.3 A number of potential impacts on seabird species, associated with the construction, operations and maintenance, and decommissioning phases of the Mona Offshore Wind Project, were identified. These included:

• Increased disturbance and displacement from airborne noise, underwater sound, and presence of vessels and infrastructure
• Indirect impacts from underwater sound affecting prey species
• Collision
• Temporary habitat loss/disturbance and increased suspended sediment concentrations (SSCs) Barrier effects.

1.7.5.4 With the measures adopted as part of the Mona Offshore Wind Project in place (e.g. an offshore EMP which will include measures to reduce disturbance to rafting birds from transiting vessels), the impacts resulted in effects of either negligible or minor adverse significance which is not significant in EIA terms.

1.7.5.5 Disturbance and displacement from airborne noise, underwater sound, and presence of vessels and infrastructure was deemed to be of either negligible to minor adverse significance (not significant in EIA terms) to the seabird species within the Mona Array Area and in the vicinity of the Mona Offshore Wind Project, due to the short-term nature of the impact during the construction and decommissioning phases. Furthermore, seabirds recorded in the site-specific surveys over the Mona Array Area (plus buffer) had a low sensitivity to this type of impact during the operations phase of the wind farm.

1.7.5.6 Indirect impacts from underwater sound affecting prey species were also deemed to be of minor adverse significance (not significant in EIA terms) on ornithological receptors due to the short-term nature of the impact. Similarly, temporary habitat loss/disturbance and increased suspended sediment concentrations (SSCs) were deemed to be of minor adverse significance (not significant in EIA terms). Crucially no significant effects of collision were predicted on seabirds and migratory non-seabirds within the Mona Array Area and the barrier effect was deemed to be of negligible adverse significance which is not significant in EIA terms.

1.7.5.7 Cumulative effects from offshore renewable developments were assessed and predicted to result in effects of negligible to minor adverse significance (not significant in EIA terms) upon seabirds within a 500km buffer of the Mona Offshore Wind Project. In addition, population modelling was carried out to explore the potential of the combined collision risk and disturbance and displacement to affect the population trajectory over time for common guillemot and great black-backed gull which confirmed the assessment that this impact was unlikely to lead to population level effects. The combined collision risk and disturbance and displacement from airborne noise, underwater sound, and presence of vessels and infrastructure was considered to be of minor adverse significance (not significant in EIA terms).

1.7.5.8 No transboundary effects with regard to offshore ornithology from the Mona Offshore Wind Project on the interests of other States were predicted.

1.7.6 Commercial fisheries ​

1.7.6.1 Commercial fisheries are defined as any form of fishing activity where the catch is sold for taxable profit. The commercial fisheries baseline was characterised via a review of publicly available data, site specific surveys and consultation with fisheries stakeholders.

1.7.6.2 Within the region, landings were dominated by dredge vessels and shellfish were the most important species group in terms of landed weight and value. Within and around the Mona Array Area there are queen scallop grounds, of particular importance to dredge vessels from the west coast of Scotland. These vessels, as well as nomadic vessels from Ireland and Northern Ireland also engage in the king scallop fishery in the region. English static gear vessels targeting whelk and crab in the Mona Array Area operate out of Fleetwood and Whitehaven. Beam trawl vessels from Belgium and the south coast of England are also occasionally present within the vicinity targeting flatfish, such as sole. Within the nearshore parts of the Mona Offshore Cable Corridor, small static gear vessels are present in low numbers, which operate out of ports along the North Wales coast.

1.7.6.3 A number of potential impacts on commercial fisheries groups, associated with the construction, operations and maintenance, and decommissioning phases of the Mona Offshore Wind Project, were identified. These included:

• Loss or restricted access to fishing grounds Displacement of fishing activity
• Interference with fishing activity
• Temporary increase in steaming distances
• Loss or damage to fishing gear due to snagging Potential impacts on commercially important fish stocks Supply chain opportunities for local fishing vessels.

1.7.6.4 With the measures adopted as part of the Mona Offshore Wind Project (e.g. development of a Fisheries Co-existence and Liaison plan) in place, and in some cases with the implementation of further mitigation, the majority of these impacts result in effects of negligible or minor adverse significance which is not significant in EIA terms.

1.7.6.5 Loss or restricted access to fishing grounds is a impact that is of particular importance for Scottish west coast vessels, who rely on a queen scallop grounds within and around the Mona Array Area. During construction, the loss or restricted access to fishing grounds is assessed as an effect no greater than minor adverse significance (not significant in EIA terms) on all commercial fisheries receptor groups, due to the temporary and intermittent nature of the works. During the operations and maintenance phase, a moderate adverse effect is predicted on the Scottish west coast scallop vessels receptor, which is significant in EIA terms. In order to mitigate this effect, options to increase the minimum distance between wind turbines and options to align the wind turbines with orientations of fishing tows are being explored by the Applicant to increase the potential for coexistence.

1.7.6.6 With the measures adopted as part of the Mona Offshore Wind Project (e.g. development of a Fisheries Co-existence and Liaison Plan), which will be fully captured in the Environmental Statement, the impact magnitude is predicted to reduce to minor and the residual effect will be of minor adverse significance, which is not significant in EIA terms.

1.7.6.7 Displacement of vessels into other fishing grounds can cause conflict with other fishing gears. During construction, the displacement of vessels into other areas, and the potential adverse impacts on existing fisheries in the areas that vessels are displaced into, is assessed as an effect no greater than minor adverse significance (not significant in EIA terms) on all commercial fisheries receptor groups. This is due to the rolling construction zones, and the temporary and intermittent nature of the works during the construction phase. During the operations and maintenance phase, the minimum spacing between wind turbines (875m) and between rows of wind turbines (1,000m) may restrict mobile gear such as the scallop and beam trawl vessels from fishing within the Mona Array Area. Based on this assumption, displacement of fishing activity is assessed as an effect of moderate adverse significance (significant in EIA terms). This impact was assessed as minor adverse for Isle of Man vessels, as they also target these fishing grounds, but do not rely as heavily on them. Following the implementation of further mitigation measures the residual impacts on Scottish west coast vessels are assessed as minor adverse, which is not significant in EIA terms.

1.7.6.8 Significant cumulative impacts, in EIA terms, were identified with the Morgan Offshore Wind Project. The main cumulative impact identified between the Mona Offshore Wind Project and the Morgan Offshore Wind Project for commercial fisheries focused on loss or restricted access to fishing grounds arising from the operations and maintenance phase. The cumulative effect of loss or restricted access to fishing grounds on Scottish west coast scallop vessels, as a result of other offshore wind developments, is of moderate adverse significance (which is significant in EIA terms). In order to mitigate this effect on the Scottish west coast scallop fleet, options to increase the minimum distance between wind turbines and options to align the wind turbines with orientations of fishing tows are being explored by the Applicant that could allow for continued scallop dredging activity within the Mona Array Area, thus potentially enabling co-existence. Following further measures, the residual impacts on Scottish west coast scallop vessels will be assessed within the Environmental Statement and are expected to be assessed as minor adverse, which is not significant in EIA terms.

1.7.6.9 Transboundary effects outside UK waters are limited to the potential displacement of effort from the Mona Offshore Wind Project into non-UK waters and potential effects on commercially important fish and shellfish resources which could occur in non-UK waters. It is not anticipated that these effects would be significant.

1.7.7 Shipping and navigation ​

1.7.7.1 The construction, operations and decommissioning of an offshore wind farm can have impacts upon maritime safety and the activities of commercial shipping, ferries, ports/harbours, commercial fisheries, recreational cruising and other maritime operations.

1.7.7.2 A shipping and navigation baseline was developed through a review of relevant publications, collection and analysis of historical vessel traffic and incident data, and consultation with key stakeholders. The Mona Offshore Wind Project is located in an area frequently utilised by a variety of different maritime users. It should be noted that during the operations and maintenance phase, there will be a minimum spacing between wind turbines of 875m and a minimum spacing between rows of wind turbines of 1,000m. Traffic separation schemes, existing offshore wind farms, oil and gas and aggregate activities occur within the shipping and navigation study area. Commercial shipping bound for the ports of Liverpool, Douglas and Heysham cross through the Mona Array Area. Regular ferry services between the UK, Isle of Man and the island of Ireland operate through or adjacent to the Mona Array Area. Fishing by static and mobile gear takes place throughout the shipping and navigation study area. Offshore recreational cruising routes between the UK and the Isle of Man were also identified, however, the numbers of vessels using them is low. Tug and service activities supporting existing offshore infrastructure is widespread. An anchorage is located to the east of Anglesey, near to the Mona Offshore Cable Corridor.

1.7.7.3 Adverse weather, particularly from the prevailing southwest, was demonstrated to have an influence of vessel traffic patterns. Historical incident data demonstrated that relatively few navigational incidents had occurred within the shipping and navigation study area, with the majority analysed occurring in the approaches to Liverpool.

1.7.7.4 A number of potential impacts on shipping and navigation, associated with the construction, operations and maintenance, and decommissioning phases of the Mona Offshore Wind Project, were identified. The impacts assessed include: impacts to vessel routeing, impacts to port operations, impacts to navigational safety and impacts to emergency response. With the measures adopted as part of the Mona Offshore Wind Project (e.g. guard vessels) in place, the majority of these impacts result in effects which are not significant. However, two significant effects were identified:

• Firstly, impacts on adverse weather routeing for some ferry service routes as a result of the presence of the Mona Array Area were assessed as significant. During adverse weather conditions, Stena vessels operating between Liverpool and Belfast, and Isle of Man Steam Packet Company vessels operating between Liverpool and Douglas navigate through the footprint of the Mona Array Area. With the wind turbines in place, vessels would be required to deviate to the southwest of the Mona Array Area to maintain safe and comfortable vessel motions. This has the potential to increase transit durations and some additional cancellations of services.
• Secondly, impacts on vessel-to-vessel collision risk due to deviations of vessel routes and increased encounters due to the presence of the Mona Array Area were assessed as significant. In particular, the impacts to commercial vessel routeing to the southwest of the Mona Array Area was assessed to lead to increased interactions and reduced the ability of ships to comply with collision regulations. Furthermore, the close proximity of the Mona Array Area with these routes increased the potential for small craft emerging from the site being involved in a collision with passing vessels.

1.7.7.5 To address these significant effects, the Applicant has committed to additional risk control options to reduce these risks to Broadly Acceptable or Tolerable if As Low as Reasonably Practicable (ALARP), including:

• Amendments to the Mona Array Area Boundary to maintain a 2nm offset between the Mona Array Area and the approaches to the Liverpool TSS
• Amendments to the Mona Array Area Boundary to reduce the northern extent of the Mona Array Area by approximately 3nm to increase the gap between the Mona and Morgan Array Areas
• Commitment to two lines of orientation.

1.7.7.6 The Applicant has committed to exploring these additional risk controls through further studies and engagement with stakeholders to ensure they are appropriate and adequate for reducing risks to as low as reasonably practicable (ALARP) prior to submission of the application. Appropriate risk controls will then be secured through project consents.

1.7.7.7 The assessment of impacts on shipping and navigation of the Mona Offshore Wind Project were considered cumulatively with other proposed and existing projects. The Applicant has been collaborating with other developers of cumulative projects to identify and address any significant effects The assessment noted that these would result in corridors between the Morgan and Mona Array Areas which increased navigational risk and were potentially unsafe to navigate in adverse weather conditions. In particular, the assessment of the cumulative impacts of the Mona, Morgan and Morecambe Array Areas identified significant effects:

• Firstly, impacts on adverse weather routeing as a result of the presence of the cumulative projects were assessed as significant. Routes from Stena, Isle of Man Steampacket Company and Seatruck were all impacted by the presence of the Array Areas and the corridors. During adverse weather, and as a result of the width of the corridors between cumulative projects, deviations were required around the array areas. These would result in some additional delays and cancellations of ferry services
• Secondly, cumulative impacts on vessel-to-vessel collision risk due to deviations of vessel routes and increased encounters due to the presence of the array areas were assessed as significant. The width of corridors and the volume of traffic was not considered sufficient for effective collision avoidance, particularly between the Mona and Morgan Array Areas. Furthermore, the likely presence of small craft including crew transfer vessels, fishing and recreational craft were at risk of collision within the corridors.
• Thirdly, a significant impact on the risk of allision (contact between a moving vessel and a stationary one) was identified. As for the risk of collision, the presence of narrow corridors, during adverse weather and avoiding other traffic, may cause commercial ships to come into contact with elements of the Mona Offshore Wind Project.

1.7.7.8 To address these significant effects, the Applicant has committed to additional risk control options to reduce these risks to Broadly Acceptable or Tolerable if ALARP, including changing the array boundaries and additional management of vessel movements (see paragraph 1.7.7.5). The Mona Offshore Wind Project has committed to exploring these additional risk controls through further studies and engagement with stakeholders to ensure they are appropriate and adequate for reducing risks to ALARP prior to Application. Appropriate risk controls will then be secured through project consents.

1.7.7.9 A screening of transboundary impacts has been carried out and any potential for significant transboundary effects with regard to shipping and navigation from the Mona Offshore Wind Project upon the interests of other States has been assessed as part of this PEIR. Each individual vessel may be internationally owned or operating between ports in different States. These impacts have been captured and assessed within this shipping and navigation chapter, Navigational Risk Assessment (NRA) and Cumulative Regional Navigational Risk Assessment (CRNRA). Therefore, no additional transboundary impacts are anticipated.

1.7.8 Marine archaeology ​

1.7.8.1 Marine archaeology is the physical remains of our human past that survive within the marine environment. This includes maritime archaeology such as shipwrecks and submerged prehistoric archaeological material associated with ancient landscapes. The marine archaeology of the Mona Offshore Wind Project was characterised via a detailed desktop review of existing data and studies alongside an assessment of site-specific geophysical surveys for the Mona Array Area.

1.7.8.2 Survey data supports that the now submerged coastal areas of the east Irish Sea would have formed a partially terrestrial landscape during the Upper Palaeolithic and into the Mesolithic periods. Final submergence of the marine archaeology study area to the modern coastline would have occurred towards the end of the Mesolithic c.6000 before present. This landscape would have allowed humans the opportunity to exploit the resources of the intertidal zone during these times and therefore there is the potential for the survival of archaeological material associated with these activities.

1.7.8.3 49 anomalies of potential archaeological interest were identified within the Mona Array Area survey data, including the identification of three wrecks and four potential wreck sites. Of the three verified wrecks, one location coincides with the known wreck site the Tijl Uilenspiegel, a late 20th century Belgian fishing trawler that was lost in 1989. The other two known wrecks have been identified as post medieval or modern lightship and a potential WWI steam ship.

1.7.8.4 Geophysical survey data for the Mona Offshore Cable Corridor is yet to be assessed, but the desktop data for the Mona Offshore Cable Corridor has identified two known wrecks within the Mona Offshore Cable Corridor with verifiable positional data. These are the Albanian and the Nydia, which are both 19th century ships that were lost in a collision with each other off the coast of Great Orme. The desktop study has also identified a further 32 entries that may correspond to the remains of archaeological material within the Mona Offshore Cable Corridor and there remains the potential for as yet unknown and or buried archaeological material to be present. The results of the geophysical survey assessment will provide further information on the baseline marine archaeology environment of the Mona Offshore Cable Corridor and will be included within the Environmental Statement.

1.7.8.5 A number of potential impacts on marine archaeology and cultural heritage receptors, associated with the construction, operations and maintenance, and decommissioning phases of the Mona Offshore Wind Project, were identified. These included:

• Sediment disturbance and deposition leading to indirect effects on marine archaeology receptors, Direct damage to marine archaeology receptors,
• Direct damage to deeply buried marine archaeology receptors
• Alteration of sediment transport regimes.

1.7.8.6 The implementation of a Written Scheme of Investigation (WSI) will ensure that, where possible, known archaeological sites are avoided, any new observations are recorded, and sites are protected or preserved by record where required. Sediment disturbance and deposition leading to effects on known marine archaeology was deemed to be of minor adverse significance which is not significant in EIA terms.

1.7.8.7 Direct damage to marine archaeology receptors will be mitigated through the implementation of Archaeological Exclusion Zones (AEZs)around each known shipwreck site and potential site, and review of pre-construction surveys to inform the refined layout of infrastructure around any newly identified archaeological constraints Provision will also be made for the recording of any new discoveries. Direct damage to marine archaeology receptors was deemed to be of minor adverse significance which is not significant in EIA terms.

1.7.8.8 The implementation of a WSI and Protocol for Archaeological Discoveries (PAD) will provide a system for the reporting of any prehistoric archaeological material that may be uncovered during the lifetime of the Mona Offshore Wind Project. Direct damage to deeply buried marine archaeology receptors was deemed to be of minor adverse significance which is not significant in EIA terms.

1.7.8.9 Physical processes modelling found that the Mona Offshore Wind Project structures do not have a significant influence on either tide or wave conditions. As such alteration of sediment transport regimes which may affect archaeological features is of negligible adverse significance which is not significant in EIA terms.

1.7.8.1 The cumulative effects assessment takes into account the impact associated with the Mona Offshore Wind Project together with other projects and plans. All cumulative impacts assessed were deemed to be of no/minor adverse significance which is not significant in EIA terms.

1.7.8.1 No transboundary effects with regard to marine archaeology from the Mona Offshore Wind Project on the interests of other States were predicted.

1.7.9 Other sea users ​

1.7.9.1 The other sea users include recreational activities, cables, pipelines, aggregate extraction, disposal activities, and oil and gas activities which included carbon capture and storage.

1.7.9.2 Within the other sea users regional study area there are a number of receptors including; offshore energy projects (including other offshore wind farms), oil and gas activities, cable and pipeline operators, aggregate extraction, offshore microwave fixed communication links, recreational diving and bathing sites and recreational activities such as sailing, motor cruising, diving, inshore water sports and recreational fishing.

1.7.9.3 A number of potential impacts on other sea users, associated with the construction, operations and maintenance, and decommissioning phases of the Mona Offshore Wind Project, were identified. The impacts assessed include:

• Displacement of recreational activities
• Impacts to existing cables or pipelines
• Impacts to aggregate extraction areas
• Reduction or restriction of oil and gas exploration activities.

1.7.9.4 With the measures adopted as part of the Mona Offshore Wind Project in place (e.g. commercial crossing agreements), these impacts result in effects which are of minor adverse significance and thus not significant in EIA terms.

1.7.9.5 Consultation with stakeholders is ongoing to determine the effect of interference with the performance of Radar Early Warning Systems (REWS), and offshore microwave fixed communication links on oil and gas platforms. This impact will be fully assessed in the Environmental Statement.

1.7.9.6 The cumulative effects assessment takes into account the impact associated with the Mona Offshore Wind Project together with other projects and plans. All cumulative impacts assessed were deemed to be of minor adverse significance and thus not significant in EIA terms.

1.7.9.7 No transboundary effects with regard to other sea users from the Mona Offshore Wind Project on the interests of other States were predicted.

1.7.10 Inter-related effects (offshore) ​

1.7.10. The EIA is required to consider indirect and secondary likely significant impacts. For example, the separate impacts of noise and habitat loss may have an effect upon a single receptor such as marine mammals. The inter-related effects assessment is presented in a separate chapter of the PEIR.

1.7.10. Based on one or a combination of the following factors the overall significance of any inter-related effects was not judged to increase above the significance value assessed for individual effects in the topic-specific chapters:

• The low sensitivity of receptors
• Small scale nature of effects
• Availability of alternative habitats
• Measures adopted as part of the Mona Offshore Wind Project.

Project lifetime effects

1.7.10. Inter-related effects can originate from impacts occurring on a receptor group over several phases of the Mona Offshore Wind Project. For example, a receptor group may experience impacts during the construction and decommissioning phase of the Mona Offshore Wind Project. These inter-related effects are collectively described as project lifetime effects.

1.7.10. For most receptor groups identified, following the implementation of measures adopted as part of the Mona Offshore Wind Project and further mitigation (if required), impacts arising during the construction, operations and maintenance and decommissioning phase of the Mona Offshore Wind Project are unlikely to result in significant project-lifetime effects. However, there is the potential for project-lifetime effects significant to EIA to occur on the following receptor groups identified in the Inter-related effects (offshore) chapter of the PEIR:

• Commercial fisheries: Potential adverse effect of the Mona array area on access to fishing grounds regarding Scottish west coast scallop vessels
• Shipping and navigation: Potential adverse effect of the Mona Offshore Wind Project on collision and allision risk of fishing vessels.

Receptor-led effects

1.7.10. Inter-related effects may also occur where a receptor group experiences impacts across several different aspects of the environment. For example, a protected species may be impacted by habitat loss, noise, and dust during the construction phase of the Mona Offshore Wind project. These inter-related effects are collectively described as receptor-led effects.

1.7.10. All the potential receptor-led effects identified during the construction, operations and maintenance and decommissioning phase of the Mona Offshore Wind Project have already been considered within the relevant chapters of the PEIR. Therefore, the potential significance of receptor-led effects of the Mona Offshore Wind Project on each of the identified receptor groups was not considered further in the Inter-related effects (offshore) chapter of the PEIR.