1.8 Potential environmental effects – Onshore ​

1.8.1 Geology, hydrogeology and ground conditions ​

1.8.1.1 As part of the Mona Offshore Wind Project, potential impacts on geology, hydrogeology and ground conditions have been assessed. Geology is the science that deals with the earth's physical structure, its history, and the processes that act on it, whereas hydrogeology is the study of groundwater and ‘ground conditions' usually refers to the geology, hydrology, soil condition and any contamination of the ground. Potential impacts were assessed during the construction, operations and maintenance, and decommissioning phases.

1.8.1.2 The assessment was based on a desktop review of available literature, both public and online data and information contained in a related report regarding the geology, hydrogeology and ground conditions (GHGC) study area. The report included targeted comprehensive information on the geological, hydrogeological and hydrological setting of the study area and other information such as pollutions incidents, abstraction licences and constraints. Historical Ordnance Survey mapping and aerial photography was also reviewed as part of the assessment.

1.8.1.3 The GHGC study area includes sections of Llandulas beach to the west of Abergele and includes a pronounced ridge that extends south-eastward towards Bodelwyddan, south of the A55 road which is formed by bedrock of the Clwyd Limestone Group and the underlying Ffernant Formation. The low-lying land situated to the north of the ridge is underlain by sandstone bedrock principally of the Warwickshire Group. Much of the high ground, south of the ridge, is underlain by old bedrock that comprises mudstones of the Silurian Elwy Formation. The limestone of the Clwyd Limestone Group and the low-lying land west of St Asaph underlain by the sandstones of the Warwickshire Group is also in the GHGC study area.

1.8.1.4 With respect to groundwater, the limestones constitute an important groundwater resource whereas the predominantly sandstone units of the Warwickshire Group and Ffernant Formation can form locally important groundwater bodies and the Silurian bedrock of the Elwy Formation yields little groundwater. However, the bedrock across the Mona Proposed Onshore Development Area is concealed beneath a surface layer of clay-rich glacial till, with only localised occurrence of groundwater. No groundwater source protection zones or licensed groundwater abstractions have been identified within the Mona Proposed Onshore Development Area.

1.8.1.5 The only geological or geomorphological sites within the Mona Proposed Onshore Development Area are the caves within the Llanddulas Limestone and Gwrych Castle Wood SSSI.

1.8.1.6 The Mona Proposed Onshore Development Area has been subject to significant deep, metal mining principally associated with the Clwyd Limestone Group. This metal mining is old, dating back to the 1800’s and is commonly associated with surface shafts and associated infrastructure. The predominant risk to the Mona onshore transmission assets posed by historical mining relates to geotechnical stability. The former NRW Llanddulas Beach landfill could represent a risk to groundwater quality given it is crossed by the Mona Proposed Onshore Development Area.

1.8.1.7 A number of potential impacts on geology, hydrogeology and ground conditions associated with the construction, operations and maintenance, and decommissioning phases of the Mona Offshore Wind Project, were identified. These included:

• The impact or loss of, or damage to, designated sites of geological and geomorphological interest
• Loss of, or damage to non-designated sites of geological and geomorphological interest
• Sterilisation of safeguarded limestone mineral resources
• Alteration and deterioration to groundwater quantity or quality in the glacial till and bedrock
• Ground stability issues associated with areas of historical deep mining operations.

1.8.1.8 However, with appropriate mitigation measures in place such as the use of trenchless techniques for the construction under the Llanddulas Limestone and Gwrych Castle Wood SSSI, implementation of Code of Construction Practice (CoCP) to ensure effective management of environmental risk and best practice measures as part of detailed design, the impacts are assessed to be either negligible or minor adverse which is not considered significant in EIA terms.

1.8.1.9 Groundwater source protection zones and licensed groundwater abstractions were deemed to not be at risk of impact given their position with the local groundwater system and therefore are not considered significant in EIA terms.

1.8.1.1 Cumulative effects from other developments were assessed and impacts of temporary and permanent activity considered upon geology, hydrogeology and ground condition receptors. The cumulative effect is predicted to be of local spatial extent and results in minor adverse and not considered significant in EIA terms.

1.8.1.1 Further surveys (e.g. the survey of private groundwater abstractions) will be undertaken in the next stages of the Mona Offshore Wind Project to evolve and refine the baseline survey information. Following this, the onshore cable route will be refined and landowners will be consulted to determine the location and details of any Private Water Supply Sources (PWSSs) present within the GHGC study area that may be affected by the Mona Offshore Wind Project.

1.8.2 Hydrology and flood risk ​

1.8.2.1 Information on hydrology and flood risk within the hydrology and flood risk study area was collected through a detailed desktop review of existing studies and datasets. The Mona Proposed Onshore Development Area makes landfall at Llandulas beach to the west of Abergele and traverses predominantly through agricultural land uses and woodland. Whilst there are no Main Rivers identified within the hydrology and flood risk study area, several ordinary watercourses are crossed by the route of the Mona Onshore Cable Corridor.

1.8.2.2 A number of potential impacts on hydrology and flood risk associated with the construction, operations and maintenance, and decommissioning phases of the Mona Offshore Wind Project were identified. These included:

• The impact of increased flood risk arising from additional surface water runoff during construction
• The impact of increased flood risk arising from the diversion of any watercourse
• The impact of increased flood risk arising from additional surface water runoff during operation of the Onshore Substation
• The impact of increased flood risk arising from damage to existing flood defences
• The impact of contaminated runoff on the quality of watercourses
• The impact of damage to existing field drainage
• The impact of damage to existing water pipelines.

1.8.2.3 With the mitigation measures adopted as part of the Mona Offshore Wind Project (e.g. cofferdams and the implementation of a CoCP) in place, the majority of these impacts result in effects of either negligible or minor adverse significance and as such are not significant in EIA terms.

1.8.2.4 Increased flood risk arising from additional surface water runoff during construction may occur as a result of the use of open cut cable installation techniques across the beach. The site selection process for the Mona Offshore Wind Project (e.g. siting of construction compounds, the haul road, construction accesses and the Mona Onshore Cable Corridor) has accounted for potential impacts on flood risk that would arise in other parts of the Mona hydrology and flood risk study area from any change in runoff over the areas affected during construction through embedded mitigation (e.g. size and location) to minimise these impacts as much as possible. The Mona Proposed Onshore Development Area and onshore substation are situated within a mainly rural area, with limited residential properties within the surrounding area. Overall, the impact on the Mona hydrology and flood risk study area was deemed to be of minor adverse significance which is not significant in EIA terms and the impact on the Mona Proposed Onshore Development Area was deemed to be of negligible adverse significance which is not significant in EIA terms.

1.8.2.5 The cumulative impact of increased flood risk arising from additional surface water runoff considered the Mona Offshore Wind Project alongside the Awel y Môr offshore wind project. The construction of Awel y Môr infrastructure (such as compounds, haul roads and the onshore cable corridor) may lead to a temporary change in surface water runoff and an increased flood risk. Overall the cumulative impact on the Mona hydrology and flood risk study area was deemed to be of minor adverse significance which is not significant in EIA terms and the cumulative impact on the Mona Proposed Onshore Development Area was deemed to be of negligible adverse significance which is not significant in EIA terms.

1.8.2.6 A screening of transboundary impacts has been carried out and has identified that there was no potential for significant transboundary effects with regard to hydrology and flood risk from the Mona Offshore Wind Project upon the interests of other states.

1.8.3 Onshore ecology ​

1.8.3.1 Ecology refers to the communities of animals and plants which live in the environment and the relationships that they have with each other and with the physical environment. As part of the Mona Offshore Wind Project, potential impact on onshore ecology was assessed during the construction, operations and maintenance, and decommissioning phases. Potential impacts on ornithology or the ‘scientific study of birds’ is not included in this section as it has been assessed separately.

1.8.3.2 The Mona onshore ecology study area starts at the intertidal zone at the Mona landfall and continues through limestone hills that are dominated by farming and improved grassland used for sheep grazing. The baseline surveys indicated a range of habitat types and of varying quality which included habitats of importance such as semi-natural broadleaved woodland, mature broadleaved trees, scrub, waterbodies, watercourses and field boundaries comprised of species-rich hedgerows. Small areas of coastal habitats such as coastal vegetated shingle are also present at the coast.

1.8.3.3 The habitats within the Mona onshore ecology study area have the potential to support a range of protected species including badgers, bats, fish and eel, great crested newts, hazel dormice, invertebrates, otters, reptiles, water voles, and white clawed crayfish. Detailed surveys identified a population of great crested newt within the Mona proposed onshore development area.

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

• Temporary and permanent habitat loss
• Habitat disturbance
• Habitat fragmentation and species isolation
• Pollution caused by accidental spills/contaminant
• The spread of INNS.

1.8.3.5 Ancient woodland is present throughout the Mona Proposed Onshore Development Area, but an assessment of the effects found that there are no effects on ancient woodland as a consequence of the commitment to avoid these areas where possible, and if not use a construction technique whereby a tunnel is drilled under the designated area known as Horizontal Directional Drilling (HDD). This method of construction avoids impacts to ancient woodland. Areas of higher value habitat are also present within the Mona Proposed Onshore Development Area, associated with the vegetated shingle beach at landfall, which is designated SSSI on the basis of the plant communities. The Mona Offshore Wind Project has committed to not installing export cables through this SSSI. Open trenching is proposed through the landfall that will result in a minor adverse effect, which is not considered significant in EIA terms.

1.8.3.6 The assessment of the impact of habitat fragmentation and species isolation found that the effects on habitats and species are generally found to be not significant. The temporary loss of habitat connectivity as a result of woodland, hedgerow, tree, watercourse fragmentation will result in a minor adverse effect which is not considered significant in EIA terms.

1.8.3.7 Cumulative effects from other developments were assessed and impacts of temporary and permanent habitat loss and habitat disturbance were assessed for protected species. The cumulative effect is predicted to be of local spatial extent and results in minor adverse effects that are not considered significant in EIA terms.

1.8.3.8 Further surveys will be undertaken in the next stages of the Mona Offshore Wind Project to evolve the baseline survey information and to refine and develop a Hydrological, Ecological and Landscape Management Plan which will seek to have a net increase in biodiversity across the site as a result of the development.

1.8.4 Historic environment ​

1.8.4.1 Historic environment encompasses all aspects of the past including buried archaeological remains, sedimentary classification and deposits and records preserved in ancient rocks built heritage and the character of the historic landscape. As part of the Mona Offshore Wind Project, potential impacts on the terrestrial historic environment were assessed through a combination of desk-based research and targeted site visits and fieldwork.

1.8.4.2 The Mona historic environment study area comprises the area of land that will be temporarily or permanently occupied during the construction, operation and maintenance and decommissioning of the Mona Offshore Wind Project. The study area includes designated historic assets of significance within 1km from the edge of the Mona Proposed Onshore Development Area and between 1-5km radius centred on the Mona Onshore Substation option sites depending on the type/importance of asset. The study area also included buried archaeology and other non-designated historic assets (as recorded on the Historic Environment Record (HER) data) within 500m from the edge of the Mona Proposed Onshore Development Area and a 1km radius centred on the Mona Onshore Substation option sites. Marine archaeology is addressed in section 1.7.8.

1.8.4.3 The assessment revealed that the Mona Proposed Onshore Development Area has the potential to contain archaeological remains of all periods, with the greatest potential probably being for remains of the Roman period in the vicinity of Glascoed Road where the alignment of a possible Roman Road is thought to traverse the local area. A survey of the Mona Landfall area found no evidence of peat or similar organic material outcropping at surface level, although there is still potential for such remains to be present at sub-surface levels. There was one small piece of peat identified but it had clearly been ex situ for some time, and there was no evidence to suggest the former location of this piece of peat prior to being detached and washed out. A historic environment geophysical survey is also ongoing. In addition, the Mona Proposed Onshore Development Area does not contain any designated historic landscape elements. However, there are numerous historic field boundaries present and these have been considered in the assessment.

1.8.4.4 Nationally important heritage assets are present within and adjacent to the Mona Proposed Onshore Development Area. Those within this defined area comprise a Registered Park and Garden of Special Historic Interest and a Grade II Listed wall forming the boundary of this park and garden.

1.8.4.5 A number of potential impacts on historic environment resources, associated with the construction, operation and maintenance, and decommissioning phases of the onshore elements of the Mona Offshore Wind Project, were identified. These included:

• Direct physical impacts on buried archaeological remains and deposits, as well as the two nationally important heritage assets
• Impacts arising from change within the setting of historic assets and changes to the character of the historic landscape.

1.8.4.6 Direct physical impacts on buried archaeological remains and deposits of interest during construction are permanent. Well designed and targeted programmes of fieldwork undertaken ahead of construction will seek to identify such remains and deposits within the Mona Proposed Onshore Development Area and hence allow impacts to be avoided or minimised through the Mona Offshore Wind Project design at those locations. However, there is always the possibility that some remains and deposits may not be identified until they are encountered during construction, and this could in some circumstances include remains and deposits of importance.

1.8.4.7 The western part of the Mona Proposed Onshore Development Area passes through a Grade II* Registered Park and Garden of Special Historic Interest, the north boundary of which comprises a Grade II Listed stone wall. Whilst it is likely that the cables would be installed beneath the wall using construction techniques known as HDD which avoids impacts, the methodologies that would be employed for the installation of the cable through the historic park and garden are not yet finalised and there is the potential for effects of up to moderate adverse significance in the event that impacts cannot be avoided or minimised to an appropriate level, which would be significant in EIA terms. However, ongoing surveys will enable scheme design to be focused ahead of the Environmental Statement such that the magnitude of impact will be reduced, and the adverse effects will be reduced in significance.

1.8.4.8 Where direct impacts on above ground historic assets cannot be avoided through scheme design, programmes of further research and investigation will be undertaken ahead of and during construction. These will not reduce the overall impacts or effects but will serve to offset such impacts and effects. The residual effects will therefore continue to be of up to moderate adverse significance, which is significant in EIA terms.

1.8.4.9 During construction and decommissioning stages, the impact of the onshore transmission assets on above ground historic assets as a result of change within their setting and on the character of historic landscape will be of up to minor adverse significance, which is not significant in EIA terms.

1.8.4.1 During operation and maintenance stages, the impact of the Mona Onshore Substation on above ground historic assets as a result of change within their setting and on the character of the historic landscape is minor adverse and not significant in EIA terms.

1.8.4.1 Cumulative effects from other defined developments within the agreed study areas were assessed and predicted to result in effects of up to minor adverse significance, which is not significant in EIA terms.

1.8.4.1 No transboundary effects with regard to the historic environment of the Mona Proposed Onshore Development Area were predicted.

1.8.5 Land use and recreation ​

1.8.5.1 This chapter considers existing land uses, including agriculture and recreation, which may be physically or indirectly affected during the construction, operations and maintenance and decommissioning phase of the Mona Offshore Wind Project. Existing land uses were identified through a combination of desk-based analysis and site-specific surveys. Desk based analysis of existing studies and datasets identified the soil types and patterns, agricultural land quality, farm holdings and recreational resources (e.g. footpaths, bridleways) likely to be affected by the Mona Offshore Wind Project. Site specific surveys were undertaken in 2022 and comprised walkover surveys of public rights of way to establish the nature and condition of recreational resources.

1.8.5.2 The desk-based analysis determined that land within the Mona Proposed Onshore Development Area predominantly comprised Agricultural Land Classification (ALC) Grade 3a and Grade 3b land and 84 landholdings. In addition, several recreational resources were identified within or near the Mona Proposed Onshore Development Area, including coastal areas (e.g. beaches), Wales Coast Path, National Cycle Route (NCR) 5 and Public Rights of Way (PRoW).

1.8.5.3 The following potential impacts were identified with respect to land use and recreation during the construction, operations and maintenance and decommissioning phase of the Mona Offshore Wind project:

• Temporary and permanent loss of best and most versatile land
• Temporary and permanent disruption to the operation of farm holdings
• Temporary and permanent impact on the recreational use of coastal areas, recreational resources and Wales Coast Path and National Cycle Route 5.

1.8.5.4 Following the implementation of measures adopted as part of the Mona Offshore Wind Project (e.g. control of the timing of soil handling operation) in place, these impacts range from minor to moderate adverse, which are not significant in EIA terms.

1.8.5.5 The temporary and permanent loss of best and most versatile land during the construction, operations and maintenance and decommissioning phase of the Mona Offshore Wind Project would result in a moderate adverse effect. Based on National Policy under Planning Policy Wales (PPW) and Technical Advice Note (TAN) 6 (Welsh Government, 2010), this is not considered to be a significant loss of the best and most versatile agricultural land, as the area affected falls well below the threshold of 20ha identified in this policy. Therefore, on this basis, the loss of a maximum of approximately 4.8ha of Subgrade 3a land is not assessed to be significant in EIA terms.

1.8.5.6 The temporary disruption caused to the operation of farm holdings during the construction phase of the Mona Offshore Wind Project would result in a moderate adverse effect, which is significant in EIA terms. The permanent disruption caused to the operation of farm holdings during the construction, operations and maintenance and decommissioning phase of the Mona Offshore Wind Project would result in a minor adverse effect, which is not significant in EIA terms.

1.8.5.7 The temporary impact on the recreational use of coastal areas, Wales Coast Path and National Cycle Route 5 during the construction phase of the Mona Offshore Wind Project would result in a minor adverse effect, which is not significant in EIA terms. The temporary impact on the recreational use of recreational resources during the construction phase of the Mona Offshore Wind Project would result in a moderate adverse effect, which is not significant in EIA terms.

1.8.5.8 A cumulative assessment was conducted for land use and recreation that considered agricultural land quality, farm holdings and recreational resources during each of the project phases. It was found that during the construction phase, all potential cumulative effects would be of minor adverse significance, which is not significant in EIA terms. No further cumulative effects for land use and recreation are identified in the operations and maintenance phase.

1.8.5.9 It is considered that there is no potential for significant transboundary effects to occur during the construction, operations and maintenance and decommissioning phase of the Mona Offshore Wind Project upon the interests of other States with respect to air quality.

1.8.6 Traffic and transport ​

1.8.6.1 Traffic and transport relates to the movement demand generated by the Mona Offshore Wind Project and its effects upon other road users and surroundings. The construction phase of the Mona Offshore Wind Project will generate the greatest number of vehicle movements as the transportation of construction materials will incur the greatest number of Heavy Goods Vehicle (HGV) and staff movements and it is this phase that the traffic and transport chapter of the PEIR focusses on.

1.8.6.2 The traffic and transport chapter of the PEIR sets out the initial traffic and transport study area, the key highway links within this, estimations on the typical daily number of construction vehicle movements and an initial environmental impact assessment that has been undertaken in advance of access points being determined and access routes being confirmed.

1.8.6.3 An initial traffic and transport study area has been identified including the A55 road and relevant parts of the local highway network determined as being likely to be used by construction generated vehicles. A base position is being established by obtaining publicly available traffic surveys, undertaking new traffic surveys, analysing road safety and analysing public transport services and provision and facilities for pedestrians and cyclists.

1.8.6.4 An initial impact assessment has been undertaken within the PEIR chapter in advance of access points being determined and access routes confirmed and has identified that the Mona Offshore Wind Project average daily construction traffic flows are low in comparison to base traffic flows throughout the initial traffic and transport study area.

1.8.6.5 The effects of the Mona Offshore Wind Project average daily construction traffic flows upon driver delay, severance of routes, pedestrian delay, pedestrian amenity, accidents and road safety and hazardous and dangerous and abnormal indivisible loads were found to be of negligible or minor adverse significance, which is not significant in EIA terms. Measures will also be adopted as part of the Mona Offshore Wind Project to reduce traffic impact (e.g. the identification of suitable HGV routes).

1.8.6.6 As the access points have not yet been determined and therefore the access routes not yet confirmed, the full extent of the highway network to be assessed has not yet been fully confirmed. Therefore, the projects to be considered cumulatively cannot yet be confirmed and a cumulative environmental assessment will therefore be set out in the application for Development Consent.

1.8.6.7 No transboundary effects with regard to traffic and transport from the Mona Offshore Wind Project on the interests of other States were predicted.

1.8.6.8 No inter-related effects with regard to traffic and transport from the Mona Offshore Wind Project were predicted.

1.8.7 Noise and vibration ​

1.8.7.1 Unwanted noise and vibration can lead to adverse impacts on existing residential amenity and public health. As such, it’s important that the impacts of noise and vibration predicted from the construction and operation of new developments be assessed and mitigated as best is reasonably practicable. The existing sound environment in the development are for the Mona Offshore Wind Project was characterised via site-specific surveys where long-term noise monitoring provided data for the determination of impact assessment criteria.

1.8.7.2 The long-term and short-term sound surveys highlight that much of the area forming the Mona Onshore Development area has a low noise climate due to the rural nature of the area. The dominant sources of noise were noted to be traffic on the A55 and other local roads, which became more influential towards the Mona landfall region.

1.8.7.3 A number of potential noise and vibration impacts associated with the construction, operational and maintenance, and decommissioning phases of the Mona Offshore Wind Project were identified. These included:

• Noise impacts arising from the construction of the offshore generation assets, the Onshore Cable Corridor, and the Onshore Substation
• Impacts due to vibration due to piling activities in the intertidal region in close proximity to static caravans along the Abergele coastline
• Operational noise impacts due to the Onshore Substation plant.

1.8.7.4 By adopting the noise control measures set out in a Construction Noise Management Plan and an Operational Noise Management Plan, the majority of these impacts will result in effects of minor adverse significance which is not significant in EIA terms.

1.8.7.5 Effects of moderate adverse significance have been identified where trenchless techniques are required to install the onshore transmission cables. This is due to the high noise levels associated with the construction plant as well as the potential need for night-time working where existing noise levels are low. The potential for moderate adverse effects has also been identified at the landfall. The significance of these effects will be reduced by providing enhanced acoustic mitigation (e.g. enclosures), particularly around equipment in continuous operation. Considering the temporary duration of this potential impact (construction only) and providing such measures are adopted, it is possible the significance of this effect may be reduced to minor adverse which is not significant in EIA terms.

1.8.7.6 Cumulative effects from nearby noise-generating developments (construction or operational) within 1 km of the Mona Offshore Wind Project were assessed and were predicted to result in minor adverse effects which is not significant in EIA terms.

1.8.7.7 No transboundary effects with regard to noise and vibration from the Mona Offshore Wind Project on the interests of other States were predicted.

1.8.8 Air quality ​

1.8.8.1 Air quality is a measure used to describe the level of pollutants present within the air. Dust and particulate matter can be generated by onsite construction activities and dust also can be tracked out onto the public road network. There may also be changes in atmospheric pollutant concentrations due to the combustion of fuel in vehicles.

1.8.8.2 During construction and decommissioning, the key pollutant is dust, covering both the particulate matter fraction that is suspended in the air that can be breathed, and the deposited dust that has fallen out of the air onto surfaces and which can potentially cause temporary annoyance effects. Property, human-health and vegetation (ecological receptors) are all potentially affected.

1.8.8.3 Additional traffic generated during the construction phase is not yet known and the potential effects of tracked out dust and changes in vehicle emissions cannot be determined at this stage. Therefore, this chapter only considers the potential risk of impacts of deposited dust and an increase in particulate matter generated during the construction and decommissioning phases of the Mona Offshore Wind Project.

1.8.8.4 The potential risk of impacts from tracked out dust and changes in vehicle emissions on air quality during the construction and decommissioning phase of the Mona Offshore Wind Project will be considered in the Environmental Statement.

1.8.8.5 A review of local monitoring of particulate matter was undertaken and compared with the Defra mapped background concentration estimates to determine a suitable baseline concentration.

1.8.8.6 The following potential impacts were identified with respect to air quality during the construction and decommissioning phase of the Mona Offshore Wind Project:

• A medium dust impact risk of dust soiling on property arising from onsite activities
• A low dust impact risk of particulate matter on people arising from onsite activities
• A high dust impact risk of particulate matter on ecology arising from onsite activities.

1.8.8.7 However, following the implementation of appropriate dust control measures (e.g. water suppression), these impacts would result in negligible effects, which are not significant in EIA terms.

1.8.8.8 The effect of dust soiling on property arising from onsite activities during the construction and decommissioning phase of the Mona Offshore Wind project was determined to be negligible, which is not significant in EIA terms.

1.8.8.9 The effect of particulate matter on people arising from onsite activities during the construction and decommissioning phase of the Mona Offshore Wind project was determined to be negligible, which is not significant in EIA terms.

1.8.8.1 The effect of particulate matter on ecology arising from onsite activities during the construction and decommissioning phase of the Mona Offshore Wind project was determined to be negligible, which is not significant in EIA terms.

1.8.8.1 Measures to reduce impact will also be adopted as part of the Mona Offshore Wind Project (e.g. the creation of a Construction Noise Management Plan).

1.8.8.1 Cumulative effects between the Mona Offshore Wind Project and other projects/plans located within 700m were assessed with respect to air quality. This included the potential impact of dust and particulate matter generated by onsite construction and decommissioning activities on property, human-health and ecological receptors. The assessment determined that cumulative effects on air quality between the Mona Offshore Wind Project and other projects/plans during the construction, operations and maintenance and decommissioning phase were unlikely to be significant in EIA terms.

1.8.8.1 It is considered that there is no potential for significant transboundary effects to occur during the construction, operations and maintenance and decommissioning phases with respect to air quality.

1.8.9 Onshore and intertidal ornithology ​

1.8.9.1 Breeding, wintering, and migratory birds use both the terrestrial and intertidal habitats located along the Mona Proposed Onshore Development Area. Waterbird and seabird species that depend on wetlands and the marine environment for survival at some point in their life cycle use the intertidal habitats and nearshore waters of the Mona Proposed Landfall in winter and during passage periods (i.e. spring and autumn). In addition, terrestrial habitats along the Mona Proposed Onshore Development Area provide a range of functions (e.g. foraging, non- foraging activities and nesting) for breeding birds (e.g. birds of prey and passerines) and wintering and migratory birds. Information on breeding, wintering and migratory birds within the onshore ornithology study area and the intertidal ornithology study area was collected through a detailed desktop review of existing studies and datasets, and site-specific surveys, including intertidal waterbird, onshore breeding, and wintering bird surveys.

1.8.9.2 The site-specific intertidal ornithological surveys indicated that the Mona Proposed Landfall supported a waterbird and a seabird assemblage that is typical of the coast of north Wales and is dominated by seaducks and divers in the nearshore waters and wader species within the intertidal zone. These species primarily comprised common redshank Tringa totanus, Eurasian oystercatcher Haematopus ostralegus, Eurasian Curlew Numenius arquata and common ringed plover Charadrius hiaticula. The site-specific breeding bird surveys undertaken within the Mona Proposed Onshore Development Area found the bird assemblage to be dominated by ground nesting farmland birds in grassland/ pasture habitat, or passerine and raptor species nesting in hedgerows, and woodland.

1.8.9.3 Several potential impacts on bird species, associated with the construction, operations and maintenance, and decommissioning phases of the Mona Offshore Wind Project, were identified. These included:

• Temporary and permanent habitat loss
• Habitat disturbance
• Habitat fragmentation and species isolation
• Pollution caused by accidental spills/contaminant release The spread of INNS.

1.8.9.4 With the measures adopted as part of the Mona Offshore Wind Project (e.g. pre-commencement breeding bird surveys) in place, most of these impacts result in either negligible, or minor adverse effects, which are not significant in EIA terms.

1.8.9.5 Temporary habitat loss was deemed to be of minor adverse significance to the seabird and waterbird species in the Mona Onshore Proposed Development Area, which is not significant in EIA terms due to the short-term nature of the impact during the construction and decommissioning phases of the Mona Offshore Wind Project. Notably, no significant effects of permanent habitat loss were predicted on breeding birds within the Mona Proposed Onshore Development Area due of the absence of overlap of breeding territories with the Mona Proposed Substations, where permanent habitat loss is expected to take place at a small scale and in habitats of low ornithological value.

1.8.9.6 Habitat disturbance was deemed to be of minor adverse significance to the ornithological receptors in the Mona Onshore Proposed Development Area and not significant in EIA terms, due to the short-term nature of the impact during the construction and decommissioning phases of the Mona Offshore Wind Project. Impacts from pollution caused by accidental spills/ contaminant release were also deemed to be of minor adverse significance on ornithological receptors and not significant in EIA terms, due to the short-term nature of the impact. Similarly, spread of INNS was deemed to be of minor adverse significance and not significant in EIA terms. Finally, there was no significant effect (no change) from the impact of habitat fragmentation and species isolation on birds.

1.8.9.7 Cumulative effects between the Mona Offshore Wind Project and other projects/plans located within 1km of the Mona Proposed Onshore Development Area were assessed with respect to onshore ornithology. This included the potential impacts of temporary and permanent habitat loss, habitat disturbance, habitat fragmentation and species isolation, pollution caused by accidental spills/ contaminant release and the spread of INNS. The assessment determined that cumulative effects on onshore ornithology between the Mona Offshore Wind Project and other plan/projects during the construction, operations and maintenance and decommissioning phase would result in negligible to minor adverse effects, which are not significant in EIA terms.

1.8.9.8 It is considered that there is no potential for significant transboundary effects to occur on the interests of other States during the construction, operations and maintenance and decommissioning phases of the Mona Offshore Wind Project with respect to onshore ornithology.

1.8.10 Inter-related effects – onshore ​

1.8.10. The EIA is required to consider the potential for inter-related effects to occur on groups of receptors (receptor groups) during the construction, operations and maintenance and decommissioning phase of the Mona Offshore Wind Project. The inter-related effects assessment (onshore) in presented a separate chapter of the PEI.

Project-lifetime effects

1.8.10. 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.

1.8.10. 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 potential for significant project-lifetime effects in EIA terms to occur on the following receptor groups:

• Socio-economic factors: potential beneficial impact of the Mona Offshore Wind project on the performance of the renewable energy industry.

Receptor-led effects

1.8.10. 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.

1.8.10. All the potential receptor-led effects identified during the construction, operations and maintenance and decommissioning phases 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 (onshore) chapter of the PEIR and considered not to be significant in EIA terms.