Sensitivity of the Receptor

80. The water quality receptors described in paragraphs 69 to 71 have been assessed individually and are considered to be of similar sensitivity. Taking into account successful implementation by maintenance vessels of the INNS provisions contained within the EMP, and based upon the extensive and dynamic nature of the marine environment (i.e. wind, tidal processes, currents) in reducing the likelihood of INNS colonisation, and professional judgement, all the receptors are deemed to be of medium vulnerability, low recoverability and high value. The sensitivity of the receptors is therefore, considered to be low.

Significance of the Effect

81. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptors is considered to be low. The effect for all receptors will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.

Secondary Mitigation and Residual Effect

82. No water quality mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 19.10) is not significant in EIA terms.

Decommissioning Phase

Magnitude of Impact

83. The presence of decommissioning vessels may lead to an increased risk of introduction and spread of INNS. The maximum design scenario for the decommissioning phase contains the same activities as the construction phase ( Table 19.16   Open ▸ ). It may be decided closer to the time that removal of cables, cable protection and scour protection may result in greater environmental impacts, however the maximum design scenario assumes that the cables, cable protection and scour protection will be removed following completion of the operation and maintenance phase representing a reduced potential habitat for INNS.
84. As set out in Table 19.21   Open ▸ , an INNS Management Plan and EMP (see volume 4, appendix 22), which will include measures such as ensuring any new infrastructure coming from another marine environment are cleaned and checked prior to installation and that vessels comply with the IMO ballast water management guidelines will be developed and adhered to for the Proposed Development. This will ensure that the risk of potential introduction and spread of INNS will be minimised.
85. The impact is predicted to be of local spatial extent, long term duration, continuous and low reversibility. It is predicted that the impact will affect the receptor indirectly. The magnitude is therefore considered to be negligible.

Sensitivity of the Receptor

86. The water quality receptors described in paragraphs 69 to 71 have been assessed individually and are considered to be of similar sensitivity. Taking into account successful implementation by decommissioning vessels of the INNS provisions contained within the EMP, and based upon the extensive and dynamic nature of the marine environment (i.e. wind, tidal processes, currents) in reducing the likelihood of INNS colonisation, and professional judgement, the receptors are deemed to be of negligible vulnerability, high recoverability and high value. The sensitivity of the receptors is therefore, considered to be low.

Significance of the Effect

87. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptors is low. The effect for all receptors will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms.

Secondary Mitigation and Residual Effect

88. No water quality mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 19.10) is not significant in EIA terms.

Accidental Release of Lubricants, Chemicals or similar

89. The accidental release of lubricants, chemicals or similar during the construction, operation and maintenance and decommissioning phases has been considered in this assessment.
90. Accidental release of lubricants, chemicals or similar within the water quality study area may increase during the construction, operation and maintenance, and decommissioning phase ( Table 19.16   Open ▸ ).
91. Accidental release of lubricants, chemicals or similar can result from activities involving any vessel, including survey, installation, crew transfer, maintenance, and cable repair vessels, entering the Proposed Development area.
92. Accidental release of lubricants, chemicals or similar can result during and after installation of wind turbines and OSPs/Offshore convertor station platforms that require lubricants, chemicals or similar as part of normal operating conditions, and from scheduled and unscheduled maintenance operations.

Construction Phase

Magnitude of Impact

93. The installation of wind turbines, inter-array cables, offshore export cables and OSPs/Offshore convertor station platforms may lead to an increased risk of accidental release of lubricants, chemicals or similar. The maximum design scenario is represented by up to 10,484 vessel round trips per year during the construction phase, which will occur over a maximum of 96 months ( Table 19.4   Open ▸ ).
94. There are a number of existing vessel movements occurring within the Proposed Development array area, including cargo vessels, tankers, fishing vessels, recreational vessels, and service vessels (volume 3, appendix 13.1). The baseline identified in volume 3, appendix 13.1 recognised 14 unique vessel movements per day over the summer survey period and 16 per day in the winter period in the Proposed Development array area: cargo vessels, tankers and commercial fishing vessels were the most common vessel type. 24 unique vessel movements per day were identified over the survey period in the Proposed Development export cable corridor shipping and navigation study area for the summer period, and 18 per day in the winter period. Therefore, the additional vessels associated with the construction phase of the Proposed Development (i.e. 29 per day) are unlikely to increase the risk of accidental release of lubricants, chemicals or similar.
95. As set out in Table 19.21   Open ▸ , an MPCP and EMP will be implemented, which will include measures to reduce the risk of accidental release resulting from transfer of lubricants, chemicals or similar to wind turbines and OSPs/Offshore convertor station platforms, and in the event of accidental release ensure their containment and avoid discharge to the marine environment. Control measures are included in the draft MPCP (volume 4, appendix 22) which will be finalised during consultation with MS-LOT.
96. The impact is predicted to be of local spatial extent, short term duration, intermittent and medium reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be low.

Sensitivity of the Receptor

97. The water quality receptors described in paragraphs 69 to 71 have been assessed individually and are considered to be of similar sensitivity. Taking into account designed-in measures for the containment of accidental release of lubricants, chemicals or similar from within the operational structures of the Proposed Development, and based upon the dispersive ability of the extensive and dynamic nature of the marine environment (i.e. wind, tidal processes, currents), and professional judgement, the receptors are deemed to be of medium vulnerability, medium recoverability and high value. The sensitivity of the receptors is therefore considered to be medium.

Significance of the Effect

98. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be medium. The effect for all receptors will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Secondary Mitigation and Residual Effect

99. No water quality mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 19.10) is not significant in EIA terms.

Operation and Maintenance Phase

Magnitude of Impact

100. The presence of operation and maintenance vessels may lead to an increased risk of accidental release of lubricants, chemicals or similar. The maximum design scenario is represented by up to 2,324 vessels round trips per year during the operation and maintenance phase ( Table 19.16   Open ▸ ) which is a reduction from the construction phase.
101. As set out in Table 19.21   Open ▸ , an MPCP and EMP will be implemented, which will include measures to reduce the risk of accidental release of lubricants, chemicals or similar from wind turbines and OSPs/Offshore convertor station platforms to the marine environment. To avoid discharge or spillage of oils, it is anticipated that transformers would be filled for their operational life and would likely not need interim oil changes, and that closed systems will be employed to avoid the requirement for operational fluids to be topped up or renewed during the operation phase.
102. The impact is predicted to be of local spatial extent, short term duration, intermittent and medium reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be low.

Sensitivity of the Receptor

103. The water quality receptors described in paragraphs 69 to 71 have been assessed individually and are considered to be of similar sensitivity. Taking into account designed-in measures for the containment of accidental release of lubricants, chemicals or similar from within the operational structures of the Proposed Development, and based upon the dispersive ability of the extensive and dynamic nature of the marine environment (i.e. wind, tidal processes, currents), and professional judgement, the receptors are deemed to be of medium vulnerability, medium recoverability and high value. The sensitivity of the receptors is therefore considered to be medium.

Significance of the Effect

104. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be medium. The effect for all receptors will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Secondary Mitigation and Residual Effect

105. No water quality mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 19.10) is not significant in EIA terms.

Decommissioning Phase

Magnitude of Impact

106. The presence of decommissioning vessels may lead to an increased risk of accidental release of lubricants, chemicals or similar. The maximum design scenario for the decommissioning phase contains the same activities as the construction phase ( Table 19.16   Open ▸ ). However, it might be decided closer to the time that removal of cable protection and scour protection may result in greater environmental impacts. The maximum design scenario therefore assumes that the scour protection and cable protection will be removed where possible and appropriate to do so, noting that this will depend on the type of scour protection used and condition of said protection at the time of removal. This approach will be reviewed at the time of decommissioning following the most up to date and best available guidance.
107. As set out in Table 19.21   Open ▸ , an MPCP and EMP will be implemented, which will include measures to reduce the risk of accidental release of lubricants, chemicals or similar to the marine environment, during decommissioning of wind turbines and OSPs/Offshore convertor station platforms.
108. The impact is predicted to be of local spatial extent, short term duration, intermittent and medium reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be low.

Sensitivity of the Receptor

109. The water quality receptors described in paragraphs 69 to 71 have been assessed individually and are considered to be of similar sensitivity. Taking into account designed-in measures for the containment of accidental release of lubricants, chemicals or similar from within the operational structures of the Proposed Development, and based upon the dispersive ability of the extensive and dynamic nature of the marine environment (i.e. wind, tidal processes, currents), and professional judgement, the receptors are deemed to be of medium vulnerability, medium recoverability and high value. The sensitivity of the receptors is therefore considered to be medium.

Significance of the effect

110. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is medium. The effect for all receptors will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Secondary Mitigation and Residual Effect

111. No water quality mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 19.10) is not significant in EIA terms.

Operational painting, and cleaning of marine growth

112. Operational painting and cleaning of marine growth during the operation and maintenance phase has been considered during this assessment.
113. The operational life of the Proposed Development is anticipated to be 35 years, and wind turbines and OSPs/Offshore convertor station platforms are expected to require regular inspection and maintenance of their exterior surfaces to address and prevent instances of corrosion and marine growth.
114. Operational painting and cleaning of marine growth within the Proposed Development area will increase during the operation and maintenance phase ( Table 19.16   Open ▸ ).

Operation and Maintenance Phase

Magnitude of Impact

115. The marine environment is expected to cause corrosion to the surfaces of wind turbine foundations and to the foundations and topside surfaces of OSPs/Offshore convertor station platforms, where coatings that were applied during the manufacturing process may have become weakened. Application of paint or other coatings, as well as surface preparation, is likely to be required to protect surfaces from corrosion.
116. The foundations of wind turbines and OSPs/Offshore convertor station platforms provide a hard substrate which offers potential habitat for encrusting organisms to colonise, and for guano to accumulate. Removal by pressure washing of encrusted growth and guano will occur ad hoc during the operation and maintenance phase, however, no quantitative assessment can be made as the volume is not possible to predict, and is therefore not known at the point of application. Dislodged material may be rapidly consumed by organisms or relocated by wind and tidal currents, and further monitoring may be required to clarify whether biological material accumulates over time (section 19.15).
117. Operational painting is anticipated to be conducted once every ten years, and cleaning of marine growth and guano is anticipated to be carried out twice on every wind turbine and OSP/Offshore convertor station platform over the lifetime of the Proposed Development. Operational painting and cleaning of marine growth will occur during scheduled maintenance visits, as detailed in volume 1, chapter 3.
118. Due to the infrequency of operational cleaning, scheduling alongside routine maintenance activities and implementation of the mitigation measures contained in the EMP and MPCP ( Table 19.21   Open ▸ ), the impact is predicted to be of local spatial extent, short term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptor directly. It is proposed that the marine grade paints will be used at the Proposed Development. The magnitude is therefore considered to be negligible.

Sensitivity of the Receptor

119. The water quality receptors described in paragraphs 69 to 71 have been considered individually and are considered to be of similar sensitivity. Taking into account the infrequency with which operational painting is expected to be required, and the ecologically benign means of cleaning naturally occurring accumulations of marine growth and guano, and based upon the dispersive ability of the extensive and dynamic nature of the marine environment (i.e. wind, tidal processes, currents), and professional judgement, the receptors are deemed to be of medium vulnerability, medium recoverability and high value. The sensitivity of the receptors is therefore considered to be medium.

Significance of the Effect

120. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptor is considered to be medium. The effect for all receptors will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Secondary Mitigation and Residual Effect

121. No water quality mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 19.10) is not significant in EIA terms.

Deterioration of water quality from cable and landfall works

122. Deterioration of water quality from offshore export cables landfall works, seabed preparation and cable installation in WFD water bodies, at bathing waters (including at bathing water sampling locations) along the export cable corridor and within the array area has been considered during this assessment and may increase (i.e. water quality may decrease) during the construction and decommissioning phases of the Proposed Development ( Table 19.13   Open ▸ ), with the potential for the ecological and chemical status of coastal water bodies to deteriorate.
123. Deterioration of water quality and ecological and chemical status can result from activities arising during installation and decommissioning of offshore export cables, landfall works, inter-array cables and interconnector cables with the potential for impacting hydrodynamics, sediment transport and beach morphology in the vicinity of designated sites.
124. The objectives of the WFD require that the Proposed Development should not result in a risk to the deterioration in the status of a water body, or prevent a water body from achieving its environmental objectives (see paragraph 16).
125. A WFD assessment has been undertaken to describe the current baseline conditions of WFD water bodies within 2 km of the Proposed Development and quantifies the potential changes due to the installation and presence of the Proposed Development. This assessment is presented in volume 2, appendix 19.

Construction Phase

Magnitude of Impact

126. The installation of export cables in the export cable corridor, and inter-array cables and interconnector cables in the array area, may lead to the mobilisation of sediment as a result of seabed preparation works and cable burial operations. Sandwave clearance via suction hopper dredging and disposal of material, and cable installation via ploughing and jet trenching, may increase SSC. The associated deposition of sediment and potential effect upon hydrodynamics has been considered as a component of the physical processes assessment in volume 2, chapter 7 following numerical modelling detailed in volume 2, appendix 7.1.
127. The increased SSC arising from cable installation works is expected to return to baseline levels within a couple of tidal cycles, and the deposition of sediment would not be of sufficient magnitude to alter the hydrodynamic regime or offshore bank or beach morphology, and has been assessed as being of negligible adverse significance.
128. The installation of cable export landfall works may lead to an increased risk of deterioration of water quality at bathing water sampling locations and within WFD water bodies. The maximum design scenario is represented by installation of up to eight HDD exit punch outs located between 488 m and 1,500 m from MHWS ( Table 19.16   Open ▸ ).
129. Four WFD water bodies and eight designated bathing water sampling locations are located within the 25 km ZoI of the offshore export cable corridor and array area ( Table 19.12   Open ▸ ), which have the potential to be impacted by altered hydrodynamics, sediment transport and beach morphology. Modelling of offshore export cables trenching assumes sediment release along the Proposed Development export cable corridor to the nearshore point at which a continuous rock outcrop is encountered and within the Proposed Development array area. The impact is predicted to be of local spatial extent, short term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be low.

Sensitivity of the Receptor

130. The water quality receptors described in paragraphs 69 to 71 have been considered individually and are considered to be of similar sensitivity. Taking into account the extensive and dynamic nature of the marine environment (i.e. wind, tidal processes, currents), modelling of sediment transport processes and professional judgement, the receptors are deemed to be of medium vulnerability, medium recoverability and high value. The sensitivity of the receptors is therefore, considered to be medium.

Significance of the Effect

131. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be medium. The effect for all receptors will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Secondary Mitigation and Residual Effect

132. No water quality mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 19.10) is not significant in EIA terms.

Decommissioning Phase

Magnitude of Impact

133. Decommissioning of offshore export cables, inter-array cables and interconnector cables and landfall works may involve complete removal of all infrastructure, but some infrastructure may be left in situ. Removal of all infrastructure may lead to an increased risk of deterioration of water quality in WFD water bodies and at bathing waters (including at bathing water sampling locations) as a result of altered hydrodynamics, sediment transport and beach morphology.
134. Eight designated bathing sites are located within the 25 km ZoI of the offshore export cables landfall works ( Table 19.12   Open ▸ ), which have the potential to be impacted by decommissioning of offshore export cables landfall works. If any infrastructure is left in situ this is expected to reduce the severity of water quality deterioration during decommissioning.
135. The impact is predicted to be of local spatial extent, short term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be low.

Sensitivity of the Receptor

136. The water quality receptors described in paragraphs 69 to 71 have been considered individually and are considered to be of similar sensitivity. Taking into account the extensive and dynamic nature of the marine environment (i.e. wind, tidal processes, currents), modelling of sediment transport processes and professional judgement, the receptors are deemed to be of medium vulnerability, medium recoverability and high value. The sensitivity of the receptors is therefore, considered to be medium.

Significance of the Effect

137. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be medium. The effect for all receptors will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Secondary Mitigation and Residual Effect

138. No water quality mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 19.10) is not significant in EIA terms.

19.11.3.         Proposed Monitoring

139. This section outlines the monitoring proposed for water quality proposed monitoring measures are outlined in Table 19.22   Open ▸ .
140. No generic water quality monitoring is considered necessary. This has been concluded because there is sufficient confidence in the assessment, of the negligible or minor long-term effects identified, and because regular water sampling is already undertaken as a statutory obligation to maintain high quality bathing water at designated sites, under the Bathing Waters (Scotland) Regulations 2008. In addition to this, SEPA will carry out the WFD monitoring on an annual basis, which will monitor any potential impacts on water quality arising from the Proposed Development. As such no additional water quality monitoring is proposed.
141. The Applicant is however committed to engaging with the SNCBs to identify suitable strategic benthic monitoring or research studies that the Project could contribute to, to improve the knowledge base for long term impacts associated with offshore wind farms. Proposed monitoring measures are outlined in Table 19.22   Open ▸ .

Table 19.22: Monitoring Commitments for Water Quality

19.12. Cumulative Effects Assessment

19.12.2.         Methodology

142. The CEA assesses the impact associated with the Proposed Development together with other relevant plans, projects and activities. Cumulative effects are therefore the combined effect of the Proposed Development with the effects from a number of different projects, on the same receptor or resource. Please see volume 1, chapter 6 for detail on CEA methodology.
143. The projects and plans selected as relevant to the CEA presented within this chapter are based upon the results of a screening exercise (see volume 3, appendix 6.4 of the Offshore EIA Report). Volume 3, appendix 6.4 further provides information regarding how information pertaining to other plans and projects is gained and applied to the assessment. Each project or plan has been considered on a case by case basis for screening in or out of this chapter's assessment based upon data confidence, effect-receptor pathways and the spatial/temporal scales involved.
144. In undertaking the CEA for the Proposed Development, it is important to bear in mind that other projects and plans under consideration will have differing potential for proceeding to an operational stage and hence a differing potential to ultimately contribute to a cumulative impact alongside the Proposed Development. Therefore, a tiered approach has be adopted. This provides a framework for placing relative weight upon the potential for each project/plan to be included in the CEA to ultimately be realised, based upon the project/plan’s current stage of maturity and certainty in the projects’ parameters. The tiered approach which will be utilised within the Proposed Development CEA employs the following tiers:

• tier 1 assessment – Proposed Development (Berwick Bank Wind Farm offshore) with Berwick Bank Wind Farm onshore;
• tier 2 assessment – All plans/projects assessed under Tier 1, plus projects which are operational since baseline characterisation, those under construction and those with consent and submitted but not yet determined;
• tier 3 assessment – All plans/projects assessed under Tier 2, plus those projects with a Scoping Report; and
• tier 4 assessment – All plans/projects assessed under Tier 3, which are reasonably foreseeable, plus those projects likely to come forward where an Agreement for Lease (AfL) has been granted.
  145. The specific projects scoped into the CEA for water quality, are outlined in Table 19.23   Open ▸ .
  146. As described in volume 1, chapter 3, the Applicant is developing an additional export cable grid connection to Blyth, Northumberland (the Cambois Connection). Applications for necessary consents (including marine licenses) will be applied for separately. The CEA for the Cambois Connection is based on information presented in the Cambois Connection Scoping Report (SSER, 2022e), submitted in October 2022. The Cambois Connection has been scoped into the CEA for water quality on the basis that the Cambois Connection will overlap spatially and temporally with the Proposed Development and the project will engage in activities such as cable burial and installation of cable protection which will impact water quality receptors.
  147. The range of potential cumulative impacts that are identified and included in Table 19.24   Open ▸ , is a subset of those considered for the Proposed Development alone. This is because some of the potential impacts identified and assessed for the Proposed Development alone, are localised and temporary in nature. It is considered therefore, that these potential impacts have limited or no potential to interact with similar changes associated with other plans or projects. These have therefore not taken forward for detailed assessment.
  148. Similarly, some of the potential impacts considered within the Proposed Development alone assessment are specific to a particular phase of development (e.g. construction, operation and maintenance or decommissioning). Where the potential for cumulative effects with other plans or projects only have potential to occur where there is spatial or temporal overlap with the Proposed Development during certain phases of development, impacts associated with a certain phase may be omitted from further consideration where no plans or projects have been identified that have the potential for cumulative effects during this period.
  149. For the purposes of this Offshore EIA Report, this cumulative impact has been assessed within a representative 25 km buffer of the Proposed Development ( Figure 19.2   Open ▸ ). This buffer, which is based on the fish and shellfish ZoI, is considered appropriate as the majority of impacts considered in section 19.11 will be localised in extent. This encompasses all offshore wind farm projects within the regional benthic subtidal and intertidal and fish and shellfish study areas, and is the greatest ZoI for all supporting chapters (see paragraph 3).

Table 19.23: List of Other Developments Considered Within the CEA for Water Quality

Figure 19.2 Other Developments Screened into the Cumulative Effects Assessment for Water Quality

19.12.3.         Maximum Design Scenario

150. The maximum design scenarios identified in Table 19.24   Open ▸ have been selected as those having the potential to result in the greatest effect on an identified receptor or receptor group. The cumulative effects presented and assessed in this section have been selected from the details provided in volume 1, chapter 3 of the Offshore EIA Report as well as the information available on other projects and plans (see volume 3, appendix 6.4), to inform a ‘maximum design scenario’. Effects of greater adverse significance are not predicted to arise should any other development scenario, based on details within the Project Design Envelope (e.g. different wind turbine layout), to that assessed here, be taken forward in the final design scheme.

Table 19.24: Maximum Design Scenario Considered for Each Impact as part of the Assessment of Likely Significant Cumulative Effects on Water Quality

19.12.4.         Cumulative Effects Assessment

151. An assessment of the likely significance of the cumulative effects of the Proposed Development upon water quality receptors arising from each identified impact is given below.

Increased risk of introduction and spread of invasive and non-native species (INNS)

Tier 2

152. The risk of introduction and spread of INNS during the construction, operation and maintenance, and decommissioning phases of the cumulative Tier 2 projects has been considered in this assessment. Magnitude has been considered for all three phases combined as the increased risk of introduction and spread of INNS is as a result of all phases combined.

Magnitude of impact

153. The construction and operation and maintenance of the projects/plans/activities shown in Table 19.24   Open ▸ may lead to cumulative introduction and spread of INNS within the water quality CEA study area as a result of vessel movements during the Proposed Development construction phase. The introduction of hard substrate into areas of predominantly soft sediments has the potential to alter community composition and biodiversity and to facilitate the introduction and spread of INNS. The latter may be particularly important with regards to cumulative effects as several offshore structures in relatively close proximity could enable the spread of INNS.
154. Table 19.24   Open ▸ lists all projects/plans/activities considered in the Tier 2 assessment which are Inch Cape Offshore Wind Farm, Neart na Gaoithe Offshore Wind Farm, Seagreen, Seagreen 1A Export Cable Corridor, Eastern Link 1 subsea cable and Eastern Link 2 subsea cable. There is small overlap between the construction phase for the Proposed Development and that of the Inch Cape Offshore Wind Farm and Seagreen 1A Project, as well as the operation and maintenance phase for Seagreen and Neart na Gaoithe Offshore Wind Farm once construction of the Proposed Development has been completed. The remaining projects will be in their operation and maintenance phase during the Proposed Development’s construction phase.
155. Inch Cape Offshore Wind Farm has the potential to introduce INNS in the construction phase through the movement of vessels associated with the installation of the wind turbines, offshore substation platforms, inter-array and offshore export cables, and the associated works (Inch Cape Offshore Limited, 2018). In the operation and maintenance phase of the Inch Cape project INNS introduction can result from the introduction of new substrate installed in the construction phase, the amount of hard substrate introduced is equivalent to the long term habitat loss which is described in volume 2, chapter 8.
156. Neart na Gaoithe Offshore Wind Farm has the potential to introduce INNS in the construction and operation and maintenance phase as a result of the introduction of hard substrate, the area of the projects which is considered to be equal to the area of long term habitat loss (Mainstream Renewable Power, 2019). This involves the introduction of wind turbines, offshore substation platforms, meteorological masts, and inter-array and offshore export cables protection. The details of which are in volume 2, chapter 8 (Mainstream Renewable Power, 2019). Vessel movements may also contribute to INNS however no quantification of this is provided in the Offshore EIA Report.
157. Seagreen did not consider the risk of INNS to be “Capable of Affect, other than insignificantly” (Seagreen Wind Energy, 2021 p. 36); however, INNS can result from introduction of foundations for 150 wind turbines, five offshore substation platforms, two meteorological masts, and inter-array and offshore export cables protection. Additionally, during operation and maintenance there is the potential for a maximum of 52,800 vessel trips by maintenance vessels over the maximum 30 year lifespan of the wind farm.
158. There are no values provided for Seagreen 1A Export Cable Corridor however up to 20% of the 110 km cable may require cable protection up to 6 m wide (Seagreen Wind Energy Ltd., 2021).
159. Assessment for the Eastern Link subsea cables concluded that the introduction and spread of INNS would be unlikely, and that any associated effects would be minor and not significant (AECOM, 2022).
160. The introduction and spread of INNS during the decommissioning phase in each project is expected to be the same as the construction phase as similar activities will occur.
161. The total cumulative area of hard structures available for colonisation is expected to be up to 15,132,896 m2. Additionally, there will be 221,318 cumulative vessel trips, not including those for NNG.
162. The cumulative effect is predicted to be of regional spatial extent, long term duration, continuous and low reversibility for the lifetime of the Proposed Development. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be low.

Sensitivity of receptor

163. The water quality receptors described in paragraphs 69 to 71 have been considered individually and are considered to be of similar sensitivity. Taking into account successful implementation by maintenance vessels of the INNS provisions contained within the EMP, and based upon the extensive and dynamic nature of the marine environment (i.e. wind, tidal processes, currents) in reducing the likelihood of INNS colonisation, and professional judgement, the receptors are deemed to be of medium vulnerability, medium recoverability and high value. The sensitivity of the receptors is therefore considered to be low.

Significance of effect

164. Overall, taking into account the proposed mitigation of the INNS management plan, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be medium. The effect for all receptors will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Further mitigation and residual effect

165. No water quality mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 19.10) is not significant in EIA terms.

Tier 3

166. One Tier 3 project with the potential to result in cumulative increased risk of introduction and spread of INNS with the Proposed Development has been identified in the CEA: the Cambois connection.

Magnitude of impact

167. The Cambois connection has the potential to create 306,000 m2 of new hard substrate habitat via installation of rock/mattress cable protection, potentially covering up to 15% of the total length of the four offshore export cables. It is therefore likely that only a proportion of the cable protection will occupy the water quality CEA study area. The cable protection represents a potential introduction of hard substrate, the effects of which are described in paragraphs 58 to 61, however as the cable protection does not extend into the water column the opportunity for colonisation by some species is reduced. The presence of the Tier 2 and Tier 3 projects has the potential to lead to cumulative impacts arising from the colonisation of up to 15,619,071 m2 of hard structures.
168. Taking into account successful implementation by maintenance vessels of the INNS provisions contained within the EMP, and based upon the extensive and dynamic nature of the marine environment (i.e. wind, tidal processes, currents) in reducing the likelihood of INNS colonisation, and professional judgement, the cumulative impact is predicted to be of local spatial extent, long term duration, continuous and high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore, considered to be low.

Sensitivity of receptor

169. The water quality receptors described in paragraphs 69 to 71 have been considered individually and are considered to be of similar sensitivity. Taking into account successful implementation by maintenance vessels of the INNS provisions contained within the EMP, and based upon the extensive and dynamic nature of the marine environment (i.e. wind, tidal processes, currents) in reducing the likelihood of INNS colonisation, and professional judgement, the receptor is deemed to be of medium vulnerability, medium recoverability and high value. The sensitivity of the receptor is therefore considered to be low

Significance of the effect

170. Overall, taking into account the proposed mitigation of the INNS management plan, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be medium. The effect for all receptors will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Further mitigation and residual effect

171. No water quality mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 19.10) is not significant in EIA terms.

Accidental Release of Lubricants, Chemicals or similar

Tier 2

172. The accidental release of lubricants, chemicals or similar during the construction, operation and maintenance and decommissioning phases of the cumulative Tier 2 projects has been considered in this assessment.
173. Cumulative accidental release of lubricants, chemicals or similar within the water quality study area may increase during the construction, operation and maintenance, and decommissioning phase of Tier 2 projects in the vicinity of the Proposed Development ( Table 19.16   Open ▸ ).
174. Accidental release of lubricants, chemicals or similar can result from activities involving any vessel, including survey, installation, crew transfer, maintenance, and cable repair vessels, entering the Proposed Development area, during the construction, operation and maintenance and decommissioning phases of the project.
175. Accidental release of lubricants, chemicals or similar can result during and after installation of wind turbines and OSPs/Offshore convertor station platforms that require lubricants, chemicals or similar as part of normal operating conditions, from scheduled and unscheduled maintenance operations and during the decommissioning phase of the Proposed Development.

Construction phase

176. The installation of wind turbines, inter-array cables, offshore export cables and OSPs/Offshore convertor station platforms may lead to an increased risk of accidental release of lubricants, chemicals or similar from vessels, or from transfer of lubricants, chemicals or similar to wind turbines before the commencement of the operation and maintenance phase.

Magnitude of impact

177. As set out in Table 19.20   Open ▸ , an MPCP and EMP are standard operational procedures for vessels involved in offshore construction, which will include measures to reduce the risk of accidental release of lubricants, chemicals or similar from cable and cable armour installation vessels to the marine environment. Specific information on the quantities used in the relevant Tier 2 projects is not currently available, but estimates are made based upon the quantities required for the Proposed Development, scaled to the size of the other projects. Quantities of lubricants, chemicals or similar required by these projects are presented in Table 19.25   Open ▸ .

Table 19.25: Volumes of Lubricants, Chemicals or Similar Required by Offshore Wind Developments Being Considered in CEA

2 Volumes of chemicals, lubricants or similar are indicative values. All compounds will be contained within the wind turbines and unlikely to be discharged into the marine environment as any leak will be contained within the nacelle.

178. All Tier 2 projects contributing to the cumulative impacts of accidental releases of lubricants, chemicals or similar to water quality receptors (i.e. those listed in Table 19.25   Open ▸ ) state within their respective assessments that containment measures have been designed into these projects to prevent the release of fluid to the marine environment.
179. The cumulative effect is predicted to be of regional spatial extent, short term duration, intermittent and high reversibility for the lifetime of the Proposed Development. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be low.

Sensitivity of receptor

180. The water quality receptors described in paragraphs 69 to 71 have been considered individually and are considered to be of similar sensitivity. Taking into account designed-in measures for the containment of accidental release of lubricants, chemicals or similar from within the operational structures of the Proposed Development, and based upon the dispersive ability of the extensive and dynamic nature of the marine environment (i.e. wind, tidal processes, currents), and professional judgement, the receptor is deemed to be of medium vulnerability, medium recoverability and high value. The sensitivity of the receptor is therefore considered to be medium.

Significance of effect

181. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be medium. The effect will for all receptors, therefore, be of minor adverse significance, which is not significant in EIA terms.

Further mitigation and residual effect

182. No water quality mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 19.10) is not significant in EIA terms.

Operation and maintenance phase

183. Under normal operational conditions designed-in mitigation measures are intended to contain any spillage of lubricants, chemicals or similar within the structure or substructure of wind turbines and OSPs/Offshore convertor station platforms, and to prevent release into the marine environment.
184. Closed systems preclude the need for many operational fluids to be replenished. Where consumable fluids (e.g. diesel fuel) are required, designated locations for replenishing these, alongside auxiliary containers or bunds of greater capacity than the volume of operational fluids, are able to contain leaks, and double-lined piping where practicable, prevents fluids from leaving the system.

Magnitude of impact

185. The volume of lubricants, chemicals or similar required during the operation and maintenance phase of the Proposed Development is similar to that estimated in Table 19.25   Open ▸ , as well as the volume of fluids carried by maintenance vessels. As such the magnitude of the impact of accidental release is comparable to that during the construction phase.
186. The cumulative effect is predicted to be of regional spatial extent, short term duration, intermittent and high reversibility for the lifetime of the Proposed Development. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be low.

Sensitivity of receptor

187. The water quality receptors described in paragraphs 69 to 71 have been considered individually and are considered to be of similar sensitivity. Taking into account designed-in measures for the containment of accidental release of lubricants, chemicals or similar from within the operational structures of the Proposed Development, and based upon the dispersive ability of the extensive and dynamic nature of the marine environment (i.e. wind, tidal processes, currents), and professional judgement, the receptor is deemed to be of medium vulnerability, medium recoverability and high value. The sensitivity of the receptor is therefore considered to be medium.

Significance of effect

188. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be medium. The effect will for all receptors, therefore, be of minor adverse significance, which is not significant in EIA terms.

Further mitigation and residual effect

189. No water quality mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 19.10) is not significant in EIA terms.