14.8. Key Parameters for Assessment

14.8.1. Maximum Design Scenario

44. The maximum design scenarios identified in Table 14.6   Open ▸ are those expected to have the potential to result in the greatest effect on an identified receptor or receptor group. These scenarios have been selected from the details provided in volume 1, chapter 3 of the Array EIA Report. Effects of greater adverse significance are not predicted to arise should any other development scenario, based on details within the Project Description (volume 1, chapter 3) (e.g. different infrastructure layout), to that assessed here, be taken forward in the final design scheme.

Table 14.6: Maximum Design Scenario Considered for Each Potential Impact as Part of the Assessment of LSE1 on Aviation, Military and Communications

14.8.2. Impacts Scoped Out of the Assessment

45. On the basis of the baseline environment and the Project Description outlined in volume 1, chapter 3 of the Array EIA Report, a number of impacts are proposed to be scoped out of the assessment for aviation, military and communications. This was either agreed with key stakeholders through consultation as discussed in volume 1, chapter 5, or otherwise, the impact was proposed to be scoped out in the Ossian Array EIA Scoping Report (Ossian OWFL, 2023) and no concerns were raised by key consultees within the Scoping Opinion (MD-LOT, 2023).
46. These impacts are outlined, together with a justification for scoping out, in Table 14.7   Open ▸ .

Table 14.7: Impacts Scoped Out of the Assessment for Aviation, Military and Communications

14.9. Methodology for Assessment of Effects

14.9.1. Overview

47. The aviation, military and communications assessment of effects has followed the methodology set out in volume 1, chapter 6 of the Array EIA Report. Specific to the aviation, military and communications Array EIA chapter, the guidance documents in Table 14.3   Open ▸ have been considered.
48. In addition to the overarching policy and legislation as described in volume 1, chapter 2 of this Array EIA Report, the legislative framework relevant to this aviation, military and communications impact assessment within CAP 393 (CAA, 2016b, as amended 2022) has been considered.

14.9.2. Criteria for Assessment of Effects

49. When determining the significance of effects, a two-stage process is used which involves defining the magnitude of the potential impacts and the sensitivity of the receptors. This section describes the criteria applied in this chapter to assign values to the magnitude of potential impacts and the sensitivity of the receptors. The terms used to define magnitude and sensitivity are based on those which are described in further detail in volume 1, chapter 6 of the Array EIA Report.
50. The criteria for defining magnitude in this chapter are outlined in Table 14.8   Open ▸ and are based upon the technical expert’s experience and judgement. Each assessment considered the spatial extent, duration, frequency and reversibility of impact when determining magnitude which are outlined within the magnitude section of each impact assessment (e.g. a duration of hours or days would be considered for most receptors to be of short-term duration, which is likely to result in a low magnitude of impact).

Table 14.8: Definition of Terms Relating to the Magnitude of an Impact

51. The criteria for defining sensitivity in this chapter are outlined in Table 14.9   Open ▸ and are based upon the technical expert’s experience and judgement.

Table 14.9: Definition of Terms Relating to the Sensitivity of the Receptor

52. The magnitude of the impact and the sensitivity of the receptor are combined when determining the significance of the effect upon aviation, military and communications stakeholders (operators). The particular method employed for this assessment is presented in Table 14.10   Open ▸ .
53. Where a range is suggested for the significance of effect, for example, minor to moderate, it is possible that this may span the significance threshold. The technical specialist’s professional judgement was applied to determine which outcome defines the most likely effect, which takes into account the sensitivity of the receptor and the magnitude of impact. Where professional judgement was applied to quantify final significance from a range, the assessment has set out the factors that result in the final assessment of significance. These factors may include the likelihood that an effect will occur, data certainty and relevant information about the wider environmental context.
54. For the purposes of this assessment:

• a level of residual effect of moderate or more will be considered a ‘significant’ effect in terms of the EIA Regulations; and
• a level of residual effect of minor or less will be considered ‘not significant’ in terms of the EIA Regulations.

55. Effects of moderate significance or above are therefore considered important in the decision-making process, whilst effects of minor significance or less warrant little, if any, weight in the decision-making process.

Table 14.10: Matrix Used for the Assessment of the Significance of the Effect

14.10. Measures Adopted as Part of the Array

56. As part of the Array design process, a number of designed in measures have been proposed to reduce the potential for impacts on aviation, military and communications (see Table 14.11   Open ▸ ). They are considered inherently part of the design of the Array and, as there is a commitment to implementing these measures, these have been considered in the assessment presented in section 14.11 (i.e. the determination of magnitude and therefore significance assumes implementation of these measures). These designed in measures are considered standard industry practice for this type of development.

Table 14.11: Designed In Measures Adopted as Part of the Array

57. As provided in the Institute of Environmental Management and Assessment (IEMA) Guide to Delivering Quality Development (IEMA, 2016), where significant effects have been identified, further mitigation measures adopted (referred to as secondary mitigation, that are not "designed in") have been identified to reduce the significance of effect to acceptable levels following the initial assessment. These are measures that could further prevent, reduce and, where possible, offset any adverse effects on the environment. These measures are set out in section 14.11 below in the sections on “Secondary Mitigation and Residual effect” and “Future Monitoring”.

14.11. Assessment of Significance

58. Table 14.6   Open ▸ summarises the potential impacts arising from the construction, operation and maintenance and decommissioning phases of the Array, as well as the MDS against which each impact has been assessed. An assessment of the likely significance of the effects of the Array on the aviation, military and communications receptors caused by each identified impact is given below.

Creation of physical obstacle to aircraft operations (including airborne search and rescue (SAR) operations and low flying aircraft)

59. The construction, operation and maintenance, and decommissioning phases of the Array will lead to the creation of a physical obstacle to aircraft operations. The MDS in regard to aviation, is represented by the 130 floating wind turbines with a maximum blade tip height of 399 m above LAT and is summarised in Table 14.6   Open ▸ .

                        Construction phase

                        Magnitude of impact

60. Wind turbine construction infrastructure above LAT could pose a physical obstruction to flight operations in the vicinity of the Array and specifically to military and other low flying operations including fisheries protection, pollution control and helicopters operating in the support of the renewable and hydrocarbon industries. Helicopter operators, the MOD and ATC service providers have been consulted with regard to the potential for the Array to create an obstruction to aviation, military and communications activities conducted in the vicinity of the floating wind turbines and OSPs. Construction infrastructure, OSPs and erected wind turbines can be difficult to see from the air, particularly in poor meteorological conditions leading to potential increased obstacle collision risk. Furthermore, during the construction phase, the presence and movement of associated infrastructure may present a potential obstacle collision risk to aircraft flight operations.
61. A range of designed in measures, in the form of appropriate notification to aviation, military and communications stakeholders, regularity of layout, and lighting and marking to minimise effects to aviation flight operations would apply to the development of the Array. These will comply with current guidelines where appropriate and be agreed with the appropriate stakeholders as outlined in Table 14.11   Open ▸ . Pilots are obliged to plan their flying activities in advance and to be familiar with any enroute obstacles they may encounter; however, during flight, weather conditions or operational requirements may necessitate route adjustments. In Visual Meteorological Conditions (VMC), pilots are ultimately responsible for seeing and avoiding obstructions such as wind turbines and will be aware through notification procedures of the Array. Furthermore, when flying in Instrument Meteorological Conditions (IMC), pilots may be under the control of ATC with an appropriate level of radar service and flying at an altitude which provides the required separation from obstacles below them.
62. Volume 3, appendix 14.1, annex A includes full details of the IFP analysis undertaken to develop the aviation, military and communications baseline and assesses those Aberdeen International Airport IFPs which are within 50 nm of the Array. The IFP assessment was completed at a maximum blade tip height of 399 m LAT and has concluded that the Array will not breach the MSA or IFPs of Aberdeen International Airport. These areas provide an altitude at which a minimum of 1,000 ft above the highest obstacle is required for IFR flights.
63. The impact is predicted to be of regional spatial extent, short term (construction phase) duration, continuous with low reversibility (once construction has started). It is predicted that the impact will affect the receptor (low flying operations) directly. The magnitude is therefore considered to be low.

                        Sensitivity of the receptor

64. Low flying operations are deemed to be of high vulnerability, high recoverability, and high value. The sensitivity of the receptor is therefore, considered to be medium.

                        Significance of the effect

65. 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, therefore, be of minor adverse significance, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

66. No aviation, military and communications focussed secondary mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 14.10) is not significant in EIA terms.

                        Operation and maintenance phase

                        Magnitude of impact

67. During the operations and maintenance phase of the Array, floating wind turbines and OSPs could pose a physical obstruction to the flight of aircraft operating in the vicinity of the Array, specifically to aircraft operating at low level. Helicopter operators, the MOD and ATC service providers have been consulted with regard to the potential for the Array to create an obstruction to aviation, military and communications activities conducted in the vicinity of the floating wind turbines and OSPs.
68. A range of designed in measures, in the form of appropriate notification to aviation, military and communications stakeholders, lighting and marking to minimise effects to aviation flight operations would apply to the development of the Array, as included in the commitments set out in Table 14.11   Open ▸ . These commitments will comply with current guidelines and be agreed with the appropriate receptor aviation stakeholders.
69. Pilots are obliged to plan their flying activities in advance and to be familiar with any en-route obstacles they may encounter; however, during flight, weather conditions or operational requirements may necessitate route adjustments. In VMC conditions, pilots are ultimately responsible for seeing and avoiding obstructions such as wind turbines and will be aware through notification procedures of the Array. When operating IMC pilots should be under the control of ATC with an appropriate level of radar service and flying at an altitude which provides the required separation from obstacles below them.
70. The impact is predicted to be of regional spatial extent, long-term duration, continuous and not reversible. It is predicted that the impact will affect the receptor (low flying operations) directly. However, with the designed in measures outlined in section 14.10, the magnitude is therefore considered to be low.

                        Sensitivity of the receptor

71. Low flying operations are deemed to be of high vulnerability, high recoverability, and high value. The sensitivity of the receptor is therefore, considered to be medium.

                        Significance of the effect

72. 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, therefore, be of minor adverse significance, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

73. No aviation, military and communications focussed secondary mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 14.10) is not significant in EIA terms.

                        Decommissioning phase

                        Magnitude of impact

74. During the decommissioning phase, the presence and movement of decommissioning infrastructure may present a potential collision risk to aircraft in the vicinity of the Array and specifically to low flying aircraft. Helicopter operators, the MOD and ATC service providers have been consulted with regard to the potential for the Array to create an obstruction to aviation, military and communications activities conducted in the vicinity of the wind turbines and OSPs.
75. A range of designed in measures, in the form of appropriate notification to aviation, military and communications stakeholders, lighting and marking to minimise effects to aviation flight operations would apply to the development of the Array, as included in the commitments set out under Table 14.11   Open ▸ . These commitments will comply with current guidelines and be agreed with the appropriate aviation, military and communications stakeholders.
76. Pilots are obliged to plan their flying activities in advance and to be familiar with any en-route obstacles they may encounter; however, during flight, weather conditions or operational requirements may necessitate route adjustments. In VMC conditions, pilots are ultimately responsible for seeing and avoiding obstructions such as wind turbines and will be aware through notification procedures of the Array. When operating IMC pilots should be under the control of ATC with an appropriate level of radar service and flying at an altitude which provides the required separation from obstacles below them. It is expected that any mitigation implemented will remain in place until the last wind turbine has been removed.
77. The impact is predicted to be of regional spatial extent, short term duration, continuous and reversible. It is predicted that the impact will affect the receptor (low flying operations) directly. The magnitude is therefore considered to be low.

                        Sensitivity of the receptor

78. Low flying operations are deemed to be of high vulnerability, high recoverability, and high value. The sensitivity of the receptor is therefore, considered to be medium.

                        Significance of the effect

79. 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, therefore, be of minor adverse significance, which is not significant in EIA terms.

                        Secondary mitigation and residual effect

80. No aviation, military and communications focussed secondary mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section 14.10) is not significant in EIA terms.

Wind turbines causing interference to aviation radar systems

81. The operational floating wind turbines in the Array would be theoretically detectable by the NATS Perwinnes PSR systems (also used by air traffic controllers at Aberdeen International Airport to provide an ATS).
82. The operational floating wind turbines in the Array would also be theoretically detectable by the RRH Buchan ADR, and occasional detection cannot be ruled out in the southernmost part of the Array by the RRH Brizlee Wood ADR.
83. Wind turbines detectable by a PSR system might degrade the system by creating false targets, reduce system sensitivity, create radar shadowing behind the wind turbines and saturate the radar receiver leading to clutter potentially concealing real aircraft targets (paragraph 25).

                        Operation and maintenance phase

                        Magnitude of impact

84. Radar LoS modelling results indicate that, due to the location of the Array and the maximum blade tip height of the floating wind turbines, theoretical radar detectability is likely to affect the operations associated of the MOD and NATS. The impact is predicted to be of regional spatial extent, long term duration, continuous and low reversibility. It is predicted that the impact will affect the receptors (NATS, MOD and Aberdeen International Airport) directly. The magnitude is therefore considered to be high.

                        Sensitivity of the receptor

85. The ability of NATS, airport authorities and MOD operators of aviation PSR systems to accurately use their respective radar systems for the provision of an ATS, could be impacted by the presence of wind turbine interference and the production of radar clutter on radar displays. All aviation PSR receptors aim to ensure ‘clutter free’ radar to continue to deliver a safe and effective ATS and to securely monitor UK airspace. NATS operations (including those at Aberdeen International Airport) are deemed to be of high vulnerability, medium recoverability, and high value. The sensitivity of the receptor is therefore, considered to be very high.
86. MOD ADR operations are deemed to be of high vulnerability, low recoverability, and high value. The sensitivity of the receptor is therefore, considered to be very high.

                        Significance of the effect

87. For NATS operations, the magnitude of the impact is deemed to be high, and the sensitivity of the receptor is considered to be very high. The effect will, therefore, be of major adverse significance, which is significant in EIA terms.
88. For the MOD ADR operations, the magnitude of the impact is deemed to be high, and the sensitivity of the receptor is considered to be very high. The effect will, therefore, be of major adverse significance, which is significant in EIA terms.

                        Secondary mitigation and residual effect

NATS

89. In the airspace in which the Array is located, operational acceptance of the effect created is unlikely to be acceptable to all ATC providers without technical PSR mitigation, as portions of airspace may be more important to some ATC establishments than others, due to the role and responsibility of ATC provision allocated to them.
90. In the case of the NATS PSR system impacted (Perwinnes), previous acceptable mitigation of wind turbine impact to this system has been achieved through agreement by NATS of radar blanking and infill. However, there are no other suitable radar systems that do not theoretically detect the Array and would provide suitable infill data to be operationally effective.
91. Any technical ATS PSR mitigation decided upon will be subject to commercial agreement between the Applicant and NATS and will be implemented by radar blanking of the affected areas of the Perwinnes PSR which will selectively remove all wind turbine radar returns. However, all other radar returns in the blanked area will also be removed.
92. To resolve the removal of radar returns through radar blanking, an application to the CAA for an airspace change and the provision of a Transponder Mandatory Zone (TMZ) will remove impact created by the Array to the effected NATS PSR. A TMZ is a defined piece of airspace in which the carriage and operation of a pressure-altitude transponder is mandatory within an aircraft. The creation of a TMZ allows the airspace within and above the development to retain its original classification, yet also allows for enhanced situational awareness for all users and for air traffic controllers. Provision can be made for non-compliant aircraft to gain access to the TMZ; the creation of the TMZ will require regulatory approval by the CAA through an airspace change proposal.
93. This impact is one that industry has substantial experience of resolving and there is no known reason why suitable mitigation will not be agreed for the Array.
94. The MOD, DESNZ, The Crown Estate (TCE) and the Offshore Wind Industry Council (OWIC) workstream ‘Programme B’ has been established working with the Department for Transport (DfT), DESNZ the CAA, and NATS, looking to establish a strategic solution around offshore TMZ and future requirements for offshore aviation Communication, Navigation and Surveillance (CNS). Overall, following application of the proposed secondary mitigation, the magnitude of the impact is deemed to be negligible, and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.

MOD

95. In the case of RRH Buchan ADR, previous acceptable secondary mitigation of wind turbine impact to the MOD ADR systems has been achieved through agreement by MOD of the use of a Non-Auto Initiation Zones (NAIZ). Employment of this mitigation solution will require agreement from the MOD that the air defence task can be maintained with this mitigation in place. Commercial agreement between the Applicant and MOD will be required and once implemented the NAIZ mitigation solutions will be implemented over the Array. If a NAIZ is not suitable to mitigate effect, it is the intention of the Applicant to follow the direction provided in the jointly signed Strategy and Implementation Plan Issue 1 dated September 2021, the output of the MOD’s air defence radar mitigation procurement programme (Programme NJORD) and the opportunity to employ the acceptable mitigation(s). The aim of this Programme is to deliver an enduring technical mitigation(s) across the UK in which the Applicant would seek to potentially use in due course, removing the need for interim mitigations such as NAIZ.
96. The UK Defence and Security Accelerator (DASA) has launched a competition seeking proposals that can provide future offshore wind farm mitigation for UK ADR. The MOD, DESNZ, TCE and the OWIC have formed a Joint Task Force (JTF) whose aim is to enable co-existence of air defence and offshore wind. In September 2021, the task force published a strategy document entitled Air Defence and Offshore Wind, Working Together Towards Net Zero (JTF, 2021)[9] which sets out the process of the development of future technical radar mitigation schemes to mitigate ADR from the impact created by the radar detectability of operational wind turbines. Potential technical radar mitigation solutions have been identified and these systems have demonstrated that they could potentially support wind farm development, the JTF are working towards the procurement of an ADR technical mitigation solution which once deployed will provide an enduring solution.

Engagement with MOD continues with the expectation that, if required, an enduring technical mitigation solution will be agreed, which will reduce the magnitude of the impact; therefore, and when secondary mitigation is in place the residual effect to the impacted MOD ADR systems will be of minor adverse significance, which is not significant in EIA terms.

Future monitoring

97. No aviation, military and communications monitoring to test the predictions made within the impact assessment is considered necessary.