14.12. Cumulative Effects Assessment

14.12.1. Methodology

  1. The Cumulative Effects Assessment (CEA) assesses the impact associated with the Array together with other relevant plans, projects and activities. Cumulative effects are defined as the combined effect of the Array in combination with the effects from a number of different projects, on the same receptor or resource. Further details on CEA methodology are provided in volume 1, chapter 6.
  2. 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 Array 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, impact-receptor pathways and the spatial/temporal scales involved.
  3. In undertaking the CEA for the Array, it should be noted 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 Array. Therefore, a tiered approach has been adopted which 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 Array CEA employs the following tiers:
  • Tier 1 assessment – Array with Proposed offshore export cable corridor(s) and Proposed onshore transmission infrastructure, and projects which became operational since baseline characterisation, those under construction and those with consent application(s) submitted but not yet determined;
  • Tier 2 assessment – All plans/projects assessed under Tier 1, plus those projects with a Scoping Report;
  • Tier 3 assessment – All plans/projects assessed under Tier 2, which are reasonably foreseeable, plus those projects likely to come forward where an Agreement for Lease (AfL) has been granted.
  1. For the purposes of the EIA process in the assessment of the creation of a physical obstacle to aircraft operations , the cumulative effect to aviation, military and communications has been assessed within 40 km from the Array, which is considered to be the maximum range where the creation of an aviation obstacle to fixed wing and rotary aircraft operating offshore may occur although some impacts are likely to be localised to the Array.
  2. For the purposes of this chapter, the assessment of wind turbines causing interference on aviation radar systems (including PSR and ADR), the cumulative effect to aviation, military and communications has been assessed within 100 km from the Array, which is considered to be the maximum range where aviation, military and communications cumulative effects may occur although some impacts are likely to be localised to the Array due to the unmitigated effect created by the detection of operational wind turbines.
  3. It should be noted that the Proposed offshore export cable corridor(s) and Proposed onshore transmission infrastructure have been scoped out of the CEA for aviation, military and communications as there is no pathway for cumulative effect.
  4. The specific projects scoped into the CEA for aviation, military and communications are outlined in Table 14.12   Open ▸ .
Table 14.12:
List of Other Projects and Plans Considered within the CEA for Aviation

Table 14.12: List of Other Projects and Plans Considered within the CEA for Aviation

 

14.12.2. Maximum Design Scenario

Table 14.13:
Maximum Design Scenario Considered for Each Impact as part of the Assessment of Likely Significant Cumulative Effects on Aviation, Military and Communications

Table 14.13: Maximum Design Scenario Considered for Each Impact as part of the Assessment of Likely Significant Cumulative Effects on Aviation, Military and Communications

 

14.12.3. Cumulative Effects Assessment

  1. An assessment of the likely significance of the cumulative effects of the Array upon aviation, military and communications receptors arising from each identified impact is given below. Certain impacts assessed for the Array alone are not considered in the cumulative assessment due to:
  • The highly localised nature of the impacts (i.e. they occur entirely within the Array).
  • Management measures in place for the Array will also be in place on other projects reducing their risk of occurring.
  • Where the potential significance of the impact from the Array alone has been assessed as negligible.
  • A lack of data or confidence in data preventing meaningful assessment (i.e. Tier 3).
  1. The MDSs identified in Table 14.13   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 Array EIA Report as well as the information available on other projects, plans and activities (see volume 3, appendix 6.4), to inform the MDS. Effects of greater adverse significance are not predicted to arise should any other development scenario, based on details within the PDE (e.g. different wind turbine layout), to that assessed here, be taken forward in the final design scheme.

CREATION OF PHYSICAL OBSTACLE TO AIRCRAFT OPERATIONS (including Airborne Search and Rescue (SAR) operations and Low Flying aircraft

  1. The construction, operation and maintenance, and decommissioning phases of the Array floating wind turbines, and Tier 1, 2 and 3 projects/plans in Table 14.12   Open ▸ , will lead to the creation of a physical obstacle to aircraft operations. The MDS is represented by the 130 floating wind turbines with a maximum blade tip height of 399 m above LAT and is summarised in Table 14.13   Open ▸ .
  2. 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 and are outlined in paragraph 61 explains pilots’ obligations for route planning and avoidance of enroute obstructions.
  3. For the purposes of this Array EIA Report chapter, this cumulative impact has been assessed within 40 km from the Array, which is considered to be the maximum range where the creation of an aviation obstacle to fixed wing and rotary aircraft operating offshore may occur although some impacts are likely to be localised to the Array. Tier 1, 2 and 3 projects/plans are listed in Table 14.12   Open ▸ .

                        Tiers 1/2/3

                        Construction phase
Magnitude of impact
  1. There is potential for cumulative effect as a result of construction activities associated with the Array.
  2. Aviation operations in the UK are highly regulated. The Array will be located in airspace where the provision of an ATS is routine. The same rules of the air which maintain a safe operating environment in the current baseline will apply in the northern North Sea off the coast of Angus, Kincardineshire and Aberdeenshire during all phases of the Array and other projects considered in the cumulative assessment; the provision of an ATS will not be affected.
  3. The cumulative impact is predicted to be of regional spatial extent, short term duration, continuous (temporal overlapping developments) with low reversibility once construction has started. It is predicted that the impact will affect the receptor directly. The magnitude is therefore, considered to be low.
Sensitivity of receptor
  1. At times of sufficient visibility VMC pilots are ultimately responsible for seeing and avoiding obstructions such as wind turbines and other infrastructure and will be aware through notification procedures of the projects. When flying in low visibility IMC pilots will be operating above the MSA and utilising on board systems which detects obstructions and be under the control of ATC with an appropriate level of radar service.
  2. 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 activities conducted in the vicinity of the floating wind turbines and OSPs.
  3. Low level flight operators’ ability to continue using the northern North Sea airspace is deemed to be of high vulnerability, high recoverability and high value. The sensitivity of the receptor is therefore, considered to be medium.
Significance of effect
  1. Overall, the magnitude of the cumulative effect is deemed to be low, and the sensitivity of the receptor is considered to be medium. The cumulative effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
Further mitigation and residual effect
  1. No further aviation, military and communications 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
  1. The cumulative impact is predicted to be of regional spatial extent, long term duration, continuous (temporal overlapping developments) and low reversibility. It is predicted that the impact will affect the receptor (low flying operations) directly and consented offshore wind farms considered in the CEA ( Table 14.12   Open ▸ ) will incorporate/adopt similar warning/notification designed-in measures ( Table 14.11   Open ▸ ). The magnitude is therefore, considered to be low.
Sensitivity of receptor
  1. As discussed in paragraphs 114 and 115, low level flight operators’ ability to continue using the northern North Sea airspace is deemed to be of high vulnerability, high recoverability and high value. The sensitivity of the receptor is therefore, considered to be medium.
Significance of effect
  1. Overall, the magnitude of the cumulative impact is deemed to be low, and the sensitivity of the receptor is considered to be medium. The cumulative effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
Further mitigation and residual effect
  1. No further aviation 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
  1. The cumulative impact is predicted to be of regional spatial extent, short term duration, continuous (temporal overlapping developments) and low reversibility once the decommissioning process has commenced. It is predicted that the impact will affect the receptor (low flying operations) directly. The magnitude is therefore, considered to be low.
Sensitivity of receptor
  1. As discussed in paragraphs 114 and 115, low level flight operators’ ability to continue using the northern North Sea airspace is deemed to be of high vulnerability, high recoverability and high value. The sensitivity of the receptor is therefore, considered to be medium.
Significance of effect
  1. Overall, the magnitude of the cumulative impact is deemed to be low, and the sensitivity of the receptor is considered to be medium. The cumulative effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Further mitigation and residual effect

  1. No further aviation, military and communications 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

  1. The operational floating wind turbines in the Array and the majority of the Tier 1, 2 and 3 projects/plans in Table 14.12   Open ▸ would be theoretically detectable to some degree by the NATS Perwinnes PSR system (also used by air traffic controllers at Aberdeen International Airport to provide an ATS).
  2. In addition, the operational floating wind turbines in the Array and the majority of the Tier 1, 2 and 3 projects/plans in Table 14.12   Open ▸ would be theoretically detectable to some degree by the RRH Buchan ADR; and occasional detection cannot be ruled out from the RRH Brizlee Wood ADR.
  3. 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).
  4. The ability of NATS, airport authorities and MOD operators of aviation PSR and ADR 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.
  5. For the purposes of this Array EIA Report chapter, this cumulative impact to aviation radar has been assessed within 100 km from the Array, which is considered to be the maximum range where radar cumulative effects may occur although some impacts are likely to be localised to the Array due to the unmitigated effect created by the detection of operational floating wind turbines. The Tier 1, 2 and 3 projects/plans are listed in Table 14.12   Open ▸ .
                        Operation and maintenance phase
Magnitude of impact

NATS

  1. The cumulative impact to NATS is predicted to be of limited regional spatial extent (due to maximum range coverage restriction of the NATS Perwinnes PSR), long-term duration, continuous (with extensive temporal overlapping developments) and low reversibility. It is predicted that the impact will affect the receptors (NATS and Aberdeen International Airport) directly. The magnitude is therefore considered to be high.

MOD

  1. The cumulative impact to the MOD is predicted to be of regional spatial extent (due to wide-ranging maximum range coverage), long term duration, continuous (with extensive temporal overlapping developments) and low reversibility. It is predicted that the impact will affect the receptor (MOD) directly. The magnitude is therefore considered to be high.
Sensitivity of receptor
  1. Theoretical radar LoS analysis for the NATS Perwinnes PSR together with theoretical detection of the operational floating wind turbines by the MOD ADR systems at Buchan and to a lesser extent Brizlee Wood indicates that the operational Array floating wind turbines with a tip height of 399 m above LAT would be considered to be detectable (by varying degrees) to the PSR and ADR systems. It is likely that those consented and operational wind farms included in the CEA are already mitigated against the effect to aviation radar through non-objection or agreements with NATS and/or the MOD leading to a withdrawal of objection. Unmitigated, the potential cumulative effect created by the detection of operational Array floating wind turbines will be to potentially add to radar screen clutter that presently may be operationally managed by the aviation stakeholder, potentially leading to an increase in the individual signal processing demands of the predicted affected aviation radar systems.
NATS
  1. NATS operations are deemed to be of medium vulnerability, medium recoverability, and high value. The sensitivity of the receptor is therefore, considered to be very high.
MOD
  1. 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 effect
NATS
  1. Overall, the magnitude of the cumulative impact to NATS is deemed to be high, and the sensitivity of the receptor (NATS and Aberdeen International Airport) is considered to be very high. The cumulative effect will, therefore be of major adverse significance, which is significant in EIA terms.
MOD
  1. Overall, for the MOD the magnitude of the cumulative 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.
Further mitigation and residual effect
  1. 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, as part of OWIC Programme A, 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.
NATS
  1. The airspace in which the Array is located, operational acceptance of the effect created is unlikely to be acceptable to all ATC providers within the whole regional airspace environment, 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.
  2. In the case of NATS PSR systems impacted (Perwinnes) the secondary mitigation described in paragraphs 89 to 94 will be agreed with NATS to reach a mutually agreeable technical solution (reducing the magnitude of the impact), and it is expected that similar measures would be agreed in regard to other project/plans in Table 14.12   Open ▸ adversely affecting NATS PSR assets, along with modified process and procedures in the provision of the ATS in the region.
  3. Overall, following application of secondary mitigation, the magnitude of the impact is deemed to be negligible, and the sensitivity of the receptor is considered to be very high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
MOD
  1. In the case of MOD ADR systems impacted (RRH Buchan and to a degree, in the south of the region, RRH Brizlee Wood) the mitigation described in paragraphs 95 to 96 will be agreed with relevant impacted aviation stakeholders (reducing the magnitude of the impact), and it is expected that similar measures would be agreed in regard to other project/plans in Table 14.12   Open ▸ adversely affecting MOD ADR assets, along with modified procedures in the provision of the ATS in the region.
  2. Overall, following application of secondary mitigation, the magnitude of the impact is deemed to be negligible, and the sensitivity of the receptor is considered to be very high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.