17 Cumulative Risk Assessment

17.1 Increased Vessel to Vessel Collision Risk Resulting from Displacement (Third Party To Third Party)

  1. Any displacement associated with the installation of the Proposed offshore export cable(s) cumulatively with the Array will be spatially limited to the area immediately around the installation vessel activities and temporary in nature. Details of the installation would be promulgated in advance via the usual means including Notice to Mariners and Kingfisher bulletins ensuring awareness will be maximised and facilitating passage planning. Once installation was complete, there would be displacement impact other than any maintenance works requiring surface vessel presence (which will likely be an infrequent event).
  2. Based on the cumulative routeing assessment (section 14.2) which considers all screened in developments, it is anticipated that the majority of vessels will choose to pass inshore of the Array, between Seagreen 1 Offshore Wind Farm and Morven Offshore Wind Farm. Further north, the Flora Floating Offshore Wind Farm may mean that vessels are more likely to pass inshore of the Hywind Offshore Wind Farm, however passing between the Flora Floating Offshore Wind Farm and the Muir Mhor Offshore Wind Farm will also be an option.
  3. Vessels choosing to pass further offshore may use the sea area between the Array and Bellrock Offshore Wind Farm, noting that general consensus during consultation including the hazard workshop was that there was sufficient sea space to accommodate likely users. There is also the option to pass further offshore, between the Campion Offshore Wind Farm and Bellrock Offshore Wind Farm. Any vessels choosing such passage would need to pass either north or south of the Cedar Offshore Wind Farm.
  4. The location of the Aspen Offshore Wind Farm is considered as being unlikely to significantly contribute to cumulative deviations, given that as discussed above most vessels on north/south are likely to pass inshore. 
  5. In addition to the Morven Offshore Wind Farm, the proximity of the Bellrock Offshore Wind Farm means that lighting and marking and also charting will need to be considered cumulatively. This will ensure vessels are aware of the projects and are able to passage plan accordingly.
  6. The frequency of occurrence is considered to be extremely unlikely based on the available sea room, the outputs of the modelling, and consideration of historical incident data. The severity of consequence is considered to be serious. The risk will, therefore, be of tolerable significance. Assuming consultation with the MCA and NLB on the cumulative lighting and marking and charting of the Array and other relevant developments, the risk is considered to be ALARP.

17.2 Displacement from Adverse Weather Routeing

  1. Any displacement associated with the installation of the Proposed offshore export cable(s) cumulatively with the Array will be spatially limited to the area immediately around the installation vessel activities and temporary in nature. Details of the installation would be promulgated in advance via the usual means including Notice to Mariners and Kingfisher bulletins ensuring awareness will be maximised and facilitating passage planning. Once installation was complete, there would be displacement impact other than any maintenance works requiring surface vessel presence (which will likely be an infrequent event). As such no notable cumulative impact on adverse weather routeing is anticipated.
  2. There is in excess of 10 nm of navigable sea area between Seagreen 1 Offshore Wind Farm and Morven Offshore Wind Farm, and therefore there is considered to be sufficient sea room to accommodate any additional transits from vessels choosing an inshore passage as a result of adverse weather. It is considered likely based on the cumulative routeing assessment (section 14.2), that most vessels will choose this routeing option for deviation, passing inshore of both the Morven Offshore Wind Farm and the Salamander Offshore Wind Farm.
  3. Any vessels choosing to pass further offshore will likely use either the sea space between the Array and Bellrock Offshore Wind Farm, or between Campion Offshore Wind Farm and Bellrock Offshore Wind Farm. Any vessels choosing such passage would need to pass either north or south of the Cedar Offshore Wind Farm. However as above, inshore transits are more likely during adverse weather.
  4. The location of the Aspen Offshore Wind Farm is considered as being unlikely to significantly contribute to cumulative deviations, given that as discussed above most vessels on north/south are likely to pass inshore, including during adverse weather. 
  5. In addition to the Morven Offshore Wind Farm, the proximity of the Bellrock Offshore Wind Farm means that lighting and marking and also charting will need to be considered cumulatively. This will ensure vessels are aware of the projects and are able to passage plan accordingly including during adverse weather.
  6. The frequency of occurrence is considered to be extremely unlikely based on the available sea room, the outputs of the modelling, and consideration of historical incident data. The severity of consequence is considered to be serious. The risk will, therefore, be of tolerable significance. Assuming consultation with the MCA and NLB on the cumulative lighting and marking and charting of the Array and other relevant developments, the risk is considered to be ALARP.

17.3 Increased Vessel to Vessel Collision Risk (Third Party to Array Vessels)

  1. Any collision risk associated with the installation or maintenance of the Proposed offshore export cable(s) cumulatively with the Array will be spatially limited to the area immediately around the vessel activities and temporary in nature. Details of the installation and maintenance would be promulgated in advance via the usual means including Notice to Mariners and Kingfisher bulletins ensuring awareness will be increased and facilitating passage planning, thus reducing any collision risk associated with the installation. Any encounters that did occur between a third party vessel and the cable installation vessel would be managed via COLREGs.
  2. All screened in projects are anticipated to implement similar vessel management mitigations to those implemented for the Array, in particular marine coordination and use of safety zones. It is also noted that the production of a VMP and NSP are standard conditions of consent, and that all vessels associated with screened in projects will be required to comply with COLREGs and SOLAS.
  3. During the construction phase, there will be elevated levels of vessels on site and in the general area (noting ports are still to be decided). There may be overlap between the construction phase, and the construction phases of other screened in developments. Ports to be used for other developments are also unknown, however, as above vessel movements will all be managed.
  4. The frequency of occurrence is considered to be extremely unlikely based on the available sea room, consideration of historical incident data, and the embedded mitigation in place to manage project vessel movements and activities. The severity of consequence is considered to be serious. The risk will, therefore, be of tolerable significance, and ALARP.