UK MCA: Guidance on navigational safety and offshore installations

Recommendations in this guidance note should be taken into consideration by all OREI (Offshore Renewable Energy Installations) developers seeking formal consent for marine works. Failure by developers to give due regard to these recommendations may result in objections to their proposals on the grounds of navigational safety or emergency response preparedness.

OREI developers should evaluate the impacts of their projects and comply with the recommendations during all phases of:

1. planning;
2. construction;
3. operation; and,
4. decommissioning.

Planning stage – Prior to consent

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Early engagement with MCA and relevant navigational stakeholders e.g. during the scoping stage, is key for early identification of potential areas of concern that may require close attention. Developers are required to produce an NRA in the planning stage as part of their application for development consent. The MCA’s “Methodology for Assessing the Marine Navigational Safety & Emergency Response Risks of Offshore Renewable Energy Installations (OREI)” provides guidance for producing an NRA, including a template. It is based on IMO Formal Safety Assessment and the latest version is available on the MCA’s website. Any substantial changes to the project that impacts on shipping and navigation may require relevant NRA updates.

Potential navigational or communications impacts or difficulties caused to mariners or emergency response services, using the site area and its environs, should be assessed. Assessments should be made of the consequences of ships deviating from normal routes to avoid proposed sites, including smaller vessels e.g. domestic, coasters, recreational or fishing vessels, entering shipping routes with larger vessels. Special regard should be given to evaluating situations which could lead to safety of navigation being compromised e.g. an increase in ‘end-on’ or ‘crossing’ encounters, reduction in sea-room or water depth for manoeuvring, leading to choke points, etc.

Issues that could contribute to a marine casualty leading to injury, death or loss of property, either at sea or amongst the population ashore, or damage to the marine environment, should be highlighted as well as those affecting emergency response.

Consultation with national search and rescue authorities should be initiated as early as possible and consideration given to the types of aircraft, vessels and equipment which might be used in emergencies. This should include the possible use of OREI structures as emergency refuges and any matters that might affect emergency response within or close to the OREI.

An MGN checklist is available on the MCA website as an aid for developers when completing and submitting their NRA to ensure all guidance has been considered and addressed.

NRA – Tides, Tidal Streams, and Weather

It should be determined whether:

1. Current maritime traffic flows and operations in the general area are affected by the depth of water in which the proposed installation is situated at various states of the tide i.e. whether the installation could pose problems at high water which do not exist at low water conditions, and vice versa.
2. The set and rate of the tidal stream, at any state of the tide, has a significant effect the handling of vessels in the area of the OREI site.
3. The maximum rate tidal stream runs parallel to the major axis of the proposed OREI site layout, and if so, its effect on vessel handling and manoeuvring.
4. The set is across the major axis of the OREI layout at any time, and, if so, at what rate.
5. In general, whether engine and/or steering failure, or other circumstance could cause vessels to be set into danger by the tidal stream. This should include unpowered vessels and small low speed craft.
6. The structures themselves could cause changes in the set and rate of the tidal stream.
7. The structures in the tidal stream could be such as to produce siltation, deposition of sediment or scouring, affecting navigable water depths in the OREI area or adjacent to the area.
8. The site, in normal, bad weather, or restricted visibility conditions, could present difficulties or dangers to all vessels that might pass through or in close proximity to it
9. The structures could create problems in the area for vessels under sail, such as wind masking, turbulence or sheer.
10. In general, taking into account the prevailing winds for the area, whether engine failure or other circumstances could cause vessels to drift into danger, particularly if in conjunction with a tidal set such as referred to above.

Development consent

The MCA will expect all appropriate aspects of this MGN and the Methodology document to be considered and adequately addressed through the MGN Checklist and submitted as part of the consent application. Any aspects missing or inadequately addressed to the satisfaction of MCA may result in delays or objection to an application.

In order to make an application, developers should aim to get agreement from all relevant navigation stakeholders for ensuring risks are assessed as ALARP and that risk mitigation measures are agreed.

Post-consent – construction and operation phases

In the UK all vessels have freedom to transit through OREIs, subject to any applied safety zones, and their own risk assessments, which should take account of factors such as vessel size, manoeuvrability, environmental factors and competency of the Master and crew. MGN 372 (or subsequent update) provides further guidance on navigation in and around OREIs.

Decommissioning

• To minimize risks to mariners and SAR Operations there is an expectation that all infrastructure above the seabed and the sea surface will be removed. In the time between when the installation ceases to be operational and its removal, appropriate mitigation measures must be applied.
• An agreed and updated ERCoP must be in place prior to the removal of any offshore infrastructure.
• In order to confirm the seabed has been returned as close to its original profile once all, or some, of the infrastructure, has been removed as required, a hydrographic survey is required of the cable route(s) and the installed generating assets area.

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