Executive Summary
The Guidance: Marine Guidance Note MGN 372 Amendment 1 (M+F), published by the UK Maritime and Coastguard Agency (MCA), provides guidance to mariners on safe navigation in the vicinity of UK Offshore Renewable Energy Installations (OREIs).
The Navigational Environment: Some OREI developments can cover very large areas, with MGN 372 noting examples approaching 400 square nautical miles, and may comprise fixed or floating wind turbines and other renewable energy installations. Key considerations identified by the MCA include radar interference within turbine arrays, visual obscuration of vessels, and the movement of floating infrastructure in varying metocean conditions.
The Operational Challenge: MGN 372 does not instruct wind farm operators to implement a specific digital system; rather, it provides the navigational context in which field operations take place. For developers, duty holders, and Marine Coordination Centres (MCCs), operating in complex OREI environments creates the practical challenge of keeping site-specific restrictions, procedures, and vessel movements coordinated during live field operations.
The Operational Layer: Technology platforms like GreenHulls SOMS are designed to support field operations as a technology-enabled coordination layer, providing a shared operational view and structured workflows across asset teams, attending charter vessels, and shoreside marine coordination.
In November 2022, the UK Maritime and Coastguard Agency (MCA) published Marine Guidance Note MGN 372 Amendment 1 (M+F): Safety of Navigation: Guidance to Mariners Operating in the Vicinity of UK Offshore Renewable Energy Installations (OREIs).
The guidance addresses the expansion of offshore renewable energy across UK waters, where operational wind farms, as well as those in development across the North Sea, East Irish Sea, Firth of Forth, Moray Firth, and Celtic Sea, present multi-faceted navigational environments.
While voyage planning and navigation are managed by vessel masters under SOLAS Chapter V (Regulation 34), MGN 372 also raises practical questions for offshore wind developers, duty holders, and Marine Coordination Centres (MCCs). It highlights the operational environment in which construction, routine inspection, and major maintenance take place.
1. What Does MGN 372 Amendment 1 Cover?
MGN 372 Amendment 1 sets out the physical parameters, lighting and marking standards, and navigational factors associated with UK offshore wind farms, floating wind arrays, and wave and tidal energy convertors.
Array Parameters and Markings
Scale and Spacing: Some OREI developments can cover very large areas, with MGN 372 noting examples approaching 400 square nautical miles. Turbine spacing varies according to the characteristics and design of the installation, including considerations such as turbine size and wake effects.
Foundations: Fixed foundation turbines (monopile, jacket, gravity base, suction bucket, tripod) are generally installed in water depths of less than 60 metres, while floating turbines (spar, semi-submersible, tension leg platform) operate in deeper waters secured by catenary, semi-taut, or taut anchor moorings.
Aids to Navigation (AtoN): Significant Peripheral Structures (SPS) on array boundaries display synchronised flashing yellow lights visible for at least 5 nautical miles. Intermediate Peripheral Structures (IPS) display flashing yellow lights visible for 2 nautical miles. Individual turbines are marked with discretely lit alphanumeric identifiers visible from a range of at least 150 metres.
Navigational Considerations Identified by the MCA
MGN 372 highlights several specific physical and electronic factors that affect navigation inside and around OREI boundaries:
Radar Interference and Target Masking: MCA-cited trials found that radar performance can deteriorate as vessels approach turbine arrays, with strong turbine echoes, multiple reflections, and side-lobe effects potentially making smaller targets more difficult to detect or discriminate.
Vessel Obscuration: High traffic densities of Crew Transfer Vessels (CTVs), Service Operation Vessels (SOVs), jack-up barges, cable-layers, and unmanned survey vessels operate within array boundaries. Turbine structures and foundations can physically obscure smaller attendant craft or passing vessels, particularly at night or in reduced visibility.
Floating OREI Dynamics: Floating turbines and wave or tidal energy devices introduce specific navigational considerations, including degrees of movement on moorings and contingency risks such as devices or moorings breaking loose.
Hydrodynamic and Aerodynamic Effects: Wind turbines can create wind-shadow and turbulent wake effects downwind, while structures and foundations can influence local water flow and vessel handling.
2. What MGN 372 Means for Marine Coordination and Duty Holders
For larger vessels where adequate safe water exists, MGN 372 notes that it is prudent in voyage planning to set tracks at least 2 nautical miles clear of turbine fields. However, attendant charter vessels such as CTVs, SOVs, and survey craft may need to enter array boundaries to perform construction, maintenance, and transfer activities.
For offshore wind operators and marine coordination teams, the guidance raises practical questions about how navigational information, site-specific restrictions, and vessel activity are coordinated during live field operations.
Duty holders and marine superintendents should evaluate five practical operational questions:
Real-Time Visibility: Given that marine radar performance can degrade inside turbine arrays, do control rooms, marine coordinators, and shoreside teams share a common operational view of vessel positions and active work windows?
Safety Zone Tracking: Under the Energy Act 2004 framework, temporary Safety Zones may be established for specified activities. Is there a reliable method to track active safety zone perimeters and stage clearances across the array?
Communication Protocols: Are work orders, transfer requests, and location updates managed through protocols that allow bridge teams to maintain safe positioning without unnecessary administrative distraction?
Emergency Coordination: In extreme emergencies, can the Marine Coordination Centre quickly verify asset status and support communications with HM Coastguard and the wind-farm operations control room?
Operational Assurance: Are there clear records of pre-entry clearances, technician transfers, and operational hold points that can support marine assurance, review, and continuous improvement?
3. Temporary 500m Safety Zones in Offshore Wind
Under the Energy Act 2004 framework, temporary Safety Zones of up to 500m radius (measured from the outer edge of surface infrastructure) may be established for specified offshore renewable energy activities, subject to the relevant statutory application process.
It is an important operational distinction that Safety Zones are granted for specific activities (such as construction, major maintenance, or decommissioning) and are not established around entire wind farm arrays.
Where a statutory Safety Zone is in force, navigation within it is subject to applicable statutory restrictions and exceptions (such as stress of weather or distress). Managing these temporary safety zones across an expanding field places a premium on clear coordination to ensure charter vessels, guard craft, and shoreside coordinators share consistent status information across the array.
4. From Navigational Guidance to Live Field Operations
The challenge is not simply knowing where vessels are. It is connecting vessel movements with the operational status of assets, work activities, site restrictions, operational checks, hold points, and the decisions that need to be made before an activity progresses.
Offshore operators typically have Safety Management Systems (SMS), marine procedures, chartering requirements, and assurance processes that define how these activities should be managed. The practical challenge is maintaining that structure when multiple vessels, assets, work scopes, and teams are operating simultaneously in the field.
This is where a technology-enabled operational coordination layer can provide value. GreenHulls SOMS is designed to connect established procedures and operational checks with live field execution, providing a shared operational view across offshore assets, attending vessels, and shoreside teams through three core capabilities:
Communication: Provides a shared operational view across vessels, offshore assets and shoreside teams to help reduce fragmented communication and support a common operating picture.
Coordination: Helps align vessel positioning, active work scopes and site restrictions across marine coordinators, asset teams and attending vessels during live operations.
Workflow: Connects established safety procedures, operational checks and hold points with live field execution through structured workflows.
5. How GreenHulls Supports and Does Not Replace Existing Marine Controls
To maintain clear regulatory and operational boundaries, a technology-enabled coordination layer must be positioned correctly within the field management structure:
Safety Management System (SMS): GreenHulls SOMS does not replace your written SMS. It is designed to support the execution of SMS controls by connecting established procedures and operational checks with live field workflows.
Statutory Requirements & MCA Guidance: GreenHulls SOMS does not replace statutory duties, SOLAS requirements, or COLREGs compliance. It can support compliance assurance by providing operational information that can be used for review and evidence.
Master & OIM / MCC Authority: GreenHulls SOMS does not replace the authority or responsibilities of the Vessel Master, OIM, or Marine Coordinator. It does support command decision-making by delivering a clear, shared visual picture to inform operational choices.
Marine Coordination Centres: GreenHulls SOMS does not replace Marine Coordination Centres or Vessel Traffic Services. It can support live operational assurance by providing visibility of operational activity during field operations.
"The SMS and marine guidance define the requirements and procedures. GreenHulls helps connect those procedures to live execution in the field."
Conclusion
MGN 372 Amendment 1 provides important guidance for safe navigation around UK offshore renewable energy installations. For offshore wind developers, duty holders, and marine coordination teams, responding effectively means evaluating whether field procedures, bridge communication channels, and vessel tracking tools support safe execution in real time.
By connecting established procedures, operational clearances, and vessel activity through a shared operational picture, field operators can help reduce operational risk, support better coordination, and strengthen assurance across offshore campaigns.
Explore GreenHulls SOMS
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To discuss your field management requirements or schedule a technical walkthrough with our marine operations specialists, visit greenhulls.com or contact the GreenHulls team directly.