4. Guidance

International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA) guidance for the marking of man-made offshore structures is contained in document number G1162 (IALA, 2021).
IALA (2021) provides guidance and information to stakeholders such as National Authorities, Lighthouse Authorities, Aviation Authorities and other competent Authorities, Aids to Navigation providers, and the Contractors, Developers and Operators involved with the offshore structures. The marking of offshore structures as defined in IALA (2021) will be considered as a minimum requirement to ensure the safety of navigation in the vicinity of the structures.
The MGN 654 published by the MCA provides recommendations and criteria to be taken into account by Offshore Renewable Energy Installations (OREIs) developers seeking formal consent for marine works regarding navigation safety or emergency response preparedness.
The following sections set out the lighting and marking specifications for the Array during construction, and operation and maintenance phases. The recommendations and proposals made in this LMP will be finalised in consultation with NLB, MCA, CAA and MOD.

5. Marine Navigation Safety

This section provides the minimum lighting and marking requirements for marine navigation safety of OREIs as defined in IALA guidance G1162 (IALA, 2021). It also outlines any proposed site-specific enhancers relevant to lighting, marking, sound signal and radar.
Marine aids to navigation will be provided throughout the lifetime of the Array in accordance with the requirements of the NLB.
Figures showing the confirmed marine lighting and marking for the Array will be included in the version of this LMP submitted for approval post-consent.

Lighting requirements are provided in this section, in accordance with IALA (2021). These are summarised in Table 5.1 Open ▸ .
When considering offshore wind farms, IALA (2021) includes the following structures: meteorological mast, wind turbine and offshore transformer/substation.
IALA (2021) classifies offshore wind farm structures as follows:

Significant Peripheral Structure (SPS), which includes the structures on the corners and other structures on the periphery of the wind farm as decided by the competent authority, normally not exceeding a 3 nm distance;
Intermediate Peripheral Structure (IPS), which includes selected locations on the periphery of the wind farm, normally not exceeding 2 nm separation; and
All other wind turbines not classified as either SPS or IPS.

Table 5.1 Open ▸ provides the requirements for the lighting of offshore structures for marine navigation in accordance with IALA (2021).

The proposed lighting requirements ( Table 5.1 Open ▸ ) have been defined during IALA (2021) and are subject to agreement with the NLB and the MCA.
MCA (2022) states that “SPS will be marked with lights visible from all directions in the horizontal plane. These lights should be synchronized to display simultaneously an IALA “special mark” characteristic, flashing yellow, with a range of not less than five (5) nautical miles. Aids to navigation on individual structures are placed below the arc of the rotor blades, typically at the top of the yellow section”. Also that “(IPS) on the boundary of a wind farm between SPSs will be marked with flashing yellow lights (typically yellow with a 0.5s flash every 2.5s) which are visible from all directions horizontally. The characteristics of these lights areas differ from those displayed on the SPSs, and have a range of not less than two (2) nautical miles. The distance between such IPS or the nearest SPS should not exceed two (2) nautical miles”.
The use of working lights, such as down lighting on ladders and access platforms, must not reduce the visibility of marking lights. Furthermore, it is recommended they are switched off when personnel are not working on, or at, the structure (IALA, 2021).
Marine navigation lighting will be remotely controlled by the Supervisory Control and Data Acquisition (SCADA) system and will be visible at night and turned off during the day.

IALA (2021) recommends that wind turbines, meteorological masts and offshore transformer/substation are painted yellow from the level of HAT up to at least 15 m.
MCA (2024) requires that each of said structures display identification panels with black letters or numbers. ID numbers must be clearly readable by an observer stationed three metres above sea level at a distance of at least 150 metres from the turbine. Each ID number plate shall be illuminated by a low intensity light visible from a vessel thus enabling the structure to be detected at a suitable distance to avoid a collision. Lighting for this purpose must be hooded or baffled so as to avoid unnecessary light pollution or confusion with navigation marks.

All wind turbines foundations to be painted yellow (RAL 1023 or similar) up to the interface level between the foundation and tower.
All OSP foundations to be painted yellow (RAL 1023 or similar) from the level of HAT up to at least 15 m above HAT.
All wind turbines and OSPs shall have identification plates consisting of a unique alphanumeric identifier of black letters and numbers. Characters shall be at least 1 m in height such that they are clearly readable by an observer stationed three metres above sea level at a distance of at least 150 metres from the turbine Three identification plates shall be positioned around the working platform so that at least one identification plate is visible from every direction. Each identification plate will be illuminated by a low-intensity light, so it is clearly readable at night. Lighting will be hooded or baffled so as to avoid unnecessary light pollution or confusion with navigation marks.
Any specific requirements in relation to floating structures will be addressed post-consent and included in the final version of this LMP submitted for approval.

Details/information regarding cumulative lighting and marking requirements (following discussion with NLB) will be confirmed post-consent.

IALA (2021) provides guidance on the marking of offshore structures by using Hazard Warning Signals (HWS), with the following recommended requirements:

located not less than 6 m and not more than 30 m above HAT;
have a minimum range of 2 nm;
have the character Mo (U) 30 s with a minimum duration for the short blast of 0.75 s; and
are operated when the meteorological visibility is 2 nm or less. For this, a visibility detector will typically be used.

The Array shall have sound signals installed on the wind turbines along the perimeter of the Array, likely on the SPS. The exact number, locations and minimum spacing of sound signals to be used at the Array will be determined once the wind turbine layout has been finalised prior to construction, however.