Offshore Structures and Their Marking Requirements


Offshore Structures and Their Marking Requirements

Offshore Structures and Their Marking Requirements

By:Sealite | March 10, 2021

An offshore structure is defined as any structure that is fixed into position and extends above or below the surface of the sea. Some examples include man-made drilling platforms, oil wells, dredging operations, offshore wind farms, ocean data platforms or aquaculture farms.

When is marking required?

There is a requirement that all offshore structures need to be marked. Whether they are installed as a temporary measure or more permanently, they are a potential hazard and pose a risk to the safety of mariners.

Offshore structures require adequate marking, not only once commissioned but also during the construction and decommissioning phases of the project. The completion of a risk assessment helps to identify the marking requirements for the structure and is based on the level of risk for the lifetime of the Aid to Navigation (AtoN).

In areas of high traffic density, additional services such as guard ships or temporary vessel traffic services (VTS) may also be needed to ensure operator safety.

How should offshore structures be marked?

IALA provides recommendations in guideline RO139 “The Marking of Man Made Offshore Structures”. Marking requirements include, but are not limited to:

  • The use of IALA-compliant AtoNs
  • Achieving 99% availability (IALA Category 2)
  • Marine lanterns with flash synchronisation
  • Remote monitoring for traceability
  • The identification of exclusion or safety zones
  • Site identification in Maritime Safety Information (MSI), nautical charts and publications

IALA Recommendation R0139 provides marking guidance by structure type. The document is free to download from the IALA website.

What type of buoy mark should be used?

Buoy marks are used to deliver a specific message and their use is dependent on the application. They are considered to be the traffic lights of the sea and in 1976, their use was harmonised under the IALA Maritime Buoyage System.

Navigational buoys provide a visual daytime aid to mariners and can also be used as a platform to affix additional navigational equipment. This can include marine lanterns, power supplies, batteries and MET Data equipment.

The IALA recommendation R1001 specifies the buoy colour, shape, and topmark. If fitted, it also stipulates the colour of the marine lantern and flash character. The types of buoy marks used to identify offshore structures include:

Type Indicates Used To
Lateral marks Edge of a channel Mark channel between structures
Cardinal marks Position of a hazard and direction to safe water Direct traffic away from a structure
Isolated Danger mark Hazard to shipping Mark a new/underwater hazard
Safe Water marks End of a channel Mark safe water ahead
Special marks Feature Mark aquaculture, speed restriction, mooring area
Emergency Wreck mark New wreck Identify new wreck not yet listed in maritime documents

The size and mooring requirements for buoys are subject to depth of water, site and tidal conditions.

The IALA Maritime Buoyage System is split into Region A and Region B. Recommendation R1001 is free to download from the IALA website.


AtoN lighting requirements

Marine lanterns provide added visibility at night or during poor weather conditions. They can incorporate options for monitoring and control such as GSM, AIS, RACON and SATCOM. These added features help AtoN managers to keep track on the status of their connected AtoN devices. They can also provide real time notifications, should a critical asset be damaged or run adrift.

On a case-by-case basis, National Authorities will use the IALA Recommendation and any additional risk assessments to help identify a site’s marking requirements. It may not be essential to light every floating AtoN, but rather use them to indicate the perimeter of exclusion or safety zones.

When should an offshore structure be lit?

Every fixed offshore structure under IALA recommendation RO139 should have the fitment of a AtoN light. This is also a requirement of the civil aviation industry, where separate regulations apply to the painting of the obstacle and the use of obstruction lighting.

Civil aviation regulations are region specific and relate to the type, size and height of the obstacle.

For further guidance visit the obstruction page on the Avlite website and check with your local aviation authority to determine what is required to make your structure compliant.