cable awareness

Why avoid submarine cables?
It is extremely dangerous to attempt to bring on board a cable fouled in fishing gear. A cable is under considerable tension; cutting or breaking the cable could cause serious or even fatal injury if it whips free.

Modern cables can carry very high voltages that can prove lethal if they are cut, or if broken cable ends are brought on board. The weight of cables also affects the stability of smaller vessels. They risk sinking if they attempt to raise a cable from the seabed. Loss of vessel and lives has resulted under these circumstances.

Loss of expensive gear, time and often a valuable catch can occur when fishing gear fouls a submarine cable. Damage to modern cables causes serious disruption to communications affecting trade, international affairs and safety at sea.

There are severe penalties for wilfully or negligently damaging a submarine cable. Under Commonwealth legislation, the vessel skipper and/or any person deliberately or recklessly interfering with a submarine cable may be penalised with a fine or imprisonment - or both. Civil damages claims by the owners of the cable against the vessel owner/operator for repairs and loss of revenue can run into tens of millions of dollars. Vessels and their gear may be impounded.

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What is done to reduce damage?
Alcatel-Lucent Submarine Networks use a variety of initiatives to reduce the risk of damage to submarine cables from fishing activities. They include from installation through to maintenance:

  • Sounding surveys of proposed cable routes to locate topographic irregularities to be avoided.
  • Side Scan Sonar surveys of proposed cable routes to identify wrecks and obstructions.
  • Consultation with the fishing community and authorities during the selection of the route and before laying cables.
  • Research on fishing gear design and maintenance practices.
  • Armouring of cables in vulnerable areas.
  • Burial of cables in vulnerable areas where possible.
  • Education and awareness programmes.
Distribution of free information and cable warning charts.

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How are submarine cables broken?
Cable breaks occur when fishing gear is towed across or anchored close to or across submarine cables. They can also be broken when a ship's anchor is dropped directly onto them or drags across.

Fishing-related damage may also be caused by trawl otter-boards, beam trawls, scallop dredges, clam dredges or net anchors. These are used directly on the seabed and in the cases of dredges and net anchors, actually penetrate the seabed. When such gear is towed across a cable, problems will occur.

Tension breaks can also occur when cables are fouled by fishing gear. This type of damage may not involve the cable being dragged to the surface. If the cable is fouled and broken by towed gear, one end of it can remain entangled and be dragged on board the fishing vessel.

Even if a vessel is equipped with strong lifting equipment, cables must NOT be brought to the surface intact and attempts must NOT be made to cut the cable and free the fishing gear.

Cable can also be damaged when shoes on beam trawls, scallop dredges, the leading edge of otter boards, or the knife on a clam dredge cut through armour wires and cable insulation. Where the cable armour has been previously damaged, the potential for a snag with resulting extensive damage to cable and gear is increased.

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How do you avoid cables?
Considering the possibility of positioning inaccuracies and repaired cables section deviations, the fishing community are advised to keep towed gear a minimum distance of one nautical mile from either side of charted cables. For safe navigation and the avoidance of vital submarine cables, the most recent charts should always be available on the fishing vessel.

The submarine cables are clearly identified on all charts used for navigation in the Atlantic. The international symbol for an active submarine cable is a wavy line coloured magenta or black.

In general the accuracy with which cables are laid varies inversely to the distance from land Navigation on cable ships is of a high standard but is limited to the techniques available when the cable was installed. Cables laid in the early 1970s, before satellite navigation became commonplace could be up to one nautical mile (nm) out of charted position.

With the use of satellites and other sophisticated navigational electronic aids, the positional accuracy of recently-laid cables is usually better than 0.5 nm.

However despite this high accuracy during laying, the cable may now be re-laid away from the original charted position due to cable repairs having been required subsequent to the original cable lay.

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Why are cables vulnerable to damage?
Many people incorrectly assume that cables lay flat and straight on the seabed and are not an obstruction to properly maintained, bottom-towed gear.

However, despite the extensive precautions taken by cable owners during the laying of submarine cables, seabed irregularities may result in unavoidable cable suspensions occurring. Where the cable is suspended, the chances of damage are significantly greater.

During repair work, when a new section is spliced in, it is necessary for the repair ship to install an amount of cable approximately equal to twice the water depth. Once a cable has been repaired, the location becomes vulnerable to further damage, as the excess cable may, despite all possible precautions being observed, form loops and stand proud of the seabed.

Cable burial can only be used where the seabed is geologically suitable and tide and current conditions are favourable. These areas don't always correspond to popular fishing grounds. Technology limitations also mean that burial is not always practical in water depths greater than 1000 metres.

Even when cable is buried below the seabed for its protection, it can still be damaged when equipment such as a clam dredge penetrates the seabed on each drag, or where dredges have made successive passes over the same area.

If a buried cable has been previously fouled and pulled up out of the seabed, it becomes even more vulnerable even if it wasn't damaged.

Despite careful route selection, armouring and laying procedures for cables, fishing areas change as fish migrate or as resources are depleted and new fishing grounds may appear over existing cable routes. Experience has shown that even heavy armour does not always provide cables with sufficient protection, especially where heavy trawl gear or anchored gear is used.

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What do I do if my fishing gear fouls on a cable?
When a cable gets accidentally entangled, great care needs to be taken when attempting to free the fouled gear. Comparatively little pressure is required to penetrate the insulation of a cable. When this happens, water will reach the centre conductor and render the cable unusable -even though it may not be broken.

If you believe gear cannot be freed without risk or damage to the cable, the gear should be abandoned. Cable owners will normally pay compensation for any gear sacrificed under these circumstances, provided such a loss can be proven and that all reasonable precautions were taken to prevent damaging the cable.

Claims for gear lost or damaged through entanglement with a submarine cable should be lodged in writing within 24 hours of arrival at the next port of call. Particulars of the incident should be given and full details recorded in the official vessel log. The report must include:

  • The vessel's name, registered licence number and captain's name and contact details.
  • Name and address of vessel owner/s.
  • Vessel's position and heading at the time of the incident (indicate land bearings and readings of electronic navigation system used).
  • Water depth.
  • Charts used at the time of the incident.
  • A description of the gear deployed at the time of the incident
  • A description of the cable if sighted.
  • Copies of the relevant page from the vessel log in which the incident was recorded.
  • Action taken to free gear and/or avoid damage to the cable.

This information is required for proper processing of claims and is used for identifying any possible cable position charting errors.

IF YOU SUSPECT THAT YOU HAVE COME FOUL OF A SUBMARINE CABLE THE FOLLOWING ACTION SHOULD BE TAKEN:

  • If weights are excessive and you suspect you are fast to a cable, DO NOT endanger your vessel and crew by attempting to recover your gear.
  • Carefully plot your ship's position as accurately as possible, checking for any cables that may be close to your position. The Kingfisher Information Services Cable Awareness charts (KIS-CA) show all in-service cables and the cable maintenance company for each {NB this is not applicable on US side}.
  • Advise your coastguard station of your situation OR if your coastguard is not obtainable call the emergency number of the cable maintenance company concerned and state that an incident is occurring concerning an underwater or Submarine Telecommunications cable.

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