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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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