Dansk

DKCPC cable awareness information

Snagging a submarine cable

Submarine cables and the risk of snagging

Subsea (submarine) cables have been laid on the seabed since the eighteen fifties. Cables installed since 1983 have been buried at the time of installation, with a target burial depth of 0.8 metres. Unfortunately there remains the possibility, in places, of the cable not being buried or becoming unburied. It is not possible to show these areas, thus the entire cable route should be treated with the utmost caution.

The vessels most at risk are those with towed gear, bottom and beam trawls and dredges. Static gear, whilst not entirely free from risk, is less likely to be affected.

In the event of becoming entangled with the cable there is a high probability of damage to or loss of fishing gear as well as fishing time and catch. If attempts are made to lift the cable to the surface or to pull the gear free there is the very real risk of loss of stability eventually leading to capsize with resultant loss of life.

Trawl door fouling a cable

Submarine cables and repair hazards

A Fibre Optic cable consists of an inner optical core encased within a copper clad high tensile steel wire rope insulated with polyethene. In water less than 1500 meters deep, protection is added against fishing and anchor damage in the form of external steel wire armour. The heaviest form of armoured cable has 70 tons breaking strength.

Power cables are in many different sizes ranging from a diameter of 7-8 cm to almost 30 cm. The smallest power cables carry 10 kV to smaller islands while the largest 200-400 kV power cables connects the power systems in Denmark with the power systems in Norway, Sweden and Germany. A power cable consists typically of 1 to 3 aluminium or copper conductors with polyethylene or oil impregnated paper insulation. All power cables have a steel wire armouring.

If a cable is broken by fishing, anchoring or other seabed activities it will be repaired. The damaged section is recovered to the surface and a new section spliced in. This spliced area represents a risk to fishermen, there will be slack cable on the seabed equal to approximately twice the water depth and post repair burial is not as effective as installation burial.

Fibre optic cable

Power cable

Snagging a submarine cable

Snagging a submarine cable can be extremely hazardous to fishing vessels. If you do snag a cable, make sure you follow the emergency procedures to safeguard your vessel and crew.

The following sequence of events shows what can happen if a vessel fouls a cable:

This project is managed by the Kingfisher Information Services department of Seafish in conjunction with the DKCPC (Danish Cable Protection Committee).

For further information, please contact Kingfisher Information Services on: Tel +44 (0)1472 252307, Email: kingfisher@seafish.co.uk