NEW SCIENTIST SUBMARINE ROBOT REPAIRS LEAKING OIL TANKER PRESTIGE

SUBMARINE STEMS TANKER'S OIL LEAKS - 5 February 2003

A submarine repairing the sunken Prestige oil tanker has finished its work - its operators claim they have stemmed 99 per cent of the leaking.

The Nautile submarine, owned by the French Research Institute for Exploitation of the Sea (IFREMER), completed its series of 18 dives on Monday.

The tanker was patched where it lies, on the floor of the Atlantic, 3.5 kilometres below the surface. It was damaged in November by severe weather off the north-west coast of Spain and was towed 200 kilometres out to sea, where it sank. Oil has already polluted hundreds of kilometres of the Spanish coastline.

Submarine robot arm (gold) working to stem oil flow

Bruno Barnouin, a spokesman for IFREMER, told New Scientist the repairs ought to reduce the amount of oil leaking from the ship's hull to less than one tonne per day. The original rate was estimated to be more than 100 tonnes per day. He says the Spanish government, who funded the work, will now inspect the repairs.

Metal shot

The Nautile performed its first dive on 16 December. The submarine's crew used the submarine's robotic arms to patch about 20 different leaks in the Prestige's hull.

The challenges posed by the leaks varied, so a number of different repair techniques were used. One solution involved placing metal plugs over ruptures and securing these using weighted bags.

In another, a bag of metal shot was inserted into a tube leaking oil. Barnouin says the patches may last up to 40 years, but admits they could deteriorate much more quickly.

Pumped up

"It's a step in the right direction," says Simon Cripps, director of the World Wildlife Fund's International Marine Programme, but even a tonne a day is a serious ecological problem, he says.

Cripps adds that the Spanish government should find a way to retrieve the remaining oil from the Prestige as quickly as possible. "It's the only solution," he told New Scientist.

Between 17,000 and 20,000 tonnes of oil is thought to have leaked from the tanker so far, leaving about 60,000 tonnes of oil still on board. Much of the leaked oil has washed up on the north-west coast of Spain, severely damaging the local fishing industry and wildlife. Some oil has reached the Atlantic coast of France.

The Spanish government is currently considering a proposal by the Dutch salvage company Smit, to drill into the Prestige and pump oil back to the surface. Barnouin believes this proposal will be selected. A decision is expected on 15 February.