Box 18D Examples of accidents ­ marine transport and offshore installations

Ixtoc I oil well blowout, Gulf of Mexico, 1979

The Ixtoc I blowout is probably the world's biggest oil spill in terms of the amount of oil released into the environment. More than 500 000 tonnes of oil were released into the sea over a period of nine months. However, since the blowout occurred well away from any coasts, the environmental damage it caused was remarkably small.

Piper Alpha oil and gas platform explosion, North Sea, 1988

On 6 July at approximately 10.00 hrs a large explosion occurred at Occidental's Piper Alpha platform, located approximately 190 km northeast of Aberdeen. The cause of the accident is unclear, but it is thought that it may have been a maintenance error. Within seconds a major crude-oil fire developed and all but the lower parts of the platform and wellhead area were engulfed in a choking black smoke.

The majority of the 226 people on board were trapped in the accommodation areas of the platform, unable to make their way to the survival craft because of the smoke and the initial fires. Approximately 20 minutes later, a major failure of a connecting pipeline occurred and a fireball more than 50 m in diameter engulfed and rose above the platform. The subsequent fires caused the platform to collapse, and 167 people lost their lives. The environmental impact of the accident was not examined in view of these human fatalities.

Amoco Cadiz oil spill, Brittany, France, 1978

After the Amoco Cadiz was wrecked off the coast of Brittany in March 1978, a total of around 220 000 tonnes of oil were spilt. Following the accident, over 4500 oiled birds of 33 species were recovered from beaches, and it was suggested that many more had actually died but had not been recovered. The most severely affected species were puffins (Fratercula arctica), razorbills (Alca torda) and guillemots (Cepphus grylle). Extensive areas of saltmarsh were damaged and some animals, such as the heart urchin (Echinocardium cordatum), were almost completely wiped out. The affected coastline was also being intensively used for oyster culture, which was severely disrupted by the spill. A high initial mortality was accompanied by heavy contamination that resulted in shellfish being unsuitable for consumption.

Braer oil tanker, Shetlands, UK, 1993

The Liberian-registered tanker Braer ran aground at Garths Ness on the Shetland coast on 3 January 1993, resulting in a spill of 80 000 tonnes of crude oil. The cause of the accident was a complete power failure which left the tanker adrift, and eventually led it to run aground. Investigations of the extent of the damage are still under way, but it seems that the environmental impact is not as bad as had been expected immediately following the accident. Fortunately there were strong winds blowing offshore which helped disperse the oil slick. Numerous salmon farms have, however, experienced large losses and one month after the accident it was estimated that 2.5 million farmed salmon worth £35 million had been contaminated. The long-term environmental effects of the damage cannot yet be assessed.