NUMBER OF OIL SPILLS FALLS SHARPLY OVER 10 YEARS

NUMBER OF OIL SPILLS FALLS SHARPLY OVER 10 YEARS

The number of major oil spills from tankers fell sharply over the past decade, with the improvement continuing last year.

Figures published Wednesday by the London-based International Tanker Owners Pollution Federation Ltd. show that the average number of oil spills a year is now only about one-third of the level seen during the 1970s.A total of 91 spills of more than 5,000 barrels were recorded during the 10 years to 1989, compared with 252 in the 1970 to 1979 period. In 1991, there were just seven spills of more than 5,000 barrels.

In volume terms, the amount of oil spilled in the 1980s was 1.2 million metric tons, against 3.5 million tons in the previous decade - a reduction of about two-thirds.

Evidence of the improvement comes at a time of heated international debate about tanker design, with the United States arguing that vessels built with double hulls provide the best protection against oil pollution and most shipowners insisting that other constructions are just as effective.

The federation's study found that many oil spills in recent years were due primarily to hull failure or fires and explosions, "which suggests that no single tanker design is likely to offer a panacea."

While it is commonly believed that groundings are more significant than collisions in terms of oil pollution, Catherine Grey, the federation's database manager, said Wednesday that over the past 21 years, both the number of spills and the total quantities of oil released following collisions and groundings were almost the same.

An International Maritime Organization committee has concluded that double hulls would be most effective in preventing oil leaking into the sea after a grounding, while a tanker built with a mid-deck through the cargo tanks may be better in other circumstances.

Marine underwriters said this week that the cost of insuring a double-hull tanker probably would be higher than a single hull because of the danger of a gas buildup between the hulls, a greater risk of corrosion in the more inaccessible parts of the ship and more expensive repair costs.