JAPANESE OIL SPILL CONTAINED

YOKOHAMA, Japan-The costs of cleaning up an oil spill in Tokyo Bay earlier this month are still being calculated, though fears that the spill would be far larger and more damaging have abated.

The Japanese owners of the Panamanian-registered tanker Diamond Grace are insured for pollution damage.

About 121 million gallons of crude oil-one-tenth of the amount initially thought to have spilled-leaked from the Diamond Grace when it struck a reef in the bay. The spill came only a few months after the disastrous Nakhodka oil spill caused widespread environmental damage to Japan's waters and coastline (BI, Jan. 13).

Investigators currently are trying to determine how the spill happened in calm and well-charted waters, and have suggested that human error was responsible. Diamond Grace, built in 1994, was carrying more than 2 billion gallons of crude oil.

The bulk of the cargo was moved from the punctured tanks into ballast tanks, preventing additional spillage, and the cleanup operation took just 10 days, involving more than 300 vessels. They were helped by the type of crude oil involved, much of which vaporized on contact with the atmosphere, according to a spokesman for the Japanese government.

Diamond Grace is owned by Mari-tech Management, whose majority shareholder is Nippon Yusen Kaisha, Japan's largest shipping line. Pollution coverage is with the United Kingdom Mutual Steam Ship Assurance Assn (Bermuda) Ltd., known as the U.K. P&I Club, which refused to comment on the incident.

Cleanup costs are still being estimated. Under international law, the ship's owner and its insurer are liable up to a limit determined by the size of the ship, or about $19.5 million. Up to about $170 million in excess of that limit would be paid by the International Oil Pollution Compensation Funds, an international organization set up by nations that are party to shipping and pollution conventions.