Sunken WWII boat mystery: Where did 3 million gallons of oil go?

It was just after sunrise on Dec. 23, 1941, when the tanker Montebello was hit by a torpedo from a Japanese submarine just off the Central California coast, taking 3 million gallons of crude oil with it as it sank.

All 38 crewmen aboard the Union Oil Co. vessel survived and rowed their way ashore. But since the World War II attack -- just weeks after Pearl Harbor -- the tanker has rested 900 feet below the ocean surface off the Cambria coast.

In recent years, worries have mounted that if crude began to leak from the 440-foot vessel it could foul the state’s waters and shoreline, creating an environmental catastrophe. Past surveys have repeatedly shown no evidence of leaking.

But now, after nearly two weeks of the most advanced testing yet, a team of researchers has concluded that not only does the vessel pose no risk, the oil is long gone.

State and federal officials announced Thursday they had found virtually no evidence of oil inside the tanker’s cargo and fuel tanks and said the sunken vessel can be scratched off the list of possible threats to the California coast.

“It turned out to be the best possible news,” said Andrew Hughan, a spokesman for the California Department of Fish and Game, whose Office of Spill Prevention and Response took part in the joint operation with the U.S. Coast Guard and the National Oceanic and Atmospheric Administration.

“At the end of the day, the Montebello is filled with seawater.”

One mystery lingers: Where did the 3 million gallons of crude go?

The answer may never be known, but scientists have developed one scenario: Some of the oil leaked out and evaporated within the first few days after the boat went down. The bulk of it probably gurgled to the surface as the ship sank, drifting south and away from the shoreline, scientists suggested.

Whatever was left inside might have washed ashore but, scattered so widely, it probably went unnoticed.

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-- Tony Barboza

Photo: The Montebello in dry dock in 1941. Credit: California Department of Fish and Game