A new, Spanish-designed submarine has a weighty problem: The vessel is more than 70 tons too heavy, and officials fear if it goes out to sea, it will not be able to surface.

And a former Spanish official says the problem can be traced to a miscalculation — someone apparently put a decimal point in the wrong place.

“It was a fatal mistake,” said Rafael Bardaji, who until recently was director of the Office of Strategic Assessment at Spain’s Defence Ministry.

The Isaac Peral, the first in a new class of diesel-electric submarines, was nearly completed when engineers discovered the problem. A U.S. Navy contractor in Connecticut, Electric Boat, has signed a deal to help the Spanish Defence Ministry find ways to slim down the 2,200-ton submarine.

The agreement with Groton, Conn.-based Electric Boat calls for Spain to pay $14 million over three years for an assessment of the problem with the S-80 submarine program and the scope of the work that would be required to correct it, the Spanish Defence Ministry said in a statement to The Associated Press.

Bardaji, now a senior fellow with the Strategic Studies Group think-tank in Madrid, said officials will review options provided by Electric Boat. But he said the preference has been to extend the length of the submarine’s hull, perhaps by 5 to 6 metres, to increase buoyancy.

Otherwise, the weight of the submarine would have to be reduced, and he said the Spanish Navy would not want to compromise features such as the combat system or an air-independent propulsion system.

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