One Last Mission for Ship Sunk in Pearl Harbor Attack

The Arizona, which was launched in 1915, is 91 and has been submerged for six decades.

Science is not sure how the metal in old ships fares for long periods under water.

The Civil War submarine CSS H.L. Hunley, which sank in 1864, was surprisingly intact when it was raised from the protective mud off the harbor of Charleston, S.C., in 2000. The turret of the USS Monitor -- which sank in the Gulf Stream off Cape Hatteras in 1862 -- was in worse shape when it was recovered in 2002.

Sooner or later, though, submerged metal wrecks are reduced to "an iron ore deposit," Foecke said.

To assess that process on the Arizona, he and guest institute scientist Li Ma have built a finite element model. They took the ship's blueprints, carved out an 80-foot section from the middle and entered its dimensions into a computer. They then used special software to break the section into about 200,000 data blocks, or elements, and entered what they knew about the properties of the metal, corrosion and damage.

Scientists also entered into the model what they knew about external forces on the vessel: such things as pressure from the water, bottom, gravity and waves.

The result is like a single frame from a movie, Foecke said, and it then becomes possible to play the movie, by adjusting the data, and see how it might turn out.

Foecke, who keeps pieces of the Arizona's steel hull in an office safe, says the model is not perfect.

It "will give us a time frame within which we can expect [the ship's] failure and the general type of failure -- upper decks breaking down, lower decks erupting up, hull tipping in or out -- but not exactly where," he wrote in a recent e-mail.

Foecke said an early version of the model has been run, gradually "corroding" the metal thickness in small increments. When it was thinned 75 percent, parts of the structure grew unstable, but that kind of corrosion is not expected to happen for 10 or 20 years, he said.

"We think that nothing serious is going to happen for about 10 years, plus or minus years," Foecke said.

When the structure collapses, Foecke said, the oil will "erupt" toward the surface. "It's going to break the wreck up and open," he said. "The oil does have buoyancy, and it's trying to find a way out, and there's quite a lot of it."

Even though Pearl Harbor is fairly industrialized, Foecke said, a big leak would create "a huge mess." A spill of 100,000 gallons of jet fuel in 1987 fouled a mangrove swamp and a wildlife refuge and took two months to clean up, according to news reports of the time.

Douglas Lentz, National Park Service superintendent of the Arizona Memorial, said extensive plans are in place should a large leak occur. But Russell, the project director, thinks any Arizona collapse would take place gradually. "There won't be any single, serious collapse that releases all the oil," he said. "But we're trying to get an indication of when the first wave of releases may occur."