But as the ravaged hull corrodes and is worn thinner by salty ocean water, researchers are using specialized computer software to model and predict how long it will take before the Arizona 's structure fails and spills greater quantities of the trapped oil and fouls the harbor.
Timothy Foecke, a metallurgist at the Gaitherburg, Md.-based National Institute of Standards and Technology (NIST), has been working for more than three years to model oil leak scenarios from the Arizona for the National Park Service and the USS Arizona Preservation Project to help predict how the wreckage will continue to deteriorate underwater.
Foecke is using finite elements analysis software from Providence, R.I.-based Abaqus Inc., which makes analytical software used in engineering and other industries to design products and evaluate large amounts of data.
Foecke's initial calculations show that there are still 10 to 20 more years before significant shifts begin to happen in the underwater wreckage that will lead to larger spills of the estimated 500,000 gallons of heavy fuel oil that went down with the battleship.
"She was fully fueled to make a Christmas trip back to the West Coast [of the U.S.] when she was sunk," Foecke said.
It has taken about two years to create a workable model of future oil leakage using the software, he said. Data parameters included so far include the pressure of the harbor mud on the decaying hull, the effects of a thick crust of biological vegetation that has grown over the wreckage since it was sunk and other factors such as water currents.
"We're just starting now to do parameter studies," such as changing pressures and changing estimates about how quickly the hull's thick plates are corroding and getting thinner due to rust, he said.
By examining the data from the models and simulations, Foecke can develop scenarios that can be used to estimate how the wreckage is holding up and when more serious leaks will occur.
The Park Service asked NIST to help with the evaluations so the agency would have as much information as possible for making decisions about preserving and protecting the wreckage, which is the home of one of the nation's most revered military memorials.
The Arizona memorial commemorates the 1,177 sailors and Marines who died on the ship during the Japanese attack. The loss aboard the Arizona made up more than half of the 2,335 U.S. servicemen from the Army, Navy and Marine Corps who died that day in the attack.
Matthew Russell, director of the USS Arizona Preservation Project, said the NIST involvement began after 2001, when the memorial was commemmorated on the 60th anniversary of the attack. A higher level of public interest in the memorial that year brought increased funding to the agency for the research into how to best preserve the site in the future, especially related to growing concerns about potential oil leakage from below, he said.
No consensus has been reached on what to do about the growing threat of leakage, Russell said, but various options will be evaluated when the modeling is completed. The options include finding ways to slow the corrosion of the wreckage and to make repairs that will not affect the memorial.
Officials plan to have a report on the situation by Dec. 7, 2007, he said. Arizona Memorial administrators and Navy and Coast Guard officials will decide what course to follow, he said.
"We have to wait until we get more finalized predictions" from the modeling software, Russell said. "It's an ongoing process."
So far, it's still not known if the continuing deterioration of the Arizona will happen slowly or quickly, Russell said. The ship has been leaking fuel oil since it was sunk, in recent years at the rate of about a gallon a day. "When you visit the memorial, you can see the oil on the surface," Russell said.
Some of the oil in the ship is still stored in multiple tanks, while more oil is trapped in voids and air pockets in various compartments, he said. The best estimates are that the oil, when it begins to escape in larger quantities over time, won't all rush out at once but will more likely escape in "smaller events," Russell said.
The oil on board the Arizona was thick Bunker C fuel oil that was used on many large military and civilian ships at the time, he said. The oil was so thick that it had to be heated and thinned so it could flow through pipes to the boilers that ran turbines and propellers to move the ship.
NIST's Foecke said the modeling software, when completed, could help evaluate hundreds of other shipwrecks off U.S. coasts and in inland waterways, where hazardous cargos or storage tanks full of fuel could be threats to the environment.
"This is the type of tool we want to develop so people can use it," he said.