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Marine archaeologists rescued the shipwrecked H.L. Hunley (above, a computer rendering) in August 2000 more than 135 years after it sank during the Civil War. (Courtesy of Friends of the Hunley)

Saving Our Shipwrecks

New technologies are aiding the search for one Civil War submarine, and the conservation of another

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(Continued from page 1)

Not far from where Overfield conducts his searchers, marine researchers at the Warren Lasch Conservation Center in Charleston work to preserve the Hunley. In February of 1864, the Hunley became the first submarine to torpedo an enemy—bringing down the USS Housatonic, the largest Union ship among those blockading the Confederate harbor. At that time, such an attack required ramming a torpedo into an opposing ship's hull and backing away to trigger an explosion. The Hunley sank on its return voyage, however, and in the end lost more men (nine) than did the Housatonic (five).

More than a century later, a search team led by novelist Clive Cussler located the lost ship. With that obstacle out of the way, the problem became dislodging the vessel safely from beneath the ocean floor. "When you find something, it doesn't always mean you'll recover it," says Robert Neyland, who is head of underwater archaeology at the Naval Historical Center and directed the Hunley's recovery.

In August of 2000, Neyland and his colleagues successfully removed the submarine with the help of a unique system that cradled the Hunley with hard-setting foam, locking the ship in place. Once the sub broke the surface, saltwater sprinklers showered the vessel to protect it from damage caused by oxygen as it made its way to the conservation facility.

Back at the lab, the ship was transferred to a state-of-the-art tank. Conservationists chilled the 300 tons of water to preserve any organic remains—including those of the crew members—locked inside the sub. Typically, chemicals must also be added to the water to prevent corrosion of the iron hull. However, such chemicals could have damaged the organic materials, so researchers instead used a new method known as "impressed current" to preserve all aspects of the ship.

"To my knowledge, it was the first time that a team of people would use this impressed current in order to avoid using chemicals," says Paul Mardikian, the Hunley's senior conservator. Put simply, the method sprays the ship's material with a stabilizing stream of electrons. "It worked," says Mardikian, "and it saved the sub."

The researchers also used a novel mapping technology to recreate the position of objects inside the submarine when it sank. To record these data points by hand would have taken a full crew 86 years; the new surveying system completed the task in four days.

These techniques made it possible for researchers to excavate the ship's artifacts with minimal damage. Eventually, however, the salts trapped in the ship after a century of submersion must be removed—otherwise, the submarine would crumble into a pile of dust after about six months of exposure to the air. To do that, researchers have decided to soak the Hunley in a high-pH solution.

Over several years—at least until 2010, says Neyland—this process will remove the salts and prepare the sub for public display. Meanwhile, Mardikian is researching a way to speed up the procedure using "subcritical fluids," a high-temperature treatment that diffuses salts more quickly than traditional soaking. If subcritical fluids test well enough, he says, "we may be able to treat two tons of ballast blocks from the submarine in two months instead of two or three years."

Today's marine archaeology is hardly recognizable from the field that, just several decades ago, had no identity at all. "There was no standard in the 1970s for how to conduct an archaeological investigation," says marine historian Tim Runyan of East Carolina University. "You couldn't just take what you do on land and transfer it underwater."

George Bass, the founder of the Institute of Nautical Archaeology who helped shape the field's current reputation as a solid science, describes the early days more crudely: "We made gaskets out of leather shoes."

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