Robot arm could remove reef bombs
Remote device set to save Puerto Rico's fish from noxious chemicals.
The best thing to do with an unexploded bomb is usually to leave it alone. But scientists working on an abandoned US Navy bombing range in Puerto Rico have an ambitious plan to remove the site's decaying explosives to prevent an ecological disaster.
The researchers have developed a remote-controlled robot arm, which sits in shallow waters and picks the bombs from where they lie off the eastern shores of the island of Vieques. Capable of lifting up to 225 kilograms, the device lifts the bombs into a cradle that floats to the surface using air tanks.
The device could be used to remove bombs from the dozens of underwater bombing ranges around the world, says the team led by coral-reef expert James Porter of the University of Georgia, Athens, who surveyed the island, and James Barton, president of Underwater Ordnance Recovery, the Norfolk, Virginia-based company that designed the robot.
"Every coastal state of the United States, as well as the Great Lakes, rivers, and reefs on Guam and Hawaii, are affected," Porter told the annual meeting of the Ecological Society of America in Montreal, Canada, this week. "Preparation for war is messy."
University of Georgia
The island's shallow waters are also the final resting place of the USS Killen, a Second World War destroyer that miraculously survived its later incarnation as a practice target for nuclear bombs in the South Pacific, and was finally buried at sea off Vieques in 1975.
The Puerto Rican authorities feared the boat might be a source of radiation, so asked Porter and his colleagues to survey the reef's ecosystem. Many fish live within the shelter of the boat's pockmarked, corroded flanks, and officials were worried that the extensive fishing around the vessel might be contaminating the human food chain.
Porter did not find high levels of radiation on the boat. But when he began to look for chemical, rather than radioactive, contaminants in the fish and corals in and around the bombs scattered around the Killen, he found high levels of explosive-derived compounds such as trinitrobenzene and trinitrotoluene (TNT).
"We found so much TNT in some corals we were scared to hit them with a hammer so we could sample them," Porter joked.
Contamination levels drop off sharply away from the bombs, showing that the pollution tends to stay within the bomb casings and the fish that live inside. "The bad news is that the site is toxic. The good news, if there is any, is that it's a point source of pollution, so all you have to do is pick up the bombs," Porter told the meeting.
"We expect the concentrations will drop precipitously and immediately after removal," says Porter.
The only problem left is funding the job. At the beginning of this year, the US Environmental Protection Agency added the area to its list of 'Superfund' sites - polluted areas in need of special cleanup attention. But the US Navy has not yet parted with the cash to clean the site.
If successful, the device could help to reduce some of the worldwide legacy left behind by military exercises. "The human cost of war is often known," notes Porter. "The environmental cost is not."