EDGEWOOD - In a small laboratory at Aberdeen Proving Ground, eight bluegills put their tails on the line every day in the name of clean water. The fish swim in tanks of treated water piped from beneath the Army base's most toxic dump, a melange of decaying chemical warfare agents such as napalm, cyanide and sarin.
If electrodes pasted to the tanks detect an unusual wriggle or cough, a computer alerts engineers that toxins may be getting past a multimillion-dollar water treatment system. Enough sick fish, and the engineers investigate. Enough dead fish, and they shut off the discharge into the Gunpowder River.
This is how quality control works at the filthiest dump on one of the nation's most polluted military bases.
The $49.6 billion cleanup of polluted defense sites in the United States has plenty of high-tech gear at its disposal, from cesium-vapor magnetometers to infrared air monitors and ground-penetrating radar. But the decision to enlist pond fish in the war on toxic waste reflects the limits of even the most advanced technology in cleanups as complex as Aberdeen's.
In the ground water beneath the dump, the soup of chemicals is so exotic that environmental scientists don't entirely trust the computer sensors that test treated water for purity. So the fish act as sentinels - like the canaries whose deaths once signaled poisonous gas in coal mines.
"The philosophy of the system," says Tommy R. Shedd, the Army research biologist who designed it, "is that you can integrate it into a very, very complex dirty world."
The grande dame of Maryland military bases, spanning some 72,500 acres between the Susquehanna and Gunpowder rivers, Aberdeen is the third most expensive base cleanup in the nation and perhaps its most complex.
In one government report, the list of pollutants in the soil and ground water runs five pages long - in small type. In buildings there, many now crumbling from disuse, scientists experimented with chemicals designed to sicken and kill. And on the firing ranges, soldiers tested small arms, took tanks for their first spin and learned to launch explosives filled with phosgene and mustard agent.
The base's environmental woes are so imposing that when a boater disappeared into the Gunpowder River in 2001, rescue crews refused to send in divers because of the risk of encountering unexploded artillery shells.
The Pentagon estimates it will cost $741 million to rid the base of toxins. And when it's all over, by the 2030s at the earliest, the cleanup will have spanned more than a half-century.
"Aberdeen has been a challenge because of the amount of contamination," says Paul Leonard, the chief regulator of federal facilities at the regional headquarters of the Environmental Protection Agency in Philadelphia. "Some of the munitions testing and some of the chemicals used in those operations were not traditionally the chemicals we knew about."
The base opened in 1917, when World War I convinced the Army that it needed a place to test artillery.
Aberdeen was close enough to shipping centers for supplies to move in and out, but far enough - at the time - from neighborhoods that the year-round testing wouldn't endanger humans or arouse opposition.
But it took an act of Congress and two presidential proclamations to sweep 3,000 people and 12,000 head of livestock off farms to make way for what became the nation's largest test site for guns, tanks and ammunition. In its heyday, the 1940s, the base newspaper was called The Flaming Bomb.
In 1971, Aberdeen Proving Ground expanded, absorbing its neighbor, the Edgewood Arsenal, the military's center for chemical weapons research and training.
Over the years, concern for the air, soil and water took a backseat to fine-tuning weapons for combat in two world wars, Korea and Vietnam.
As recently as the 1970s, workers were disposing of mustard agent, tear gas, nerve agents and white phosphorus by throwing the substances into long trenches and setting them on fire.
In the late 1980s, three senior managers at a chemical weapons research plant were convicted of felony violations of hazardous-waste laws, for dumping dangerous chemicals. "The allegations in this indictment reflect the absolute disregard that the Army had for federal and state laws governing hazardous waste," Breckinridge L. Willcox, then U.S. attorney for Maryland, said at the time.
In 1994, state and federal regulators fined the base $140,000 for toxic waste violations, including the storage of more than 3,000 gallons of white phosphorus for 10 years, rather than the 90 days allowed.
It wasn't until Congress passed stringent cleanup laws in the 1980s that the military undertook its first systematic survey of Aberdeen's environmental problems. In some places, tests of ground water and soil found concentrations of toxins so high that scientists were measuring them in parts per 100, rather than the standard environmental yardstick of parts per billion.