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.
The results were worrisome enough that by 1990 the EPA had placed the entire Edgewood area and parts of the Aberdeen area on its Superfund list of high-priority cleanups.
Over the past two decades, a small army of federal agencies has tried to map and categorize Aberdeen's pollution. Their work fills phonebook-thick volumes covering two walls in one engineer's office. Yet despite this air of thoroughness, the base's environmental ills can at times resemble a mythical hydra: When one head is cut off, two appear in its place.
In 1997, a chance brush fire revealed a major dump that two decades of environmental surveys had missed. What had looked like a tranquil field of marsh reeds by the Gunpowder River became a $5 million toxic waste cleanup.
"When you go down to a site many many times and you look at this beautiful phragmites marsh and the next day the phragmites is gone and you see these whole piles of concrete and metal and demilled munitions, it is definitely a shock," recalls Cindy C. Powels, an environmental engineer at the base since 1981. "We had to rethink everything."
A more alarming discovery came last year, when perchlorate, a rocket fuel component linked to thyroid disorders, was found in the city of Aberdeen's tap water. City officials shut down one well and halved production at three others.
In neighborhoods near the base, the shock once triggered by such discoveries has given way to cynicism. "The attitude is, 'Here we go again,"' says Ruth Ann Young, a retired school guidance counselor and member of a watchdog group called the Aberdeen Proving Ground Superfund Citizens Coalition.
The toxic dump patrolled by the bluegills is known simply as O-Field.
To get there, John T. Paul Jr., the base's environmental risk manager, shows his ID at two guardhouses, signs his name and employee number in a log, and radios ahead to a safety office for permission to proceed.
A few minutes later, he parks his van and gestures over his left shoulder at a flat rectangle of gravel hemmed by a low chain-link fence: O-Field. "If it wasn't the Army's worst environmental dump," Paul says warily, "it was right up there."
In the 1940s and early 1950s, workers packed the 5-acre lot with the base's most noxious refuse: lethal nerve agents, tear gas, explosives, fuels, cyanide, unexploded shells, chemical weapons.
In the 1960s, freak underground explosions sent pieces of O-Field flying into nearby Watson Creek. An Army report later forecast one to three "explosive events" at O-Field every decade.
Seven years ago, when the Army finally decided to blanket the dump with a protective sand cap, it played it safe and had remote-controlled robots do the work. A layer of gravel was spread on top of the cap, to absorb the impact of any explosions. A grid of sprinkler pipes fans out over the gravel, to spray down toxic clouds.
Though there have been no explosions or gas releases at O-Field since the cap, chemicals have been seeping into the ground water.
A ring of wells draws the ground water into the nearby treatment system, where the bluegills form the last line of defense before a pipe shoots the treated water into the Gunpowder River.
'Rake and scrape'
Some of the most dangerous cleanup work at Aberdeen falls to the likes of Billy Sanders, an Army explosives specialist with a connoisseur's eye for vintage ordnance.
Sanders is leading a cleanup of a sprawling firing range on the banks of Lauderick Creek.
He takes a photo each time his workers dig up a round of buried ammunition. More than 170 pictures now fill an album he calls "our own little scrapbook."
"We do have some nice looking rounds in here," he says one afternoon, flipping through the pages until he finds to a photo of a dented shell covered in rust. "That's a pretty nice 4.2-inch mortar there."
From 1920 to 1951, soldiers at the Army's chemical school trooped out to the range to fire shells of mustard agent, phosgene and other chemical agents. The unexploded projectiles now lie rusting beneath the creek's banks.
Since June 2001, the lives of Sanders' workers have revolved around a single question: Are the metal objects in the soil beneath their feet chemical shells, or just spoons, soup cans or other harmless scrap?
To find out, they shuffle through the fall leaves waving metal detectors over the moist soil. When the detectors whine, they know there is metal underfoot. They sink small yellow flags in the earth to mark these "magnetic anomalies."
Then the digging begins. It's called "rake and scrape," and is in many ways no more sophisticated than it sounds.
On this day, two workers in camouflage uniforms draw a rake over the springy soil above one "anomaly."
The work would resemble a version of Russian roulette were it not for the painstaking safeguards against chance detonations. Around the site, a half-dozen green tanks that fought oil fires in the Persian Gulf war stand ready to release 250 gallons of pressurized water in the event of a chemical explosion.
The slightest trace of gas will trip sensors, which in turn ring an alarm at the cleanup's command post.
The command post, a few hundred yards away, is a small trailer crammed with computers. Inside, a man tugs on a joystick to aim a surveillance camera at workers prodding the unknown piece of metal. He makes sure workers follow safety rules. He also watches for accidents so severe that the injured would be unable to call for help.
Two seats down, Dawn Pisarski, a civil engineer with the Army corps, studies a computer screen showing how real-time wind and weather conditions would disperse a chemical cloud should the worst happen.
This afternoon, the would-be plume forms an ellipse veering southeast from the dig site. In an explosion, many people inside the ellipse would probably die.
"If the plume goes over the school," says Pisarski, referring to a group of three schools nearby, "I won't let them dig."
But the sun is shining today, and the wind a mere caress. So the two men in camouflage keep raking. Then rake's teeth strike metal. It is with a note of disappointment that one of them men announces his find. "A soda can," he says.
Not every day is as dull.
In late October, crews dug away soil and found an anti-tank mine the size of a birthday cake. It was an "alligator," a booby-trapped mine that looked rigged to blow at the slightest touch. Workers rolled out X-ray machines, and summoned firefighters and emergency decontamination crews.
"None of the records indicated that this type of training had been done out there," Sanders recalls. "Even the experts were surprised by the booby trap."
To everyone's relief, the mine was a dud. "Fortunately," Sanders says, smiling, "it was a practice mine."
Sun staff researcher Jean Packard contributed to this article.