Jun. 3--To walk the grounds of the Joliet Army Ammunition Plant in 2009 is to see nature's best effort to heal the scars of a once-heralded manufacturing empire.

Rich, green grass has returned to the small ridge known simply as "the burning grounds," where TNT and old munitions were melted and recast decades ago. Lush cottonwood and hackberry trees now stand on the high grass where smoke stacks spewed noxious fumes into the air. Beavers and birds cool themselves in the winding creek that was a dumping ground for harmful solvents and chemicals.

But below ground, the picture is different. The chemical residue from the production of ammunition during and after World War II continues to infiltrate the soil and water tables at the 24,000-acre former arsenal south of Joliet.

More than 30 years after it stopped building explosives, the Joliet plant is listed among the most hazardous environmental sites in the U.S. And, like the state's four other major ammunition plants no longer in use, Joliet remains under close watch by the Illinois Environmental Protection Agency.

"These sites are part of the legacy of the war effort," said Clarence Smith, who oversees federal cleanup of the former plants for the agency. "We did things in this country that were useful and necessary because of the war we were fighting. But it came at a steep cost environmentally that we're still paying today."

At Joliet and elsewhere, the soil is embedded with heavy metals and harmful solvents and acids. At one site, a farmer dug up several 90 mm anti-tank shells. Two other sites near the Iowa border, the Green River Ordnance Plant and the Savanna Army Depot, are believed to have active explosives buried somewhere, Smith said.

"We know they exist; we have the records," he said. "We just haven't found them yet. It presents an incredibly hazardous situation."

The federal government has spent hundreds of millions of dollars to clean up the five major arsenals in Illinois, which combined to produce more ammunition during the war than any other state in the U.S. The Joliet arsenal employed about 22,000 people at its peak in the 1940s, manufacturing millions of tons of artillery shells, bombs, mines and other munitions. The Joliet plant remained active until it ceased TNT production in 1976. After that, the Army kept the plant on standby in case the country entered another prolonged war. The plant was closed in the late 1990s.

"It was like a small city," said Sam Herr, 74, a Joliet resident who was a photographer at the plant in the 1950s. "Growing up in Joliet at that time, that's where you looked for work.