When the cage door opens, Milan Jovanovich steps into an underground world of concrete tunnels and steel. Light bulbs illuminate damp rock, bolts jut from tunnel walls and groundwater drips onto a platform where Jovanovich stands in a hard hat and steel-toed boots.

It is his world, these tunnels, the life Jovanovich chose when he descended into his first mine shaft at age 18, back when Jimmy Carter was president. Since then, the burly miner with the big beard and huge hands has blasted through some 35 miles of limestone, drilling his way from Skokie to South Holland to help build Chicago's Deep Tunnel.

"This isn't a boring eight-hour job," said Jovanovich, 45, breathing in dank air heavy with the smell of concrete and damp wood. "It's an addictive trade."

Miners have plied that trade beneath Chicago's streets, out of sight of the bustling life above ground, since engineers dreamed up the Deep Tunnel plan in the early 1970s and put it into action in 1976. They detonated their first stick of dynamite that year at Howard Street and McCormick Boulevard in Skokie.

Since that first blast, they have bored through 101 miles of limestone, dodging gushing water and falling rock, to build a web of tunnels 300 feet underground that can hold up to 20 billion gallons of rainwater and sewage. The aim: to clean up Chicago waterways once filled with so much muck that riverfront property often did not face the water.

Deep Tunnel planners say they're reaching that goal. Fish are returning to the Chicago River. And this week workers are continuing the last 7.7-mile stretch of the last leg of the project, based in South Holland, building underground scaffolding and pouring concrete into the shaft. By this time next year, the final web of tunnels will come online.

When that happens, Jovanovich and some 250 other workers, the itinerant miners and fathers and sons who have built these damp passageways for decades, will migrate to the next underground job to build tunnels and subways and deep water reservoirs in other towns and cities.

Unusual job fosters friendship

But for now, Jovanovich concentrates on a project that has kept his attention, challenging him, exciting him, giving him a sense of community--even breaking his legs and robbing him of a fingertip--since he began blasting 27 years ago.

The competition, the danger, the camaraderie he has developed among the gruff men, and a few women, keep him interested in a job that demands precision, skill and stamina, he said.

"Every job is different," Jovanovich said. "You enjoy the challenge. You get the satisfaction of blowing something up."

At 8 a.m. he steps into the cage, suspended by a single wire, that will take him down a narrow shaft 240 feet below ground. The cage descends slowly until it reaches a platform in a manmade cavern, a miner's Magic Mountain, where wooden spillways look like roller-coaster tracks and water seeps through layers of limestone netted with steel.

The buzz of construction echoes down two giant tunnels smooth with 4-foot-thick concrete lining. Miners wear earplugs and earmuffs to dampen the noise and use hand signals to communicate. But each man knows his job.

It begins with a series of blasts used to blow a vertical hole in the ground, and another series of blasts clears away enough rock to fit a 200-foot-long tunnel-boring machine, or TBM, into a horizontal space.

The machine, a massive contraption of sharp blades and steel, cuts through stone at a fast clip and transfers the shards to a conveyor belt that carries the debris up the shaft.

Crew members stand along the TBM, assembly-line workers in a cylinder cave. They grease machine parts, run drills so the earth doesn't cave in and lay rail underneath the TMB as it advances in the tunnel.

A mechanic and an electrician keep parts and utilities running, including a pump in case the crew runs into a gush of water. A railroad car brings supplies from above ground. At the helm, a worker operates the blade, which rotates like a giant fan as it cuts through the rock. Jovanovich, as foreman, oversees the operation.

"It's pretty loud," he said.

But the crew has brought a few creature comforts from home. Behind the blade operator's air-conditioned cab, the men have added a refrigerator and a microwave. A high-tech ventilation system, a canary in a coal mine of sorts, pumps fresh air into the tunnel to flush out carbon monoxide and other poisons generated by the drilling.

"It's a pretty sophisticated canary," said Tom Bradshaw, a foreman who has been working on the Deep Tunnel for two years.

The job is easier with the modern amenities and the TBM than it was back in the day when a miner's life was like a page from the Wild West and miners sometimes showed up at work drunk and ready to brawl, Bradshaw said.

`Where the devil is'

Nowadays, there aren't many mishaps with explosions, and miners are rarely injured by cave-ins and falling rocks. But the job can still be dangerous, and both Bradshaw and Jovanovich have been severely injured in underground accidents. Falling rocks broke Jovanovich's legs, and the tip of a forefinger was sliced off when it got caught in the chain of a conveyor. Bradshaw has his "share of scars," he said.

He jokes that the injuries come with the territory.

"The deeper you go, the hotter it gets, so that tells you where the devil is," Bradshaw said.

While a sense of adventure drew the miners to the profession, lifelong friendships and friendly competition have kept them there. Miners cross paths as they crisscross the country in search of jobs, they said.

Many of them belong to the Ground Hogs Club, which holds a swank dinner at a luxury hotel each year. They greet other, Jovanovich said, by saying, "You look pretty good all cleaned up."

Crews compete to see who can cut the most limestone and lay the most concrete in a single shift. The Little Calumet crew has set the record three times--for best day (99.1 meters), best week (562.2 meters) and best month (2,163 meters), according to statistics keptby Robbins Tunnel Boring Machines, a company that manufactures TBMs.

"It takes organization and everybody working as a team," Jovanovich said. "Plus the right rock conditions: not too hard, not too soft."

On Friday afternoons, they carry an electric grill into the tunnel to cook bratwurst, steaks and chicken, Jovanovich said. They take turns eating so that the work never stops.

Once, when Jovanovich was drilling near Brookfield Zoo, a near-accident forced his crew to warn zookeepers in advance of an impending blast, he said.

After a blast, "one of the keepers just about got bit by a tiger or a lion," Jovanovich said, a smile creeping across his large face. "After that, we had to call."

Jovanovich insists the years spent underground haven't changed him. His job is no different than a cop's job on a dangerous beat or a fisherman plying the high seas, he said.

When he first started on the job, people would marvel at the novelty of his work, he said. It's a reaction he never understood.

On sunny days he has to squint when he comes up the shaft until his eyes adjust to the light, he said. But rainy days never affect his work. He' has never been snowed out of a job. And when ice packs Chicago's streets, the tunnels remain nice and warm.

"Some people get scared underground," Jovanovich said. "They don't like it. It just seems natural to me."

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Deep Tunnel project nearing completion

Workers on Wednesday finished drilling the last underground segment of the $3 billion Tunnel and Reservoir Plan begun in 1976. The 109.4 miles of deep tunnels and three reservoirs are designed to hold sewer overflow before it is sent to treatment plants.

KEY:

Tunnel: Drains water from overloaded sewer systems during storms.

Under construction

Completed

Reservoir: Holds water the tunnels will carry.

Under construction

Completed

Last 7.7-mile stretch

Drilling is complete.

Final work is scheduled for completion in 2006.

Transitional reservoir

Currently is in use.

Sources: Jack Farnan, Metropolitan Water

Reclamation District of Greater Chicago.

Chicago Tribune/Haeyoun Park and Phil Geib.

- See microfilm for complete graphic.