One hundred and sixty feet above the surface of Washington, Ron Uplinger is concentrating on the job at hand: saving a crumbling smokestack that has towered over Georgetown and the Potomac River for nearly 70 years. Every few minutes, he checks his safety harness as the winds whip against his face and shake the scaffolding on which he stands.

It's a long way down.

Once in a while, Uplinger pauses, looks up from his work and takes in a view of the nation's capital that few have seen. During a lunch of burgers and fries, he'll study the traffic jams on the Key Bridge, the vehicles appearing no bigger than Matchbox cars. He'll notice the president's helicopter buzzing by below, or snap photos of the monuments.

And occasionally, he'll reflect on the strange mission that keeps him high above the Earth through 10-hour shifts. "I thought it was unusual they were saving this smokestack," he said. "It's not that ornamental. It's just basically a smokestack."

For much of the 20th century, that smokestack spewed clouds of malodorous fumes into the air, the product of a city incinerator below that burned as much as 170 tons of garbage a day. Naturally, the good citizens of Georgetown protested in 1932 when the District decided to build it--and cheered when the city closed it in 1971.

But today, Georgetown residents refuse to let anyone tear it down. They say the Georgetown Incinerator, near Wisconsin Avenue and K Street NW, must be preserved for posterity because it has historic value as an example of art deco architecture and a remnant of the once-industrial Georgetown waterfront.

And so it is that the developers who bought the last major tract of undeveloped land in Georgetown, one with a commanding view of the Potomac River, are trying to build a $150 million luxury hotel, shopping and theater complex around a giant red-brick chimney.

"As projects go, this must be one of the most complex anybody has ever done," said Anthony Lanier, the local partner of the New York-based group selected by the city to develop the site. "Rarely will you find a project where you need to dig an extremely deep hole through rock, with a historic building and a high, fragile structure like a chimney sticking out in the middle, all right next to a highway.

"My nightmare is to wake up and find the smokestack across the Whitehurst Freeway," he said. "But believe me, we're doing everything humanly possible to avoid that."

Doug Larson, the project superintendent for Bovis Construction Corp., said preserving the incinerator presented two challenges.

First, engineers needed to figure out how to dig a 75-foot hole around the building--for a parking garage and 12-screen cinema--without letting the building itself slide into the hole. To accomplish that, construction crews have shored up the dirt and rock base below the incinerator by putting steel beams deep into the ground and have further braced the structure with steel cables.

But because the crews will need to blast through solid rock to dig the hole, engineers had another problem: What would the tremors do to the incinerator's smokestack? Would it collapse or topple over?

"It's a unique situation. No one has ever done any blasting around a big chimney when they wanted the chimney to stay up," said Jim Fleming, project manager for the International Chimney Corp. "They ran computer modeling of the seismic impact on the chimney, but there's no history or field experience to go by. It's all educated guesses."

The computers said that the chimney would not fall apart but that it would surely crack at the top and perhaps lose its round shape and become an oval. So the company sent Uplinger climbing up the smokestack to see what he could do.

The Buffalo-based International Chimney Corp. specializes in this sort of thing, "basically anything that's tall--smokestacks, lighthouses, monuments," Fleming said. The company builds them, demolishes them, repairs them and sometimes even moves them. International Chimney found a way to pick up the 200-foot-tall, 4,400-ton Cape Hatteras lighthouse and slowly move it more than a half-mile inland so it wouldn't be washed away by the ocean.

The engineers thought about moving the Georgetown smokestack too but decided it would cost too much. So they came up with another plan.

In essence, Uplinger and two other workers dismantled an inner smokestack nestled within the exterior structure and then built a metal "corset" around the top half of the chimney, using large metal hoops and wooden two-by-fours. They did it all in four months, finishing in late November.

"It's a small one, so it's not that bad," said Uplinger, 42, a 22-year veteran of the business who has climbed up smokestacks as tall as 1,000 feet.

If all goes well, the corset will help the smokestack retain its shape during the blasting, and Uplinger will return to repair the cracks. A series of test blasts are scheduled for Monday. Seismographs have been installed on the chimney, the Whitehurst Freeway and other surrounding structures, and if the measurements match the computer predictions, the real blasting could begin within weeks.

Lanier said the entire project won't be done until 2001. When it is, the incinerator building will serve as a lobby area for a Ritz-Carlton hotel, but the architects haven't figured out what to do with the chimney.

"We're still grappling over how to integrate it into the design," Lanier said. "We might put a skylight on top. Maybe it will be a wine cellar--or a winestack."

CAPTION: Ron Uplinger, construction foreman from International Chimney Corp., climbs to the rim of the former Georgetown Incinerator smokestack.

CAPTION: Uplinger and others built a metal "corset" around the top of the chimney to protect it from blasts.

CAPTION: The circular walkway tops the 163-foot-tall chimney being restored as part of a $150 million hotel, shopping and theater complex near K Street and Wisconsin Avenue NW.

CAPTION: With a view of Washington over his shoulder, Ron Uplinger, a construction foreman, affixes an electronic sensor to the top rim of the smokestack.