NEW YORK — Tom Canavan saw the stairs through the smoke after tunneling out of debris that buried him when the World Trade Center's south tower collapsed. The sun fell on a section of gold awning that led him down the stairs to safety on a nearby street.

The north tower collapsed a few minutes later.

"Without that staircase, I don't see myself getting out of that plaza before the north tower comes down and kills me," said Canavan, one of countless Sept. 11 survivors who escaped the burning ruins by the same route.

That staircase — 37 stairs that once connected the outdoor plaza outside the twin towers to the street below — survived Sept. 11 and remains the only above-ground remnant of the trade center complex.

After years of debate over whether and how to preserve the structure, though, the staircase will be moved this weekend for the first time. The stairs are moving about 200 feet west on the site, to be stored until they can be installed at the Sept. 11 memorial.

"I would have liked it if they could have left it where it was," said Canavan, 48. "I realize they couldn't do that."

Preservationists and survivors of the 2001 terrorist attack began campaigning years ago to leave the staircase as it stood, while developers refined plans for office towers, a transit hub and Sept. 11 memorial on the 16-acre site. The staircase, which had weighed 175 tons and stood 22 feet, sits in the middle of the footprint of a 1,278-foot skyscraper, one of five being built to replace the destroyed towers.

In 2006, state officials announced they would demolish all but one or two slabs of the staircase to make way for the new tower, undeterred by a preservation group that named the steps one of the nation's most endangered historic places.

The site's owner, the Port Authority of New York and New Jersey, said the piece could not be taken off the site because it is too tall for traffic lights and overhead poles and possibly too heavy for bridges.

"You would have to have started moving light poles" to move the staircase intact, said Steve Plate, the agency's director of World Trade Center construction.

Leaders in Gov. Eliot Spitzer's administration worked out a compromise last year to separate the stairs from their concrete base and install them at the Sept. 11 memorial.

"The goal was always to preserve enough of this staircase to really communicate its power," said Joe Daniels, president of the foundation building the memorial. "We can reduce the whole size of this thing but still capture the essence of the stairs."

Avi Schick, chairman of the Lower Manhattan Development Corp. rebuilding agency that brokered the compromise, said that debate over the staircase became a symbolic struggle between the site's history and the long-delayed progress rebuilding it.

"You were pitting memory and preservation and loss and family against redevelopment and construction, as if you could have one or the other but you couldn't coexist," he said. "What we proved is in fact they could coexist."

To prepare it to move, the staircase was whittled down to 65 tons, which includes the weight of an elaborate steel bracing system that took three months to build.

This weekend, a 500-ton crane will lift the piece onto a flatbed and move it next to some construction trailers on the west side of the site, its stairs covered with plywood and Styrofoam for protection, Plate said. The Port Authority is spending $2 million on the move.

By summertime, the stairs will move again: This time a crane will lift them 70 feet in the air and across the site to the memorial, where it will be installed 50 feet from the twin towers' footprints, with stairs on either side for visitors to stand alongside.

The memorial is expected to house several other trade center relics, including pieces of the trident steel columns that once supported the 110-story towers and other artifacts currently in storage at a hangar at John F. Kennedy International Airport. Below ground, a wall that housed the towers' foundation is the last remnant to survive the 2001 terrorist attacks.

Canavan said the day the stairs are installed at the memorial will be the most important to him for the staircase since the day it saved him.

"Once it's in the museum and people can see it, that's the main thing. I think there's a little reverence to it," he said. "It's like a tombstone. This is sort of a tombstone for a lot of people who couldn't get out."