The 30-foot girder survived when the twin towers collapsed into a mountain of 1.8 million tons of rubble Sept. 11. For months it was covered by debris, but as the pile shrank the column was revealed, still standing where it was erected when the south tower was built three decades ago.
During the last few months, workers topped it with a flag and covered the sides with spray-painted messages and photographs of victims.
"It means a lot to people - it's like a flag, which is a piece of cloth, but it represents our country and an idea. The idea of the beam is our strength, our resilience, " said Richard Streeter, who has operated an excavator at the site since Sept. 12.
Hundreds of construction workers who have labored at the site planned to watch as the column was severed with a cutting torch and draped with a flag while bagpipers played.
The ceremony was the first of three planned for construction workers, rescue workers and families in a gradual farewell to the round-the-clock recovery operation.
On Thursday, the beam will be removed from the site in a procession past an honor guard of police officers and firefighters. It will be put into storage and might be used someday in a memorial.
A Fire Department bell will ring the signal for a fallen firefighter, after which a stretcher with a folded flag will be carried out of the site, honoring the victims whose remains have not been found.
To accommodate those who could not attend the ceremony in the middle of the work week, victims' families have planned their own service at ground zero on Sunday. The city has issued permits for the event.
Of the 2,823 people killed in the attack, the remains of just 1,088 have been identified. But nearly 20,000 body parts have been recovered, and the medical examiner expects to continue identification work for at least eight more months.
At the site on Tuesday, "everybody's pretty somber, because we've been doing this for almost nine months and we don't want to leave, " said Port Authority police Lt. Mark Winslow. "But we did all we could here. "
Thursday's ceremony is expected to draw thousands and was intended for city officials, ground zero workers and victims' families. Still, some families were unhappy that Mayor Michael Bloomberg planned it for a weekday.
Several family groups had asked Bloomberg to schedule the service on a weekend, so that work and school would not be disrupted. But the mayor said the city did not want the ceremony to conflict with religious observances.
Jennie Farrell, whose brother died in the attack, wrote to Bloomberg on behalf of the families, saying the ceremony should at least be held on "a day that will not add to the nightmare we live in every day."