New York ? At ground zero, now comes the hard part.

In 37 weeks, a small army has removed 1.8 million tons of World Trade Center debris, sifted through grime and ash for human remains, and consumed 3.2 million meals served by a volunteer force of more than 7,000.

Recovery efforts are complete at the World Trade Center disaster site. A ceremony marking the official end is scheduled for this morning.

This morning the recovery and cleanup of the Sept. 11 attacks officially ends. For the army that became a community on the site of unspeakable horror, this is hard to take.

“This is very difficult for all of us,” said Sean Callan, a stonemason who has worked on the site since October. “First we faced the enormity of this, then we supported each other as a family, and now we’re scattering to the four winds.”

The site now looks like any 16-acre construction zone. But the fact that workers achieved a monumental, emotionally draining feat ahead of schedule and under budget offers small comfort to some.

Tim Cahill, who operates cranes and other heavy equipment, finished lunch in the huge “bubble” where workers eat, shower and decompress, then talked about the emotional toll and the sense of an incomplete task.

“Emotionally, many of us just shut down. Construction guys aren’t used to finding pieces of people every day,” he said, nudging at his helmet. “There’s no preparation for it. I just became numb.”

Cahill and Callan also spoke of the grim reality of the arithmetic: 2,823 known victims, but the remains of only a third have been found. The medical examiner’s office hopes that DNA tests may eventually identify some others.

“Psychologically, that’s what’s hard to take,” said Callan. “We realize most are gone without a trace.”

Molly Shotzberger, a counselor and major in the Salvation Army, has worked on the site since “Day 2,” Sept. 12, and will be part of the honor guard at Thursday’s ceremony. An empty, flag-draped stretcher will be taken from “the pit” to honor the victims never found.

Shotzberger is afraid that many workers are experiencing a delayed reaction to the enormity they have experienced. Their work is visually dramatic. The toll on them is largely hidden.

“There’s a feeling of relief and achievement, but there’s an overwhelming sadness that just grips at you,” she said. “Many people have put off thinking about it, and they can’t talk to their families about it.”

Shotzberger likes to use the analogy of a video freeze frame to describe what workers are going through: “For months we’ve been caught in that freeze frame, now it’s time to get it moving forward and see the rest of the story.”