At Pier 25, a Quiet Finale to an Unfathomable Job   Two weeks before the city ceremoniously ended its recovery operation at Ground Zero, the barge men of Pier 25 had a little ceremony of their own. Here on the Tribeca waterfront, where 1.1 million tons of mangled steel and unrecognizable debris had been offloaded around the clock for eight months, the last of more than 60,000 truckloads had come and gone. The remaining crane, one of the two that had hoisted it all onto barges, would soon be tugged away. It was time to mark the end of the cleanup operation on Pier 25. At this ceremony, on the bright afternoon of May 15, there were no speeches. Just a cookout and some group photos. Then, as the workers stared silently, Jerard Geary locked the steel jaws of his excavator onto the roofs of the two small wooden shacks that had been their shelter for all those months, and in a matter of seconds the machine smashed the sheds into scrap.   John Devlin followed with his front-end loader, pushing the wood into a single pile, the last debris to be carted away from Pier 25. Somewhere amid the splintered wood were the spray-painted words: "Some gave all, all gave some." "There goes our home, Tommy. No more shanty left," Robert Lang, who maintained the heavy equipment from the beginning, said to dockbuilder Tommy Vario. "I hope all the families get closure some time, some way," said Mike Mazzei, who had directed the seemingly unending caravan of trucks since September.   "It’s over," the men kept saying, and some talked of their relief that the 12-hours-a-day, seven-day work weeks were over. But not everyone. "I started work at 19 and I’ve never liked my job," said dockbuilder foreman Danny Harkin, 43. "This is one job I got up and came to work every day and I was happy to come to work. "The only good thing about me leaving here is I get to reacquaint myself with my son," added Harkin, the single father of a 15-year-old. There was still some final business to attend to. The 100 cubic yards of sand on the pier’s volleyball court had to be replaced before the barge and the crane and the crews could leave for good on May 17. No sooner would they be gone than bikers and joggers would appear—for the first time since that sunny Sept. 11 morning—along what had been their waterfront bike path. "I can’t believe it’s over," Harkin said, shaking his head. "It might take me a week or two to realize what really went on."