"It's still pretty mixed-up feelings right now, taking the measure of what happened," said John Moon, 53, a 30-year veteran of the job. "Mike Boyce was hanging for 20 minutes by two or three fingers," he said of one of the injured men who clung to the icy tunnel's side after the winch fell on Wednesday. "Something gave him the will. Just thinking about his kids gave him the strength to pull himself up." Survivor of an Accident

A man with curly gray hair and thick glasses, Mr. Moon himself survived an accident in 1977 in a shaft in the Bronx, an example of how even the smallest of dangers can turn deadly in tunnel work. He was struck on the left side of his face by a falling clump of ice the size of a basketball, formed by tiny droplets of water that froze and accumulated on the shaft's wall.

"It will knock your head right off," said Mr. Moon, who said others have died from fallen ice. "It knocked me right to the ground."

Ice is perhaps the least obvious hazard: every day, cranes and winches lower into the holes enormous drills, bulldozers, buckets that weigh 32,000 pounds when filled with rock. Sandhogs handle explosives that shatter tons of bedrock in a blast. Rocks fall and tunnels flood, sometimes fatally.

"All of it is pretty dangerous," said Dennis O'Neill, 42, who is the general supervisor at a water shaft under construction in Park Slope, Brooklyn. "You've got to stay on your toes." In 1985, he and other workers nearly died when a gush of water and rock hammered into a shaft on Roosevelt Island. A History of Hazards

The sandhogs first organized in 1872 in protest of the hazardous working conditions during the construction of the Brooklyn Bridge, itself a project on a scale never before imagined. The issue was two sandhog deaths from the bends, a potentially fatal condition caused by exposure to the pressurized air inside the enormous wooden boxes that served as part of the bridge's foundation. (The bridge's chief engineer, John A. Roebling, also suffered from the bends.)

Many other accidents followed, though no one is certain of the exact number of deaths in part because unscrupulous contractors removed bodies from construction sites or fudged the causes of death, according to "Sandhogs: A History of the Tunnel Workers of New York" (The Longfield Press: 1983) by Paul E. Delaney.