A 73-year-old man who was repairing a pump in a back yard well in Upper Marlboro lost his grip and plummeted down the narrow 53-foot well yesterday, prompting a dramatic but futile 5 1/2-hour rescue attempt by Prince George's emergency crews.

Charles Bailley, who operated the Home Water Pump Service for more than 30 years in the rural sections of the county, slipped off a chain ladder that he had hung over the edge of the two-foot-wide well and fell about 35 feet, becoming wedged up to his chin in water, according to Prince George's Fire Department spokesman Tony V. DeStefano.

Bailley had been working in the well of S.C. Tyrell at 3007 Eton Dr., and was hanging several feet below the surface fixing Tyrell's pump, when he lost his grip, shouting "Oh no!" Tyrell told authorities.

About an hour after Bailley fell, the fire department lowered a rescue worker with a rope tied around his waist into the well in a desperate effort to reach Bailley, according to DeStefano.

But the rescue worker became stuck in the well about 14 feet underground and passed out from lack of oxygen, officials said.

While the first rescue worker was being rushed to Prince George's Hospital Center, where he was later listed in good condition, a second rescue worker, Richard Riley, was lowered feet-first into the well. Rescue workers had dug down about six feet to aid the rescue effort and had pumped oxygen into the well. Riley was equipped with an oxygen mask and a radio for his descent.

Riley, who is smaller than the first rescue worker, was able to reach Bailley. Riley, who said that the well was "dark, cold and stunk," felt for Bailley's neck for a pulse, but found no vital signs.

"At the time," Riley said, "gas started seeping into my mask and I had trouble breathing, so I radioed for them to pull me out."

Fire and rescue workers then hoisted Bailley out of the well using a hook and rope at about 3:30 p.m. Bailley's body was taken to Baltimore for autopsy.

Rescue officials said they were uncertain whether Bailley was killed from the impact of his fall or died later.

Bailley was well known in the community and for many years did much of the plumbing work in the area, according to neighbors at the accident scene in Brock Hall Estates, a tree-lined neighborhood of houses with estimated values of more than $100,000.

"He was the type of guy who would take on any task and stay until the job was done," said a neighbor who did not want to be identified and who knew Bailley for many years. "He was like a postman. He did the job no matter what the circumstances."

According to neighbor Pete Hagan, Bailley operated the pump repair service from his home on Old Marlboro Pike, where he lived for more than 50 years. In recent years, as Prince George's became more urban, most of Bailley's customers lived in the rural Upper Marlboro section of the county.

"He was one of the few experienced repairmen available to people for service in this area," Hagan said.

"He was an old guy to have such an occupation . . . . Lots of people said he was a little old for it," said Bailley's son-in-law, Bob Hoffman of Silver Spring, "but he was a tough customer. An independent and hard-working guy . . . . He could dig a ditch faster and farther than I could."

Bailley had supported his wife and nine children with his business and was reluctant to retire, Hoffman said, although he had been cutting down on his workload in recent years. "I had been working with him on a retirement plan," Hoffman said.

Bailley had been trying to pull out a pipeline in the well to repair it. "He was very good at what he did," Hoffman said, "but this particular kind of job was a dangerous one. This was a wide-bore well" instead of having a narrow opening.