Head east on Route 488, a quiet, hilly two-lane road in the heart of Charles County, and after a few miles, you will likely see a car, or two, or eight, stopped on the shoulder, piled high with crates of plastic gallon jugs.

You'll find folks from as far as Washington, Baltimore and Virginia and lifelong locals alike, all filling dozens upon dozens of containers with the sparkling clear, cold spring water that has risen from the ground for decades.

Many regularly make long drives because the spring water tastes just that good. At least a few are poor rural residents, the 2 to 3 percent of the county population without indoor plumbing. All appreciate that the spring water comes straight from the earth--not a faucet--and has never been chlorinated, fluoridated, packaged or shipped.

"I call that spring the fountain of youth," said Samuel Lyles, 80, who has been drinking the water for about 35 years and who looks barely a day past 60.

Regulars greet each other as they wait for their turn at the watering hole--a steady flow streaming from a pipe encased in a large concrete bunker that diverts water from the roadway. On sweltering summer days, a tall, chilly drink from here can quench the deepest thirst.

But the spring is not as idyllic as it seems.

On a recent day, a water sample that The Washington Post had laboratory-tested failed quality standards, showing the presence of coliform bacteria. Previous samples have failed just about every test that's been conducted in recent memory by the county health department and a local laboratory.

"We have to consider the supply as unsatisfactory for human consumption," said Gary Davis, director of environmental health for the Charles County Health Department.

Passersby noticed the bubbling spring when, in 1937, the state paved what had been a dirt country road nearby, according to Lyles, a construction worker until he retired. A local doctor installed a pipe to make it easier to draw the cool water from the ground, Lyles recalls.

Then in 1976, the Maryland highway department installed the larger pipe when it widened and straightened the road, said Valerie Edgar, a spokeswoman for the State Highway Administration. The new pipe was designed to protect the road from the damage a steady flow of water could cause, she said. But it also made it easy for people to access the spring.

Fed by a shallow aquifer that is replenished with rainwater, the spring is highly susceptible to ground contamination, Davis said. So when the state paved the shoulder of Route 488 in the early 1990s, the county health department spent about a year taking regular samples, most of which tested positive for coliform bacteria, he said.

The coliform bacteria is not necessarily harmful, Davis said, but its presence signifies that material from the ground is seeping into the spring. Anything spilled on the ground, including human and animal waste, pesticides, fertilizer or gasoline, could end up in the water.

So even if the water has never made anyone sick, that doesn't mean it is safe to drink, in Davis's opinion.

"As development along 488 may increase, the potential for the water to be contaminated by something harmful also increases," Davis said. "If someone did something stupid like dump pesticides on 488, and it rained, people could be drinking the pesticide."

Several years ago, the county asked the state to remove the pipe, Davis said. Instead, the highway department posted health advisory signs warning people not to drink the water, he said. Within days, the signs disappeared. But David Buck, a highway department spokesman, insists no one ever contacted the department about the pipe.

No agency--state or local--is responsible for monitoring or policing the many small springs around Maryland, said Quentin Banks, a spokesman for the Maryland Department of the Environment. There is little that can be done, he said, to keep people from drinking from questionable water sources.

"The spring is coming through with the force of Mother Nature," Banks said. "And you just can't stop it."

Removing the pipe might be a good idea, Davis said, but "the melee in the community could be substantial."

Highway department officials are willing to discuss alternatives to the pipe, Edgar said, but she added, "We haven't gotten any complaints, and it's not our business to tell people where to get their drinking water."

For some, removing the pipe would create a hardship. Lyles doesn't have indoor plumbing, like 2.7 percent of Charles County's population, according to the 1990 U.S. Census. He has a hand-dug well in the woods near his trailer, but is partial to the "nice, sweet-tasting water" from the spring. Almost every day, he makes early morning trips to collect it for drinking, cooking and gardening.

Others, who prefer the spring over water from their taps, insist that it tastes better and makes them feel healthier.

"It's just pearl, clear water," said Mary Thompson, 57, of Waldorf, adding that it doesn't look like it has anything in it. She said she has been drinking from the spring for 10 years. "I have a well, but I don't like the water as much as this."

"This is the best water," exclaimed Doris Tabbs-Steward, 55, of Anacostia, who travels from Washington once every month or two on the way to the Amish market in St. Mary's County. Like most, she collects as many jugs as she can fit into her car and always keeps one in the fridge.

Almost daily, the routine is repeated by the roadside as enthusiasts arrive with plastic containers as big as office coolers and as small as water bottles, then line them up on the concrete bunker as each is filled. Then they lug them back to their cars, sometimes running them in relays with spouses and children.

It is an arduous process under the summer's burning sun, but the water is its own reward. And everyone waits patiently for a turn, often helping strangers carry their jugs.

Most scoff at the notion that the water may not be fit for drinking.

"If the water was bad, don't you think the hundreds of people who've come here every week for years" would have become sick, said 61-year-old Willie Hall, who drove down from Fort Washington to fill 54 gallon jugs.

"It's worth it," he said, sweat soaking his straw hat on a 100-plus-degree day. "This water's just better. It comes from nature."