For the residents of the affluent Woodhaven Section of Bethesda, the story of the abandoned gold mine nearby floated somewhere in the half-world between legend and fact, a pleasant anecdote passed along by the real estate agents who sold them their homes.

But that was before some developers proposed building 16 new $150,000 homes on the wooded hill just behind their backyards.

That wooded hill, the neighbors are convinced is honeycombed with the tunnels left by the prospector who bought the land in 1889. It is probably unsafe to build on, they say.

Balderdash, says Mary Uranium Hymes, the 73-year-old daughter of the prospector who bought the land 88 years ago. "He didn't work it but a few years," she said yesterday. "They used picks and shovels back then. How much digging could he do?"

Mrs. Hymes had given developers Robert and Sheldon Blitz an otion to buy her 5 1/2 acre tract, and the two had gone ahead to recent months making plans to extend Poe Road toward Whittier Boulevard, divide the land into 16 lots, and build.

At the same time, in the living rooms along Poe and Alcott Roads, in the dens of the executives and government officials who inhabit Woodhaven, groups of neighbors organized themselves to fight the proposal.

They immersed themselves in the arcane complexities of access, easements, and slope requirements. They became instant experts on question of traffic flow. And, with the verve of a high school history class, they set out to find out all they could about the mine and where its tunnels went.

"This search took us from the Floradora Hotel in the Yukon to Antigua," Alvin J. Arnett, organizer of the Woodhaven group, told the Maryland-National Capital Park and Planning Commissioners yesterday as the commission met to consider the Biltz proposal.

"This has been two-month search for us," he added. And the facts he and his neighbors found, he said, explained "the mystery of our community since we've been there - the underground water problem.

"I have seen on my property the geysering of water from what a geologist would call snake holes" - small, seemingly bottomless holes that have opened up to his backyard.

The reason for all of this, he said, is the old mine. In his speech and in the sheaf of documents he and his neighbors collected for the commissioners. Arnett detailed the legacy of Charles Miller, the prospector who obtained the rights to the land in the last century so he could mine part of the thin vein of gold that ran through the hard clay from Great Falls to Rock Creek.

Area histories show that more than 70 gold mines once pockmarked south-western Montgomery County, but they have left little more than a few anonymous gullies to mark their existence. The memory of most, like that of the Miller mine, has almost faded away.

That is, until the Woodhaven residents started their research. They pieced together a picture of the inside of the Miller mine from the memories of middle-aged men who as children sneaked into the tunnels to explore that subtereanean world more than three decades ago.

Those memories painted the picture of a tunnel leading to a great chamber, perhaps 30 by 60 feet, which was largely filled with water. Small boys built rafts and poled into the tunnels deeper inside, until the mine was closed off in the 1920s.

"That's a lot of crap," developer Robert Blitz said after yesterday's hearing. Earlier, a geologist hired by Blitz had told the commissioners what he had found after the Blitz earth moving machines broke open the mine entrance Wednesday night.

"One shaft goes 325 feet into the property," geologist Sachinder Gupta, of the Towson firm Century Engineering, told the commissioners. "But it doesn't underlie any of the proposed houses."

One shaft running laterally from the main one might come under one house, he conceded. But he said that there would be no problems of subsidence - or sinking of the new homes - because of the nine-foot high tunnels. "We don't believe that subsidence, even if it occurs, can reach the surface."

Mary Uranium Hynes agrees. "I have a terrible curiosity for a woman and in 25 I dug a hold large enough to get in there, borrowed a kid's boat, and took a lantern," she said yesterday, she said, is what she found 52 years ago - no cavern, just three tunnels in an "F" formation.

Yet after all the historical lore that had been laid before them, after the claims and counterclaims on the configuration of the mine, the commissioners voted unanimously to disapprove the preliminary plans because of teh inadequacy of the proposed access road.

"The issue of the mine is fascinated, but I'm not entirely sure how relevant it all is," chairman Royce Hanson said.

However, he noted that he agreed with an earlier comment by commissioner Mable Granke who said, "There's a real doubt in my mind that a determination can be made that this land is safe to build on."