Call this item No. 16,853 in the seemingly endless parade of incidents wherein a few jerks can ruin a treasured resource.

Robert Mumford, a retired Navy captain from Bethesda, has been enjoying a small, island-studded stretch of the Potomac above Great Falls since 1963, when a friend showed him a road in.

The route is an unmarked dirt road that runs off River Road for a quarter-mile into property shared by the Washington Suburban Sanitary Commission, the National Park Service and two gas pipeline companies, which have rights of way. It ends near the river.

Mumford found that by using the dirt road he and the other lucky few who knew about it could enjoy an untrammeled stretch of river where the smallmouth bass fishing and duck hunting were good. "It's really a beautiful, beautiful area," Mumford said last week.

On October 9 Mumford pulled in before dawn, unloaded a small aluminum boat, some decoys, his shotgun and some other gear and set out for a day of duck-hunting during Maryland's three-day early season. He did poorly but stuck it out, returning to his car at 6, drenched after an attempt to retrieve a duck.

He found a note on his windshield, saying: "Notice: You are on private property and are locked in. To get out, come to the (WSSC) water plant. The Montgomery County Police have your tag number and you will be charged with any damage."

Mumford said four or five other cars parked there all got notices, too. A padlocked gate was up over the River Road entrance. There had been no warning of WSSC's intention to close the access.

He went to the water plant, where he said workers were "embarrassed and sympathetic." They told him a nearby homeowner had complained to WSSC headquarters that morning about some shooting down by the river, and workmen had immediately been dispatched to build the gate and padlock it.

Mumford wrote to WSSC chairman Jesse Maury, explaining that in 18 years he had "never damaged anything or caused any problem whatsoever on WSSC land. I respect others' property and would certainly not want to jeopardize access to cherished recreation."

He wrote, "If it is true that your new policy is to prohibit public use of the access road, I solicit your reconsideration. . . Punishing the many for the sins of one is bad policy." Mumford offered to meet with WSSC officials and volunteered his help "as my contribution to keeping the road open for the public."

But Maury wrote back, "The incident . . . was only the most recent in a series of incidents which include shootings, destruction of property, trash dumping and tampering with equipment." He wrote that the police "unfortunately . . . do not have the resources, nor do we, to let the good guys in and keep the bad guys out." The gate stayed up.

That made the bad guys mad. A few weeks ago, according to Wayne Fallin, WSSC water operations chief, someone knocked down a section of fence, drove down to the river, shot two deer out of season with high-powered rifles, skinned them out and left the carcasses near the gate.

Fallin said that in recent years things have been getting dangerous along the dirt road. "They've been using it as a dump and a shooting gallery," he said. "They're dumping mattresses, tires, all kinds of trash. They're shooting at fence gates, electrical transformers, locks, the gas company equipment. We have evidence of shots coming throught the windows of our plants. Everything that's sticking up, they shoot."

Fallin said the final straw was indeed a complaint from a neighboring landowner. He said, "The commission figured it's not public land, so let's finally draw a halt to it.

"We're not talking about some people back there fishing. If one of my men is out working and somebody takes a shot at him, that's warfare."

Sadly, the victims of this silly war are people like Mumford, whose ambition is only to escape urban sprawl in a pretty place for a few hours.

He said that because of shallow water below the access road and rapids above it, he now has no way to get in to his little haven, which he describes as "really an amazing area for that close to Washington."

Mumford figures the WSSC, being a semipublic agency, has something of an obligation to share its recreational resources, where possible, with the public. He reckons that it would take someone half an hour a week to clean up the trash that accumulates along the dirt road, and said he'd be willing to donate his time for that purpose.

On the WSSC's behalf, Fallin guessed that "If we sat down with the lawful people who are affected, maybe we could work out something where the people could still use this property."

Mumford suggested a permit system or a check-in program at the WSSC plant; anything to give right-thinking folks a way around the barricade. Said he, "I just can't believe the whole world is evil -- that everyone would abuse that land."