Residents of the Mount Vernon subdivision of Wellington Villa have been given another chance to prove their claims to a half-acre park on the Potomac River that a Fairfax resident says belongs to him.

At a recent hearing, Fairfax Circuit Court Judge Thomas J. Middleton agreed to continue the case and admit new evidence. Before the continuance was granted, residents said that they believed that the park had been all but lost because Middleton had said in the case's first hearing in September that Wellington residents had a right to an easement to the park's beach rather than a right to prevent Richard C. Morauer from building a house on the property. Middleton did not make a final ruling at that time because he needed to know the park's exact boundaries.

"The judge had ruled that he [Morauer] could build on it [the park]," said Virginia Edge, whose property abuts the north side of the park. "I think the fact that we got a continuance is a favorable factor . . . . "

The dispute over rights to the land started in 1983 after Morauer, who owns an excavating firm in Maryland and a ready-mix concrete business in Arlington, bought the park for $5,000. The county had assessed the property at $89,250. Morauer secured a deed from the heirs of the subdivision's original owners, Eugene and Harriet Frost.

Longtime residents of Wellington Villa, surprised by the sale, said that they had always assumed that the lot, marked as "Park" on the original 1912 subdivision plat, was a common area owned by the neighborhood.

During the past 72 years, they said, the park has been used for picnicking, swimming, boating and nature hiking.

The residents filed a lawsuit against Morauer in November 1983. Five of the residents are represented by attorney Marian K. Agnew, who has been active in Fairfax land use issues. Other residents are represented by Jeffery Knapp and David Frantz of Mehler and Lamb, a District law firm.

Two weeks ago, Wellington residents, some of whom are involved in the lawsuit over the park on the Potomac river, formed the Red House Cove Association Inc., to unite the neighborhood against possible future encroachments by real estate developers.

"Riverfront property is very hard to come by and very valuable if they develop it," said one person familiar with the dispute.

"It's the kind of acreage on the river that somebody would love," noted association member Joan Lyon, a Wellington resident for more than 20 years.

The homeowners association, named after Red House Cove, a section of the Potomac River marked on an 1864 map of the area, is still recruiting members.

"It seems a great many people are interested in joining. We hope to get most of the community, all of the people who live in the original 49 plots of the subdivision," said association president Ann Miller. In the event that the community retains rights to the park, the Red House Cove group plans to maintain the park, she added.

The judge is expected to make a final decision in the case at a March 7 hearing.