Residents in a Southeast Washington neighborhood are threatened by a deteriorating retaining wall that geologists say could collapse and cause a landslide with the next heavy rainfall, taking lives and homes with it.

The Penn-Branch community, a neighborhood of more than 500 homes east of the Anacostia River, has mobilized to save the wall, which is restraining a gradually moving landslide. The wall, constructed with federal funds almost 20 years ago, stretches along O Street SE, from Carpenter Street on the east to Branch Avenue on the west.

The back yards of four homes on Highwood Drive, which runs parallel to O Street, are sliding away as the wall below them deteriorates.

The heavy rain and snows of last winter started the soil shifting again, creating a six-foot drop only a few feet from the houses' back doors.

Residents have pleaded with city and federal officials for help and money, so far to little avail. The minimum bill to repair the wall is estimated at a half-million dollars. So more than 100 residents gathered at a weekend community meeting at Pennsylvania Avenue Baptist Church, near the wall, to create a task force to mobilize the community and search for a quick resolution.

"You have gone from a natural hazard to a potentially nasty disaster," James O'Connor, the former city geologist, told the crowd. "If you look at the history of O Street, basically every time it rained, {the soil} moved."

O'Connor, a former geology professor at the University of the District of Columbia who lost his job in the latest round of firings, dubbed the site the "California Landslide East." He looked at the site for the first time in 1972 and has been studying it for the last 25 years. Residents discovered him at the wall in February and enlisted his help.

O'Connor warned residents that they couldn't do anything about the geology -- the wall sits on unstable red clay that turns to "liquid pudding" when it rains. A heavy rain makes the clay weightier, so it exerts more force to push the wall down. The wall, which already has one "severe compression crack" where water is draining, could collapse with the next heavy rainfall, he said.

If the wall collapses, the damage will not be confined to the homes at the top of the slope.

"It may have a domino effect," said Herbert Boyd Jr., who lives on Highwood Drive with his wife and 11-year-old daughter, though not in one of the four most threatened homes. The slide "will affect not just my home but the other 551 homes in the Penn-Branch area."

Homes on Highwood Drive would slide onto O Street, then topple onto homes on the other side of O Street, pulling other homes down with them, said Boyd, who is co-chairman of the wall committee for the Penn-Branch Citizens/Civic Association. Residents also are concerned that a landslide could break gas lines and cause an explosion.

In April, residents began to alert city officials to the problem, including Mayor Marion Barry (D), D.C. Council member Kevin P. Chavous (D-Ward 7), Del. Eleanor Holmes Norton (D-D.C.) and officials at the Department of Public Works, Department of Consumer and Regulatory Affairs, Washington Gas and several federal agencies. Their contacts prompted site visits by Chavous, the Department of Public Works, the gas company, the mayor and the U.S. Department of Transportation.

Although Boyd said the wall does not lack for visitors, there still "has been no long-term action or suggestions of how we should fund this process."

Chavous, who visited the site several times, said he plans this week to introduce a D.C. Council resolution to declare an emergency. If the mayor would then declare the site a disaster area, the residents could be eligible for federal funding. Barry visited in November but did not declare it a disaster area.

"We have legislatively and budgetarily expressed a commitment to that wall, and I think we have to follow through with that commitment," Chavous said. "The bottom line is . . . we are going to find a way to reinforce that wall."

The Department of Public Works intervened to do some short-term remedial work, such as drilling more drainage holes in the wall and laying a mesh covering on the soil so it wouldn't absorb water. The department also set up a temporary plastic drainage system.

Last April, the department also contracted Thomas L. Brown Associates, P.C., to conduct a $210,000 geotechnical survey.

"It is evident that the retaining wall and slopes described in this report are sliding at an alarming rate," the study concluded. "When and if the wall completely fails, the houses that are at the crest of the slope will likely experience significant, if not catastrophic structural damage. Depending on where the occupants are at that time, the situation could be life-threatening."

Residents whose homes sit on the top of the slide say they live in terror.

"There's a possibility that we could just slide right down the hill," said Geraldine Boykin, who lives with her daughter in one of the four high-risk Highwood Drive homes. "You just don't sleep at night. . . . You don't know when you may go."

Boykin, whose back yard sidewalk cracked in half last winter, looked despondently at the slope a few feet from her back door. A lonely blossoming cherry tree, which she planted about a year ago, now is stranded among a patchwork of plastic tubing and mesh cloth. There is a crack in the foundation of her brick home, and she has lost a substantial part of her back yard.

Those at the community meeting agreed to lobby for the emergency city legislation such as Chavous promised to introduce, ask for federal assistance and organize a fund-raising effort. They have asked Norton to see whether $2 million allocated for the now-dead Barney Circle project could be used to restore the wall.

The O Street landslide, which has been in existence for almost 60 years, became a concern after heavy rains that were brought by Hurricane Agnes in 1972. The sliding earth eventually blocked off half of O Street and forced the construction of the wall. But the perpetrator of the slide -- the pudding-like clay -- was never removed, so the deterioration continued.

O'Connor explained that part of the District sits on a belt of red clay that stretches from Martha's Vineyard to Richmond. At one time, there were 20 active landslides in the city, he said.

A group home for youths, designated by O'Connor as the home in the most danger because it is sliding down the slope, suffered so much foundation damage to its garage that the department of Consumer and Regulatory Affairs said they couldn't use it. CAPTION: The retaining wall, cracked from top to bottom, is in danger of collapsing. CAPTION: Herbert Boyd Jr. warned that the wall's collapse could have a domino effect. CAPTION: The retaining wall, which stretches along O Street in Southeast, was build with federal funds almost 20 years ago. CAPTION: Residents stand above the wall behind several homes in the Penn-Branch neighborhood that have suffered foundation cracks in the gradual landslide.