Prince George’s work crews cut down large trees in danger of falling, exposing the hillside where a landslide triggered evacuations for residents in the Fort Washington neighborhood of Piscataway Hills, they are seen here on May 16, 2014. (Arelis R. Hernandez/The Washington Post)

Fort Washington residents left homeless after a landslide this month were hit with more bad news Thursday, as an official warned that they likely will be out of their houses for months and an engineering firm blamed the collapse of the hillside neighborhood on heavy downpours.

“There is no quick fix,” Darrell Mobley, director of the Prince George’s County Department of Public Works and Transportation, said at a community meeting Thursday night. “We have to prepare for the reality that we are talking months, not weeks.”

KCI Technologies’ report, released late Wednesday, concluded that intense rain saturated a layer of clay inside the 65-foot- high ridge near the Potomac River, triggering the landslide that sent trees buckling, cracked the main road and ruptured water and sewer lines.

But some homeowners in the Piscataway Hills neighborhood say those conclusions disregard decades of reports from residents that the slope was sliding and nothing was being done to stop it.

“I don’t believe that it’s the rain,” said Tracy Rookard, 48, whose house sits on top of the hill and was deemed uninhabitable after the landslide. “It was not a monsoon, and it did not cause all this damage. The conditions deteriorated way before the rains.”

County Executive for Prince George's County, Rushern Baker, surveyed storm damage in Fort Washington that prompted officials to evacuate nearby homes. (Arelis Hernandez/The Washington Post)

Engineers said they can stabilize the hillside by reinforcing the land with steel and concrete, building a retaining wall and drilling micropiles — steel casings filled with cement — into the slope.

But it is unclear how long that work would take, who would pay for it and when more than two dozen displaced families in the Piscataway Hills subdivision can return to their homes.

The solutions are complex, data are still needed and cost-analysis is taking place — complicated further because the slope is private land, Mobley said.

His declaration squashed hope some residents might be able to return home soon while work continued.

The impact of the news was visible as residents placed their hands on their foreheads and closed their eyes in resignation.

County officials have asked the Maryland state geologist and the U.S. Geological Survey to independently review the engineering report.

Meanwhile, the earth continues to move, inch by inch, experts say.

(The Washington Post)

Scott Peterson, a spokesman for County Executive Rushern L. Baker III (D), said in an interview before the meeting that because the hillside is private, the county’s only essential responsibility is repairing Piscataway Drive.

Tensions have been rising as families grow weary of asking for answers that don’t seem to come — or to come quickly enough. Homeowners have hired an engineering firm, which they say will review the KCI report. And Prince George’s officials brought their attorney to a previous community meeting, stirring concern among some residents.

State Sen. C. Anthony Muse (D-Prince George’s) is helping homeowners find their own attorneys.

The county government evacuated the homes along the road on May 5, saying six of the structures appeared to have been damaged and the rest could not be safely accessed because of damage to the road. The houses ranged from a few years to four decades old and were custom-built and purchased by families drawn to the bucolic waterfront setting and nearby federal parkland.

Engineers detected a 30-foot-thick layer of Marlboro clay sandwiched between two other soil layers in the sloping landslide, the report says. The clay is common in Southern Maryland, where it was deposited 50 million years ago in shallow marine environments such as the Piscataway Creek valley, according to the state geological survey.

Moisture from heavy rains in late April and early May caused the landslide, KCI’s report says.

Rain seeps through the top soil layer until it reaches the impermeable clay and is forced to move along the surface, which becomes slippery.

“Over time, this water may gradually dissipate with little easing of the pore-pressures and causing little or no slope movements,” the report said. “However, during the recent intense and rapid rainfall recorded at the project site, the infiltrated water was not able to quickly dissipate in the Marlboro Clay and generated massive pore-pressure built up in the saturated sediments.”

There is no storm drainage system near the slope, the report said.

Piscataway Hills residents say they have long complained of minor land shifts in the neighborhood, but the hillside was never shored up or repaired.

A similar landslide occurred a mile away in the Forest Knolls neighborhood in the 1970s. Rainwater seeped into the steep slopes, causing weak spots that eventually led to cracks in roads and building foundations, according to a geotechnical investigation by Woodward-Clyde Consultants in 1976.

John Pomeroy, a geologist with the U.S. Geological Survey, gave Marlboro clay deposits the highest degree of susceptibility to landslides in a 1989 report. He noted that the Fort Washington-Indian Head peninsula region was particularly vulnerable to this kind of earth movement. And in 1982, the Maryland-National Capital Park and Planning Commission reported that about 24,000 acres of Prince George’s soil contains the slippery clay and requires “special attention during development.”

Absent from the engineering report were timetables. There were no estimates of how long any of three proposals to stabilize the hillside could take or how much they could cost.

Rookard wondered Thursday whether her home will remain uninhabitable.

Her homeowners insurance won’t cover the damage if her house is permanently condemned or if the catastrophe is classified as an “act of God,” Rookard said.

Her insurance has stopped paying her bill at an extended-stay hotel in Virginia, and she is using Red Cross vouchers to keep her in a room there with her two pets.

“I think we were all anticipating this report [by KCI] to be a silver bullet, and it wasn’t,” said Miles Cullen, another resident. “But now all eyes are on the county, and we need some decisive ­decision-making.”