Prince George’s County government officials have issued a mandatory evacuation for homes in a Fort Washington subdivision where a slope failure over the weekend destabilized homes, collapsed a road and triggered a water main break. (Arelis R. Hernandez/The Washington Post)

Geotechnical engineers extracted soil samples Wednesday from the Fort Washington neighborhood that was destabilized by a landslide over the weekend, trying to determine if there is enough solid ground to save the collapsing road and six homes atop a crumbling ridge.

A total of 28 homes in the riverfront Piscataway Hills neighborhood are under an evacuation order, six because they were damaged by what engineers are calling “slope failure” and the rest because the collapse ruptured water and sewer lines and left the road unsafe.

A few Piscataway Drive residents who did not want to comply with the order have signed waivers releasing the Prince George’s County government from liability if they are injured by collapsing structures or falling debris.

“By unlawfully remaining in your home/structure, you agree that you do so at your own risk and assume the risk of any and all injury,” the document said.

They’ve been warned, said Gary Cunningham, deputy director of the Prince George’s Department of Permitting, Inspections and Enforcement. “They’re going to have to make their own decisions.”

Officials said Pepco’s decision to cut off power to the houses Tuesday night helped convince some reluctant residents that it would be better to seek shelter elsewhere. While some evacuees are staying with family or friends, the county negotiated a discounted rate for those affected at nearby hotels.

At least one couple, who asked not to be publicly identified, agreed to leave their house late Wednesday afternoon after vowing to stay.

“I wouldn’t have my family in there,” said Maryland state geologist Richard Ortt, who visited the site Tuesday.

Neil Ayers, a board member of the Piscataway Hills Citizens Association, said the homeowners who want to stay feel that their houses were not directly affected by the rupture. Most, if not all, “are going to end up rolling out because they don’t have water or power,” Ayers said. “They feel like the county is pushing them out.”

At a community meeting Tuesday night, Ayers was one of several neighborhood residents who tried to offer alternatives to the evacuations, such as running power cables underground to homes on Piscataway Drive that are not in danger of sliding down the hill.

Ayers, who lives on a different street in the community and did not have to evacuate, said uncertainty about when the order would be lifted is driving the residents’ anxiety. Residents are being told that it will take at least until the end of next week for engineers to complete a report that will offer the first indication of whether their homes — and their neighborhood — can be saved.

“What if that takes three months?” Ayers said. “Those who live below the break [in the road] or have no imminent risk to their homes . . . are going to be some angry homeowners if kept out of their homes for months.”

Residents are also worried that their homeowners insurance will not cover damage if the landslide is declared a natural disaster.

The enclave of custom-built homes on heavily wooded individual lots is tucked against National Park Service land about seven miles south of the Capital Beltway. The houses were built over the past four decades.

On Wednesday, the engineers from KCI Technologies bored into the soil with hollow tubes to extract samples for analysis.

Evacuees were allowed to visit their homes briefly during the day to remove valuables, riding with an escort on all-terrain vehicles.

Rain fell steadily in the morning and more is expected over the weekend, which could complicate stabilization efforts.

Behind one home in the 13700 block of Piscataway Drive, large trees leaned at a 45-degree angle, tilting precariously over the missing layer of soil that had sustained them just days earlier. Many trees had given way to the pull of gravity, tumbling down the hill as their roots pulled out of the rain-saturated ground.

Ortt, the state geologist, said an outcropping of clay deposited in the hillside becomes as slippery as an ice rink when wet, making the area vulnerable to landslides.

Engineers still don’t know what caused the soil to become so wet. Possibilities include rainwater, underground springs and sewage.

If the earth keeps moving, officials may have to remove the few holdouts forcibly, but Cunningham said the situation has not reached that point.

“These are their homes and they don’t want to leave,” Cunningham said.