SENECA — The cover soil that slid down a slope on the southwest side of the Ontario County Landfill last week has been moved to create a berm to keep stormwater from flowing off the site.

In addition, pumps were installed to remove any accumulating stormwater from the bottom of the slope, where 3½ acres of clay-based cover cap moved from an inactive, seven-acre cover portion of the 389-acre landfill.

County Administrator Chris DeBolt said Monday that work was done starting last Friday in hopes of avoiding the rainfall predicted for the weekend. He said the berm and pumps appear to have worked.

“In addition, two of the vertical wells on the slope that were damaged by the sliding soil have been sealed to lessen chances of bad odors,” DeBolt said.

Casella Waste Services of Ontario, which operates the facility through an agreement with the county, posted an alert on its website saying the veneer soil movement on one of the exterior soil slopes during a capping and closure project caused a two-foot-thick layer of soil to move part of the membrane near a perimeter road.

“There is no impact to waste materials or any of the site’s buffer or adjoining properties,” the alert said.

DeBolt said Carla Jordan, the county’s director of sustainability and solid waste management, monitored the situation Monday.

“The state Department of Environmental Conservation regional engineer was there as well,” DeBolt noted. “There is still a lot of soil left to move. Soil samples are being taken to determine what may have caused this and how to prevent it from happening again.”

DEC’s Division of Materials Management was notified by landfill officials and Casella. DEC officials said the incident did not cause structural damage to the cap or expose garbage. Any additional impacts are being assessed, officials said.

Casella officials said they are working with the DEC and county on the cause and to ensure no environmental risk to human health or the environment takes place.