A drone photograph of the landslide that occurred Wednesday on the Presumpscot River behind Les Wiison & Sons at 161 Warren Ave., Westbrook. Photo by Henry Riley Productions

The U.S. Army Corps of Engineers took a firsthand look at the site of the Presumpscot River landslide in Westbrook on Saturday, but local officials and others involved say it could still be awhile before the next steps in stabilizing the riverbank or preventing future slides are determined.

About 20 people, including several members of the Army Corps, met at the landslide site off Warren Avenue on Saturday morning, said Westbrook Mayor Michael Foley. Besides the engineers, others present were Westbrook city staff, property owners, utility officials and representatives of the Maine Geological Survey and the Maine Department of Environmental Protection.

An area estimated at 300-by-300-feet – the equivalent of two football fields or 2 acres – collapsed and slid into the river Wednesday morning, taking with it trees and soil. The landslide, which happened directly behind Les Wilson & Sons excavators at 161 Warren Ave., also took a large area of soil, a pile of fill, and a salt shed, in addition to damaging construction equipment. The landslide blocked the river temporarily, and the water level behind the blockage quickly rose about 13 feet.

Foley said he wasn’t sure how long it would be before the Army Corps team would have a recommendation on what needs to be done to stabilize the riverbank and restore the river’s flow. The Army Corps of Engineers would be the issuing body for any permits needed for work on the river. But Foley said he expected there might be more news on the future of the site this coming week.

“It happened fast, but it’s going to take awhile before we’re advised on the best plan of attack,” Foley said Saturday. “Thankfully the river is flowing and the risk of flood is no longer there.”

Officials had been concerned about sediment or trees pushing downriver and damaging water or gas mains that cross the river, but so far no such damage has been reported.

On Saturday the site of the landslide was blocked off by police tape, no trespassing signs and fencing, to keep people out of dangerous areas, Foley said. No one from the Army Corps of Engineers returned a phone call and emails asking about the purpose of Saturday’s site visit.

The broad cause of the landslide is that the area is part of the Presumpscot Formation, a layer of soft clay that lies beneath the surface and extends deep underground, said Lindsay Spigel, a geologist with the Maine Geological Survey, who was at the site on Saturday.

The softness of the clay means that the material behaves like a viscous fluid that can “flow” rather than break into discrete pieces, Spigel said. But what exactly triggered the landslide won’t be known until test borings are made into the riverbank and analyzed, Spigel said. Spigel is gathering information that may hopefully help prevent future landslides, she said.

Property owner Chris Wilson, of Les Wilson & Sons, was also at the site Saturday. He said the meeting with Army Corps representatives and other officials was about “information gathering” and that no developments related to the landslide were discussed.