Slope still posing a threat

Uncertainty surrounds not only when Highway 97 will reopen but also, just how much rock will fall.

Tom Kneale with the Ministry of Transportation and Infrastructure told media Thursday they are trying to determine the boundary of the failure.

“Every day we seem to be faced with new movements in different locations,” said Kneale. “We don’t know exactly how large this thing is but we are monitoring it and every day that we get information we are getting a better handle on the extent of it.”

UBC Okanagan engineering professor Dwayne Tannant has researched the history of rockslides in the area and said there is potentially much more rock moving below the surface than has been visible.

“We could have 20, maybe 25,000 cubic metres of rock moving,” he said.

On Saturday, about 4,000 to 6,000 cubic metres of boulders and debris fell onto the road, closing Highway 97 indefinitely.

The new crack started about 10 or 15 feet above the current boundary of the slide, continuing 50 metres north and south of it. 

Tannant says crews will be working now to determine how quickly this rock section is moving. 

“They will have to determine how much rock will need to be removed to stabilize the slope, not necessarily all of it will have to be removed,” he said. 

He added hopefully it won’t trigger another slope higher up, which could result in crews up "chasing it up the mountain."

“If it moves slowly there is less of a risk… but if it moves as we saw in that spectacular video from Saturday, we don’t want to have anyone near there,” said Tannant.

Right now, Kneale says monitoring equipment is located on the slope so they can identify movement  in the slope of just two millimetres.

Prevention of the slide would have been near impossible according to Tannant. 

“It’s a steep slope that has been undercut by widening the highway and there are geological structures in that rock that slope towards Okanagan Lake so it is sliding on those structures,” he said. 

Highway 97 remains closed with no estimated time of reopening. For now, two detours have been set up and drivers are being advised not to take alternate routes. 

Crews will be working to create a diverted route on Highway 97 by Callan Road. It will take about four to five days to create if all goes smoothly. 

“Mother Nature wants to move all mountains down to sea level,” said Tannant.