Ground movement that led to a break in a Husky Energy oil pipeline happens often along Saskatchewan riverbanks, according to a geology engineer at the University of Saskatchewan.

This week, Husky Energy released a postmortem on an oil spill this past summer which saw 225,000 litres of heavy oil and diluent leak, of which about 40 per cent entered the North Saskatchewan River.

The report said oil from the pipeline break entered the North Saskatchewan River about 50 kilometres northeast of Lloydminster. As the oil moved downstream, communities including North Battleford and Prince Albert that rely on the river scrambled to disconnect from river intakes and set up alternate supplies of fresh water.

On Friday, Grant Ferguson, associate professor in civil geological and environmental engineering with the U of S, told reporters that ground movement and slope failures along the riverbank are common and all infrastructure near the rivers is at risk of ground movement.

"If the intent (of the report) is to make it seem like a slope failure is a one-off event, that's not the case," Ferguson said.

He said all infrastructure built near the riverbank is susceptible to ground movement and engineering studies should be done to help assess the risk of slope instability.

"There's risk in all projects along the riverbank, whether it's worrying about your house's foundation or if we're going to develop more potholes on the roads this winter," Ferguson said while making reference to Saskatoon's recent slope failures on Saskatchewan Crescent and Cherry Lane.

Grant Ferguson

Grant Ferguson with the University of Saskatchewan says instability exists along the North and South Saskatchewan riverbanks and ground movement isn't uncommon. (Don Somers/CBC)

"We're living with these rivers in the province and if we choose to have infrastructure over them, then we have to acknowledge these risks."

The Husky Energy pipeline was installed in 1997 and the final Husky report said an assessment prepared for Husky concluded that ground in the area where the pipeline sat was inactive.

Steady rainfall, high water table

Having studied and researched the riverbanks of the North and South Saskatchewan Rivers, Ferguson said there are slope stability issues throughout. This is mainly due to Saskatchewan seeing a lot of wet weather which raises the water table and loosens underground soil.

"We know that when the water tables come up, the soils become weaker and these things are more likely to happen," Ferguson said, adding that although engineers deemed the site for the pipeline inactive, overtime conditions changed.

"What might have been deemed a safe slope 20 years ago or something that wasn't moving, whether or not someone had the foresight to see exactly how things would change, and they can change and we've seen that."

Husky said it was making changes in light of what they discovered during its investigation. Those changes included ensuring that geotechnical risks are addressed and reassessed over the lifetime of a pipeline.

In a statement, the NDP said the provincial government should play a more prominent role in the oversight of pipelines.

"We are reaffirming our call to move away from having companies police themselves when it comes to pipeline inspections," Cathy Sproule, the NDP's environment critic, said in the statement.

"The [Husky] spill showed how devastating an incident like that can be to the water that many families drink and use in everyday life, but it also showed what little work is being done by the Sask. Party government to make pipeline safety a priority."

According to the NDP, Saskatchewan officials only conducted 78 pipeline inspections last year, while the government of Alberta conducted more than 2,000.

With files from Devin Heroux