A pipeline historian says oil spills such as the one that occurred on the Ocean Man First Nation, Sask., last week are not uncommon or surprising.

"Pipeline spills have been part of Canadian history since the mid-20th century," said Sean Kheraj, who teaches Canadian and environmental history at York University in Toronto.

He said the size of the Saskatchewan spill — approximately 200,000 litres — is a bit unusual but not surprising when considered amidst the thousands of oil spills in the country over the past 60 years.

That said, Kheraj was initially shocked that another major spill would happen in Saskatchewan so soon after the 225,000-litre Husky Energy oil spill in July.

The majority of spills in Canada have been much smaller, but large breaches are not unprecedented. Kheraj said they're usually caused by unforeseen circumstances or accidents, which leak detection systems might not account for, such as human error, material failure or third-party incidents.

In a scenario where oil is leaked onto the ground, reclamation efforts usually involve scooping up the soil and extracting as much oil as possible.

When it comes to an oil spill such as the one on the Ocean Man First Nation, low temperatures and location are probably helping cleanup efforts, Kheraj said.

The spill was not located next to a flowing water source, such as with the Husky oil spill, in which some entered the North Saskatchewan River. The oil would also flow slower in the winter.

The impact and reach of spills tend to accelerate as more oil is being shipped, he added.

"Even though we are seeing 200,000 litres spilling into the environment in southern Saskatchewan this week, that's a fraction of what's actually being shipped."

Although the Ocean Man First Nation spill occurred on Friday, the public was only notified Monday — a delay that has happened before.

Kheraj noted the 2011 Little Buffalo oil spill in Alberta, which leaked nearly 4.5 million litres of oil into muskeg and beaver ponds. The leak was announced the day after it was detected, he said, although he's unsure why.

When it comes to spill detection, the delay in discovery is not uncommon. Kheraj pointed to the Nexen spill in 2015, which he said was discovered not by remote monitoring systems but by someone walking along the pipeline. That spill saw five million litres pour out of the pipelines near Fort McMurray, Alta.

The perception is oil spill detection seems to be improving in smaller scale spills, Kheraj said, "but on the larger spills, it seems to be a persistent problem."