An in situ mining site in Long Lake, Alberta. Image: Flickr/jasonwoodhead23

Canada's oil sands are notoriously dirty, but in situ extraction—which involves blasting high-pressure steam into the ground to warm and soften bitumen, and then pumping it up to the surface—has been pitched as their environmentally friendlier future.

In the wake of a new report suggesting that the long-term effects of this extraction method could be damaging, the Alberta government has committed to stepping up its environmental monitoring of in situ oilsands, according to the Canadian Press. This technique is being relied upon more and more, and its consequences are not well understood.

In situ mining sites don't create the same massive (and highly visible) ecological disruption as open-pit mining, so they're often touted as being better for the environment than the alternative. In situ mining produced just over half of all the bitumen recovered in Alberta in 2014, and the Alberta Energy Regulator expects the method to account for 60 percent of bitumen production by 2024.

In fact, eighty percent of the estimated bitumen reserves in Canada's oil-producing province of Alberta are only reachable with in situ methods.

"If [contaminants] do increase high enough, they can be toxic to wildlife"

In the new study, Canadian scientists looked at pollution levels in a body of water located two kilometres away from the Primrose in situ mining site, which is near Cold Lake, Alberta. They found that increased use of the technique lined up with a major uptick in potentially harmful metals and other contaminants in the lake sediment.

"What we see is that after 1980, when that site became operational, we have an increase in contaminants," said York University's Jennifer Korosi, lead author of the paper. That increase "accelerates after the site was expanded about a decade ago," she added.

When she heard about the government's new commitment to monitor in situ sites more closely, she was "glad to hear it," Korosi said.

According to the study, a version of which was published last week in Environmental Pollution, pollutants have increased by 140 percent in the sampled area since in situ operations began. That's not enough to have a toxic effect, Korosi said, but a greater reliance on in situ mining in the oil sands could push contaminant levels over the top.

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"If [contaminants] do increase high enough, they can be toxic to wildlife," Korosi said. "If they get into the groundwater and it's used for drinking, that could also be a problem."

In situ mining in Canada has come under increased scrutiny in recent years, partly because of an incident in 2013 at the same Primrose site that resulted in an uncontrolled flow of bitumen to the surface. The water near the leak was drained and the sediment collected, and a subsequent investigation concluded that too much steam was the problem.

Still, the method's potentially damaging effects remain vastly understudied, Korosi said, because most scientific efforts so far have focused on open-pit mines.

The researchers conclude that if in situ mining is really the future of the Albertan oil sands, then its effects need to become a research priority, alongside better monitoring.

"We've reached a point where production massively outpaces our scientific knowledge of the environmental impacts," Korosi said.