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There's been a series of mysterious oil spills around tar sands operations in Alberta. Thick oil has been gurgling up unexpectedly from the ground instead of flowing through the wells that were built to collect it. Canadian regulators are investigating, and the spills are raising questions about a technology that's rapidly expanding. In Canada, oil companies are using it to extract fossil fuels that could ultimately end up in the controversial Keystone XL pipeline.
NPR's Richard Harris reports.
RICHARD HARRIS, BYLINE: When you think of Alberta tar sands, chances are you picture open pit mines and big pools of waste on the surface. But for the past 30 years, oil companies have also been drilling deep wells to get at these deposits. They often inject pressurized steam deep underground to loosen up the tar sands and extract thick oil called bitumen. The bitumen is supposed to be pumped back up through the wells.
But Chris Severson-Baker, at an environmental think-tank called the Pembina Institute, says it doesn't always work that way.
CHRIS SEVERSON-BAKER: We've had incidents in the past where there's been an explosive blowout as a result of pressure building up and then moving up through the rock formations until it emerges at the surface. This one is a bit unusual in that when it reached the surface, it sort of oozed out as opposed to blowing out.
HARRIS: The first of these oozing incidents started in 2009. Government regulators spent several years trying to figure out what caused it. Cara Tobin, spokesman for the Alberta Energy Regulator, says they still don't know...
CARA TOBIN: Whether it has to do with technology, operating practices, mechanical issues, geology - that sort of thing.
HARRIS: And as that investigation stretches on, the regulators have three more of these oozing incidents to deal with. They are all occurring inside the Cold Lake Air Weapons Range, an area that's off limits to casual visitors. And in total, these four seep sites have contaminated about 50 acres, far less than the scars from open pit mining. Total volume is 950 cubic meters of bitumen, she says. That amount would fill up a community swimming pool.
TOBIN: It's all very slow release but they're all still ongoing.
HARRIS: Tobin says the oil company has strung up absorbent boom and fences around the four spill areas in order to contain the damage.
Nikki Booth from Alberta's Environment Ministry considers this a significant event. She says her agency has personnel on the scene monitoring the damage.
NIKKI BOOTH: Unfortunately, there have been some wildlife mortalities, including waterfowl, beavers, tadpoles, frogs, muskrats and shrews. But there are wildlife deterrents that are now in place and that should prevent any future wildlife mortalities from occurring.
HARRIS: But because the bitumen continues to ooze from the ground, there's no telling how long they'll have to manage the mess. The company, Canadian Natural Resources Limited, didn't respond to an interview request but it said in a statement that it has 120 people dedicated to the clean-up.
The sludge of oil on the surface is only part of the environmental impact. Chris Severson-Baker, at Pembina, says the thick oil could also create an environmental hazard as it passes up through more than a quarter of a mile of rock.
SEVERSON-BAKER: Eventually, it would come in contact with groundwater resources. You know, the fresh groundwater resources that are close to the surface, which are the most valuable in the sense that they can be used for domestic drinking water and other purposes.
HARRIS: And more broadly, Severson-Baker is concerned about what will happen as this steam-pumping technology expands throughout the region, to tap the vast tar sand resources there. He says, if they don't understand why these four incidents occurred, how can they prevent future problems? These operations already have a big environmental impact because oil companies burn a lot of natural gas to generate the steam. These contamination issues add another wrinkle.
SEVERSON-BAKER: And so, it's really important to be able to understand under what circumstances those issues might occur, in order to design projects that eliminate that risk.
HARRIS: And it's also a major test for Alberta's new oil field regulators. The government there is pushing for the U.S. to approve the proposed Keystone XL pipeline, which would take diluted bitumen from this region to refineries in the United States. The environmental impact of those operations factors into that decision.
Richard Harris, NPR News.