Three months after several northern Alberta oil sands leaks were first discovered, the provincial government has ordered Canadian Natural Resources Ltd. to temporarily drain a small, shallow lake so the exact source of one point of seepage can be identified, and the spill halted.

Alberta's department of Environment and Sustainable Resource Development said it's crucial the water is removed from the "bitumen-affected water body" at CNRL's Primrose operation on the Cold Lake Air Weapons Range before the winter freeze. The government said doing the work over the winter months when the ground is frozen will minimize the environmental effects on the lake. The environmental protection order requires the temporary dewatering of approximately two-thirds of the 53-hectare lake, and that the leak be stopped and the area cleaned up. Much of the water will be returned in the spring.

"We just felt that an environmental protection order ensures the necessary work gets done in a timely manner," said Trevor Gemmell, a spokesman for the environment department.

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At the Primrose site, CNRL uses steam-injection wells or "in situ" methods to produce bitumen instead of more recognizable open-pit oil sands mining. Although both the Alberta government and the industry tout in situ for its reduced land disturbance, the four CNRL leaks at the Primrose site this year are raising environmental concerns. Since June, a number of birds, small mammals and amphibians have died as more than 10,000 barrels of bitumen have spilled from the four Primrose sites over a 13.5-hectare area – a footprint that has now been reduced to 7.4 hectares.

CNRL has described the unnamed water body as a 1.5 metres deep, shallow slough with no fish, and not connected to other water bodies. CNRL said company officials requested and received the government's environmental order. "Multiple options were considered. Moving the water body was chosen because it will be the least environmentally impactful and provides the best approach to contain the entire fissure," CNRL spokeswoman Zoe Addington said in an e-mail.

The ministry said it was first notified of the leak on June 24, but it's unknown how long the release had been going before that. Three other bitumen release locations have also been identified at sites approximately 10 km from this location, but those sites are not subject to Tuesday's order. The seepage rate from all four sites has been reduced to less than 20 barrels a day, according to CNRL.

Edmonton-based Greenpeace Canada campaigner Mike Hudema, who has been keeping close tabs on the spill, said CNRL has maintained its spills are contained and under control.

"Now we find out that the company has been ordered to drain a lake in order to try to deal with the continuing disaster," Mr. Hudema said in an e-mail. "It's crazy that it has come to this."

Mr. Gemmell said his department is leading the investigation into the environmental impacts of the spills, the Alberta Energy Regulator is leading the investigating into the cause of the bitumen leaks, and Environment Canada is looking at the impacts on wildlife.

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