(Reuters) - The spillage of industrial waste water at Suncor Energy Inc's main oil sands project had a limited impact on the local river, Canada's No. 1 oil producer said.
Waste water from Suncor's oil sands operation north of Fort McMurray, Alberta, escaped on Monday morning when a pipe broke after freezing.
The Athabasca River is the main source of drinking water for aboriginal and other communities downstream and has been the subject of several controversial reports on its water quality.
"Based on modeling, preliminary volume calculations and the current flow rate of the river, the process affected water may have had a short term, negligible impact on the river," company spokeswoman Sneh Seetal said in an emailed statement on Wednesday.
An estimated 350 cubic meters of contaminated water was released into the river over a 10-hour period, the company said, adding that it did not contain tar-like bitumen.
Oil sands firms store contaminated water, a byproduct of stripping bitumen from the sands, in holding ponds.
Those ponds became the focus of environmental protests in 2008, when 1,600 ducks died after landing on a tailings pond operated by Syncrude Canada Ltd.
While new regulations introduced after the mass duck deaths aim to eliminate the toxic ponds, they remain controversial because of the risk of spills into the Athabasca River.
"This process affected water was mixed with treated water, prior to entering the river," Suncor said. "The ratio was approximately six parts treated water to one part process-affected water."
Reporting by Ratul Ray Chaudhuri in Bangalore; Editing by Joseph Radford