Oil spills at a major tar sands extraction operation in Cold Lake, Alberta have been occurring for six weeks, contaminating a lake, forest, muskeg and killing beavers and loons. Canadian Natural Resources has been unable to stop the underground blowout. Documents indicate 26,000 barrels of bitumen and water have been removed since cleanup began in May. The company says it is effectively managing the four spill zones. 30,600 kgs of oily vegetation has been removed. A government scientist who has visited the site said the spills cast doubt on the safety of a in situ operation "in chaos", and "everybody is freaking out about this" since no one apparently understands how to stop the spills. The government scientist asked not to be named for fear of unemployment [photo credit]. Underground extraction of bitumen involves the injection of high-pressure steam underground to melt the hard bitumen deposit which then flows to the surface through cracks and a drill pipe. In the course of injecting steam the company apparently created fissures through to the surface they did not expect.Although in situ extraction does not require damaging strip mining, it uses more energy and water. Underground extraction may account for as much as 40% of Alberta's future bitumen production. Potentially, the leaks might not stop until the formation becomes de-pressurized which could take months. Environmentalists are concerned that underground extraction presents more difficult mitigation and cleanup problems if operations go awry. Media has been unable to access the site because the operations are on the Cold Lake Air Weapons Range, an active test range used by the Canadian military. Canadian Natural Resources' operations are also in the traditional territory of the Beaver Lake Cree tribe which is pursuing a constitutional challenge to oil sands development they say infringes on their treaty rights to hunt, fish and trap.