11/15/2013 07:26 EST | Updated 01/23/2014 06:58 EST

Alberta coal mine spill heading to N.W.T.

The Northwest Territories’ Environment Minister says toxins from a massive coal mine spill in Alberta are making their way north.

On Oct. 31, Sherritt International's Obed Mountain coal mine spilled about 1 billion litres of contaminated water into the Athabasca River. The mine is no longer operating. The spill happened when a retaining wall collapsed, unleashing the equivalent of about 400 Olympic-sized swimming pools of contaminated water. 

The Alberta government says the contaminated water is now making its way through the Athabasca River and the Peace River. It should reach the Slave River and Great Slave Lake close to the beginning of December.

MIltenberger says he wasn’t informed of the spill of toxic water until Nov. 4, four days after it happened.

“We are going to keep doing monitoring as it makes its way north,” Miltenberger said. “This is the first coal mine spill of this magnitude. A huge amount of water filled with these waste substances... In my recollection, this is the first of this type of catastrophic failure.”

According to Environment Canada, the water being stored at the mine contained potentially damaging compounds, including a suspected carcinogen known to cause tumours in laboratory animals. There's also arsenic, mercury, cadmium, lead and manganese found at the disposal site.

The Alberta government says the contaminated water will dilute and be safe once it reaches the Slave River in the N.W.T. Miltenberger says his department will continue to test the water for contaminants as it moves downstream.

Miltenberger says there have been oil spills that have leaked into the local watersheds in the past, but they've never affected drinking water.

The Alberta government says it's doing comprehensive testing for heavy metals on clay, mud, shale and coal particles moving through the Athabasca River. Alberta Health maintains there are no immediate health concerns.

Fort Smith resident worried

Fort Smith resident Francois Paulette says that’s far from the truth.

“They've been saying that for 40 years,” Paulette says. “The environmental people are saying this is a highly toxic contaminant in the water. We've been instructed that people shouldn't be taking water from the river in that week.”

The Alberta government says it’s hoping to share the test results from the affected areas in the Athabasca River early next week.