A main sewer line break occurred yesterday in the town of Cochrane, causing an overland sewage discharge that flowed into the Bow River at the Highway 22 bridge.
Cochrane drinking water is not affected by the sewage and remains safe to drink.
Stacy Loe is the executive director of protective and community services for Cochrane. She said the town found out about the problem at 6 p.m. on Saturday.
"Crews have been onsite overnight, and the mitigation efforts continue to be underway," she told CBC News.
She said the problem occurred when a contractor, working on behalf of the town, was setting up drilling work near the wastewater line.
The Town of Cochrane has activated an Emergency Coordination Centre. The City of Calgary, Rocky View County, and Alberta Environment and Parks are all working to fix the problem.
Loe said that, as of Sunday morning, only "minimal flow" of sewage was reaching the Bow River.
She said couldn't estimate how much sewage reached the river before it was diverted.
In a media update released at 12:15 p.m. on Sunday, the Town of Cochrane said earlier reports that wastewater was no longer entering the river and was being contained on site were "inaccurate."
"Although the discharge has been significantly reduced, wastewater is continuing to flow into the Bow River at this time," the update said.
In a later statement on Sunday evening, the town said that "a significant amount of water and wastewater has entered the Bow River" since the sewer line break.
Officials are asking people to avoid the area so crews can respond to the incident. Eastbound Griffin Road is down to one lane of traffic. All pathways adjacent to the Bow River have been closed – from Riverfront Park to Griffin Industrial Point. This includes the Jim Uffelmann Memorial Park.
The town has also implemented Level 3 water restrictions, requiring residents to conserve water. All outdoor water use is prohibited, water pressure will be reduced as required, and residents are requested to limit water use to essential activities only.
As of Sunday evening, the town said that it made an additional request for its larger water consumers to voluntarily reduce water consumption, as "the impact to the water pipeline has resulted in a significant loss of water from our water storage facilities," according to a statement. The town said that as a result, Spray Lakes Sawmills Centre volunteered to temporarily close for the rest of the evening.
In a statement to the media on Sunday morning, the City of Calgary said it was advised of the sewer line break in Cochrane on Saturday evening and activated its Water Services Response team. The city said it has been carefully monitoring the situation and working with the Town of Cochrane.
"As of Sunday morning, we have seen no change in water quality at the Bearspaw Water Treatment Plant. Calgary's water remains safe to drink," the statement said.
As a precaution, the city is asking Calgarians to stay out of the Bow River for the remainder of Sunday. Extra water quality sampling on the Bow is being done, and the city says it will provide updates as they are available.