Municipal wastewater crews had to make a tough choice during last weekend’s rain storm: risk overwhelming the sewer system and flood entire neighbourhoods, or dump into the river one of the largest amounts of raw sewage in Winnipeg history.
Nearly 60 million litres of raw sewage was allowed to flow into the Red River, from Saturday night to Monday morning, in an effort to prevent additional basement flooding at homes upstream of the South End Wastewater Treatment Plant.
It’s one of the largest outflows of sewage in recent years, but it represented only about five per cent of the record-high flow volume dealt with by the city’s three wastewater treatment plants during the rainstorm.
"These are the highest flows that we’ve seen at the plants in 20 years," said Chris Carroll, manager of wastewater services for the city’s water and waste department.
"It’s really an unprecedented event."
The pumps were overcapacity and the water had nowhere to go. Wastewater was building up and was in danger of flooding upstream homes, so it had to be diverted downstream: into the river. Typically, the city doesn’t see heavy rain in the days immediately following heavy snow and blizzard conditions.
"I’ve never seen anything like this in my career, so I know this is a very unusual situation," said Carroll.
"Usually we see these storms later in the season, after the ground has had some time to get rid of the snow and be able to (absorb) some water."
Staff shut off all four pumps at the south end plant and then shut off all pumps at three other wastewater pumping stations that would have pumped water to the south end plant. An estimated 59.6 million litres of untreated sewage flowed into the Red River.
The pumping stations resumed operations around 10 a.m. April 25, when it was determined the south end plant could keep up with incoming flows.
Carroll said it’s unfortunate, as stewards of the community, that staff had to allow raw sewage into the river, but they had to protect public property and public health.
"We have to make choices of, do we want entire neighbourhoods with sewage in their basements, or do we go this other route?"
Some homes were flooded after heavy rain and thunderstorms hit the city, and crews worked around the clock responding to calls.
"On a whole, our system responded really well and we dealt with issues that came our way Saturday, Sunday, Monday. We’re still trying to recover from this now," Carroll said.
Katie May is a general-assignment reporter for the Free Press.