Since 2004, Winnipeg's antiquated combined sewer system has dumped at least 185 million litres of untreated raw sewage into the city's waterways, and it could cost the city up to $4 billion to fix the problem.

A CBC News analysis of incident reports going back to 2004 revealed that at least 73 million litres of raw sewage has flowed into the Red, Assiniboine and Seine rivers due to system and mechanical failures.

That doesn't include the deluge of rain and snow that can overwhelm the system — the city says storms can add 10 million more litres of raw sewage every year into the rivers.

'Sewage isn't sexy'

Groups like the Lake Winnipeg Foundation have been keeping a close eye on the city's plans to address the issue.

The city of Winnipeg's request to change funding formula comes with some conditions for the provincial government. (Jacques Marcoux/CBC) "Sewage isn't sexy. But if we care about our water, we need to start paying attention to it. All the water that flows in and out of Winnipeg ends up in our great lake," said Alexis Kanu, the foundation's executive director.

Prior to the 1940s, sewage and storm runoff flowed untreated into the rivers down the same sewer pipe. Gates called "weir dams" were later installed in each of the 79 outlet pipes in order to divert the mixed water toward municipal treatment plants. Approximately 30 per cent of the city — mostly older core neighbourhoods — are built over this system.

Geoffrey Patton, the manager of engineering for the City of Winnipeg's water and waste department, explains that during periods of heavy precipitation — about 20 times per year — the system gets overwhelmed, leading to what the city calls "combined sewer outflows."

"The combined sewers are actually functioning properly when they're overflowing, because that's the way they were designed — to protect private, like basements, and public property," he said.

The city treats about one billion litres of raw sewage annually and estimates that about one per cent of that volume ends up in the river.

Sewer system breakdowns and unknowns

Heavy rainfall might cause combined sewer outfalls (CSO), but according to an analysis of the 114 incident reports dating back 11 years, malfunctions and breakdowns are responsible for close to 40 per cent of the raw sewage flowing into waterways.

Geoffrey Patton, manager of engineering for the City of Winnipeg's water and waste department, holds a monitoring sensor designed to notify his team as to when raw sewage is being discharged. (Jacques Marcoux/CBC) However, the analysis revealed that the true volume of raw sewage flowing into the river is significantly higher than what the data suggests, since about half of the incidents indicate that the total amount and duration time of each discharge is unknown.

The city says that until massive upgrades are made to the older sewer system, monitoring sensors have been installed in 39 primary outfalls to gather data and sound the alarm bells when sewage is flowing.

"The model we're working on and the instruments that are going in will help more tighten that number up so we'll know exactly what's going on," said Patton.

Blocked sewers and watermain breaks caused half of the reported CSOs. Mechanical breakdowns of gates and equipment led to nine incidents. Weather-related power outages, which prevented pumping stations from moving sewage to treatment facilities, occurred on 23 occasions.

"Twigs, lumber, bats, toys, you'll see a lot of those things in sewers. The most unusual thing was a gecko lizard we basically saw crawling on the camera as we drove by it," said Patton.

He added that an increased use of so-called "disposable baby wipes" contribute to the problem.

"People use them, but they'll clog pumps and cause these types of overflows," he said. "They don't degrade and we discourage these types of products in our system."

Paddlers notice smells after rainstorms

Those who spend the most time on the waterways are also mindful of the water conditions.

"The CSOs are most noticeable along the Assiniboine River after a rainstorm, as it's narrower," said Robin McLure of the Manitoba Paddling Association.

"We'll notice odour and debris. It can be frothier and I think to myself, 'Gee, it's not a good day to fall in!'"

The city is currently evaluating several options on how to reduce their number of CSOs, including infrastructure upgrades such as sewer separation, in-line storage, offline storage, end-of-pipe treatment and green infrastructure. These options range in cost from hundreds of millions to billions of dollars.

The Manitoba government has set a deadline of 2017 for the city to submit a final master plan.



Notes from most recent incident report:

Sept. 4, 2015

Dumoulin/Taché outfall

830,000 litres (14 hours 17 minutes)

"A crew attended the station at approximately 6:30 a.m. and found the station had flooded to the motor floor level however both pumps were found to be running. By 8:30 a.m. the water was pumped out and the cause of the flooding was determined to be a leaking pump seal. Pump #1 had to be taken off line for servicing at this time and was put back in service at 8 p.m. to draw down the system and then again taken off-line for repairs once the overflow event had stopped.

"Due to the rain event occurring September 4 the Dumulin combined system remained surcharged and overflowing for most of the day. Normal operation of the station is for both pumps to be running during overflow events."