City looks at unique way to reduce sewage discharge into rivers

City of Winnipeg staff have been directed to find out whether a boost in storage could prevent some diluted sewage from spilling into rivers.

Council’s water and waste committee recently ordered a verbal report on combined sewer overflow tunnels to capture diluted sewage that would otherwise spill into the city’s rivers. The head of the committee hopes this could speed up work to reduce the pollution leaving the city’s oldest sewage pipes.

“Yes, there (would be) a cost, but if we can cut decades off our (combined sewer overflow reduction) program, that is worth considering,” said Coun. Brian Mayes, the committee’s chairman.

In combined sewers, a single pipe collects both wastewater and precipitation. During heavy rain and snow events, these older pipes can overflow into rivers.

In 2022, the problem sent 27.5 billion litres of diluted sewage into local rivers.

The Manitoba government has ordered the city to complete an up-to $2.3-billion plan to reduce combined sewer overflows by 2045.

Mayes has repeatedly advocated to speed up the combined-sewer overflow reduction project to meet that deadline, such as by ramping up annual spending to $60 million per year. Council did increase that spending to $45 million per year, up from about $30 million, between 2024 and 2027, but currently expects to complete the work by 2095.

Mayes said many other cities have turned to sewage storage to prevent such pollution in recent years, rather than just separating combined sewers into separate pipes. He hopes adding more of this type of storage could help greatly speed up the work to reduce river pollution, since he believes just one storage tunnel is included in Winnipeg’s reduction plan so far.

“Instead of doing all this detailed work in each individual district, you’d basically just have a big storage facility… My sense is it just seems much quicker than our proposed 20-year to 70-year plan,” said Mayes.

He said the storage solution would create space to hold back wastewater during storms until the sewage system resumes capacity to treat it.

“The current problem is the safety valve is the river. In ‘high rain’ events, the combined sewer is overwhelmed, so it’s a mix of rainwater and untreated sewage (that enters the river). This essentially takes that mixture and stores it until the rain stops and then you can send it up to the treatment plant. You’re treating it as you normally would… but you reduce the amount being dumped in the river,” said Mayes.

The councillor said several cities have adopted the strategy, including Ottawa, Paris, Auckland and Hartford, Conn.

“It’s certainly not untested technology. It (comes with) an upfront cost, but we’re planning to spend one to two billion (to reduce combine sewer overflow) anyway,” he said.

A local advocate to protect the Seine River welcomed the idea.

“We totally agree with Coun. Mayes’ view that the combined sewer situation requires innovative solutions and options that allow onsite storage capacity… Save our Seine is very interested in the potential of water retention and alternative technologies when it comes to the ability of the city of Winnipeg to … reduce combined sewer overflows and ensure there is not excess (algae-promoting) nutrient loading into waterways,” said Ryan Palmquist, the managing director of Save Our Seine.

Palmquist noted Save Our Seine has also pursued “green” infrastructure ideas to reduce water pollution, which are not part of the combined sewer overflows reduction strategy.

For example, the Niakwa Trail Rain Garden was built to collect storm water runoff from the roof and parking lot of the Real Canadian Superstore on St. Anne’s Road and uses 670 native plants to filter pollution and contaminants out of the water before it drains into the Seine River.

Palmquist said additional wastewater storage would complement sewer separation efforts by ensuring more water is treated before it enters waterways.

A request to interview a Winnipeg water and waste official about the storage idea was not granted on Thursday. Spokesperson Lisa Marquardson noted the verbal report is expected in June.

joyanne.pursaga@freepress.mb.ca

X: @joyanne_pursaga