Heavy rain sends millions of litres of raw sewage into the Ottawa River this summer

Rain falls at LeBreton Flats on Wednesday. (Jackie Perez/CTV News Ottawa)

Heavy rain has sent more than 51 million litres of raw sewage flowing into the Ottawa River this summer.

Environment Canada says 303.5 mm of rain was recorded at the Ottawa International Airport in June and July.

Statistics available on the City of Ottawa's website show 51,356,000 litres of storm water and wastewater overflowed the sewage system and into the Ottawa River.

There have been four sewage overflow incidents in June and July.

The biggest sewage overflow was on June 6, when Ottawa received 44.1 mm of rain. The city's website says 50.1 million litres of combined overflow mixture overflowed the system and into the Ottawa River.

There were also overflow events on July 6 (593,000 litres overflowed), July 13 (233,000 litres overflowed) and July 24 (410,000 litres overflowed).

The city reported 11 sewage overflow events in 2022, with 464 million litres of raw sewage overflowing the sewage system. On Aug 10, 316 million litres of untreated water overflowed the system following heavy rain.

The rainfall has also been blamed for several no-swimming advisories at Ottawa's public beaches during the summer. Ottawa Public Health will issue no-swimming advisories due to rainfall causing high levels of e.coli in the water.

The City of Ottawa built the Combined Sewage Storage Tunnel, designed to intercept and store surface runoff and wastewater until it can be treated at the Robert O. Pickard Environmental Centre and then returned to the Ottawa River. The $232 million project includes six kilometres of tunnels underground designed to stop sewage from flowing into the river during heavy rainfall events.

The underground Combined Sewage Storage Tunnel includes two tunnels: an east-west tunnel through the downtown core from LeBreton Flats to New Edinburgh Park, and a north-south tunnel along Kent Street from Chamberlain Avenue to existing infrastructure behind the Supreme Court of Canada building.

According to the city, the two interconnected tunnels reduce the volume of wastewater flowing into the Ottawa River by 43 million litres an event.