Heavy rain has caused more than 340 million litres of diluted sewage to run into the Ottawa River this week.
The sewage is from the City of Ottawa's older combined sewers, which carry both raw sewage and stormwater. When the sewers fill with rain, the overflow goes to the river.
The city recorded about 320 million litres of overflow during the rainfalls on Wednesday. There was about 22 million litres of overflow on Monday.
On top of that, the city recorded 274,000 litres of raw sewage spilling from the sewers on Thursday.
The city is building a $232.3-million sewage-intercepting tunnel to reduce the combined sewer overflows.