Saskatoon storm 'overwhelmed' treatment plant

Saskatoon's wastewater treatment plant struggled to keep up during the June 20 rainstorm that battered the city.

The plant measures its flow in millions of litres per day (MLD).

A city report outlines how 270 million MLD of water was rushing through the plant during the storm's peak. The typical average daily flow sits around 79 MLD, according to the city.

The highest flow rate "in recent history" happened in 2017, with 170 MLD, according to the report.

During the storm, the plant was "overwhelmed" resulting in a minor spill of 70 cubic metres of raw sewage into the South Saskatchewan River, the report said.

"Due to the minimal amount of sewage spilled, there is no risk to the public to utilize the river for recreation," the report said.

By comparison, an Olympic-sized swimming pool holds 2,500 cubic metres of water.

The city's sanitary and storm systems operate independently.

However, water can infiltrate the storm system through avenues such as manholes, pipes and sump pump connections, the report said.

During the storm, city residents were asked via social media to refrain from unnecessarily flushing toilets and running washing machines and dishwashers.

The plant was switched to manual operation during the storm, which diverted millions of litres of water and prevented "longer-term quality impacts," the report said.