Record-breaking rainfall puts wastewater treatment plant into bypass mode

The 53 millimetres of rain over the weekend caused a secondary bypass at the Woodward plant, which, according to the city, means the partially treated sewage would not include large solids and floatables.

The bypass started Saturday, and now six combined sewer overflow (CSO) tanks have also reached their capacity

The bypass started Saturday and is still ongoing according to the city website. (Adam Carter/CBC)

Partially treated sewage has been flowing into Red Hill Creek since Saturday morning following record-breaking rainfall that soaked Hamilton this weekend.

The drizzle started Friday and led to a downpour on Saturday which caused the Woodward Wastewater Treatment Plant to reach max capacity and enter bypass mode at 11:21 a.m., the city said in a release.

The bypass stopped about  4 a.m. Monday, with six combined sewer overflow (CSO) tanks also reaching their capacity. 

The Red Hill CSO Pipe, Eastwood, Royal Stroud, Greenhill and Main/King tanks have been overflowing since Saturday afternoon while McMaster reached its limit on Sunday morning.

The 53 millimetres of rain caused a secondary bypass at the Woodward plant, which, according to the city, means the partially treated sewage would not include large solids and floatables.

The city said basements would flood if it didn't allow the partially treated sewage to enter the Red Hill Creek.

"Flooding from large volumes of storm water at the treatment plants can cause significant damage to mechanical and electrical equipment as well as 'wash out' the microscopic organisms needed for secondary wastewater treatment, which can affect the wastewater treatment plant's ability to function for several days or weeks," reads a webpage from the city website.

The admission of the plant's bypass comes as the city launched a monitoring and public reporting process for CSO tank overflows after 24 billion litres of runoff and sewage spilled into Chedoke Creek.

This marks the first bypass of 2020, though it is poised to be one of the longest and largest since the reporting started.

Record-breaking rainfall

Hamilton received 53 millimetres of rain between Friday and Sunday which, along with melting snow, caused the bypass.

Environment Canada meteorologist Gerald Cheng told CBC there was 41.2 millimetres of rain on Saturday alone, breaking two records — one for the amount of rainfall on Jan. 11, and every other day in the month of January.

"That beat the old daily record of 26.6 setback in 1980 and if we look at all daily records for rainfall in month of January, the extreme was 39.3 set back on Jan. 15, 1995," he said.

"We knew going in it would be a rainy system, especially for Hamilton and the Niagara peninsula, and it certainly was a very rainy system."

There was 41.2 millimetres of rain on Saturday alone. This broke two records - one for the amount of rainfall on Jan. 11, and every other day in the month of January. (Samantha Craggs/CBC)

The Hamilton Conservation Authority warned of flooding in Middleton Road near Spencer Creek while the Grand River Conservation Authority issued a flood warning for the entire Grand River watershed.

"This event produced the highest January rainfall on record for this part of the province and resulted in substantial flooding in a number of communities in the northern and central portions of the watershed," read a release from the conservation authority.

On Tuesday, the city reported it flooded.

Hamilton Police Service told CBC there were no significant events regarding the weather this weekend.

When flooding is forecasted, residents can take a number of steps to be prepared:

  • Keep catch basins in front of your home clear of snow and ice, or other debris. ‎
  • If your home has a backwater valve installed, follow the manufacturer's instructions for cleaning to ensure that it is functioning properly.
  • Check your sump pump to make sure it is working properly. 
  • If your home or area is prone to flooding you may want to consider ensuring any valuables are up off of basement floors.


Bobby Hristova is a journalist with CBC Hamilton. He reports on all issues, but has a knack for stories that hold people accountable, stories that focus on social issues and investigative journalism. He previously worked for the National Post and CityNews in Toronto. You can contact him at bobby.hristova@cbc.ca.


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