Lots of wet weather in 2023 is what’s responsible for an annual increase in untreated and partially treated sewer overflows that spilled into Hamilton Harbour last year.
An annual report on Hamilton’s wastewater management says 21 “bypasses” put about 821 million more litres of wastewater into the natural environment compared to 2022.
The city says 17 of the 21 bypass events involved partially treated wastewater sinking into city waterways.
Bypasses happen when precipitation from inclement weather overwhelms the city’s wastewater treatment capability, resulting in the discharges.
City staff say runoff and elevated lake levels are what typically “infiltrate” the system.
There are two wastewater treatment plants in Hamilton — Woodward Avenue, which discharges into the Red Hill Creek and the Dundas plant on King Street East, which unloads into the Desjardins Canal.
Both are connected to and discharge into Hamilton Harbour.
The 2.495 billion litres of affected water discharged was higher than the 1.674 billion let out from treatment centres in 2022 and is also above the five-year average of around 2.1 billion litres passed.
The 21 reported bypasses are up from 11 in 2022, but down compared to 23 incidents in 2021.
Director of Water & Wastewater Operations Shane McCauley told councillors on Monday that both plants currently only have a combined treatment capacity of roughly around 630 million litres per day.
Upon completion of ongoing upgrades to the Woodward plant, it’s expected 1 billion litres will be able to be treated each day.
The Dundas plant can deal with around 18 million litres each day.
Nick Winters, Director of Water, says longer-term trends over the last 20 years suggest the volume of wastewater treatment plant bypasses is decreasing.
“That is a result of infrastructure investments that the city has made over those years, building combined sewer overflow tanks to capture combined sewage and keep it away from the wastewater treatment plant,” Winters explained.
He went on to say the quality of water being bypassed is improved with infrastructure upgrades over the last decade and give some level of “primary” if not “full” treatment by one of the two facilities.
“So historically, if you went back to 2012 for example, you would see that primarily in those years, the wastewater treatment plant bypasses were receiving no treatment at all,” he said.
In late 2022, Ontario’s Ministry of Environment, Conservation and Parks (MECP) issued an order “requiring” the City of Hamilton to undertake an audit of its sewage infrastructure following discovery of a leak dumping sewage into Hamilton Harbour over 26 years from homes near Burlington and Wentworth streets.
The city has invested in a long term ‘flooding and drainage improvement framework’ that will see $1 billion spent over 30 years to complete sewer separations to reduce bypass events.