The major winter storm that hit Hamilton on Sunday caused 78 million litres of "partially treated" wastewater to be released into Hamilton Harbour before "harmful bacteria" could be removed.

A media release by the city of Hamilton says that as of 12:03 p.m. on Sunday, "the amount of wastewater entering the sewer system exceeded the capacity at the Woodward Wastewater Treatment Plant, and the plant began bypassing partially treated wastewater into Hamilton Harbour."

The notification is part of protocol mandated during fallout of the Chedoke Creek leak, which sent 24 billion litres of untreated runoff and sewage into the environment.

Andrew Grice, director of water, confirmed that 78 mega-litres of wastewater was sent into the harbour before it could be fully treated. The waste had undergone a screening process where large materials like personal care products and grit from the roads are removed, and a solids removal process, which removes some phosphorus and suspended solids.

But the wastewater did not go through the "biological process," which means "harmful bacteria" was not removed before it flowed out into the environment.

It also didn't go through the final screening. Grice confirmed that since the wastewater was only partially treated, it would be damaging to the harbour.

"It does have a negative impact on the harbour — that's why we do have a treatment plant there to remove everything before it goes back in," he said. "To what extent, that would be very difficult to say."

Grice said that the plant is designed for a specific capacity, and when that limit is reached the only outlet is to the natural environment. But one positive aspect is that this plant can send the wastewater through a couple stages of treatment before it is released.

"We have an ability to do the primary treatment during bypass so we actually can treat for at least some of the parameters before it gets sent out to the harbour," he said. "Not everybody has that benefit."

The city began posting notifications about bypasses after fallout surrounding the four-year leak of 24 billion litres of untreated sewage and runoff into Chedoke Creek. (Patrick Moreell/CBC)

The bypass comes on the heels of an apology and release of documents by Hamilton's mayor and city council regarding a four-year leak of 24 billion litres of runoff and untreated sewage into Chedoke Creek.

The waste in this leak came from a combined sewage overflow tank, which normally stores waste until it can be sent for treatment at the Woodward centre. But a gate was left slightly open, allowing litres of waste to flow into Hamilton's waterways.



Although city council knew about the leak, its magnitude wasn't immediately shared with the public, a decision councillors attributed to legal advice.

As part of some measures addressing transparency with the public, council approved an "enhanced public notification protocol" for bypasses.

This is the first bypass since the protocol was put in place.

Public to be notified within 24 hours

The city says it will publish an announcement within 24 hours of a bypass event at the treatment plant. Notifications will be available on the city's website and will also come for bypasses at 14 of the city's combined sewer overflow tanks.

Grice said that there are plans for the new year to make the notifications more interactive with an information at your fingertips feel. The new system will come out in the second quarter of 2020.

The media release explains that bypasses happen during storms, "when the amount of wastewater entering the sewer system exceeds the capacity of the treatment plant."

Spring is normally the busy time for bypasses

The Woodward treatment plant holds around 409 million litres of wastewater. The capacity can be bumped up to around 600 million litres, said Grice, but cannot be sustained for a long time.

Sunday's freezing rain and melting ice and snow caused the amount to peak at 900 mega litres, which Grice said is "well above" what the treatment centre can treat.

It also comes at an atypical time, as spring is normally the busy season for bypasses. But since it wasn't cold enough, the water overwhelmed the treatment centre. Grice said he expects it to die down in early December, as temperatures drop and things start to freeze.

The bypass lasted 12 hours and ended just before midnight on Sunday.