Rain has forced the Woodward Wastewater Treatment Plant into bypass mode, allowing partially treated sewage to flow into Red Hill Creek.

The bypass began at 11:21 a.m. Saturday, Jan. 11, the City of Hamilton said in a release.

Bypasses happen in "extreme wet weather," when the amount of wastewater entering the sewer exceeds the capacity at the plant.

The city allows partly treated sewage to flow directly into Red Hill Creek rather than risk sewer backups into resident basements.

By Sunday morning, all of the city's combined sewer overflow tanks were overflowing or near capacity, according to the city's website.

An Environment Canada rainfall warning was in effect for Hamilton Saturday, with rain becoming heavier in the evening.

Environment Canada reported Hamilton saw a total 41.2 millimetres of rain Saturday.

This is on the lower-end of what had been forecast, with the national weather agency warning total rainfall amounts of 40 to 60 mm were possible.

There were some reports online of small, localized flooding.

Ferrie Street East at Victoria Avenue was closed with barricades because of flooding Saturday night.

On Sunday, Hamilton police said there were no major issues related to weather reported overnight.

Late Saturday, the Grand River Conservation Authority (GRCA) issued a flood warning for the Grand River watershed.

Significant rainfall resulted in "much higher" river flows than previously forecast, according to a news release from the GRCA.

The conservation authority is warning that communities along the Grand River, including Paris, Brantford, Caledonia, Cayuga and Dunnville, should prepare for flooding similar to levels experienced in June 2017.

Waves of up to 1.6 metres were expected in the Lake Erie surge event, Haldimand County said in a news release.

The Port Maitland pier has been closed due to high winds and waves.

Haldimand County Fire Chief Jason Gallagher is urging residents to stay away from the area and all other shorelines because of strong waves and elevated water levels.

The City of Hamilton started posting online public notification of sewage treatment plant bypasses last fall.

Loading... Loading... Loading... Loading... Loading... Loading...

Once the bypass and overflows are done, information about how long and how much wastewater overflowed will be added to the website.

The plant's capacity is impacted by ongoing construction, with the amount of water it can handle shrunk by about 100 megalitres per day.

That construction — which will eventually help the plant spit out cleaner treated effluent into Hamilton Harbour — is set to last through 2021.

"That does reduce our capacity and trigger more frequent bypasses," said water director Andrew Grice.

The city also dumped more partly treated sewage than normal in 2019 because of high lake levels, which pushed more of Lake Ontario into the sewers along the harbour and beach strip.

While dumping partly treated sewage is not good for the harbour, Grice said bypassing at the plant is still preferable to combined sewage overflows elsewhere out of tanks or old pipes.

That's because "bypassed" sewage is first screened for large "floatables" like needles and tampons and also shot with disinfectant.

"If a combined sewage overflow tank overflows, you don't get any of that protection," he said.

noreilly@thespec.com

905-526-3199 | @NicoleatTheSpec

with files from Matthew Van Dongen