The city of Hamilton says heavy rainfall and an equipment failure were the cause of about 353 million litres of partially or untreated sewage being dumped into Hamilton Harbour overnight on Monday.
In a release, officials say they’ve determined that the wastewater went into the harbour after two of four bar screens failed and forced a bypass at the Woodward Avenue treatment plant to avoid damage to the facility and surrounding infrastructure.
“Due to the storm, Hamilton’s treatment plant experienced a wastewater bypass, which often occurs during significant wet weather,” the city said in the release.
“Typically, when the plant enters secondary or primary bypass mode, there is some level of treatment to the wastewater before it is discharged into Hamilton Harbour.”
In a statement, city staff estimates for roughly six hours there was a full plant bypass discharging 48 million litres of completely untreated sewage.
For about 27 hours, the plant had two levels of partial bypass with around 40 million litres of mixed treated and untreated wastewater spilling into the harbour and another 265 million of almost fully treated liquid put into the waterway.
The city said the circumstance was unusual and that equipment has since been repaired with the plant back at full operating capacity.
The incident has been reported to the ministry of the environment.
Staff revealed there were eight other overflow events in the city during the storm including sewer tanks at Royal Avenue, Main and King, Greenhill Avenue and Red Hill Valley Pipe.
Pier 4 at Hamilton harbour still closed toxic blue-green algae
The city is still urging residents to stay away from the water at Pier 4 Beach due to the presence of toxic blue-green algae.
Officials say none of the beaches are safe in terms of water contact on Hamilton Harbour with Bayfront Beach permanently closed due to a history of poor water quality.
The reported toxins are harmful to people and pets, if ingested, and coming into contact with it can have a range of health impacts, according to public health.
All of the city’s other beaches are currently listed as safe including Lake Ontario, from the Burlington lift bridge to Confederation Park and the beach areas at Valens, Christie and Binbrook conservation areas.
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