The city says it has determined the cause of an equipment failure that resulted in 353 million litres of untreated or partially wastewater being discharged into Hamilton Harbour earlier this month.
The incident happened during heavy rain on Oct. 3, when two of four bar screens failed at the Woodward Avenue Wastewater Treatment Plant (WWTP), resulting in a temporary full plant bypass.
The city says it has determined that the plant’s old pumping station, which has since been decommissioned as a result of capital upgrades, was operational at the time due to high flow.
It’s believed excessive solids, like rags and plastics, had settled to the bottom of the wet well during periods of inactivity and were drawn through the pumps on the night of Oct. 3, causing the equipment failure.
The city says the scenario can’t be repeated, since the old pumping station is now permanently offline as construction of the new main pumping station at the WWTP approaches completion.
The city adds that it has reported both the incident and its subsequent findings to the Ministry of the Environment, Conservation and Parks (MECP).
This week’s heavy rains also resulted in the temporary bypass of partially treated wastewater from three of the city’s combined sewage overflow (CSO) tanks and the Woodward Avenue Wastewater Treatment Plant.
The city’s website shows that those bypass incidents have now ended.
There’s no word on the volume of material that was discharged into the watershed because of the latest wet weather.