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The City of Hamilton is estimating that approximately 59 million litres of waste has been dumped into Lake Ontario for more than two decades as the result of a sewage leak discovered this week.Nathan Denette/The Canadian Press

The City of Hamilton is estimating that approximately 59 million litres of waste has been dumped into Lake Ontario over more than two decades as the result of a sewage leak discovered this week.

The city says it developed the estimate based on water meter usage data from the 11 residential properties connected to the combined sewer pipe in the 27 years it went undetected.

The revelation comes after the city reported in November that a leak also discovered to be from 1996 had dumped 337 million litres of sewage into the Hamilton Harbour, which lies on the western tip of Lake Ontario.

The city confirmed the latest leak on Monday and says repairs were completed Wednesday, with repair costs totalling $37,529.

It says city staff are in communication with the Ministry of Environment, Conservation and Parks’ Spills Action Centre and shared the estimated amount of discharge with them Friday morning.

Hamilton has said the latest leak was found as part of a pilot program that inspects areas of the sewer system where the same cross connections responsible for the leak uncovered in November could be present.

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