When the City of Hamilton learned that some of its storm sewer lines were cross-connected with a sanitary sewer and had been discharging into Hamilton Harbour for decades, local officials took action in accordance with industry best practices, according to the city’s auditor general.
The City of Hamilton’s Office of the Auditor General released a new report in November that found the cross-connections were the result of faulty design and construction drawings, as well as complex piping network drawings that made issues difficult to identify. In at least one instance, contractors were directed to make a connection to misidentified pipes.
The report conducted by 30 Forensic Engineering also determined a “lack of recognition” that the cross-connections were being constructed — and not deemed a significant risk — during the construction process.
All three of the identified cross-connection leaks were resolved by Hamilton Water.
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“The three spills investigated in this report and spills of this nature are a concerning reality within many cities across Canada given aging water and wastewater infrastructure,” announced Hamilton Auditor General Charles Brown in a statement. “There is no simple solution, however following this investigation, I am encouraged by the actions taken and underway, and I would underscore the importance of implementing the recommendations we have made in this report.”
The most significant leak, on Burlington Street, dates back to 1996. City officials estimated that some 337 million litres of sewage discharged into Hamilton Harbour as a result of the cross-connection. The other smaller leaks, one of which dates back to 1982, discharged a combined estimated total of about 60 million litres, the report states.
In at least one instance, the leak was finally discovered during a separate maintenance review of old closed-circuit video files.
The report also notes that one of the leaks occurred when the overflow connection between the combined and storm sewers was located in the “precise spot where flows were prone to discharge directly into the overflow connection even under dry weather.”
The Ontario Ministry of Environment, Conservation and Parks ordered Hamilton to undertake an audit of its sewage infrastructure following the discovery of the leaks in November 2022.
A previous report on the cross-connection leaks had been undertaken by Stantec Consulting and released in May 2023. In the latest report, City of Hamilton officials are urged to consider the approach recommended by Stantec. This includes continuing actions such as the Sewer Lateral Cross-Connection Program, and potentially expanding the Risk-Based Proactive Pilot Program in the high-risk central Hamilton combined sewer system. The report suggests this could be used as a launching pad for a permanent System-wide Unauthorized Discharges Removal and Inspection Program.
The new report also notes that transparency and response planning should remain top-of-mind as Hamilton prepares its communication and response for potentially undiscovered leaks from other cross-connections.
The audit report further recommends that Hamilton officials integrate wastewater asset management information across three Hamilton Water databases and prioritize communication between internal divisions.
Additionally, the audit report suggests that Hamilton Water and Engineering Services review city design and construction projects at key milestones, particularly those wastewater projects with higher risks of cross-connections.