Routine environmental monitoring conducted by Canadian Nuclear Laboratories (CNL) at the Port Hope Area Initiative (PHAI) Water Treatment Plant identified an abnormal result during testing of treated wastewater released from the facility.
As part of routine monitoring, samples of treated wastewater were collected on May 11, 2026, and submitted for laboratory analysis on May 12, 2026. Preliminary results received on May 19, 2026, indicated that a sample did not pass one of the required environmental compliance tests for treated wastewater.
As a precaution, discharge from the treatment plant was immediately stopped while the issue is being investigated.
At the time of the event, the treatment plant continued to operate normally and monitoring confirmed water quality and radiation-related measurements remained within expected ranges.
Additional samples have been collected and submitted for further testing. The investigation into the cause of the result remains ongoing.
This event has been reported to the Canadian Nuclear Safety Commission and the Ontario Ministry of the Environment, Conservation and Parks. There was no risk to public safety or impacts to drinking water resulting from this event.