Fault leads to overflow of new sewer tunnel

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A faulty meter is blamed for a $232 million flood of Ottawa’s year-old combined sewer tunnel.

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Just over 300 cubic meters of sewage flowed into the Ottawa River on Nov. 16, the city’s director of water services said in a memo to the city council Monday afternoon.

The CSST was used to store wastewater while maintenance work was being done on the city’s sewage treatment plant, Marilyn Journeaux said in her memo.

“The instrument that measures wastewater levels in the Stanley Park shaft malfunctioned, causing the CSST to fill up. This resulted in a minor spill in the Ottawa River,” she wrote.

Staff acted quickly to stop the overflow as soon as it was spotted, she wrote. The total overflow was only 0.1 percent of the daily wastewater received and treated at the Robert O. Pickard Environmental Center.

Approximately 154 cubic meters were spilled at the Stanley Avenue and Keefer Street outlets, 82 cubic meters were spilled at the Kent Street outlet and a further 70 cubic meters were spilled at the Booth and Wellington Street outlets.

The spill has been reported to the Ministry of the Environment and further investigation is underway to prevent a recurrence.

The massive 6.2-kilometer long combined sewer storage tunnel was commissioned in November 2020.

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