Malfunction in sewage storage tunnel leads to spill into Ottawa River

Photo courtesy City of Ottawa

OTTAWA — The City of Ottawa says a malfunction in its combined sewage storage tunnel, meant to keep sewage out of the Ottawa River, led to an overflow of wastewater into the river last week.

In a memo, public works director Marilyn Journeaux said the instrument that measures the sewage levels in the Stanley Park shaft malfunctioned on Nov. 16 causing the tunnel to fill to capacity.

"This resulted in a small spill into the Ottawa River," Journeaux wrote. "Staff were closely monitoring the system and were able to rapidly stop the overflow. An investigation is currently underway that will identify more precise information on the malfunction allowing staff to minimize reoccurrence."

According to the memo, a total of 306 cubic metres of sewage spilled into the river.

"For context, 300 m3 represents approximately 0.1% of the daily volume received and treated at Robert O. Pickard Environmental Centre (ROPEC) on a typical day," Journeaux said in the memo.

About 154 cubic metres spilled into the river in the Stanley Avenue and Keefer Street area, 70 cubic metres spilled in the Booth Street and Wellington Street area and 82 cubic meters spilled near Kent Street.

The spill was reported to the environment ministry.

The $232 million underground combined sewage storage tunnel is located eight storeys underground and can hold up to 43,000 cubic meters of sewage overflow during major rainfalls. It began operation in November 2020.