Mayor Mark Sutcliffe Directs $75 Million for Ottawa River Combined Sewage Overflow Storage Tanks

OTTAWA — Mayor Mark Sutcliffe and Ottawa City Council voted on Monday to approve a $75 million municipal water and wastewater capital allocation to engineer and construct two 30-million-litre underground reinforced concrete stormwater holding vaults and high-rate treatment facilities adjacent to the Combined Sewage Storage Tunnel (CSST) in downtown Ottawa.

The project captures and temporarily stores extreme storm runoff from century-old combined sewer mains across Centretown, the ByWard Market, and Sandy Hill during severe convective cloudburst rainstorms, preventing millions of litres of untreated combined stormwater and sanitary sewage from overflowing into the historic Ottawa River.

Protecting the National Capital Watershed and Public River Beaches The Ottawa River is the lifeblood of Canada's National Capital Region, supporting municipal drinking water intakes, scenic multi-use shoreline pathways, and public swimming beaches at Petrie Island, Britannia, and Westboro. Extreme summer rainstorms historically triggered emergency beach closures due to elevated E. coli levels.

"The Ottawa River is the natural centerpiece of our nation's capital, and protecting its water quality is an absolute priority for our city," Mayor Mark Sutcliffe said at the Robert O. Pickard Environmental Centre in Gloucester. "This $75 million investment expands our underground storage capacity by 60 million litres, ensuring that even during the heaviest summer cloudbursts, stormwater is captured, safely contained, and fully treated before returning clean water back into the Ottawa River."

Storage Facility Engineering Features The $75 million package funds:

• Two 30-Million-Litre Underground Storage Vaults: Constructed 20 meters below grade with post-tensioned reinforced concrete walls.
• High-Volume Submersible Dewatering Pumps: Capable of pumping 5,000 litres per second to the sewage treatment plant once storm surges subside.
• Automated Odor Control Bio-Filters: Installing advanced activated-carbon and biological air scrubbers to eliminate urban odor emissions.

Urban water engineers, environmental conservation groups, and river paddlers praised the city council vote, highlighting that underground retention tanks provide a permanent engineering solution to protect river water quality.