Virtually eliminating Ottawa sewage overflows and keeping the river clean
A combined sewer system uses the same infrastructure to transport sewage and stormwater drainage in wet weather. So, when a big storm fills up that system, the water comes back up and discharges—relieving the system and reducing the risk of flooding. That’s called a combined sewer overflow (CSO), and systems are designed so that CSOs happen infrequently to protect the environment while still protecting the community against flooding.
Ottawa’s goal was ambitious. They wanted to drastically reduce CSOs into the Ottawa River. We started with an environmental assessment, and we found (through a triple bottom line analysis) that the preferred solution was deep tunnel storage. Basically, there would be tunnels acting as storage reservoirs inside the combined sewer system, which would capture overflow and hold it until the system could handle the excess.
The tunnels are 4.2 kilometres (2.6 miles) and 2 kilometres (1.2 miles) long respectively and 3 metres (9.8 feet) in diameter each, adding approximately 43000 cubic metres (1.5 million cubic feet) of storage. The tunnels range from 20 metres (65.6 feet) to 35 metres (114.8 feet) deep with six major drop shafts transferring the flow into the tunnel. This project was constructed from 2016 to 2020 and commissioned for operation in 2020.
A previous project of ours upgraded the city’s flow-regulating structures and implemented an automated real-time control system. That project reduced annual CSO volume by 60-70%, and with the addition of the combined sewage storage tunnels, Ottawa will virtually eliminate combined sewage overflow during a typical year.
At a Glance
Meet Our Team
-
Susan Alarcon
Senior Associate, Water
-
Gerald Bauer
Principal, Water
-
Adrien Comeau
Vice President, Water, Wet Weather Practice Leader, Water Delivery Group
-
Stéphane D’Aoust
Principal, Water
-
Anil Dean
Tunnels and Trenchless Practice Leader
-
Steve Fradkin
Tunneling Technology Manager
-
Colin Goodwin
Environmental Engineer
-
Fangbiao Lin
Vice President, Global Practice Leader for Environmental Hydraulics
-
Jon Pearson
Tunnel and Trenchless Engineer
-
Jill Peters-Dechman
Senior Environmental Engineer
-
Pascal Pitre
Managing Principal
-
Julian Prada
Senior Principal
-
James Ricker
Associate, Water
-
John Take
Executive Vice President, Chief Growth & Innovation Officer
-
Joe Uglevich
Senior Vice President, Director of Water Project Delivery
We're better together
-
Become a client
Partner with us today to change how tomorrow looks. You’re exactly what’s needed to help us make it happen in your community.
Contact Us -
Design your career
Work with passionate people who are experts in their field. Our teams love what they do and are driven by how their work makes an impact on the communities they serve.
Join the Team