Ottawa River

Project Update

Combined Sewage Storage Tunnel (CSST)

Building a healthy and resilient future for the Ottawa River

This $232.3 million construction project is a key part of the Ottawa River Action Plan (ORAP), which is aimed at enhancing the health of the Ottawa River and protecting our water environment for future generations. A healthy water environment provides safe, abundant drinking water; supports agriculture, recreation and tourism; lessens the impact of flood events; and helps sustain fish and wildlife.

Fun Fact

The CSST will hold up to 43,000m³ of sewer overflow during major rainfalls - equivalent to approximately 18 Olympic-sized pools!
Project Facts

Connecting with Communities

Al Hart Field Ambassador
Alistair (Al) Hart, Field Ambassador
 Already a familiar face to many, Al Hart, our Field Ambassador, is always present at the various CSST sites. He's our main "eyes and ears," observing the construction activities and helping the project team to identify and address potential issues.

When you call 613-580-2424 ext. 2CSST (22778), there's a good chance it's Al on the other end of the line. He acts as a liaison between the project team and the communities we're in, and his primary goal is to ensure that residents' concerns are heard.  When Al finds or hears of a problem, he helps figure out the best way to fix it – and, as a result, he's quickly become a valued part of the community.
"Getting to know these communities and working with their residents has been great. I really enjoy being a voice for the residents, a familiar face for them to approach, and collaborating with them and the project team to address any issues that arise. Working on a project as important as the CSST is a good feeling; it's going to benefit all of us across this city, and I'm mesmerized by the engineering and design involved. I get to see and hear peoples' interest in the CSST first-hand, and I am glad to be a part of it all."

Construction Activity Progress

This map identifies construction sites for the CSST project within the City of Ottawa.
Map of the CSST sites numbers 1 to 10. Sites 5, 6 and 10 are green, site 7 is grey and all other sites are red
The East-West tunnel will run through the downtown core from LeBreton Flats to New Edinburgh, and the North-South tunnel will run below Kent Street from Chamberlain Avenue to behind the Supreme Court.

Construction has already started at several of the sites indicated in orange.  Site 7, identified with the grey dot, was eliminated during the design phase of the project.
Please continue to visit for updated information and construction site activity.

North South Tunnel (NST)

Tunneling of the North-South Tunnel (NST) from Kent and Chamberlain Streets to the Ottawa River will begin later this summer.

Site 10: Chamberlain Shaft – Kent and Chamberlain Street

Site 10 will be the access point for the tunnel boring machine (TBM); a shaft is being constructed to launch the tunneling operation for the North-South Tunnel to the Ottawa River.

The TBM has been specifically designed to cut through solid rock at the pace of roughly 20 to 25 meters per day.

Site 10 construction activities of interest:
  • Installation of temporary water service into the access shaft to support the TBM during tunneling
  • Pre-assembly of the TBM is underway in preparation for installation at the access shaft
  • Line drilling, rock-splitting and excavation for the TBM's tail and advance tunnels inside the access shaft
  • Micro-piling to install the foundation for the gantry crane – a multipurpose crane adjacent to the access shaft
Drilling around the tail tunnel at Site 10A in preparation for rock breaking
Drilling around the tail tunnel at Site 10A in preparation for rock breaking
Rock breaking inside of the tail tunnel in preparation for the Tunnel Boring Machine (TBM) placement
Rock breaking inside of the tail tunnel in preparation for the Tunnel Boring Machine (TBM) placement

Site 6: North South Tunnel (NST) Overflow/Kent Street Outfall - Ottawa River Pathway

Construction activity will begin later this summer. This site will be the exit point for the TBM after it completes the tunnelling of the North-South Tunnel. It will also be a permanent access point to the CSST once complete. Fencing has been installed around the site, and a temporary pathway connection has been paved to allow pedestrians and cyclists continued access to the existing pathway along the Ottawa River.
Installation of wooden hoarding for site enclosure at Site 6
Installation of wooden hoarding for site enclosure at Site 6

Site 5: East West Tunnel Outlet/Rideau River Collector Diversion – Stanley Park/New Edinburgh Park

Construction activity continues in New Edinburgh, in Stanley Park and at River Lane/Queen Victoria.

Site 5 construction activities of interest:
  • Relocation of underground utilities at Site 5C
  • Plans completed for the relocation of utility poles and associated wires at Site 5C
  • Completion of the insulation and waterproofing of the Odour Control Facility (OCF) foundation walls, as well as the installation of electrical conduits
  • Commencement of work on the Interceptor Outfall Sewer shaft
  • Continual monitoring of air quality and noise levels
  • Installation of water services to the shaft at Site 5A in preparation for the TBM
  • Completion of the Crichton Street landscaping

While not part of the CSST project, the Stanley Park playground renewal has also begun adjacent to the site. Road work along Stanley, planned as part of the CSST works, will be coordinated with the playground renewal - expect more to come on these roadway improvements!
Pouring of concrete for the secant guide wall at Site 5A
Pouring of concrete for the secant guide wall at Site 5A
Concrete pour for Odour Control Facility floor
Concrete pour for the Odour Control Facility floor

Mobility & You

Stay informed about capital infrastructure projects. Check out the City's interactive traffic map and traffic report or call 3-1-1 for updates about when and where construction is happening.

Contact Us

The CSST Project Team is committed to sharing information that may help affected residents and businesses plan around construction in their neighbourhoods. For more information, please contact us using any of the following methods:

The CSST dedicated  phone number is 613-580-2424 ext 2CSST (22778) and does not replace 3-1-1.
If your matter requires urgent attention, please report your concern by calling 3-1-1. Voice messages will be returned the next business day.
Email the project team at
Please continue to visit for updated information and construction activity. 
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