Ottawa River

August 2017 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.
Project Facts

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 (Site 10 to Site 6) will begin this fall.

Site 10: Chamberlain Shaft (Kent and Chamberlain Streets)

Site 10 will be the access point for the tunneling operation for the North-South Tunnel to the Ottawa River; a 13-metre-diameter shaft is being constructed to launch the tunnel boring machine (TBM).

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:
  • Pre-assembly of the TBM is underway at the former school board land on Chamberlain Avenue near Bronson Avenue in preparation for installation at the access shaft
  • Line drilling, rock-splitting and excavation for the TBM's tail and starter tunnels (needed to assemble the TBM) continue
  • Foundation installation for the gantry crane – a multipurpose crane adjacent to the access shaft
View Looking out of Access Shaft 10A
View Looking out of Access Shaft 10A
Site 10 Tail Tunnel
Site 10 Tail Tunnel        

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

Construction activity will begin later this summer/early fall, as crews re-mobilize to start constructing two chambers and the new outfall. This site will be the exit portal for the TBM after it completes the tunneling 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.
Temporary pathway connection along the Ottawa River
Temporary pathway connection along the Ottawa River

Site 5: East-West Tunnel Outlet and Rideau River Collector Diversion (New Edinburgh)

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

Site 5 construction activities of interest:
  • Line drilling inside the shaft at 5A was completed in preparation for controlled blasting
  • Relocation of utility poles and associated wires at Site 5C is underway
  • The secant wall at the Interceptor Outfall Sewer shaft is readied for line drilling
  • Line drilling within the shaft at 5B is underway
  • Continual monitoring of air quality, vibration and noise level
Line drilling in the shaft at Site 5A
Line drilling in the shaft at Site 5A

Collaborating with Communities

The City values the input and efforts of residents and the New Edinburgh Community Alliance on several fronts, including:
  • Temporary cycling/pedestrian detours – With the help of residents, the City has implemented temporary cycling and pedestrian detour routes and associated signage to help direct cyclists and pedestrians through the neighbourhood.
  • Stanley Avenue improvements – Working with members of the community, the City has planned improvements to traffic and pedestrian safety and the reinstatement of greenery. Work is expected to commence soon.
  • Odour Control Facility – Residents and the City have together refined a design for the Odour Control Facility that will replace the existing biofilter in Stanley Park.

The City looks forward to continuing to collaborate with communities through the CSST project.

School's Back!

Our communities' children will soon head back to school, and the City has reminded those involved in the CSST's construction to pay particularly close attention to students and school buses.

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.
Visit us on the web at or email the project team at
Banner with ORAP logo and City of Ottawa logo with wording that sayd, Supporting an environmentally sustainable Ottawa.
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