Project Update - Combined Sewage Storage Tunnel (CSST) - November 2017

Ottawa River

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.

City readies for cross-town tunneling – Watch it here!

In October 2016, the City put shovels in the ground at Chamberlain Avenue and Kent Street to create an access shaft to tunnel north. A year later, the 23-metre deep shaft and 88m starter tunnel are complete, the tunnel boring machine (TBM) has been lowered underground, and tunneling will begin soon!

The fully-assembled TBM will be 250 metres long fully assembled, and will work as deep as 31 metres below surface, with up to nine people inside it. At the other end of the future North-South Tunnel, work is underway on the exit portal near the Ottawa River, where in the spring of 2018, the machine will complete its 2-kilometre journey under the city, exiting behind the Supreme Court of Canada.
CSST Project Facts

Construction Site Map

The map below identifies construction sites for the CSST project within the City of Ottawa, which are described in more detail here.
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 CSST will consist of two inter-connected tunnels over six kilometres in total length, three metres in diameter, located 10 to 31 metres below surface level. The North-South Tunnel will run below Kent Street, from Chamberlain Avenue to just behind the Supreme Court of Canada, and the East-West Tunnel will run through the downtown core, from Stanley Park to LeBreton Flats, generally under Cumberland and Slater Streets.

Construction has already started at several sites. 

Construction Activity Progress

North South Tunnel (NST)

Tunneling of the North-South Tunnel (NST) from Kent/Chamberlain Streets to the Ottawa River (Site 10 to Site 6) will begin soon!

Site 10: Chamberlain Shaft (Kent/Chamberlain Streets)

Site 10 is the tunnel boring machine (TBM) launch shaft for the north-south tunneling operation.

Site 10 construction activities of interest:
  • A 50-tonne gantry crane has been assembled  to remove excavated rock and deliver pre-cast concrete tunnel pieces – all by remote control
  • The transfer of TBM segments, related equipment and pre-cast tunnel segments from the staging area at Bronson Avenue and Chamberlain Street to the access shaft at Kent Street and Chamberlain Street is ongoing
  • Assembly of the TBM within the starter and tail tunnel is complete
  • Tunneling operations begin soon 
Tunnel Boring Machine (TBM) train inside of the tail tunnel
Tunnel Boring Machine (TBM) train inside of the tail tunnel 
Gantry crane assembled for use during tunneling operations
Gantry crane assembled for use during tunneling operations 

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

Site 6 will be the exit point for the TBM and the northern end of the North-South Tunnel. It is expected that the TBM will emerge here, along the Ottawa River behind the Supreme Court of Canada, in the spring of 2018.

Site 6 construction activities of interest:
  • Crews have re-mobilized on-site, complete with a site trailer and equipment
  • Geotechnical surveying equipment has been installed
  • General site grading is complete
  • Excavation, including rock removal, on the slope has commenced, in preparation for TBM exit location
  • Work is underway to install the overflow sewer 
Excavation of the slope behind the Supreme Court of Canada to expose the rock face
Excavation of the slope behind the Supreme Court of Canada to expose the rock face 
Concrete pouring in preparation for construction of the Kent storm sewer bypass
Concrete pouring in preparation for construction of the Kent storm sewer bypass

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

Construction continues in New Edinburgh's Stanley Park, where the TBM will start its East-West journey later in 2018, and has re-commenced at the intersection of Queen Victoria Street and River Lane (to connect to existing sewer infrastructure).

Site 5 construction activities of interest:
  • Controlled blasting for rock excavation at shaft 5A (near the middle of Stanley Park) - as well as mechanical rock excavation at 5B (close to the construction site entrance) and the Interceptor Outfall Sewer (IOS) shaft - continues
  • Structural and roofing work for the Odour Control Facility is complete, and interior and exterior finishing underway
  • Construction has resumed at Site 5C (Queen Victoria and River Lane) with site grading and the installation of a noise barrier
  • "Microtunneling" – drilling horizontally to connect shafts 5A and 5B with a small tunnel – is underway
  • Monitoring of vibration and noise levels continues
Pattern drilling within the access shaft in preparation for controlled blasting
Pattern drilling within the access shaft in preparation for controlled blasting 
Odour Control Facility (OCF) at Site 5
Odour Control Facility (OCF) at Site 5

Tunnel Boring Machine

Once completely assembled, the Tunnel Boring Machine will be 250m long.  That's like running the Ottawa RedBlacks home field from one end-zone to the other and back, or skating the length of the Ottawa Senators' home ice four times.

The TBM has been specifically designed to cut through solid rock at the pace of roughly 20 to 25 meters per day. Its 23 cutters each weigh between 70 – 90 kg.
Tunnel Boring Machine (TBM)
Tunnel Boring Machine (TBM), showing cutter head wheels (yellow) in the factory 

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:

The CSST dedicated phone number is 613-580-2424 ext 2CSST (22778).  (This does not replace 3-1-1).
Visit us on the web at or email the project team at
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