Project Update - Combined Sewage Storage Tunnel (CSST) - December 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.
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) has begun! 
The tunnel boring machine (TBM) has been specifically designed to cut through solid rock at the pace of roughly 20 to 25 meters per day. However, progress in the first several weeks is much slower, and will accelerate in early 2018.
Tunnel Boring Machine (TBM)
Tunnel boring machine (TBM), showing cutter head wheels (yellow) in the factory 

Site 10: Chamberlain Shaft (Kent/Chamberlain Streets)

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

Site 10 construction activities of interest:
  • Geotechnical monitoring continues
  • Final testing of the tunnel boring machine has been completed
  • Tunneling has begun! 
Conveyor used for underground tunneling operations
Conveyor used for underground tunneling operations 
Removal of excavated rock from the access shaft at 10A, during tunneling operations
Removal of excavated rock from the access shaft at 10A, 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:
  • Reinforcing and grouting of micropiles for the headwall foundation are complete
  • Temporary by-pass for the existing overflow sewer has been installed
  • Excavation of slope face continues, with transportation of excavated material off-site
  • Preparation for installation of new Kent Street outfall is well underway 
Installation of temporary by-pass for the existing overflow sewer
Installation of temporary by-pass for the existing overflow sewer  
Excavation of rock/earth in order to expose slope face
Excavation of rock/earth in order to expose slope face 

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 overflow 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
  • Interior and exterior finishing of the Odour Control Facility is well underway
  • Noise barrier and geotechnical monitoring equipment have been installed at site 5C (Queen Victoria and River Lane)
  • "Microtunneling" – drilling horizontally to connect shafts 5A and 5B with a small tunnel – is well underway, with initial drilling of a pilot hole complete
  • Monitoring of vibration and noise levels continues
Rock excavation within the Interceptor Outfall Sewer (IOS) shaft
Rock excavation within the Interceptor Outfall Sewer (IOS) shaft 
Exterior vinyl and masonry on Odour Control Facility (OCF) at Site 5
Exterior vinyl and masonry on Odour Control Facility (OCF) at Site 5

Q & A with our Lead Tunnel Inspector 

Tunnel boring machine segment with inspector inside]

What does a Lead Tunnel Inspector do, exactly?

My role is to oversee all the tunnel inspection staff, reporting and records submissions. Most importantly, I help to ensure that the tunnels are constructed according to the design and contract requirements, and I report progress back to the rest of the CSST team.

What’s the coolest part about your job?

Because of the limited physical access and complexity of tunneling operations, there are very few people who have the required training to do what I do. I’m one of the few people that actually get to go into the tunnel and the tunnel boring machine (TBM) and see what’s going on – so that is pretty cool. Whatever happens, I am usually the first person to see and know. 

What is the most interesting thing you’ve found underground while tunneling?

I was working on a project in Israel and we came across an old car, from the 1940s or ‘50s, buried underneath a very old highway between Tel-Aviv and Jerusalem. It was very strange, because the road was over 1,000 years old. We had to stop work, support the tunnel, then remove the car in pieces.

Do you get to “drive” the machine? 

No, the operator is specially trained and has many years of experience operating a TBM. The machine is complicated - it has hundreds of sensors and video screens and essential moving parts – so the operator must know everything about it. In addition, the TBM is very small inside, which makes it so important for the ten or so people inside it to know their roles – where to go, what to do, and when. The operator is like the captain of a ship or the pilot of a plane; nobody moves without them.

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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