The CSST project will include the following:
- An east-west tunnel (EWT) through the downtown core from LeBreton Flats to New Edinburgh Park
- A north-south tunnel (NST) along Kent Street from Catherine Street to existing storm sewer outfall at the Ottawa River north of Wellington Street
- Support facilities, such as odour control buildings
The tunnels will be a total length of 6 kilometres and will be approximately 10 to 31 metres below surface level. The inside diameter of the finished tunnel will be 3 metres.
Aerial photo [ PDF – 456 KB ]
Overview of CSST project
The Ottawa River Action Plan (ORAP) is a long-term strategy to improve stormwater management and to enhance the health of the Ottawa River through 17 water infrastructure projects. The CSST is one of the most important projects of the ORAP.
The CSST will greatly reduce the frequency of overflows from entering the Ottawa River.
The CSST will hold up to 43,000m3 of combined sewage during major rainfalls. Up to this volume of combined sewage will be held in the CSST until after the rain event. It will then be treated at the treatment plant and returned safely to the Ottawa River.
Additional benefits of the CSST project include:
- Reducing the risk of basement flooding for several low-lying lands in the Glebe/O’Connor area
- Increasing operational flexibility and redundancy to major collector sewers in the downtown
Combined Sewer Overflows (CSOs) to the River originate from the sewer shed serviced by the Interceptor-Outfall Sewer (IOS) that services a population of 350,000. This one pipe conveys wastewater from a 107 km2 area to the Robert O. Pickard Environmental Centre for treatment. When the IOS or collector sewers reach capacity under wet weather conditions, they can cause overflows (CSO) to the Ottawa River. A key objective of the Ottawa River Action Plan is to minimize overflows to the River.
Ottawa’s combined sewer system
This diagram shows how the control system uses sensors to maximize flow to the sewage treatment facility. With this system, we can capture the flow from a bigger storm that would have caused an overflow in the past.
Future with CSST
This diagram shows that during large rainfall events, excess wet weather flow is sent to the combined sewage storage tunnel. Once the event has passed, the stored water is transferred to the interceptor sewer and treatment facility.
Planning and design
To date, the City has completed an Environmental Assessment study and detailed design of the CSST project.
The CSST is a Term of Council Strategic Initiative and one of the most important projects of the Ottawa River Action Plan (ORAP). Below is a summary of important milestones to date:
- November 2009: CSST Environmental Assessment is initiated through ORAP
- February 2010: ORAP and service levels for CSOs approved by Council
- September 2011: ORAP Year One Update Report outlines the status of the 17 ORAP projects, including the CSST, Project 3 – CSO Storage for Ultimate Combined Sewer Area (UCSA). approved by Council
- February 2013: CSST Environmental Assessment completed, with summary of the options reviewed and the preferred alternative recommended
- August 2013: Design of CSST commences
- April 2014: CSST EA Addendum filed with evaluation of alternative NST construction staging area on Chamberlain Street
- Summer/Fall 2015: The City initiates property negotiations for the CSST
- December 2015: CSST tendered for construction
To date, nine public open houses have been held throughout the City to support the CSST Environmental Assessment study.
Next steps and project communications
Thank you for coming to our open house.
If you have any questions about the CSST Project, please feel free to ask any City or design team representatives present.
The City will keep residents updated through a variety of information tools, including:
- Regularly distributed e-newsletter with updates on construction activities, impacts, and progress. Residents can sign up to receive updates automatically at Ottawa.ca/esubscriptions.
- Webpage Ottawa.ca/CSST with information on the overall project including updates
- Email address CSST@ottawa.ca for inquiries
Comments received may become part of the public record. Information will be collected in accordance with the Freedom of Information and Protection of Privacy Act.
Collector sewer: A conduit that receives sewage and/or stormwater from local sewers. A main conduit that receives sewage and/or stormwater from the local sewer system serving a defined serviced area such as a neighbourhood or district. Acting as the main spine of a sewer system, collector sewers in the City of Ottawa generally range from 750 mm in diameter to 2100 mm in diameter (or larger in some cases).
Design year: The meteorological and flow conditions used as the basis for designing the facilities. In Ottawa, the Ontario Ministry of Environment and Climate change has accepted rainfall conditions measured in 1980 as representing the “design year” because it had “average” wet weather patterns for engineering design purposes.
Interceptor Outfall Sewer (IOS): The primary conduit through the City’s downtown core that captures the wastewater flow from the collectors and combined sewers and conveys it to the wastewater treatment plant, the Robert O Pickard Environmental Centre (ROPEC).
Odour control facility: A building and system for the collection and treatment of odorous air from the CSST.
Real time control: An automated or manually operated system that adjusts the operation of facilities in response to online measurements in the field.
Flow regulator: A structure that directs and controls flows in the sewer system.
Shaft: An access point from the surface to an underground facility that allows for construction and/or inspection and maintenance of this or other underground facilities, such as the CSST.
Wet weather event: A period of rainfall or snow melt that results in stormwater being captured and conveyed in the sewer system.
Site 5 – What’s happening
Map of CSST [ PDF – 333 KB ]
Construction has begun at Site 10. Site 5 (Stanley/New Edinburgh Park) will be occupied from March 2017 to October 2019. The sites are as follows:
- Site 1: West End Shaft – Lebreton Flats
- Site 2: EWT/NST Intersection – Kent and Slater Streets
- Site 3a: Rideau Canal Interceptor Diversion/Drop – Confederation Park
- Site 3b: Rideau Canal Regulator – Rideau Canal
- Site 3c: Nicholas Street Shaft – Nicholas Street
- Site 4: St Patrick Shaft – York and Cumberland Streets
- Site 5: EWT Outlet / RRC Diversion – New Edinburgh Park
- Site 6: NST Overflow and Kent Street Outfall – Ottawa River Parkway
- Site 7: (Eliminated)
- Site 8: McLeod Street Drop – Kent and McLeod Streets
- Site 9: Catherine Street Drop – Kent and Catherine Streets
- Site 10: Chamberlain Shaft – Kent and Chamberlain Streets
The Contractor will have available the use of two areas:
- Stanley Park will be the primary construction area and will have a permanent access point to the CSST.
- The intersection of Queen Victoria Street and River Lane will be a second construction area to connect the CSST to the existing Rideau River Collector overflow sewer.
Construction activities and schedule
- Temporary advance activities commenced in October and November of 2016 with installation of underground conduits, archaeological investigations and locating the IOS.
- Tree removal may start in early 2017—Construction work will begin in spring 2017 with installation of fencing and trailers.
- A 13-metre diameter shaft will be excavated to launch a tunnel boring machine (TBM); the TBM will be brought to the site and placed in the bottom of the shaft to excavate the tunnel.
- After the tunnel is completed, an access chamber will be constructed within the shaft to allow for future maintenance of the CSST.
- The existing biofilter will be removed and a new odour control facility will be constructed.
- Work is scheduled to commence in March 2017 and be completed and the site restored by fall 2019.
Stanley Park staging plan [ PDF - 950 KB ]
Stanley Park plan and profile [ PDF - 166 KB ]
Stanley Park restoration plan [ PDF - 565 KB ]
Stanley Park proposed odour control facility [ PDF – 947 KB ]
Queen Victoria Street and River Lane
- Work will begin with installation of fencing and signs.
- A 6.5-metre by 6.5 m shaft will be excavated to construct a diversion chamber and access shaft.
- Work is scheduled to commence in March 2017 and be completed and the site restored by March 2018.
Queen Victoria Street and River Lane [ PDF - 461 KB ]
Queen Victoria Street and River Lane - Projected Construction Sequencing Summary
Site 5c (Rideau River Collector - Overflow Diversion Chamber - At intersection of River Lane & Queen Victoria)
|Details of Work
||Expected Noise/Truck Levels
Early March 2017
|Relocation of communication lines by the utility companies from above-ground to underground.
|Traffic Control, Hoarding/Fencing, Site Setup, Utility Relocation and Temporary Sewer Bypass
March Early 2017
|Early May 2017
||Site setup activities, including installation of the fencing and relocation of utilities and sewers as required. Modest noise and trucking (delivery of fences/piping, hauling away of some material excavated for these relocations, etc).
||Early May 2017
||Late May 2017
Includes driving shoring piles into the soil down to the rock elevation and line grouting to permit excavation of soils inside the shored area while supporting the surrounding areas. Installing the shoring will generate some noise - limited to daytime. Modest trucking - limited to hauling shoring material and it is possible that some small volume of soils may be hauled away.
Loud noise driving sheet piles
|Late May 2017
||Late May 2017
||Once shoring is installed, soil material will be excavated and trucked away (maybe 3 trucks per hour - small volume). The same frequency of empty trucks would also return to the site.
Late May 2017
|Late July 2017
|Rock excavation will involve drilling, controlled blasting, hoe-ramming, shotcrete and bolt installation, as well as trucking away excavated rock. Trucking frequency will be low as rock removal is a slow operation compared to earth removal.
Loud noise resulting from hoe-ramming and rock handling.Modest trucking
Micro-Tunneling of Diversion Sewer (5b to River Lane)
Early August 2017
|Early October 2017
Includes installation of tunneling equipment, pilot hole tunneling, back reaming along that pilot hole, and finishing the grouting. The back reaming operation (which consists of enlarging the smaller pilot hole to the size required for the sewer) is expected to produce the most trucking as it generates spoils (crushed rock) to be hauled away, and will last approximately 5-6 weeks. For this section of the diversion tunnel, it is proposed by the contractor that these reaming spoils be extracted from the shaft located that the intersection of River Lane / Queen Victoria - to be confirmed. Could fill four trucks per day at its peak.
Some modest noise associated with motor for auger
|Construction of Chambers (once micro-tunneling complete)
||Early October 2017
||Early February 2018
||16-18 weeks (4 months)
Construction of chambers includes the following components: structure floor, walls and roof construction, installation of weir, ladders and steps, demolition of section of existing overflow sewer, new connections, backfill and removal of shoring. Materials and concrete being delivered to site as required. This phase includes backfill around the chamber, estimated to generate 3-4 trucks per hour hauling backfill material to the site and the same frequency of empty trucks leaving the site - over a period of approximately 1-2 weeks in late January / early February. Other trucking would include concrete trucks during the pours.
Heavier trucking during backfill (1-2 weeks), modest otherwise
|Grading and Rough Reinstatement
||Early February 2018
||Early March 2018
||Grading of the surface, base-coat paving, curbs, sidewalks, rough grading of landscaped areas to prepare for sodding later in the spring (since weather will not permit sodding at this time). Opening of the intersection. Heavier trucking will be during delivery of granular material for road construction (3-4 trucks per hour for a week or so).
Heavier trucking for 1-2 weeks, otherwise modest
|Post-Construction Final Reinstatement
||Early May 2018
||Mid May 2018
Once weather is warmer, application of final layer of pavement and placement of sod and plantings. No long-term roadway impact as top-lift pavement is expected to be completed in a single day.
1. This table should be considered to be a living document and presents a best estimate based on the contractor's submitted construction schedule and the project team's general experience with similar activities. The contractor will be required to submit detailed schedules and management plans prior to undertaking this work.
2. All work at Site 5c (River Lane / Queen Victoria) is limited to daytime activities as defined in the City's Noise Bylaw (7:00AM-10:00PM). No nighttime work is currently permitted at this site. Contractor may submit a special request for a specific task that is impractical to be completed during daytime, but it would need to be submitted for review and approval by the project team and Councillor as it is not currently permitted.
Site 5 - Construction impacts
Construction activities will have the potential to impact businesses and residents along the corridor and the adjacent community. The following construction impacts may be expected:
- Closure of the Queen Victoria / River Lane intersection
- Conversion of River Lane to two way traffic between Queen Victoria and Keefer and between Queen Victoria and Union Street
- Temporary closure of the Rideau River Eastern Pathway between Union and Stanley with alternate pathway routes within Stanley Park
- Tree removal in Stanley Park
- Temporary loss of use of park space
- Temporary closure and diversion of pathways
- Construction traffic to and from staging areas
- Construction noise and dust
- Localized vibrations as the tunneling operations pass in close proximity to homes
Construction management requirements have been included in the design and tender. A vibration/seismic monitoring program will track surface level vibrations as the tunnel boring machine moves across the City.
A Noise By-law Exemption is in place to allow work on the CSST tunneling to proceed 24 hours per day, 7 days per week.
Project funding and partners
- The total project cost for the CSST is $232 million and funding has been approved by City Council through the budget process.
- The City of Ottawa has contributed $108 million.
- The Government of Canada and Province of Ontario have each committed $62.09 million towards the project.
- On March 23, 2016, Council passed a motion to approve these funding agreements.
- Stantec Consulting Ltd., CH2M and Golder Associates are working with the City on the design and contract administration of the CSST project.
- Dragados Tomlinson Joint Venture has been selected as the construction team to build the CSST.