Bearspaw South Feeder Main
Background
The Bearspaw South Feeder Main is the largest in Calgary’s network, and distributes a significant portion of the city’s treated water supply. The feeder main experienced a break on June 5, 2024.
Since then, 29 pipe segment repairs have taken place to support the stabilization of feeder main and the pipe has undergone an investigation to gain an understanding of the conditions that lead to the failure.
Pipe investigation
The purpose of the Pipe Investigation, undertaken by Associated Engineering and Pure Technologies is to understand the factors that led to the deterioration of the feeder main and its failure on June 5, 2024.
From these findings, the report indicated that there was not one specific factor that led to the failure of the feeder main in June.
Findings
The findings indicate that several different factors may have contributed to the feeder main failure, including:
- Some pipes showed visible mortar cracking and delamination upon excavation, while other pipe had intactmortar.
- Soil testing along the feedermain showed significantly aggressive soils in certain areas, predominantly due tohigh chloride concentrations.
- Laboratory testing confirmed that some distressed pipes did have chlorides penetrate the mortar, while otherpipes showed no evidence of chloride penetration.
- Severe pitting and corrosion of the prestress wires was present, as well as significant quantities of brittle wirefailure. Laboratory testing determined that prestress wires were prone to splitting.
- Evidence of Hydrogen Embrittlement and Stress Corrosion Cracking of the prestress wires was found. Both inthis case appear to be due to chloride penetration of the mortar and/or microcracking.
The review of the design and operations also confirmed the original design of the pipe was consistent with the proper guidelines of the time and operations of the pipeline were well within the design parameters of the pipe.
Note: Due to extensive report findings, it is best to download on a desktop computer.
Repair and construction
Short term repairs on the Bearspaw South Feeder Main are now complete. The pipe has stabilized and is responding well to the 29 repairs.
| Repair | Need | Start date | Completion date |
|---|---|---|---|
| Feeder Main Break | Original Feeder Main Break emergency response and repair. | June 5, 2024 | June 16, 2024 |
| 5 Emergency hot spots | Emergency hot spots identified with the original feeder main break requiring immediate repair. | June 14, 2024 | June 27, 2024 |
| 21 Planned urgent repairs | 21 segments identified needing urgent repair through further investigation. | August 26, 2024 | September 22, 2024 |
| 2 Planned urgent repairs | 2 segments identified needing urgent repair not located in an area requiring city-wide water restrictions. | October 16, 2024 | November 26, 2024 |
Next steps
The City is currently reviewing options for long term rehabilitation of the feeder main. Findings from the Pipe Investigation will support this work. Next steps for long-term rehabilitation will be shared in 2025.
Frequently Asked Questions
Moving into 2025, can you speak to the upcoming repair or replacement plans for the Bearspaw Feeder Main and the impacts to residents and businesses?
The City has recently closed a request for proposal for the detailed design for the work related to the Bearspaw South Feeder Main Reliability Project. The City will share additional information with public as it becomes available.
Will the Bearspaw South Feeder Main remain operational throughout repairs?
Yes, it is expected that the feeder main will continue to remain in service, except for short durations when the new pipe needs to be tied into the existing feeder main.
Are there any plans for system wide redundancy, if so, what?
Feeder main projects will increase Calgary’s water capacity, to serve growth, provide redundancy and reduce reliance on existing feeder mains.
Two feeder main projects, North Calgary and South Calgary Water Servicing projects will reduce the reliance on the Bearspaw South Feeder Main to supply water during average day demand conditions, but the Bearspaw South Feeder Main will continue to be relied upon in the future to provide maximum daily demand. It is also a key piece of infrastructure that will enable the Glenmore Water Treatment Plant to be taken out of service for planned maintenance and upgrades.
Water treatment plant projects, will increase Calgary’s water treatment and raw water capacity, ensuring sufficient drinking water supply to serve growth. Additionally, the Glenmore Water Treatment Plant Expansion investment will eliminate single points of failure improving the reliability of the treatment plant.
- The Glenmore Water Treatment Plant Expansion includes a new treated water storage reservoir (called a “clearwell’), high lift pump station and electrical building. These projects will be complete by 2031.
- The Water Treatment Expansion program includes a new water treatment plant, and a new and/or upgraded raw water intake. The new infrastructure will be located along the Bow River and will be complete in 2035.
What happens if another major failure occurs before the new redundancy projects are completed?
While our third-party experts have told us that a failure of the feeder main is extremely unlikely, the City continues to monitor the Bearspaw South Feeder Main and has an emergency and spare parts plan in place to anticipate and proactively respond to a failure.
How long do you anticipate taking to develop and implement long term rehabilitation for the feeder main and when this will be shared?
The city will be returning to Council in Q3 2025 with additional details regarding the necessary work, including the project phasing, construction technique, alignment and cost estimate.
Why is only a portion of the Bearspaw Feeder Main currently being monitored? When will the remainder of this feeder main begin to be monitored? Is there no concern that other areas of this aging asset will break?
The City is using a combination of permanent and temporary monitoring along the length of the feeder main, with plans to replace the temporary locations with permanent monitoring equipment in Q2 2025. This monitoring, along with the completed repairs, third party experts’ statistical structural analysis and an emergency and spare parts plan is in place to manage the risk related to future breaks, and in fact allow us to proactively plan for a repair, if necessary.
How are you planning to improve the reliability of the Bearspaw South feeder main?
To improve the reliability of the Prestressed Concrete Cylinder Pipe portion of the Bearspaw South Feeder Main, several rehabilitation and replacement options have been identified and are currently being explored. The options include open cut pipe replacement, external reinforcement, internal lining, and microtunnelling of a new line.
The microtunnelling option has been selected as the most promising option at this time, as the construction technique minimizes traffic impact and water service disruption to Calgarians as well as minimizing the impact to adjacent homeowners and businesses.
What is microtunnelling?
A tunnel construction technique used to construct pipe underground. It includes a micro tunnel boring machine that creates the tunnel and then pipes are inserted behind the machine. This construction technique has been used by the water utility for other large diameter pipes, including the Inglewood Sanitary Trunk crossing of the Bow River and Nose Creek Sanitary trunk adjacent to Deerfoot Trail.
Can you provide details on the upcoming feeder main projects?
The North Calgary Water Servicing Project will provide partial system redundancy to the Bearspaw South feeder main. It will also provide redundancy to six other feeder mains. This project will be complete by 2028.
The South Calgary Water Servicing is in early development and will provide the remaining system redundancy to the Bearspaw South feeder main and two other feeder mains. This project is a new feeder main to move water to south Calgary from the Bearspaw Water Treatment Plant that is planned to be complete by 2031.
Crosstie Feeder main. This project will improve the redundancy of the feeder main network in NE Calgary and improve system pressures in Saddle Ridge, Taradale, Martindale and Falconridge. This feeder main extends along Country Hills Blvd from Coventry Hills Blvd to 60th Street NE and will be constructed by 2029.
How will these projects be funded, and will there be any impact on water rates for Calgarians?
There are no operating or capital costs associated with the recommendation in report IP 2025-0150. Consistent with current processes within these lines of service, construction budget may be requested separately from when design budget is needed. As projects move through stages of development, and when better cost estimates are available, a budget request for construction may come forward, which will also highlight any impact on rates.