
2024 No-Dig North Project of the Year Rehabilitation
Rehabilitating the Kenilworth Trunk Watermain
The Kenilworth Trunk Watermain is a1,050 cement mortar lined steal watermain, constructed in 1960, to serve the upper portion of the City of Hamilton, Ontario.
When it comes to maintaining underground infrastructure there is no disputing that Hamilton is one of the forefathers when it comes to condition assessment, asset management and rehabilitation of underground assets in Canada.
An early adopter of all the above, Hamilton has a long history of being proactive when it comes to its critical underground infrastructure. Such was the case with its Kenilworth Trunk Watermain, which is one of two transmission mains that serve the the upper portion of the of the city at the top of the Niagara Escarpment — known locally as Hamilton Mountain.
The watermain’s normal operating pressure ranges from 1,089 kPa (~158 psi) to 1,275 kPa (~185 psi) and has a daily flow between 40 and 50 MLD.
Knowing the criticality of this watermain, leadership in Hamilton’s Public Works department put a plan in place to inspect and monitor the pipeline in 2013. The first phase included a visual and ultrasonic inspection. The inspection identified the deterioration of the steel wall and loss of wall thickness in some locations that resulted in two emergency repairs.
Inspections on the pipe were completed between 2014 and 2024 to assess the continued deterioration and maintain the system that provides approximately 50 per cent of the community’s water. In 2016, an internal inspection of pipe revealed that the cement mortar lining was in good condition.
Looking for a Solution
Working with Stantec, the city began looking for the best solution to repair the pipeline – specifically a 300 m section between the Kenilworth pump station and top of the Niagara Escarpment – to ensure uninterrupted service to residents in the upper portion of the city.
Based on the many investigations of the pipeline and its location – inside of a 2.44 m diameter tunnel – it was quickly determined that a trenchless approach to the repair was needed.
While Stantec explored several trenchless options, because the internal coating on the pipe was intact, an external coating on the pipe was deemed to be the best solution. It’s important to note that 250 m of the pipe was in a 2.44 m diameter horizontal tunnel and 50 m of the pipe was in a 2.44 m diameter vertical shaft.
“What we specified in the tender was what the product had to meet in terms of structural needs and corrosion proofing,” says Harry Krinas, senior project manager, engineering services for the City of Hamilton. “The bidders were able to respond with a product and technology they determined could meet those technical requirements.”
Ultimately it was determined that wrapping the pipe using carbon or glass fibre sheeting would be the solution. As a matter of fact, the two general contractors that bid on the project both came to the table with the same subcontractor and product application.
“External carbon fibre offered the ability to rehabilitate the existing in-tunnel pipe in a timely manner,” says Krinas. “Having the pipe out of service for a prolonged period presents a significant risk on service levels and conflicts with other capital initiatives.”
The contract was awarded to Clearway Construction with the trenchless works subcontracted to Pullman using Structural Technologies products and carbon fibre engineering design by Simpson Gumpertz & Heger (SGH).
Ensuring a Proper Repair of the Kenilworth Trunk Watermain
Before work began the project team at Stantec developed a series of repair categories, and as the construction was being completed, verified that the appropriate structural repair took place at the right location based on current site conditions.
According to Joe Grieci, C.E.T., one of the unique aspects of this project is that the deterioration of the pipe varied greatly throughout meaning that different levels of repairs were necessary. Grieci is a project manager – subsurface infrastructure/infrastructure renewal for engineering services for the City of Hamilton.
The design Stantec proposed was based on the five established rehabilitation categories:
- Where less than 10 percent pipe loss existed,
- Where pipe loss ranged between 11 and 30 percent,
- Where pipe loss ranged between 31 to 50 percent,
- Where pipe loss ranged between 51 to 75 percent,
- Where the pipe loss required the installation of a steel patch.
“Each category required a different number of layers and orientation to deliver the close to the 200 psi operating pressure of the pipeline,” says Gerald Bauer, principal, water at Stantec. “The A-E coding allowed for a cooperative process where the contractor knew what each level required in terms of repair. It’s an approach that was fair to city and contractor because it eliminated some of the unknowns and unknowns always cost money.”
The project was broken into two phases. Because the pipe could only be taken offline during off-peak season — roughly November to May — the most critical and urgent repairs were addressed in early 2023 with the remainder completed from Fall 2023 to Spring 2024. Approximately 130 sections of pipe were repaired.
Challenging Site Conditions
Given that the pipe was in a tunnel environment, there were myriad challenges that the project team faced. The chief among them was accessing the pipe and providing proper air circulation and humidity levels during construction to maintain worker safety and not impede curing time. To combat these issues the contractor deployed ventilation, heaters and dehumidifiers throughout the pipeline, all needing to be balanced to meet the varying project needs.
While access to the vertical portion of the project wasn’t necessarily easy, working on the 50 m vertical portion required removing the severely deteriorated ladders and platforms and the erection of a scaffolding system to allow access to the pipe. Following the completion of the project, new ladders and platforms made from corrosion resistant materials were installed.
According to Grieci, the vertical section repairs were provisional. The city knew there would be problem areas, but it did not know the extent. This was partially because the ladder and platform system were so deteriorated a proper condition assessment of the vertical structure was next to impossible.
“We anticipated that it would require some repairs, but not that the entire vertical section would need extended work,” Krinas says. “That’s a lesson learned. We had indications from limited inspection that some problem areas needed attention. If we knew about this vertical section needing the extensive repairs, we would have put in scaffolding and completed a full inspection of the vertical before going into the contract.”
A Cooperative Working Group
As the project team from Clearway and Pullman would work through the pipeline, they would thoroughly sandblast the pipe, confirm the pipe wall loss per Stantec’s plans and complete the desired repair. If the wall loss differed a discussion as had among the project team to ensure the proper amount of wrap was applied to maintain the proper structural integrity of the pipeline.
Bauer notes that this approach requires a cooperative working relationship between the city, Stantec and the contracting team. Additionally, it highlights the importance of working with an experienced and qualified contracting team that has previous similar experience.
Krinas adds, “This was a challenging project that — at least internally at the city — is not one anyone had experience undertaking and that posed some challenges.”
“With this product on it, we have a completely wrapped pipe, that is protected from corrosion,” says Grieci. “We are in a good spot.”
Bauer also gives kudos to the city. “The City of Hamilton has taken a proactive approach to understand their infrastructures condition,” he says. “This has allowed them to fiscally plan renewal of their infrastructure in a timely manner, thus avoiding costly unexpected failures for the larger infrastructure.”
Mike Kezdi is managing editor of Trenchless Technology Canada.