Completing the Woodward Greenhill Feedermain Emergency Repair

The Woodward Greenhill Feedermain (WGFM) is a 2,250-mm C301(E) prestressed concrete cylinder pipe (PCCP). It supplies water from the Woodward Water Treatment Plant on Woodward Avenue to the Greenhill Reservoir. The reservoir is at the base of the Niagara Escarpment on Greenhill Avenue in the City of Hamilton. The feedermain directly feeds water to three pressure zones of the lower city. It is one of two mains supplying water to the escarpment on the south side of the City.

The City of Hamilton has a proactive approach to un-derstanding the condition of their large diameter feedermains. This is done in a variety of ways, including using various inspection and condition assessment tools.

These inspection tools include electromagnetic (EM) and acoustic leak detection methods.
In November 2023, a routine acoustic leak detection of the WGFM using a free-swimming acoustic leak detection tool was completed.

In December 2023, the leak detection vendor submitted a report to the City outlining the inspection findings. These findings identified one acoustic event, characteristic of a large leak, and zero acoustic events characteristic of trapped air pockets.

Based on the results of this investigation and the identified leak, the City conducted an options analysis to evaluate the best option for repairing the pipe. The options analysis considered the following methods for repairing the leak:

• Open cut replacement
• Sliplining
• Carbon fibre reinforced polymer (CFRP)

Due to site constraints and risk considerations, CFRP was selected as the preferred rehabilitation method.

Planning and Approval

There were concerns of a major rupture causing damage to surface infrastructure around the pipe. An emergency repair strategy was implemented to address identified deficiencies in the feedermain. The City prepared a council report requesting completion of the emergency repair under a sole-sourced contract. It also focues on using a trenchless solution to minimise disruption and maintain service reliability.

The report outlined the funds and scope required to make an in-situ repair using CFRP. The scope of work included conducting a detailed inspection to validate the pipe’s condition and refine the design approach.

To support project delivery, the City, Robinson Consultants Inc. (RCI), and Vector Restoration worked together to provide engineering design, material selection, and construction planning.

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