The ‘Thin-walled Cast Iron Watermain Rehabilitation Project’ began as a pilot program on 11 October tackling Guelph Avenue which is expected to be completed in early December. The practice of using thin-walled cast iron for pipes was introduced some five decades ago and thought to be more durable and corrosion resistant than the traditional cast-iron watermains. However, through intensive inspections and historical data, staff determined that these pipes needed attention.

Commissioner of Transportation and Public Works George Elliott said, “We are implementing pilot projects while we develop the longer-term strategy to address the infrastructure needs of the water distribution system. We are focusing on rehabilitation through trenchless methods, replacement where necessary, and overall corrosion protection of our watermains,”

Mr Elliott said that the development of the strategic plan is expected to be completed in summer 2012.

Through the award-winning asset management system, the city identified a backlog of approximately $CDN54 million worth of watermain repairs needed throughout Cambridge. This knowledge-based system allowed staff greater abilities to set priorities and address them in the most cost effective manner.

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The Thin-walled Cast Iron Watermain Rehabilitation Project is another area for the city to step outside the box and introduce new innovation. For example, the rehabilitation of the 12 inch watermain on Guelph Avenue includes lining the watermain using a cured-in-place-pipe (CIPP) liner as well as installing new hydrants and valves.

As Guelph Avenue recently underwent an asphalt replacement program, the process also uses Trenchless Technology which means that crews don’t have to rip up the road to access and repair underground infrastructure.

Director of Engineering Kealy Dedman said, “The CIPP liner is essentially a double fire hose that is infused with a binder resin that is pulled through the watermain, inflated and cured into place using hot water.”

Ms Deadman notes the city has undertaken this method on smaller, 6 inch pipes before, however this is a first for the larger-diameter watermains.

“There is a significant advantage to this method of watermain rehabilitation as we are essentially getting a new pipe formed inside the existing one, preventing water leakage and saving money. Conservation is an important part of the mix and we are working proactively to address this kind of potential leakage,” Ms Deadman said.

The project for the City of Cambridge will be undertaken over the next three years at a cost of approximately $CDN7 million. The inspection program results have accelerated the need for renewal and funding was secured through borrowing or what’s known as debenturing.

“This is a critical piece of infrastructure for the city and our approach can add nearly a half a century to the life of the watermains,” Mr Elliott said.

Exploring the frontiers of the ‘return to service’ subject in turning around rehabilitation projects during replacement or repairs is of vital interest to the city and municipalities across the world. It’s a new territory in the North American market and one that the city is actively pursuing.