City Of Montreal Sahara® leak detection program reduces loss of non-revenue water
The City of Montreal believes that the best medicine is preventative medicine, especially as it applies to its water network.
Montreal has an impressive water system that supplies drinking water to a population of nearly 1.9 million people. Since 2002, the historic city, the second largest metropolis in Canada, began a long-term major rehabilitation of its extensive network of water main (770 kilometers) and distribution pipes (4,600 kilometers).
In 2015, as part of a pre-emptive program to reduce loss of non-revenue water, the City partnered with Pure Technologies (Pure) to conduct an ongoing, three-year leak detection survey on a series of critical pipes within its network, several of which are located in the downtown core.
Stopping small leaks from developing into major breaks
The City recognized the value of detecting leaks, however small, to prevent these from developing into greater problems. Compared to a major pipe rupture, which can cause catastrophic damage and incur immediate excavation and costly repairs, small leaks are less obvious at first, and can seep underground for some time without obvious detection.
In addition to physical losses of water caused by a series of small leaks, the escaping non-revenue water can eventually erode the surrounding soil making the area more prone to washouts or sinkholes, a major headache especially in densely populated areas. Unplanned excavations to repair unforeseen leaks can also erode consumer confidence in a public utility.
Leak detection strategy includes Sahara acoustic video inspection
For its multi-year leak detection program, the City requested Pure to deploy its highly reliable and precise Sahara® acoustic video inspection on 46 kilometers of pipelines chiefly in the downtown core. The pipeline sections consist of bar wrapped, steel and cast iron pipe.
The Sahara platform is modular, and can be configured with a variety of sensor tools to perform the condition assessment. This includes an acoustic sensor to perform leak and gas pocket detection, a high-resolution video camera to assess internal pipe conditions, and an electromagnetic sensor to identify stress in the pipe wall.
Because the Sahara tool is drawn by product flow via a small drag chute, and is tethered to a data acquisition unit on the surface, it gives the operator close control to confirm suspected leaks, gas pockets and other pipeline anomalies. The tool can visually confirm pipe irregularities, continuously recording, allowing for both real-time and post-processing analysis.
Data used to shape urgency and timing of rehabilitation efforts
For the Montreal project, the purpose of the Sahara inspection was to assess the condition of the pipeline by identifying and locating leaks, pockets of trapped gas and to identify larger visual anomalies utilizing Closed Circuit Television (CCTV) footage collected during the inspection. The data would help shape the rehabilitation urgency and timing.
The leak detection program has not been without challenges. Valve operations were needed to achieve required pressure flows, and mobilization had to be based on hours of demand, and inspections conducted during those hours. A number of tight chamber clearances meant the creation of new insertions taps, and because of the urban environment, markings had to be precise, and crews had to deal with traffic issues.
Despite challenges, the assessment is proving its worth from a verification viewpoint, and the leaks have been either repaired or addressed for prioritization. The current program is scheduled for completion by 2017.
With its pre-emptive leak detection program, the City is Montreal is a great example of a smart water manager taking proactive efforts at keeping its network in healthy shape.