The Regional Municipality of Peel (Peel Region) is the third largest water utility in Canada servicing a population of approximately 1.38 million people in the cities of Mississauga, Brampton and Caledon, Ontario, Canada. The Region’s water system is comprised of 4,500 km of water mains ranging in size from 100 to 2,500 mm. The majority of these water mains are PVC and relatively new, but there is over 510 km of older metallic piping (from 150 to 300 mm) remaining. The majority of issues with leaks and water main failures are found within these older metallic mains.
Peel Region currently uses the State of Good Repair program to plan their water main renewal. Based on industry standard lifecycle assessment, the existing metallic mains have approximately 10 to 15 years of expected service life remaining and the region has been replacing 15 to 20 km of metallic water mains per year over the last five years.
“The current program plan is to replace all remaining metallic water mains within the next 20 years, so identifying and prioritizing replacement of the pipes in the worst condition is very important in order to minimize leakage and pipe bursts during this time frame,” said Nimarta Gill, M.Eng., project manager, State of Good Repair for Region of Peel.
Jay Shah, P.Eng., Echologics’ manager of major projects for Mueller Canada adds, “Savings can be gained by replacing the right pipe at the right time. This ensures that limited capital budgets for pipe replacement are utilized as efficiently as possible.”
The current decision matrix for the selection of water mains to replace is “desktop based,” meaning that decisions are based on subjective components such as performance, age and hydraulic information. Specifically, the Peel Region uses pipe age, a water main break frequency (=>7 breaks/km), hydraulic limitations, pipe criticality and adjacent utility renewals such as sewer and storm in its current desktop approach. However, no actual measure of pipeline condition is taken into consideration, and so the Peel Region began looking for ways to enhance its decision matrix using evidence-based condition assessment. An improved decision matrix can help provide better prioritization and maximize capital spending. Thorough market research led the Peel Region to select acoustic velocity testing for an initial pilot study.
Using Echologics ePulse acoustic velocity (AV) testing, utilities can identify sections of pipeline with reduced structural stiffness and estimate the average remaining structural strength or wall thickness of a pipeline. Non-invasive and non-intrusive, this technology enables rapid inspection of large areas of a water distribution network without removing the pipelines from service, avoiding service interruptions, pipeline dewatering/cleaning, or costly excavations.
The ePulse technology involves inducing acoustic waves inside pipelines by either lightly flowing a hydrant or “tapping” on a pipe appurtenance such as a hydrant or valve. These acoustic waves are measured using sophisticated acoustic sensors connected externally to the pipe appurtenances, then analyzing the acoustic data to determine pipe condition by measuring the velocity of the acoustic wave. The acoustic waves cause the pipe wall to “flex” on a microscopic level, affecting the speed of the wave being detected by the acoustic sensors.
Thicker pipe walls are resistant to this pipe flexing, causing the acoustic wave to travel faster within pipes in good condition. In contrast, slower waves indicate pipe wall degradation and internal/external corrosion. Using the captured data, Echologics field engineers apply advanced algorithms to calculate the average minimum remaining wall thickness of the measured pipe segment without ever entering the pipe itself.
The pilot involved six neighborhoods in Mississauga and Brampton, totaling 16.2 km of water mains. The water mains selected included; pipes that were already earmarked for replacement in 2019, pipes with varying break frequency in the area, as well as pipes with no or little break occurrences, pipes in the size range of 150 to 200 mm and a mixture of cast iron and ductile iron (DI) pipes. The 16 km of testing was segregated into condition ratings for 133 segments of pipe, 125m in average length.
“Because of the nature of the ePulse technology we were able to get this work done in the winter, which is typically a down time for road work, so it’s a good time to allocate resources,” says Gill.
Testing was completed within 3 weeks, averaging 1 km per day of field testing. It only required minimal Peel Region operations staff support to locate and provide access to valves and hydrants. Using ePulse required no excavating and no disruptions to service as it is performed during normal system operating conditions. Testing is all done externally using existing access points (valves and hydrants) so no tools are ever inserted into the pipe or in the water column.
Once analyzed through proprietary algorithms, results are easy to interpret and support proper decision making for prioritizing water main renewal programs. Interestingly, the findings showed there was no correlation between pipe age and pipe condition in the Peel Region pilot area. Some of the pipe sections earmarked for replacement in 2019 were actually in moderate condition and could be deferred, while some of the pipe that had no or very few breaks were actually in poor condition and needed to be replaced before they were scheduled to be replaced. None of the DI pipe was found to be in Good condition.
Pipe replacement in the Peel Region, costs on average $1 million/km. Using the desktop break model to determine pipe replacement is around 80 percent accurate (although they have seen as low as 60 percent), which amounts to a cost error of 20 percent or $200,000 / km for replacing good pipe. This does not include the time and cost it takes to conduct the desktop study itself. With ePulse technology, pipe replacement accuracy can be improved to at least 90 percent, bringing the cost of error down 10 percent or $100,000/km. It cost $20,000/km to conduct the acoustic testing bringing the total pipe replacement cost to $120,000/km saving the municipality $80,000/km.
“With 15 to 20 km of pipe on the annual replacement program, these savings add up real fast,” says Shah.
An additional benefit of acoustic leak detection is the simultaneous detection of existing leaks.
“We found three confirmed leaks, including two full circumferential ring breaks that we did not know about. With this information we were able to send out crews to the exact location for repair, avoiding a costly emergency situation as the leak escalated,” says Gill.
Ultimately the cost of acoustic inspection was less than 1.9 percent of current pipe replacement cost. The Peel Region is now incorporating pipe condition ratings into the Decision Support System (DSS) which is easily done via GIS integration of results. This process can help to ensure that future capital spending is maximized and help to lower the occurrence of water main failures and emergency repairs.