Halifax Water employs "transformative" leak reduction

Halifax Water was recently recognized for its efforts in substantially reducing water system leakage by the Blue Economy Initiative, a collaborative program of the Royal Bank of Canada’s Blue Water Project, the Canadian Water Network and the Walter and Duncan Gordon Foundation.

The utility is Canada’s first regulated water, wastewater and stormwater utility serving 350,000 people. Substantial improvement in the water system began following the 1996 amalgamation of the water utilities of Halifax, Dartmouth and Halifax County and construction of a new water treatment plant in Dartmouth in 1999.

“The logical place to build that plant was near the shoreline of Lake Major in Dartmouth, but we quickly found that 35 per cent of the water was not making it to customer taps,” says Carl Yates, general manager of Halifax Water. “Treated water is a valuable commodity and we didn’t want to keep fueling those leaks, so we went in search of best practices to address those problems.”

Yates says that a search for a “transformative” leak reduction methodology led the utility to Europe and the new AWWA/IWA Water Loss Methodology developed by the International Water Association with the participation of the American Water Works Association.

“We jumped in on the ground floor and were the first utility in North America to take advantage of this methodology,” says Yates.

Under the program, the utility analyzed its 55 pressure zones and converted them into 75 district metered areas (DMAs) — sections of the system that could be isolated through topography or system design and monitored using a Supervisory Control and Data Acquisition (SCADA) system. The utility also purchased sophisticated instrumentation and meters to monitor flow and a data historian to store the masses of data gathered.

The best time to check for water loss is between 3 and 4 a.m. when customers aren’t normally using water.

“By isolating the DMAs we were able to determine how much water flowed into each area, and how much metered water our customers were using,” says Yates. “Once we determined which DMAs were showing the most leakage, we let loose the dogs of war, using acoustic leak detectors to listen for leaks in the middle of the night, when there are no planes, trains and automobiles to interfere with acoustic leak signals.”

Digital correlators, which receive noise signals between two points on the water system, were used to pinpoint leaks to within two or three feet. The leaks were then fixed on an accelerated schedule.

“Over 10 years, we were able to reduce our daily water system input from 168 million litres per day to 130 million litres per day, capturing all of the low hanging fruit that would otherwise have been lost to system leakage,” says Yates.

In 2007, the city began to experiment with advanced pressure control, deliberately dropping water pressure inside certain control areas by an average of 20 pounds per square inch below daytime pressures.

“Easily 60 to 70 per cent of watermain breaks occur between midnight and 5 a.m.,” says Yates. “By reducing pressure during that period, we reduced watermain breaks by half without any appreciable difference in service to our customers. The bonus is that background leakage is reduced because of the reduction in pressure.”

Yates says that the utility continues to refine the technique to the point where it has developed an algorithm that will allow two feeds into the same control area to communicate across the SCADA system, balancing flows and pressure for optimum control. This year, that achievement has earned Halifax Water an Excellence in Innovation in Civil Engineering Award from the Canadian Society of Civil Engineering.

Applying these and other methods, the utility has reduced its Level of Leakage as measured by the Infrastructure Leakage Index (ILI) — annual water losses divided by annual unavoidable losses — from 9.0 to a consistent 2.5. At this ILI level it would cost Halifax Water more to further pursue leaks than the cost of the remaining water losses.

“Our guiding principle with leaks is to fix them when they’re small and to fix them fast,” says Yates.

“We also find that the best people to deal with both leak detection and repair and pressure management are in-house staff who are intimate with the system.”