Halifax engineers share tips on controlling water leaks with Shanghai delegation

Six Chinese officials representing the massive state-owned Qingcaosha Raw Water Project in Shanghai met with senior managers at the consulting engineering firm CBCL Limited in Halifax on August 14.

Sponsored by the World Bank, the Chinese officials’ North American study tour focused on energy efficiency in raw water production and operations. Lu Xiaoru, president of Shanghai Qingcaosha Investment Construction and Development Company led the delegation.

The $2.67 billion Qingcaosha reservoir project, which provides water from the Yangtze River to Shanghai, includes nine water treatment plants downtown and six in the city’s suburban areas. The designed water supply capacity of 7.19 million cubic metres per day is serving 11 million people — 66 per cent of the population of the tenth largest city in the world. The system became operational in June 2011.

Discussions during the two-hour meeting at CBCL focused on areas such as the proper sizing and cleaning of intake structures between the reservoir and pumping stations, the relining of existing water lines, leak detection, and monitoring water usage via metering.

Regarding intake structures, “if you don’t size them properly,” explains David Lea, senior project manager at CBCL, “if the velocities are too high, marine life is not able to escape getting caught up in the stream and it gets trapped on the intake screens. They then clog more frequently and become a maintenance problem.”

Also of interest to the Chinese delegation was the relining of existing water pipes. During the maintenance cycle, relining can introduce significant efficiencies, explains Lea. As an example, CBCL is completing a project in which a 42″ diameter steel liner was inserted in a 3-km long section of 48″ concrete pressure pipe for Halifax Water. The new liner, he says, provides a smooth surface with much lower frictional resistance. “There’s a lot less leakage,” Lea says, “and the overall carrying capacity is as great as, or greater than, the old line.”

Regarding preventing wastage, Lea and Dave Jessop, senior director at CBCL, discussed Halifax Water’s leak detection program for older distribution piping. Over the past 10 years, the leak detection and repair program has gradually reduced system leaks to an average of 38,000 cubic metres per day — 27 per cent of the current average daily consumption. A rigorous system has been set up to check the piping based on age, explains Lea, and ultrasonic detection equipment assists in identifying the extent of the leak.

He adds that when water leaks into an underground stream (as opposed to rising to the surface), the wastage can go undetected for years. “In Shanghai’s old city, there’s a large amount of small-diameter distribution piping and they don’t have a well integrated system for leak detection,” he reports.

They also discussed using metering technology to monitor water usage; individual residences in Shanghai are not equipped with meters.

Regarding next steps, Lea said, “We will maintain correspondence with the corporation. They expressed an interest in receiving correspondence from Canadian firms who may have expertise, processes, or knowledge of systems that can complement their own with regard to energy efficiencies.” He added that the Chinese are interested in learning about treatment technologies to reduce excess levels of contamination in the raw water.