ARCHIVED - Planning the renewal of aging water systems
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February 08, 2008— Ottawa, Ontario
Canadian municipalities face a daunting multibillion-dollar bill to upgrade water treatment, supply and distribution systems across the country. However, new software developed by NRC researchers will make it easier for planners to decide which water pipes are most in need of replacement – so they can get the biggest bang for their buck.
According to a November 2007 report by the Canadian Federation of Municipalities, our municipalities need to spend $31 billion to rehabilitate water and sewage treatment infrastructure that has reached the end of its service life. This estimate includes the cost of upgrading deteriorating water mains and distribution pipes.
|Canadian municipalities face a daunting bill to upgrade deteriorating and broken water pipes.|
"The replacement of aging water pipes is a very expensive problem," agrees Dr. Yehuda Kleiner, who leads the buried utilities research group at the NRC Institute for Research in Construction (NRC-IRC). "I've read estimates that range from $160 billion to $1 trillion over the next 20 years for all of North America."
In the late 1990s, Dr. Kleiner's group began studying historical breakage patterns in water mains to help predict future breaks. "The direct inspection of all water mains in a distribution network is very laborious and expensive," he says. "But the use of statistical methods to identify breakage patterns is an effective and inexpensive alternative."
Based on about six years of research, Dr. Kleiner and his colleague Dr. Balvant Rajani, with help from Dr. Ahmed Abdel Akher and Solomon Tesfamariam developed a software tool called the Distribution Water mAins Renewal Planner (D-WARP) to help municipalities plan and manage the renewal of water mains. D-WARP analyzes patterns of historical breakage rates of water mains, projects future breakage rates, computes life-cycle costs, and generates planning scenarios. It takes into account time-dependent effects such as temperature, soil moisture and rainfall, and "cathodic protection" strategies for controlling corrosion [see sidebar].
Preventing corrosion in water mains
Corrosion is the main mode of failure of iron water mains, which represent up to 70 percent of the water mains in North America. "Fortunately, corrosion is an electrochemical process that you can mitigate to some extent," says Dr. Kleiner.
In a battery, current flows from the anode to the cathode. When corrosion occurs in metallic water mains, the iron surface acts like an anode and is gradually depleted. One way to prevent this is to turn the iron into a cathode – a technique called cathodic protection. "Basically, you put another metal, such as zinc or magnesium, near the water main. The other metal will now act as an anode to the water main, so it will be depleted while the iron is protected," he explains.
"D-WARP is the first and so far the only approach that enables planners to consider dynamic factors such as climate and cathodic protection," says Dr. Kleiner. "D-WARP is also the only approach that allows municipalities to consider cathodic protection strategies in forecasting the life cycle costs of water mains," he adds.
Potential users of D-WARP include municipal engineers, planners and consulting engineers. "It's available on our website for a free one-year download and we would eventually like to license it to a software developer," says Dr. Kleiner. To download a copy of D-WARP, visit: http://irc.nrc-cnrc.gc.ca/ui/software/dwarp/index_e.html.
The NRC researchers are currently developing complementary software tools in order to expand the power of D-WARP and address other water infrastructure renewal needs. "In its current form, D-WARP allows only the analysis of groups of water mains, which is useful for high-level planning," says Dr. Kleiner. "We are now developing strategies for prioritizing individual water mains for renewal, with funding from the American Water Works Association Research Foundation (AwwaRF)."
In a related initiative, his team has developed a prototype "Transmission Water mAins Renewal Planner" (T-WARP) that is designed to prevent water pipe failures by forecasting their deterioration rate. "You can tolerate a certain frequency of failure in small distribution mains," says Dr. Kleiner. "But not in large-diameter water transmission mains, whose failure can have major consequences – including the cost of repairs, water losses, severe traffic disruption and sometimes heavy damage to adjacent buildings and the environment." This project was co-sponsored by AwwaRF and nine water utilities in Canada, the U.S. and Australia.
|Broken water transmission mains can have major consequences, as shown in this 1999 photo of a water main rupture in Gatineau, Quebec. Photo credit: Gatineau Fire Department.|
The researchers are also studying the impact of water pipe deterioration on water quality. In this project, the aim is to develop a computer model called Q-WARP that can identify the likely pipe-related causes of drinking water contamination and prioritize remediation measures. Potential pathways of water contamination may include corrosion of system components, leaching of chemicals, the re-growth of microbes in water pipes, or other routes.
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