Life-cycle Costs and Corrosion
The flaws in municipal asset management outlined by Professor Mirza underscore the need to consider the life-cycle cost of underground infrastructure, since it is essential to assessing the performance of different pipe materials. A two-year study conducted in the 1990s by the National Research Council of Canada showed that various pipe materials had very different break rates. Unfortunately, little information exists in this regard, and it is essential that more be gathered to help water utilities increase their efficiency.
Among the various factors affecting pipe performance - age, material type (cast iron, ductile iron, concrete, PVC, etc.), soil conditions, topography, cold weather, etc. - corrosion is the most significant since it undermines the durability of our water systems.
According to the study, corrosion, not age, is to blame for most water main breaks. In fact, corrosion is the main contributor to the more than 700 water main breaks that occur every day in North America. Further, a two-year congressional study released in 2000 found that corrosion costs US water utilities $36 billion annually. In Canada, the yearly figure would be $4 to $5 billion.
The reason corrosion is so pervasive in North American water networks lies with the pipe materials used predominantly over the last two centuries. At first, these consisted of cast iron, and then ductile iron became the leading pipe material in the 1950s - both are now deteriorating. Moreover, ductile iron's use is problematic since it is thinner and has a shorter lifespan.
According to former Gloucester, Massachusetts Mayor Bruce Tobey, the leading cause of water main breaks is the "simultaneous expiration of the useful life of water infrastructure installed at different times ... the newer the infrastructure the more likely it is to be deteriorating." He said this before a US Senate Subcommittee during his March 2001 testimony on behalf of the National League of Cities. And given the history of water main installation in Canada, the same argument applies here.