Expert feedback sought to improve prediction of corrosion in water mains

April 26, 2004 -- Researchers in IRC's Urban Infrastructure Rehabilitation (UIR) program have developed a model to predict the deterioration of ductile and cast-iron water mains.

They are now seeking support from the water industry to validate and improve the model. This support can come in two ways: feedback from experts in the water industry and/or field data from practitioners and pipe owners. The model will serve as a tool that can help lower maintenance and repair costs for municipalities and ensure a sustainable water transmission and distribution system.

Several factors contribute to the structural failure of ductile and cast-iron water mains, the most important of which is corrosion. If municipalities were able to identify environments in which corrosion was most likely to occur, they could work proactively to prevent failures by installing externally coated pipes or providing cathodic protection for them.

Furthermore, they could prioritize pipes for condition assessment programs, thus avoiding the cost of inspecting pipes that are at a lower risk of deterioration.

The current method of predicting corrosion

The most common method for predicting corrosion is based on soil properties. Using "The 10-point scoring method," published by the American Water Works Association, soil properties (such as resistivity and pH) are evaluated for their contribution toward corrosivity. If the total score is more than 10, the soil is considered corrosive to ductile and cast-iron water mains, and those water mains are flagged for protection.

This method, however, cannot quantify the intensity of soil corrosivity nor can it deal with uncertainties associated with imprecise and incomplete information on the soil properties.

IRC's corrosion model

IRC's corrosion model is designed to identify problem areas with greater ease and accuracy. The model is based on a fuzzy logic expert system, which evolves over time by incorporating expert opinion and field data.

Currently, the knowledge base contains information gleaned from research literature on the corrosion of ductile and cast-iron water mains. The next step is to augment the information in the knowledge base by adding experience and field data from corrosion experts, water utility managers, municipal engineers and others with pertinent information. The addition of this information will enhance the performance of the expert system and help municipalities make better-informed decisions about the protection and renewal of their metallic water mains.

Online survey available

IRC researchers have posted an online survey at ftp://contact.irc.nrc.ca/pub/corrosivity/survey.pdf to help gather the required information in a convenient way. Field data (such as corrosion measurements from exhumed pipes, soil properties and GIS data) that experts are willing to share can be submitted at the end of the survey.

For more information on this project, or to explore possibilities for collaboration, contact Dr. Homayoun Najjaran at (613) 993-3806, fax (613) 952-8102, or e-mail [email protected].