Failure Assessment Model to Prioritize Pipe Replacement in Water Utility Asset Management

Abstract

OF DISSERTATION FAILURE ASSESSMENT MODEL TO PRIORITIZE PIPE REPLACEMENT IN WATER UTILITY ASSET MANAGEMENTThe condition of a water distribution system has strong correlations with community health and economic development. However, studies indicate an urgent need to upgrade the nation's aging and deteriorating distribution systems if they are to continue to provide customers with reliable and safe water supplies.In response, water utilities are using various performance measurement initiatives including pipeline asset management. These require assessment of each pipeline's condition to identify failure-prone pipes and prioritize their renewal. However, the below ground location of the pipes and lack of standard guidelines or tools to assist in assessment make pipeline assessment and renewal decisions difficult.In this research, a pipe failure assessment model was developed and tested to assist water utilities with their pipe renewal decisions. A conceptual model was created from a review of case studies, theories and asset The conceptual model was refined through collaboration of a focus group of water utility professionals. By drawing on the knowledge and experience of these experts, the review process added unique features that facilitate the model's use and responsiveness to the industry's needs. The model was tested using pipe inventory and break history information contributed by Laramie (Wyoming) Water and Colorado Springs Utilities. Although each water supplier differs in population served, operating conditions, pipe inventories, and pipe break histories, both utilities were able to provide their pipe inventory and break history in electronic form which facilitated the model processing.Evaluations from the participating utilities indicated that the pipe failure assessment model would enhance the industry's ability to prioritize pipe renewal decisions and improve their return on investment. Utility personnel indicated that the model's use of routine pipeline operation and maintenance records, combined with its consequence modeling features, addresses both the data limitations and risk avoidance characteristics of the industry in a way that is intuitive and understandable to utility staff. Utility personnel also commented that the model adds knowledge and transparency to the decision process, which is critical in an environment in which decisions will have to withstand scrutiny from various interest groups. Lastly, the investigation illustrates the need for better iv inventory and break data since this data plays such an important role in the industry's buried infrastructure planning programs.

Condition assessment modeling for distribution systems using shared frailty analysis

“…A key component in developing condition assessment models is the availability of a database in which the elements have been collected so that they are amenable to statistical analysis. For this study the authors used such a database provided by Laramie's Utility Division (Laramie Water), which provides Laramie residents with water and sewer services (Rogers, 2006). Laramie is located 45 mi (72.4 km) northwest of the state's capital, Cheyenne, and approximately 130 mi (209.2 km) northwest of Denver, Colo. Laramie has a population of approximately 30,000 people and draws its water from the Laramie River and from well fields that tap into the Casper Aquifer.…”

“…It was assumed that breaks would require pipe excavation and replacement. Pipe leaks normally produce smaller, less easily detected and less disruptive changes in pressure and may go undetected and/or uncorrected (Rogers, 2006). Leaks can frequently be repaired through the use of repair clamps.…”

“…They concluded that these types of models can be useful in short-term planning for water main rehabilitation and renewal. Rogers (2006) developed a pipe failure assessment model in order to assist water utilities with their pipe renewal decisions. He created a conceptual model from a review of case studies, theories, and asset management tools.…”

Risk Assessment for Water Mains Using Fuzzy Approach

“…Al- Barqawi (2006) designed two condition rating models for water mains using artificial neural networks (ANN) and the analytical hierarchy process (AHP). Rogers (2006) developed a model to assess water main failure risk using the Power Law form of a Non-Homogeneous Poisson Process (NHPP) and Multi-Criteria Decision Analysis (MCDA) based on the Weighted Average Method. From the literature review, it is obvious that the works that have addressed the problem of water main failure risk have certain limitations, and therefore a research that addresses the problem with a broad, concrete, and robust approach is still needed.…”

“…Other efforts were too specific to certain network characteristics (such as pipe material, diameter, function, etc…) and thus are not applicable to different water distribution networks. The most relevant and solid research was done by Rogers (2006); however, there are some limitations inherent to his research such as: the model uses the weighted average method which does not address the uncertainty and the model is too sensitive to the weights of the factors. Moreover, Rogers' failure consequence model is not well-established and depends solely on the input of the model user.…”