Available at: http://digitalcommons.calpoly.edu/theses/1035
Date of Award
MS in Civil and Environmental Engineering
Civil and Environmental Engineering
The efficient delivery of potable water for a community through its distribution system has historically been the backbone of nearly all metropolitan developments. Much of these systems are comprised of pipe networks made of various materials including concrete, iron, PVC, and even steel. As these communities expand and urbanize, water demand and population density simultaneously increase. This develops higher strains and stresses in the community‟s water distribution network causing pipes to corrode, crack, or rupture prematurely while in service. As a result, the deterioration of water distribution systems in growing cities is increasingly becoming a major concern for our nation. There have been several publications on the subject of evaluating pipe conditions within a water distribution network that use statistical models, estimation, and other mathematical analyses. However, many of these publications are cumbersome and are difficult to understand from a non-engineering perspective. In order to simplify the evaluation process for all varying professions in a city‟s public works division, the primary objective of this study was to develop a user-friendly risk assessment model that was practical, cost effective, and easy to follow. This risk assessment model focuses primarily on the physical condition of pipes in a water distribution system. It assesses the installation year, age, material, and break history of these water mains. It does not consider pipe fittings, pumps, or other network components. A pipe‟s probability of failure is determined from its physical condition. Page v The model then considers various economic degrees of impact that may affect the rehabilitation or replacement of these water mains. These degrees of impact include raw material costs, customer criticality, land use, demand, pipe material, and traffic impact. By focusing on pipes having the highest probability of failure and considering their economic impacts, this model identifies and prioritizes the most vulnerable water mains that require immediate attention. In order to validate this developed risk assessment model, the method was applied to a real water distribution system. Data from the City of Arroyo Grande, California was used in conjunction with WaterCAD and geographic information systems (ArcGIS) software during analysis. Application of the risk assessment model identified six cast iron pipes in Arroyo Grande‟s water distribution system as having a high risk of failure. Of the city‟s 3,057 individual pipe segments, recognizing only five of these pipes as high risk indicated that the assessment model was functional. Developing and testing this risk assessment model with real city data effectively demonstrated its practicality and easy application to a real water distribution system. If utilized, city officials can quickly identify and prioritize pipes needing rehabilitation or replacement by using reliable, up-to-date water distribution data from their city with this risk assessment model. Furthermore, use of this model may also simplify allocation of capital funds for future pipe improvement projects as the city continues its urbanization.