Water Main Life Cycle Analysis Framework for the Economic Evaluation of OM&R (Operation, Maintenance and Renovation) Strategies.

Abstract

Municipal water systems deliver potable water to residents, businesses, and industries. The potable water infrastructure was mostly laid in 1880-1970`s in North America. Being a buried asset i.e. an out of sight network, it did not capture the attention of the public at the time and once inside the ground, was forgotten about. Until recently, the pipes that were installed well over 80-100 years ago have started to leak and break with a frequency that increases with every passing year. Municipalities are facing ever-increasing challenges in maintaining their buried infrastructure due to increasing backlogs (aging infrastructure assets), constantly rising OM&R (Operation, Maintenance, and Renovation) requirements to sustain the assets and maintaining the current levels of services towards the consumers, businesses, and environment. All these problems of water distributions systems can be traced back to a lack of fiscal and technical resources by the municipalities. This thesis identifies the gaps causing uncertainties in the decision-making process and prioritizing the maintenance operations. An OM&R and replacement strategy has been proposed that explains and clearly establishes the variables that need to be defined to come up with a viable asset management plan that can reduce the life cycle costs while still being able to maintain the assets over an extended period of time. The strategy is then further built upon to come up with an extensive framework consisting of a number of modules that cover the existing conventional rehabilitation and maintenance approaches such as fix upon break approach, total replacement, lining approach and/or a combination of them. A proposed strategy module is added to the framework both in its basic as well as an advanced version that comes up with a cost-optimized OM&R and replacement strategy covering a planning horizon of 100 years which is the same as the life cycle of a typical water distribution system. The proposed framework based on a number of input variables generates a cross-comparison of all the conventional approaches as well as the proposed strategy by distributing the pipe network into different age bins, assigning them priority based on age, and analyzing the future OM&R and replacement costs for that very age bin. The age bins are individually analyzed continuously until the whole network is analyzed and a cumulative life cycle cost is generated for all the conventional approach modules as well as the proposed strategy. Based on the analysis, plots are generated which gives a clear cost comparison analysis as well as different cut-offs among the policies at certain points in time which helps in decision making regarding the optimal time to adapt a certain policy. The framework is then validated using the SDLC V-Model (software development life cycle validation and verification model). A software that is designed around the framework presented in this research to make it accessible to the asset managers, contractors as well as other stakeholders so they can have an overview of the estimated cumulative future OM&R costs of the utility concerned. The software is again tested and verified using the SDLC V-Model. A sensitivity analysis is also carried out for the framework using a case study in the designated software. All the concerned variables are tested and their sensitivity is reported in this research. Results indicate that applying the proposed strategy modules of the framework to case studies consistently resulted in considerable cost savings over the life cycle of the network. Results also highlighted that the more historical (analysis ready) information a utility has about its buried infrastructure, the more is the potential of realizing OM&R cost savings over the network`s life cycle.