Environmental and Economic Life-Cycle Assessment of Municipal Water-Storage Options: Infrastructure Refurbishment versus Replacement

Abstract

A large proportion of U.S. civil infrastructure will need to be refurbished or replaced in the coming decades. How to do so while considering various aspects of sustainability is a major challenge for engineers, utilities, and government agencies. Additionally, infrastructure decisions have a long time horizon and, as such, the implications of these decisions need to be considered over the life cycle of each project. This study describes a triple-bottom-line analysis that was performed in cooperation with a water utility in the Northeast to quantify the life-cycle economic, environmental, and social impacts of refurbishing or replacing a large water-storage tank. A hybrid environmental life-cycle assessment (LCA) was conducted and included both on-site use of resources and emissions, as well as those that occur during production and transport of the various materials used in site preparation, construction, and maintenance. The proposed new tank would achieve better water quality and a different overall usable capacity, introducing additional complexity into the comparison. The analysis considered capital and maintenance costs, life-cycle greenhouse gas emissions, water consumption, human health impacts, and ecotoxicity, as well as local societal impacts such as congestion costs, noise, and the effect of aesthetic changes on property values. The results show that refurbishing the existing tank is preferable to new tank construction across all environmental impact categories, both in absolute terms and when normalized by the amount of high-quality water storage provided. Economic and societal cost analyses also preferred tank refurbishment, with significant variations depending on maintenance schedule and assumed tank lifetimes. This analysis provides detailed, quantitative data to support project decision making at the municipal level and demonstrates generally the application of multicriteria sustainability assessment to civil infrastructure planning.