Analysis of Wastewater and Water System Renewal Decision-Making Tools and Approaches

Abstract

In regards to the development of software for decision support for pipeline renewal, most of the attention to date has been paid to the development of asset management models, which help an owner decide on which portions of a system to prioritize for needed actions. There has not been much work in terms of providing guidance on whether to rehabilitate or replace the pipeline asset and choosing the most appropriate methods for that work. These decisions involve the evaluation of many criteria, which must be considered thoroughly to determine the optimal way of rehabilitating or replacing these systems efficiently and cost effectively. As part of the U.S. EPA Aging Water Infrastructure (AWI) Research Program, one key area of research, conducted in collaboration with wastewater and water utilities, was a study of the current approaches available for making rehabilitation versus replacement decisions. The purpose of this study was to (1) identify the current methodologies and decision support systems (DSS) being used for determining how to rehabilitate or replace underground utilities; (2) identify the critical gaps of these current models through comparison with case history data collected from utilities; and (3) assess the feasibility of substantially improving upon existing approaches. This paper provides a detailed review of DSS and methodologies that have been proposed for use around the world over the past 15 years for renewal decision support and summarizes the findings from visits with eight large utilities in the United States to discuss how each makes their rehabilitation versus replacement decision. Recommendations for the next steps needed to improve upon the existing models to make them more directly useful in terms of decision support are also discussed.