AWWA DSS60317

This paper describes the results of a recently completed American Water Works Association Research Foundation (AwwaRF) and Kiwa funded project. The objectives of this project were to: identify the criteria for assessing the water quality benefits of flushing operations; develop a methodology (and software) for conducting cost-benefit analysis for a utility's main flushing program; and, evaluate the costs and benefits of flushing. The recommended 6-step approach to quantifying the costs and benefits of flushing consist of: identifing current flushing strategies (e.g. spot flushing, stagnant area flushing, and system-wide flushing) and methods (conventional, unidirectional, continuous blow-off); defining flushing objectives (e.g. enhance chlorine residual); identifing benefits, costs, and associated performance measures (e.g., number of customer complaints reduced per unit cost); organizing the data collection process; implementing changes in the flushing program; and, evaluating alternative flushing practices. A software program was developed to compare flushing programs and assess their costs and benefits. The program was tested at participating water utilities. This paper describes a typical use of the software program based on actual data collected through the surveys and utility case studies.