The purpose of the AwwaRF UV Disinfection for Large Water Treatment Plants project is to provide utilities with design and cost guidelines for implementing ultraviolet (UV) disinfection at their treatment plant through a web-based program. In order to develop this program known as the decision tree, information was gathered on the issues surrounding UV disinfection and implementation. These issues were further explored through UV conceptual designs, which were conducted for five utilities. These conceptual designs served as a framework for the development of a decision tree program that can be used by large utilities to evaluate how UV disinfection would fit into their treatment scheme. Includes 5 references, tables.