Faced with the immediate need to expand water treatment capacity during a period of changing drinking water regulations, the City of Phoenix authorized a study of system-wide disinfection practices and surface water treatment processes and procedures. A key element of the Water Quality Master Plan (WQMP) development was an evaluation of the relationship between cost and water quality (defined in terms of disinfection byproducts) for a wide range of treatment options offering incremental improvements in water quality. Alternative treatment strategies were identified for those areas where changes in water quality requirements are anticipated. Bench and pilot-scale process studies were conducted to identify the improvements in surface water quality which could be achieved by each alternative strategy. Conceptual design parameters were established to permit the development of realistic budgetary cost estimates for implementing the strategies at each water treatment plant. Utilizing the anticipated water quality results, costs estimates and the analysis of non-financial factors, each of the alternative strategies was critically evaluated. Based on these evaluations and project workshop discussions, a plan of water quality improvements was established for the surface water treatment plants. This paper presents a summary of the development of the plan. A detailed presentation of the treatability testing results and costs estimates can be found in the WQMP.