Cooperative improvements were sought by three Ithaca, New York, water purveyors to enable regional consolidation of the area water supply. The water purveyors are Cornell University (privately operated), the City of Ithaca, and the SouthernCayuga Lake Inter-municipal Water Supply Commission (SCLIWSC), representing five towns and villages. Each entity seeks to break down administrative barriers to serve an optimum geographic area and preserve its own revenue base. A long-termmaster plan for economical delivery of water throughout the region was developed with the assistance of O'Brien & Gere Engineers. Each system faces different issues related to providing dependable, cost- effective water service. The masterplan assessed whether cooperative efforts between the systems would lead to greater benefits and potentially lower costs. The approach was to first complete a comprehensive water supply evaluation, without regard to service area or municipal boundaries, that focused on how to serve the optimum geographic area. A regional water system master hydraulic model was created, consisting of 5,000 pipe segments and integrating the hydraulic models of each individual water system. This model allowed objective evaluation of a variety of system interconnections, and redistricting options. A series of integrated systemimprovements were identified and assembled into four integrated water supply alternatives. These alternatives were carried forward to evaluate the total economic, operational and reliability issues. The recommended alternative, basedon cost, reliability and energy usage, consisted of taking the City water treatment plant out of service and using the Cornell and SCLIWC plants to serve the City customers. O'Brien & Gere acted as facilitator to the administrative representatives of each of the three purveyors as they reviewed options for financing and administration of the regional improvements. Discussions focused on contracted service arrangements, water authority formation and the complexity of the private/public partnerships. Several models were developed for cost-sharing formulas that achieved maximum benefit to all three purveyors. The cost sharing models resulted in reasonable water costs and savings to the customers in each system. The reference point for cost savings were the costs that would be incurred if each system pursued its individual goals independently. The administrative group is currently evaluating the recommended consolidation, along with the cooperative sharing/cost reductions in services such as maintenance, billing, administration, and in-house engineering support. Contracted service agreements are currently near final stages of negotiation and are expected to be complete by the end of the year 2001. Includes table.