Both the Water Authority and Metropolitan are taking steps to improve supply reliability. In the meantime however, SDG&E has recognized the opportunity to greatly improve the reliability of their water supply. In October 1993, SDG&E selected Boyle Engineering Corporation (Boyle) to provide engineering consulting services to determine the feasibility of desalting ocean water for use at their Encina power plant. Fresh water needs are purchased from the local water district and potable uses include drinking, landscape irrigation, fire protection, and sanitation. Non-potable uses include boiler feed make up, condenser cleaning, pump sealing, boiler cleaning, and other maintenance activities. Potable and non-potable requirements are variable, and can be met with a system that is sized to provide 400 gallons per minute (gpm). To meet SDG&E's system requirements, Boyle needed to determine the technical feasibility and costs associated with an ocean water reverse osmosis (RO) treatment plant to supply the water requirements of the Encina plant. SDG&E divided the project into two phases, a Preliminary Engineering Phase (PEP and a Detailed Engineering Phase (DEP). This paper describes the results of the PEP, and discusses the following issues: water supply requirements such as potable reuse, non-potable use, and future water supply options; hydrogeologic investigation including well design and development, aquifer testing, and water quality; reverse osmosis treatment system; liquid and solid wastes; and project costs.