This paper presents a new technology for pond surfacing based on the use of rubber sheet which will be used in the construction of the world's first seawater pumped-storage power plant. The plant, presently under construction on Okinawa Main Island, is planned and financed by the Ministry of International Trade and Industry (MITI), Japan, with the Electric Power Development Co., Ltd. (EPDC), under a consignment contract with MITI, being in charge of surveys, research, designs and supervision of the construction. In designing this pilot plant, the sheet foundation design, the sheet anchoring method, selection of the sheet material, structural designs, and leakage water detection and dewatering system have been newly developed in consideration of the requirements imposed on a seawater pumped-storage power plant. This paper presents the design concept, construction work and the method and outcome of the quality management.