The overall objective of this field experiment is to demonstrate the engineering and economic feasibility of the utilization of moderate temperature geothermal heat, on a pilot scale, in the City of EI Centro for space cooling, space heating and domestic hot water heating. This paper describes the preliminary design for a geothermal hot water/chilled water plant utilizing the Heber geothermal resource for heating and cooling the EI Centro Community Center. This field experiment will be utilized as a test bed for evaluating engineering variables essential to the design of cost effective geothermal hot and chilled water distribution systems.