ABSTRACT The Hutton Tension Leg Platform poses several new problems for the design of the foundations. This paper describes the design considerations and the process of design, with emphasis on special aspects prescribed by the Hutton TLP concept. The method of analysis of the template structure is described, and the interactive effects of the template and the connection points for the tension legs and piles are discussed. The special requirements for installing the foundations are also addressed. The TLP concept dictates that the foundation piles are always in tension. This condition introduces factors not normally of concern for piles primarily loaded in compression. The manner in which these factors were assessed and the method of determining the pile safety factors are presented. INTRODUCTION The Hutton Field Development is located in the northern part of the U.K. sector of the North Sea where for the first time a Tension Leg Platform (TLP) will be utilised(l). The TLP is to be positioned over a preinstalled well template and connected by sixteen tension legs, four at each corner, to four separate foundation templates on the seabed 148 metres below the sea surface. (Fig. 1). The TLP is subjected to both horizontal and vertical forces from environmental loading, which cause a steady and oscillatory lateral movement and variation in leg tension. An excess of buoyancy over weight maintains the legs in tension for all weather and loading conditions. The tension legs provide the restoring force to control platform motions. The functions of the foundations are to provide anchorages for the tension legs and to transmit the tension leg loads to the subsoil formation. FOUNDATION DESIGN CONSIDERATIONS Tension Leg Loads The loads in the tension legs which are imparted to the foundations consist principally of four components:-Static tension - the vertical force required to maintain equilibrium with the positive buoyancy of the platform, at lowest astronomical tide (LAT).Variable static tension - the change in static tension caused by variation of the water depth about LAT, due to tide and storm surge.Static offset tension - the increase in static tension caused by platform offset, and thus increased buoyancy, due to the action on the platform of steady current, wind and wave drift forces.Dynamic tension - principally the cyclic variations in tension due to the action of waves passing through the structure, causing changes in platform offset and water depth. These load components are summed in the worst combinations to give the maximum quasi-static loads on a foundation. (Fig. 2). Requirements and Considerations Four major requirements were imposed on the design of each independent foundation:-Provide an anchorage for the four tension legs.Transfer the extreme (lOD-year return storm) loads to the subsoil, even with one tension leg removed.Retain structural and geotechnical integrity for a design life of 20 years.Be capable of being installed with existing marine equipment.