Efficient Design and Execution of Site Investigations for Offshore Wind Farms: Learning from Experience

Abstract

This paper demonstrates how a phased site investigation approach complements the design process for offshore wind farms. Examples are given showing how three-dimensional (3D) engineering ground models and real-time data analysis have been utilized by integrated project teams to maximize efficiencies, achieve cost and program savings, and reduce risk. In general, the aim of a site investigation should be to ensure that: Sufficient ground data is obtained for design, certification, and construction;Data collected is fit for purpose and fully integrated; andA comprehensive interpretation can be carried out with consideration of engineering design and construction requirements. In the authors’ experience, offshore site investigations are most effective when a ‘geoteam’ (an integrated team of ground specialists including geologists, geotechnical engineers, geophysicists, and others) is assembled at an early stage in the project and carries out early optioneering studies followed by scoping, supervision, and interpretation of a phased site investigation program. Crucially, the geoteam must be able to read and communicate the ground from a designer's perspective and appreciate the Client's constraints and requirements. If they do this effectively, the geoteam will be able to scope a more efficient, targeted site investigation, and provide almost live updates to the engineering ground model. The model can in turn be used to inform real-time decisions being made by the developer, their offshore site investigation representative (Client Representative), and the wind farm's designer. Consideration of the 3D ground conditions is paramount and should always be combined with an appreciation of the site's geological history and earth surface processes to assess how geological variability and ground hazards may affect design. This will provide strong justification for the scope of site investigation works. While the UK and European wind farm market is maturing, with the first offshore wind farm in the UK constructed in the year 2000, the US market is currently in a period of rapid early development. Drawing on considerable experience gained from work in the UK and Europe, the authors present a designer's perspective of site investigation, describing lessons learnt from the scoping, execution, and interpretation of numerous site investigations for offshore wind farms.