IMPORTANCE OF REGIONAL GEOPHYSICAL AND GEOLOGICAL STUDIES OF OFFSHORE WIND ENERGY AREAS

The eastern continental shelf of the United States (US) is the location of several proposed offshore wind projects. The Mid-Atlantic Bight portion of the shelf, extending from off eastern Long Island to North Carolina, currently has four Bureau of Ocean Energy Management designated Wind Energy Areas (WEAs) for potential development. Given the primary focus on wind resources, water depths, proximity to onshore grid infrastructure, and ecological and human impacts, an underutilized dataset in planning for offshore wind projects are a site’s geological and geotechnical parameters. The complex evolution of the eastern US continental shelf has created a highly variable distribution of surficial and sub-surface sediments. This variability has significant implications for the type selection, design, location, installation, and subsequent scouring in the vicinity of offshore wind turbine foundations. Turbine foundations are a significant financial component of offshore wind projects, accounting for up to 25% of total costs. If project siting including turbine foundation placement can take advantage of preferred geotechnical sediment properties, more economical foundation solutions can be designed, and overall project costs can be reduced.

This case-study utilizes chirp sub-bottom and multi-beam bathymetry data from the Maryland WEA acquired from the High-Resolution Geophysical Survey conducted by Coastal Planning & Engineering Inc. for the State of Maryland Energy Administration to illustrate how geophysical data can be used to constrain optimal location(s) and type selection for offshore wind turbine foundations. Integration of this data with previously conducted geologic investigations enables the mapping of features of interest such as surficial sand ridges, boundaries between sediment types, stratigraphic features (e.g., ravinement surfaces, unconformities), and paleochannel systems. Paleochannels consist of heterogeneous infill; creating undesirable conditions for foundation placement. The results of this study illustrate the importance of initial, regional seafloor mapping and geophysical analyses to reduce uncertainties associated with offshore wind project site selection including foundation design and location.