Geological and geotechnical challenges of the East Coast United States for offshore energy transition

Offshore wind integrated site characterisation work being conducted at US East Coast lease areas relies on experiences gained in the European market although several unique challenges are emerging. Significant layering and spatial variability of soil units, boulders to the north, and calcareous soils to the south, and sediment mobility and scour each present challenges to ground model development. Furthermore, one of the more pressing challenges in the region is glauconite. This iron potassium mica characterises as a sand but transforms into a fine-grained soil upon shearing due to particle crushing. CPTu data show unique signatures of soil behaviour creating significant uncertainty for pile drivability analyses. Even routine soil index and classification testing is problematic. The paper covers the geologic history of the region and presents examples from site investigation work and research that highlight these geotechnical challenges and how they relate to foundation selection and cable routing.