In Situ Geotechnical Early Site Assessment of a Proposed Wave Energy Converter Site in Yakutat, Alaska, Using a Portable Free-Fall Penetrometer

Wave energy converters (WECs) are promising techniques with regard to the production of sustainable energy. However, the geotechnical and sedimentological site assessment, and the resulting foundation or anchoring design, can still represent a major challenge due to the energetic environmental conditions in the targeted areas. Most recently, portable free-fall penetrometers were suggested for the early site assessment of WEC projects as an innovative cost-effective method to investigate the uppermost layers of the seabed with regard to sediment strength and possible sediment transport processes. In this study, early site assessment was conducted at a proposed WEC site near Cannon Beach, Yakutat, Alaska, using the free fall penetrometer BlueDrop. 151 deployments were performed in water depths of 3-40 m during three survey days in May and July, 2014. The results suggested an average quasi-static bearing capacities of 125 ± 18 kPa (normalized for a constant penetration velocity of 2 cm/s) at the uppermost seafloor surface, generally increasing with distance to the shore and water depth. A loose top layer of reworked sediments of up to 4 cm in thickness was detected, indicating moderate sediment remobilization processes. Lower strength and abundance of loose sediment top layers were particularly observed at water depths less than about 15 m.