Risk Assessment of Underwater Glider Turbine Interaction

The presence of offshore wind infrastructure in the Northeast U.S. ocean is rapidly increasing to achieve the national goal of 30 gigawatts power by 2030. With varying foundation configurations and grid layouts, construction of offshore wind farms will impact several state and federal surveys that provide invaluable insight to stock management and the impacts of climate change on marine species, habitats, and ecosystems. In addition to the risk of active and derelict gear entanglement from vessels engaged in bottom trawling or dredging with offshore wind infrastructure, alternative non-extractive survey methods (e.g., autonomous underwater vehicles such as ocean gliders) share the risk of entanglement and interacting with infrastructure highlighting the need for careful operational planning and risk mitigation strategies. Our study aims to assess the risk of interaction between ocean gliders and offshore wind turbines within the Wind Energy Areas (WEAs) OCS-A 0498, OCS-A 0499, and OCS-A 0512 using a decade of historic glider track data in a simulated environment of turbine pylons. We utilized 142 historical glider deployments from 2013 to 2023, incorporating an interaction algorithm that accounts for varying buffer zones (0, 2, 4, 20, and 30 meters) beyond monopile foundations to model potential interaction scenarios. It was found that about 1 interaction per deployment occurred across our 142 deployments where no avoidance routines were used. The analysis revealed that risk varies across different WEAs and buffer zones. Simulated interactions were more frequent in larger buffer zones and WEAs that had an increased number of deployments, with a noticeable difference in interaction rates between turbine structures and substations. Specifically, simulated interactions with turbines at depth were more prevalent than surface and substation interactions. While surface interactions are less common, they may pose greater risks due to environmental conditions near the surface (e.g., waves, winds, currents, storms, etc.). Additionally, the infrequent substation interactions could pose a greater risk to the glider due to its foundation type (i.e., piled jacket) which has more underwater structure to interact with. The study highlights a trend where increased time spent in WEAs translates to higher interaction frequencies and reduced time between interactions. This study highlights the baseline interaction rates and thus importance of enhanced operational strategies, vehicle vulnerability awareness, and real-time monitoring to mitigate interaction risks in areas of active offshore wind development.