Hydroacoustic measurements during construction of the first US offshore windfarm—Methodologies to address regulatory requirements

Abstract

The regulations governing underwater noise from offshore wind farm development in the United States have not been as explicit as in other countries. The Block Island Wind Farm represents the first case study. In this context, it is important to disseminate information about the relevant noise sources, address evolving guideline criteria, and develop noise measurement and analysis procedures to address regulatory reporting requirements. Tetra Tech led the hydroacoustic monitoring program which occurred in two distinct stages. The first involved short-term monitoring of the installation of the initial wind turbine generator foundation using both mobile real-time and static monitoring techniques used for daily reporting. Long-term monitoring of the remaining four foundations with static recorders documented the inherent variability in the data set. Received sound levels measured at pre-determined distances were used to assess site-specific propagation characteristics and to verify ranges to the relevant sound exposure thresholds. This involved the evaluation of multiple metrics including the apparent sound source level of pile-driving activities and the confirmation of the Exclusion and Monitoring Zone established to ensure the protection of marine life. All of the monitoring objectives were met, including the field verification of modeling results established during the environmental permitting process.