Underwater noise and seabed vibrations from vibratory pile driving: findings from an experimental campaign

The global shift from fossil fuels to renewable energy sources is accelerating, with offshore wind energy playing a crucial role in this transition. Impact pile driving, the predominant method for monopile installation, is encountering substantial difficulties in complying with environmental noise regulations, thus hindering progress toward achieving energy transition goals. Impact pile driving generates high levels of underwater noise and seabed vibrations, which can negatively impact marine life. Various mitigation techniques are currently in use, such as deploying air-bubble curtains at a distance around the pile. However, the most effective solution would be to address the noise issue directly at its source. To this end, alternative techniques for monopile installation are being explored. Vibratory driving has emerged as a promising environmentally friendly alternative. Its currently limited application offshore stems from a lack of comprehensive field data and limited experience with offshore drivability, lateral load response, and noise emissions. This study presents experimental measurements and interpretation regarding environmental noise and vibration produced by vibratory pile driving from a full-scale offshore experimental campaign. More specifically, far-field (i.e., 750 m and 5 km away) underwater noise is presented as well as near-field sea-bed vibration. The noise-and-vibration measurements are correlated to the pile vibrations which were also monitored. These field observations can contribute toward more environmentally sustainable offshore monopile installation, showcasing the potential of vibratory techniques for offshore applications.