Measurement of the underwater noise levels generated from marine piling associated with the installation of offshore wind turbines.

Abstract

Marine piling is the most commonly used method for the installation of offshore wind turbines in the shallow coastal waters in the UK and consists of steel mono-piles being driven into the seabed using powerful hydraulic hammers. This is a source of impulsive sound, of potentially high level, that can travel a considerable distance in the water column and has the potential for impact on marine life. This presentation describes methodologies developed for measurement of marine piling and for the estimation of the energy source level. Measurements are presented for piles of typically 5 m in diameter driven by hammers with typical strike energies of 1000 kJ. Data were recorded as a function of range from the source using vessel-deployed hydrophones, and using fixed acoustic buoys that recorded the entire piling sequence, including soft start. The methodology of measurement is described along with the method of estimation of the energy source level. Limitations and knowledge gaps are discussed.