The noise radiated by marine piling for the construction of offshore wind farms

The most commonly used method for the installation of offshore wind turbine foundations in the shallow coastal waters in the UK is pile driving. The construction technique consists of large steel piles being driven up to around 30 m into the seabed using powerful hydraulic hammers, in water depths up to around 25 to 30 m. It is a source of high-amplitude impulsive sound and has the potential for impact on marine life. Methodologies developed for the measurement of underwater sound radiated from marine piling, for the estimation of source level are described in this paper. Data are presented for piles of 5.2 m in diameter driven by hammers with typical strike energies of up to 1350 kJ. Data were recorded as a function of range from the source using vessel-deployed hydrophones, with the data then used to estimate the energy source level. In addition, fixed acoustic buoys were used to record the entire piling sequence, including soft-start period. The dependencies of the radiated noise on the physical parameters of the piling operation are discussed, along with limitations and knowledge gaps.