Acoustic monitoring of pile driving activities at the proposed NaiKun wind farm site.

Abstract

Underwater sound level measurements were obtained during marine pile driving activities at the proposed NaiKun wind farm site in Hecate Strait, British Columbia, Canada. Three hollow steel piles 0.9 m in diameter were driven into the seafloor to secure in place a truss to support a meteorological instrumentation mast. The activities involved both vibro‐hammering and impact hammering. Measurements were collected at 10 m range to fulfill regulatory requirements for real‐time monitoring of the near‐source sound pressure levels and also at a selection of longer ranges to allow a characterization of the propagation conditions of the environment. A bubble curtain was utilized to mitigate the underwater noise generated by impact hammering after trial measurements over a few hammer strikes showed that unmitigated levels exceeded a regulatory threshold. Results from this study were used to derive source level estimates for a subsequent sound propagation modeling study conducted as part of the environmental assessment process. Results from the real‐time monitoring at 10 m from the source (with and without the use of the bubble curtain) and from measurements obtained between 100 m and 3 km range will be presented.