10.6.1.4 Impact 4 Underwater noise and vibration 212. The installation of monopile foundations or pin piles for jackets would require them to be driven into the sea bed (as described in Chapter 5 Description of the Development). If piled foundations are installed, this could potentially have an adverse impact on the benthos in the immediate vicinity of each wind turbine, collector or convertor station.
213. Chapter 9 Underwater Noise and Vibration contains further details of noise that would be created by the construction activities. The worst case as outlined in this chapter would be the use of a 3,500KJ energy hammer with up to two piles being driven at the same time.
214. The effects of noise on benthic species are poorly understood. A number of studies have shown that some species are able to detect sound. Horridge (1966) found the hair-fan organ of the common lobster Homarus vulgaris to act as an underwater vibration receptor. Lovell et al. (2005) showed that the common prawn Palaemon serratus is capable of hearing sounds within a range of 100 to 3,000Hz, and the brown shrimp, which was identified as present within the East Anglia site and offshore cable corridor, has shown behavioural changes at frequencies around 170Hz (Heinisch and Weise 1987).
215. It is therefore clear that the noise created by certain construction activities would be audible to certain benthic species. Although the benthos is likely to be habituated to ambient noise such as that created by shipping or wave action, the sporadic noise created by piling may cause alarm and fear mechanisms. This has been found to be the case during seismic explorations involving noise up to 250dB at 10 to 120Hz (Richardson et al. 1995) whereby polychaetes tended to retreat into the bottom of their burrows or retracted their palps, and bivalve species withdrew their siphons. Furthermore, the air-filled cavities within certain invertebrate species may alter the transmission of sound waves through their bodies, which could potentially cause physiological damage. Therefore, taking a conservative approach the sensitivity of benthic species is considered medium.
216. The extent of any risk of physiological damage or mortality would be localised around foundations where noise generation would be at the highest magnitude. Therefore, the magnitude of the impact of noise and vibration on benthic species is considered to be low. A medium sensitivity and low magnitude equates to an impact ofminor adverse significance.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 1 Introduction Page 70
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