ENVIRONMENTAL STATEMENT BARDOLINO DEVELOPMENT

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Bardolino Development Environmental Statement the site would be 187 dB re 1µPa dB @ 1 m. The estimated total noise during the pipeline installation operations, including the potential noise from the trenching operations, would be 189 re 1µPa dB @ 1 m, which is lower than the estimated noise levels during the piling operations (194 dB) which have been modeled. Applying the equation provided by Richardson et al. (1995): [Lr = Ls – 15.log(range km) - 5.log(depth m) - 60 (dB re 1mPa)] the predicted source noise levels for the pipeline installation and vessel activities gives estimates of the received noise levels with increasing distance from source (Table 6.7), and the estimated distance to a received level of 120 dB is 0.9 km. For many marine mammals, disturbance occurs at broadband received noise levels of about 120 dB re 1µPa for continuous noise (Erbe and Farmer, 2000). Table 6.7: The predicted received noise level at distance from the source noise level during pipeline installation operations at the Bardolino location Range (km) 1 2 5 10 20 50 100 Received Level (dB) 119.6 115.0 109.1 104.6 100.0 94.1 89.6 Note: Water depth is 85 m Source level of 189 dB without absorption Noise produced during drilling operations The Bardolino development well would be drilled from a semi-submersible drilling rig. The drilling rig would be towed to the Bardolino location by three AHTVs, with a stand-by and a guard vessel in attendance. Drilling operations are scheduled to last for 3 months (Section 3.3.2). The estimated underwater noise level during drilling operations would be 184 dB re 1µPa dB @ 1 m, based on the presence and operation of a semi-submersible drilling rig (127 dB), standby vessel (180 dB), three AHTVs (3 x 170 dB) and guard vessel (180 dB) (Table 6.6). The estimated noise levels during the drilling operations are lower than the estimated noise levels during the piling operations which have been modeled. Applying the equation provided by Richardson et al. (1995): [Lr = Ls – 15.log(range km) - 5.log(depth m) - 60 (dB re 1mPa)] the predicted source noise levels for the drilling and vessel activities gives estimates of the received noise levels with increasing distance from source (Table 6.8), and the estimated distance to a received level of 120 dB is 0.4 km. Table 6.8: The predicted received noise level at distance from the source noise level during drilling operations at the Bardolino location Range (km) 1 2 5 10 20 50 100 Received Level (dB) 114.0 109.4 103.5 99.0 94.4 88.5 84.0 Note: Water depth is 85 m Source level of 184 dB without absorption 6.7.3 Impact on sensitive receptors or designated sites Sound is important for marine mammals and serves three main functions: (i) it provides information about their environment; (ii) it is used for communication; and Page 6-22 April 2008
Bardolino Development Environmental Statement (iii) it enables the remote detection of prey. Therefore excessive underwater noise has the potential to cause disturbance through interference with communication, navigation and foraging. The effects of underwater noise on marine mammals may vary depending on the received noise level, and there are several different levels of response quoted in the literature (e.g. David, 2006; Masden et al., 2006; Richardson et al., 1995): • Detection level (zone of audibility) – the noise level that the species would normally be able to detect in a quiet sea state. The zone of audibility is defined as ‘the range at which an animal can barely detect the sound source’ (Masden et al., 2006). • Avoidance level (zone of responsiveness) – the noise level at which the species would start to exhibit active avoidance behaviour, such as moving away. The zone of responsiveness is defined as ‘the zone in which the animal responds to the sound exposure either behaviourally or physiologically’ (Masden et al., 2006). It is proposed that levels of 90 dBht(species) and above would cause significant avoidance reaction, with strong avoidance by most individuals at 100 dB ht(species). Mild avoidance reaction occurs in a minority of individuals at levels above about 75 dBht(species) (dBht is a measure of the level of sound above the animals hearing threshold, or its “perception level”) (Nedwell et al., 2004). • Masking level (zone of masking) – the noise level that could mask the species vocalisation (communication and echolocation signals). The zone of masking is defined as ‘the range at which the anthropogenic noise adds significant energy to the ambient noise in frequency bands that overlap with the signals of interest’ (Masden et al., 2006). Masking is predicted when noise levels are above the received vocalisation level and hearing threshold. • Temporary threshold shift (TTS) threshold – the noise level that would cause a temporary but reversible shift (change in hearing ability) in the individual’s hearing sensitivity. When an animal is exposed to a loud noise for a period of time, the acuteness of its hearing may be temporarily diminished, i.e. it may be unable to detect noise levels that it would normally be expected to hear. This phenomenon is reversible (or disappears) some time after the animal is removed from the loud noise source. In a review of threshold levels, Ketten (1998) concluded that a noise level of 140 dB, that is also 80 – 90 dB above the species hearing threshold at each frequency, is necessary to produce a significant temporary change in hearing ability. • Permanent threshold shift (PTS) – the noise level that would cause a permanent shift in the individual’s hearing sensitivity. • Physical damage level – the noise level or pressure level that would result in gross physical damage to the organism’s auditory system, other organs or tissues. The threshold peak impulse sound pressure for direct physical trauma in marine mammals is generally considered to be >200 dB (McCauley, 1994; Richardson et al., 1995; Gordon et al., 2004). Underwater noise may result in the exclusion of cetaceans from important habitats or impede reproductive and feeding patterns (Richardson et al., 1995). In addition, underwater noise also has the potential to disturb prey species. The potential effects of changes in prey availability or access to foraging areas on marine mammals is largely unknown. Most marine mammal species may be able to change their diet and feeding areas in response to shortterm changes in prey availability. However, long-term changes have the potential to affect their distribution, body condition, susceptibility to disease, exposure to contaminants, reproductive success, and survival. April 2008 Page 6-23
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Page 181 and 182: 13 th March 2008 Dear Sir or Madam,
Page 183 and 184: To: Paul Wood Shell U.K Limited, Se
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What risks to marine mammals do pil
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Noise propagation modelling. Noise
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If, for any reason, piling operatio
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APPPENDIX 1 MARINE MAMMAL RECORDING
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ENVIRONMENTAL STATEMENT BARDOLINO DEVELOPMENT

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