Impact Assessment of Offshore Pile Driving Noise on Red Sea Marine Mammals

Abstract

Abstract-Red Sea is one of the most important repositories of the marine biodiversity in the world. Red Sea oil and gas reserves are estimated to be around 100 billion barrel of oil equivalent necistate the use of offshore structure to extract it. Most of offshore drilling rigs and production platforms are found on group of large diameter piles which are driving into sea bed producing high amount of underwater noise. Underwater noise emitted during pile construction can mask biologically relevant signals for marine mammals. This noise might lead to behavioral reactions, harassment, and at very high levels can injure or even kill the mammal. Range-dependent Acoustic Model, Rogers Model, was used to assess underwater noise propagation of offshore pile driving taking into account seabed bathymetry, temperature, and salinity. It was found that an offshore pile driven with 235 kJ rated energy diesel hammer can cause behavioral disturbance to the marine mammal within a distance of 1000 m from the pile location; temporary threshold shift within a distance of 30 m; permanent threshold shift within a distance of 50 m; and injury, or even death, within a distance of 20 m. I. INTRODUCTIONRed Sea is one of the most important repositories of the marine biodiversity in the world, it support populations for many species of marine mammals (about 15 species of dolphins and whales, and one dugong species). Red Sea Governorate tourism industry, which depends mainly on marinewildlife and recreation tourism, contributed significantly to the Egyptian economy in 2003 to reach about 10% of GDP and 4% of total employment [1]. At the same time, Red Sea oil and gas reserves are estimated to be around 100 billion barrel of oil equivalent. Kingdom of Saudi Arabia is planning to employ 200 drilling rigs in 2014 most of it will be in the Red Sea [2] which, in the absence of proper environmental studies, will affect significantly the Red-Sea eco-system. Most of offshore drilling rigs and production platforms are found on group of large diameter piles which are driving into sea bed. During pile driving; extremely high sound levels are produced in both the surrounding air and underwater environment. In terms of the underwater environment, field observations show peak acoustic pressures of 1.0 kPa measured at a range of 3000 m [3], around 10 kPa measured at a range of 60 m [4], and around 100 kPa measured at a range of 10 m [5] from the pile driving operation. Such pressures are known to produce deleterious effects on both fish and marine mammals [6].Underwater noise effects on marine mammals are of particular interest because marine mammals has a wide distribution area in the coastal waters of the Red Sea, acute hearing, and functional hearing over a very wide frequency range [7]-[10]. Marine mammals are relatively easily deterred by anthropogenic underwater noises [11]. Avoidance threshold levels of harbor porpoises have been determined for noise bands and tonal signals around 12 kHz, a continuous 50 kHz tone, and continuous and pulsed 70 and 1...

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