Investigations into Gas Pipeline Operational Noise and its Potential to Impact Toothed and Baleen Whales

Abstract

Pipeline operational noise has been largely ignored with respect to its potential significance to marine mammals such as toothed whales (Odontocetes) and baleen whales (Mystecetes). The potential impact of pipeline operational noise on toothed whales and baleen whales was examined using a combination of field measurements, laboratory investigation and pipeline component analysis coupled with available literature on the acoustic sensitivities of toothed and baleen whales. Measurements made over a 25.4 cm (10") outside diameter (O.D.) high pressure gas pipeline suggest that the pipeline was not producing any clearly resolvable noise. Tests on concrete-coated steel plate and pipeline segments with characteristics similar to a proposed gas pipeline indicated that the total acoustic energy, which would enter a surrounding water column, is on the order of 15 decibels (dB) lower than the energy expected in the absence of the coating. Data also suggest that the steel concrete interface can influence the acoustic transmission properties of coated steel pipelines. An upstream compressor is the primary noise-generating source in gas pipelines rather than gas flow generated noise. Important factors are: the whale species involved; compressor type; presence of other pipeline components (e.g., valves, aftercoolers); pipe wall thickness, coating and exposure; water depth, chemistry and substrate. Given the low intensity of gas pipeline noise and the fact that whales typically occupy ranges over many thousands of square kilometres, significant compromise to whale communication or foraging efficiency is unlikely. To some extent, pipelines may reduce the need for vessel traffic for the conveyance of hydrocarbons and as such, significantly compensate for what little noise they do make.