Centre Alliance Senator Rex Patrick has criticised the validity of the National Offshore Petroleum Safety and Environmental Management Authority's (NOPSEMA) recent decision to allow oil and gas exploration services company PGS to conduct seismic surveys in the Great Australian Bight.
Senator Patrick, a former submariner and trainer in acoustic theory, questioned NOPSEMA’s environmental director on its decision making process at Estimates last week.
"I think the decision is unsound," said Rex. "Marine life will be put at risk because, on the face of it, the surveyor has not used worst case oceanography to calculate the distance at which the sound from the seismic noise source will disturb or damage the hearing of marine life.
"Imagine walking slowly towards a jet engine, there will be some distance when the engine sound will disturb you and, at an even closer distance, when it will damage your ears.
"The same is true for marine life, except the distance at which the disturbance or the damage occurs varies dramatically depending on something referred to as the sound velocity profile."
Senator Patrick said the noise level of the seismic source to be used in the testing is a "very high" 256 decibels, compared to the loudest utilised navy sonar, at around 235 decibels.
He also argued that NOPSEMA had not properly considered worst case sound propagation in its decision and that in cases when "the sound velocity profile results in a strong surface duct" (which traps sound) dolphins would need to be well beyond 100km from the survey vessel, before they were safe from hearing damage.
During Estimates, Senator Patrick discussed PGS' submission to NOPSEMA which he said used four mean sound velocity profiles for the months of May, September, October and November.
Surveying will take place from September to November this year, with the May sound velocity profile included because it was the worst case mean.
"They only got it half right in picking the worse case mean," said Rex, "but this could prove fatal to sea life. Whales are known to become disoriented and beach themselves when subjected to high sound levels.
"What NOPSEMA should have done is looked at worst case on a day to day basis for the period over the proposed survey schedule. When acoustic conditions are worse than the mean (which will happen for about half of the month) sea life could be in danger."
Senator Patrick said he has requested an urgent meeting with acoustics engineers at NOPSEMA to discuss the issue further.
"I want to discuss my concerns with them and let them convince me I’m wrong. If they can’t, I’ll be formally asking them to set aside the decision they have made until such time as safety of marine life can be guaranteed."
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