A Newcastle University professor has questioned Centennial Coal's claim that its seismic testing in Lake Macquarie will not harm marine animals.
The coal company agreed on Friday to delay by one week the start of a planned seismic survey and drilling program between Swansea and Murrays Beach this week after an outcry from local environmentalists, fishermen and politicians.
Lake Macquarie MP Greg Piper wrote to Environment Minister Matt Kean and Planning Minister Rob Stokes asking them to intervene to give the community time to find out more about the survey, which came to light only four days before it was due to start.
Centennial said on Friday that the work would have "no environmental impacts below the surface to marine life", despite a consultant's report it commissioned last year suggesting otherwise.
The company said that report "unfortunately contains several inaccuracies".
Newcastle University's Dr Vincent Raoult, who is conducting post-doctoral research on how noise affects fish and whales in Australia, said the "sparker" technology Centennial planned to use was less harmful than seismic air guns, but its impacts were unclear.
The spark-gap or plasma sound source (PSS) produces noise levels from 216 to 227 decibels.
To say that it does not have an impact is something the research just doesn't suggest.Dr Vincent Raoult, Newcastle University
"It works on a much more constrained frequency than air guns, so in that sense it's likely to impact a smaller range of organisms, but what organisms it does impact is not well known," Dr Raoult said.
"With the audiograms of cetaceans that we have, whales and dolphins, I would definitely suggest that these organisms could hear the plasma testing and they may be impacted by it.
"I think they can definitely make the claim that the technology they're using is going to be less impactful than the alternatives, but to say that it does not have an impact is something the research just doesn't suggest."
The survey will assess the geology of the lake floor, test the quality of coal seams and ensure the safety of miners working under the lake.
Associate Professor Robert McCauley, from Curtin University's Centre for Marine Science and Technology, told the Newcastle Herald that the sparker technology was less damaging than a seismic air gun and was unlikely to affect animals outside a range of "tens of metres".
The technology uses a high-voltage charge released in an arc across electrodes in the water. The underwater spark creates a high-pressure plasma or vapour bubble which expands then collapses, generating a low-frequency sound pulse.
Mr Piper said he was encouraged by Associate Professor McCauley's views but would seek more information from the NSW Chief Scientist or another government expert.
"What I'm trying to do is find the facts. If this is a relatively benign process, one they're required to do anyway, and they're choosing a lesser impact, then I think everyone needs to take a deep breath and understand this got out of hand," he said.
"On the other hand, those people who raised concerns, they're legitimate concerns. We've done so much damage in the past by just glibly or blindly accepting that this is how it's done.
"The community are saying, 'We don't accept that any more.'"
A 2002 report by the University of Texas Space and Naval Warfare Systems Center said the sparker technology produced an acoustic signature "similar to the signatures generated by air guns, underwater explosions and combustible sources".
Centennial has suggested the technology produces a "pop" which does not harm animals, but Dr Raoult said the science did not support this view.
"A short burst of sound is obviously better than a long exposure to sound ... but, if the noise is above a certain range that is damaging to organisms, the short length of the noise will still be damaging to animals.
"We know too little about the audiograms of many animals to say whether the noise exposure from these kind of exposures are having no impacts."
Consultants GHD wrote in their report for Centennial that the "seismic survey and drilling are expected to generate noise thresholds that give potential to cause a temporary or permanent hearing shift in animals".
The University of Texas prepared its technical document for the US government to investigate non-lethal ways of deterring swimmers and scuba divers from restricted areas.
It used a spark-gap sound source in the Gulf of Mexico which "caused no obvious environmental impact", but "UT dive team members refuse to be in the water, even on the surface, when the PSS is operating".
Centennial will start surveying 4 square kilometres of the lake floor between Wangi Wangi Point, Swansea, Pulbah Island and Murrays Beach from Monday.
Centennial's survey activities are covered by its 2013 mining lease