A confidential report on an exploratory gas drilling project off the coast of Newcastle has revealed the proposal's potential environmental risks, including the possibility of oil spills.
The NSW government refused to release the report, saying it did not have to be made public under Commonwealth law.
But the Newcastle Herald has obtained a copy, which details the plan's potential risks to the environment and the possibility of an oil spill.
Advent Energy, through its subsidiary company Asset Energy, plans to begin drilling for natural gas 55 kilometres off Newcastle next month.
Asset Energy prepared the report for the state and federal governments, which are considering whether to allow the drilling.
The report listed the plan's environmental risks and potential effects, which included:
¦ An uncontrolled blow-out causing an oil spill that continues for up to 11 weeks.
¦ A whale colliding with the drilling rig, threatening workers' lives.
¦ Physiological damage to sensitive marine fauna from underwater noise from drilling and seismic activity.
¦ Chemical, oil and diesel spills causing acute toxic effects on marine organisms.
¦ Marine life negatively affected by water discharges 15 to 20 degrees above the sea temperature.
Advent Energy executive director David Breeze said the company was "very confident the risks are being adequately addressed".
Lake Macquarie councillor Phillipa Parsons, who leads a coalition of groups opposed to the drilling plan, said she had "serious concerns" about the potential for environmental damage to the coast and marine life.
The report said galley waste and sewage disposal would "almost certainly" cause pollution and nutrient enrichment in the surrounding ocean.
Another near certainty was that the Ocean Patriot drilling rig would disturb marine organisms on the ocean floor.
Crushed rock would be discharged continuously to the seabed, smothering marine life in a 1.1-kilometre radius from the drilling site.
The drilling rig would be well lit and a 500-metre exclusion zone established, the report said. Up to 12 anchors would hold the rig in place, causing further seabed disturbance.
The rig's location would be communicated to commercial fishers, shipping operators and port authorities.
The rig will have support helicopters, which could disturb seabirds.
Four scenarios were listed that could cause an oil spill, including a refuelling incident, collision, subsea blow-out and subsea rupture.
Emergency plans would be enacted in the "unlikely event of an accidental oil spill into the ocean" and an oil spill contingency plan had been prepared.
In the report, the company played down many of the more extreme risks, saying they were unlikely. It admitted that commercial fishing and shipping activity would probably be disrupted.
It was considered possible that the rig could cause hydrocarbons and metals' pollution.
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