The federal government has delayed approval for the construction of the world's biggest coal port in Queensland until after the federal election.
Environment minister Mark Butler said several new reports into the impact of dredging for the expanded coal-loading terminal at Abbot Point, about 25 kilometres north of Bowen on the Queensland coast, would be released to the public before a decision was made.
The planned port expansion would see 3 million tonnes of mud dredged up and dumped in the Great Barrier Reef Marine Park.
The development is seen as a keystone for allowing a massive expansion of coal exports from Queensland's Galilee Basin, which could lead to over 100 million tonnes of greenhouse gases being released, seriously damaging efforts to tackle climate change.
"A number of reports have only just been delivered to me, which potentially impact on the Abbot Point assessment," Mr Butler said in a statement.
They include an initial report on findings of the Independent Review of the Port of Gladstone, ship anchorage management in the World Heritage Area, a report into environmental best practice port developments, and a report prepared for his department called Research on Improving Dredge Material Management in the Great Barrier Reef Region.
"Given the significance of the Abbot Point development both in terms of the economic development of the region and the potential environmental impacts on the Great Barrier Reef I have decided to release these reports for public information," Mr Butler said.
"I am conscious of the balance between the economic benefits and environmental concerns associated with any decision on Abbot Point. The various significant environmental imperatives must be considered, as does the potential for jobs growth, which is vital for a range of coastal and inland communities."
Former environment minister Peter Garrett, who is not contesting his federal seat of Kingsford Smith at the election, had entered the debate earlier in the day, using social media to call the dredging plan "dumb and damaging" and urging Mr Butler to block it.
The proponent, the North Queensland Bulk Ports Corporation, wants six new berths at the port for bulk coal carriers to dock. The decision was originally slated for July 9, but had been pushed back a month.
The Research on Improving Dredge Material Management in the Great Barrier Reef Region report, completed earlier this year, found significant uncertainties around the impacts of dredging, which can spread mud and contaminants over a wide area.
"The modelling, which was based on hypothetical dredging campaigns and a 'maximum credible sediment dispersal' scenario, indicates that dredge material placed at sea has the potential to migrate on a much greater scale than previously thought," said the report, which was prepared for the federal Department of Sustainability, Environment, Water, Population and Communities.
"The research highlights the need for future dredge and disposal studies to include larger geographical footprints and longer modelling durations to account for the fact that dredge plumes and sedimentation may occur at distances further away from the dredging and disposal sites than originally thought."
The UN body UNESCO wrote to the Australian government on Thursday, seeking more information about the dredging proposed for Abbot Point, and its effect on the reef.
UNESCO has previously cited the prospect of major industrial developments along the reef coast as being one reason that it may review its world heritage status. A UNESCO decision on whether the reef should be listed as a "World Heritage Site In Danger" is expected next year.
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