Dredge Disposal on Caley Valley Raises Concerns

Expert advice provided to WWF-Australia has raised alarming concerns about the plan to dump dredge spoil on the Caley Valley wetlands at Abbot Point.

These include that the ponds may be too small to hold the dredge spoil, that sediment flowing to Reef waters has been seriously underestimated, and that acid sulphate impacts have not been properly considered.

WWF-Australia Reef campaigner Louise Matthiesson said the expert evidence had been included in WWF’s submission on the Queensland Government’s Abbot Point proposal now being considered by Federal Environment Minister Greg Hunt.

“The proposal is full of information gaps big enough to drive a truck through. It contains errors, out-of-date information, and doesn’t even consider some dangers. That’s what happens when a project is fast tracked without a full environmental impact assessment.

“The world’s best reef deserves the world’s best management, but this is nowhere near the standard Australians expect for a huge project that will directly impact the Great Barrier Reef and a sensitive wetland,” she said.

According to the Preliminary Assessment documents for the project, 1.7 million cubic meters of dredged seabed will be mixed with seawater to create a total of 14 million cubic meters of dredge slurry. The slurry will be settled out in the ponds, with tail-waters discharged back into the waters of the World Heritage Area.

Brett Miller, of the University of NSW School of Civil and Environmental Engineering has advised WWF-Australia that the amount of disturbed dredge material that needs to be stored is likely to be greater than the capacity of the ponds built to hold it in the short term.

Mr Miller also said that the project’s modelling underestimates by almost 30% the amount of water and sediment to be discharged by pipe to the ocean from these ponds during the second dredging stage. WWF is concerned because these fine sediments cause water pollution and will smother nearby seagrass beds.

Professor Richard Bush from Southern Cross University provided advice to WWF Australia raising serious concerns about the risks of acid sulphate problems in the dredge material and below the spoil ponds. He said the project’s acid sulfate soil assessment did not adequately identify or quantify potential impacts.

Professor Bush also said treating acidic waters with lime prior to discharge, as proposed, often results in the formation of ‘iron floc’ which can be harmful to marine life and yet this risk was not identified or assessed.

Former GBRMPA Director Jon Day advised that the project assessed impacts on World Heritage attributes based on a 1997 report which is significantly out of date and contains errors. He said the finding that only 3 out of 29 natural heritage attributes were identified as being relevant to Abbot Point was “clearly wrong in the light of today’s knowledge”.

Ms Matthiesson said there were many other concerns including that the ponds will not be lined, allowing seepage, and their construction is proposed in January and February 2015 during the wet season.

“There’s a risk of storm surge and cyclone damage, impacts on turtle hatchlings on the adjacent beach, and there will be maximum disruption to wetland birds as their numbers swell at this time of year.

“We urge the Queensland Government to reconsider this proposal. Instead the Government should properly examine building longer jetties into deeper water to minimise the need for dredging. Any dredge spoil should be disposed of at a less environmentally sensitive location away from the wetlands,” she said.

Source: wwf.org.au