The Mackay Port Authority has clarified claims made in a Brisbane newspaper  that the Department of Environment and Heritage has vetoed a plan by the MPA to undertake a major dredging exercise at Mackay Harbour.

Environmental Manager Scott Keane said the department had asked the MPA for additional information regarding its proposal to vary an existing dredging permit.

MPA Environm ental Manager Scott Keane.

This has resulted in the elimination of the preferred option to utilize the dredger “Brisbane” on its northward passage along the Queensland coast later this month.

Efforts are now being directed towards gaining approval to undertake the works in September on the return southward passage of the vessel.

“This variation would allow the MPA to remove and deposit at sea about 120,000m3 of spoil from the harbour every three years supplemented by minor follow up maintenance, rather than an on-going program that excavates 50,000m3 each year,” he said.

The material originates from suspended material entering the harbour on each tidal inflow and settling out of suspension,

It has been deposited at a spoil ground north-east of Slade Island for more than a quarter of a century. Over the five year permit life, the amount to be moved remains the same and even with the planned concentrated program, the volume to be deposited equates to less than 85mm over the spoil ground.

Mr Keane said the MPA had engaged consultants to investigate what impact, if any, the new dredging procedure would have on the spoil ground.

“We have been depositing material in the same area for more than 25 years.” he said.

“Detailed studies by the Co-operative Research Centre (Reef) and the State Department of Primary Industries have shown no discernable differences between the spoil grounds and bordering areas. The material disperses quickly as it’s subject to high energy current and wave action.”

Mr Keane said the MPA recognised it had a responsibility to ensure that the new practice would not impact on the environment.

He said the new dredging regime had the potential to provide significant cost benefits.

“The proposal is to utilize the MV Brisbane, a trailing suction hopper dredge, to extract the material from the harbour once every three years. At the moment we use a grab dredge and hopper barge system that’s proving to be more costly and not as efficient,” Mr Keane said.

“At the end of the day we would like to use the MV Brisbane during its southbound return run down the coast later this year, but let’s wait and see what the consultants have to say. Hopefully the report will be available by the end of the week.”