The Great Sandy Strait and Cooloola are World Heritage listed.
The Great Sandy Strait and Cooloola are World Heritage listed. Contributed

Heavy metals threat to Sandy Strait hidden by miscalculation

THE proposed Colton coal mine on the north bank of the Mary River 8km from Maryborough has the potential to seriously affect the Susan and Mary rivers and large sections of heritage-listed Great Sandy Strait, says environmental campaigner Dr John Sinclair.

Dr Sinclair has suggested that a misunderstanding of water flow and hydrology from the Mary into the Strait has minimised the affects of large amounts of heavy metals being released into the river from the coal mine.

"Heavy metals, at many, many times background levels, are set to be released into the river," he said. "Of these cadmium is the worst as it is absorbed readily by plants, and moves through the food chain causing human health problems similar to mercury."

He said that heavily contaminated acidic waste water at the rate of 200 litres per second all day every day will go into the river.

"That amount of water can be a bit above 5 per cent of river flow," Dr Sinclair said.

The Mary runs from south to north and the assumption has been made that it continues to flow north into Hervey Bay where the contaminants can be flushed through into the ocean.

"Unfortunately for that hope, the water from the Mary is impeded by Woody Island off Urangan and turns south," Dr Sinclair said.

"This flow is slowed down, dropping sediment when it meets the tide moving up the Strait."

"Historically, sediment to a measured depth of 100m has been dropped in the area a bit north of Maaroom."

Dr Sinclair said the sediments are nutrient-rich and have formed a great place for seagrass, dugong and other marine life to thrive.

"This would be the very spot that would have all the high concentrations of heavy metals deposited," he said.

"The Mary River Catchment Coordinating Committee and the Fraser Island Defenders Organisation have joined together to gather more definite scientific information on the hydrology of the area."

Dr Sinclair said the basic and erroneous assumption of the direction of the water flow from the Mary has meant that the problems that will occur from contaminated releases have been severely downplayed.