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Concrete inside unstable Paradise Dam wall may have failed design standard, inquiry finds

By Johanna Marie, Saturday May 23, 2020 - 14:22 EST
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SunWater revealed concerns about the structure of Paradise Dam last September. - ABC

Concrete used in the construction of Paradise Dam near Bundaberg may have been "intrinsically incapable" of meeting design standards, an independent inquiry has determined.

Natural Resources Minister Anthony Lynham tabled the 580-page report in State Parliament today.

It details structural and stability issues at the troubled dam, which was built by the Queensland Government in 2005.

"We commissioned a public, independent inquiry which has confirmed there are indeed structural and stability issues with Paradise Dam," Dr Lynham told Parliament.

Dam operator SunWater revealed last September the dam needed to be lowered to 42 per cent of its capacity and the spillway lowered by 5 metres because of safety concerns regarding the roller-compacted-concrete (RCC) in the dam wall.

John Byrne's commission of inquiry has reached much the same conclusion.

"The commission notes that the concrete mix used to build the dam may have been intrinsically incapable of meeting the required design values," Dr Lynham said.

Locals worried about safety

Nearby resident Helen Dayman said Goodnight Scrub residents were concerned after hearing the dam was at risk of failing.

"Where I live, I'm right in the curve of the river — I would have a wall of water going straight over the top of my place, so that's our lives at risk," she said.

Mrs Dayman said the Goodnight Scrub community had been cut off in previous floods and residents were afraid they would not escape if the dam failed.

"Our community has no evacuation route, we are completely isolated," she said.

"It is scary if there is a big issue, we want the works happening as soon as possible," said Mrs Dayman.

"The question is the steps that they're taking, are they the right steps?"

SunWater told the ABC today it would begin bringing the wall down next Monday, after receiving federal approval to proceed with rectification work.

Paradise Dam was the first RCC dam of its kind to be built in Australia.

The inquiry also determined the design of the primary spillway apron is not wide enough and could be at risk of collapse in the event of a flood like the one that occurred in 2013.

"Evidence before the commission suggested that if the 2013 floods had lasted longer, the erosion due to the insufficient downstream protection may have undermined the dam, giving rise to a risk of a dam failure by overturning," Dr Lynham said.

The inquiry made eight recommendations intended to prevent similar incidents from occurring in future, including that materials be subject to inspection and physical testing to confirm they met critical design parameters.

During the inquiry, it was revealed no shear strength testing was carried out on the dam after it was built.

Dr Lynham said seven of the recommendations have been adopted by the State Government, with one "in principle".

"As always, the Government's priority remains community safety — with Paradise Dam to continue to provide long-term water security and underpin economic prosperity in Bundaberg and the Burnett for generations to come."

The Minister said the report had validated SunWater's response to the risk and the decision to lower the dam wall, however, more investigations were needed into the dam's stability.

A spokesperson from SunWater said they had only received the report findings today and would not be making any comment until after it had been considered in its entirety.


© ABC 2020

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