THERE is no doubt the failure of a power station ash dam wall leading to liquefied tailings hitting lower ground with virtually no notice is the stuff of nightmares.
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A review of potential risks posed by Origin Energy's Eraring ash dams, released by the NSW Government on Wednesday, spelt out what can happen in such a scenario.
"A sudden rapid failure of the embankment, such as would occur on liquefied soils after a seismic event, would have little to no warning of a flood wave," said the review published four months after the NSW Office of Sport abruptly closed Myuna Bay Sport and Recreation Centre because of the Eraring ash dams.
It raises the question about how many people might die if there's a failure, based on "the likely mechanisms that will trap people and not let them escape an inundation wave".
The review warns that any potential loss of life based on figures used in the dams industry are likely to underestimate the loss of life caused in a tailings dam catastrophe, because dam losses relate to clean water while fatalities from "liquefied tailings or mud flows" are "intuitively likely to be higher".
It is alarming, and sobering.
But it's one thing to spell out what can happen with a tailings ash dam collapse if there's an earthquake of a certain magnitude and if that causes material in the ash dam to liquefy, cause a breach of the ash dam and the material start hurtling towards the Myuna Bay centre.
And that's a lot of ifs in a review that certainly raises more questions about the precipitous decision in March to close the much-loved centre.
Certainly there's conflicting information about the risks.
The review notes that after concerns were raised about the Eraring ash dam within Origin Energy in 2018 it completed an internal qualitative risk assessment of the risk to employees carrying out day to day operations on the dam.
The assessment concluded that "operational activities could be allowed to continue essentially as before".
The review released on Wednesday noted there were no further details of that report and how it reached that conclusion.
It is not unreasonable for Myuna Bay employees left in limbo by the centre's closure, and the community in general, to ask why Origin Energy hasn't released that internal assessment.
Wednesday's review repeatedly noted the absence of information and data to reach firm conclusions, including much clearer information about the nature of Wangi ash and natural foundation soils, without which "it is very difficult to verify the likelihood of the materials liquefying".
That is just one of many seemingly central and important issues left up in the air when the community is entitled to answers.
Issue: 39,371.
