Expert slams 'irrational' decision to shut Myuna Bay

14th September 2019

Source: Newcastle Herald | By: Donna Page | Posted: September 14, 2019

A LEADING Australian geo-technical engineer has made a scathing assessment of the controversial closure of Myuna Bay Sport and Recreation Centre describing it as "totally irrational" and "ill considered".

In a no-holds-barred appraisal of the centre's shock closure in March, due to concerns Eraring power station's nearby ash dam wall could rupture in an extreme earthquake, Dr Philip Pells described the decision as "not making any logical sense".

The retired University of NSW professor said if the state government stood by its decision to close the centre due to earthquake risk, "we should also abandon society".

It's understood that an earthquake of 5.7 or 5.9 and above magnitude was the reason for closing the centre, but Dr Pells - who examined the technical reports for the Newcastle Herald - revealed the decision was based on a 6.4 to 6.6 magnitude earthquake.

His findings stand in stark contrast to what the public has been told about the size of the potential earthquake that forced the closure of Myuna.

According to Geoscience Australia, a 6.6 magnitude earthquake could occur every 70,000 years in Lake Macquarie and a 6.4 magnitude earthquake every 40,000 years.

A 6.6 magnitude earthquake would have more energy release than the Hiroshima atomic bomb.

An event Dr Pells described as "very extreme", that would cause "total and absolute chaos".

"Even before we start considering the ash dam, let us be quite clear that if the Sydney-Newcastle area was struck by the 6.6 event there would be catastrophic destruction on a massive scale and the ash dam would be the least of our problems," he said.

"There would be no road and rail transport, bridges would be down, multiple buildings would have collapsed, the coal fired power stations at Eraring and Munmorah would be substantially damaged, hospitals would be on life support, there would be hundreds of miners trapped in underground coal mines. And I could go on and on.

"So on the above basis alone, I consider that the closure of the centre is illogical to the point of being bizarre."

Myuna closed abruptly on March 29 after Origin Energy warned the Office of Sport that it was at risk if Eraring power station's ash dam wall ruptured in an earthquake.

The government was in caretaker mode at the time.

The Office of Sport, a NSW government agency, told employees that remediation work to strengthen the ash dam, or moving the centre to a nearby site, would take at least two years.

The agency's chief executive at the time, Matt Miller, left his post only a few weeks after the closure.

In May, new Sports Minister John Sidoti ordered a a review of the engineering reports which led to the closure of the centre that sits downhill from the ash dam.

The review, overseen by the NSW Dams Safety Committee, returned in July but bizarrely did not assess the actual risk to the centre that was previously used for school camps, seniors programs and as a community recreational facility.

"The independent reviewer has concluded the assessments of risk in the original reports were reasonable, and the closure of the Myuna Bay Centre as a means of risk reduction, was consistent with NSW Dam regulation policy in relation to such risk, or potential risk," Mr Sidoti said.

He commissioned a further review, which is due back this month, to determine if the risk to the centre is manageable.

Since the closure of Myuna, there has been conflicting advice about the size of the earthquake that could threaten the dam.

Just days after the closure, Origin said the dam had been assessed for its ability to withstand a "major", or 5.7 magnitude, earthquake.

Lake Macquarie MP Greg Piper, who has been highly critical of Myuna's closure, said he was led to believe the assessment was made on a 5.9 or above magnitude earthquake.

But after reading the reports, Dr Pells said the decision to close Myuna was made based on technical advice that assessed an "operational basis earthquake", meaning the dam should remain functional, at moment magnitude 6.4 and a "maximum design earthquake", meaning the dam should exist but may not be functional, at 6.6 moment magnitude.

He said the difference between a 5.7 or 5.9 and 6.4 or 6.6 magnitude earthquake was "extremely significant".

"We are talking about totally different animals," he said.

"Nobody has made, to my mind, a rational assessment of what happens when 6.6 or 6.4 earthquake hits this part of the world.

"If it makes sense to close the sports centre, we are going to have to close down most schools, the M1 freeway because not a single bridge is designed to withstand that magnitude earthquake and every other place that is just as vulnerable."

When asked for clarification on the discrepancy of the size of the earthquake, Origin Energy's spokesman pointed out it referenced a 5.7 earthquake as measured on the Richter scale.

The Origin Energy-commissioned reports, that investigate the stability of the ash dam, reference 6.4 and 6.6 moment magnitude earthquakes.

The moment magnitude scale is the universal earthquake measurement that replaced the Richter scale from about 1990.

According to the Australian National Committee on Large Dams (ANCOLD), "the magnitude scales give similar values".

Professor Sandy Steacy, head of physical science at the University of Adelaide, said the two scales were "more or less the same" and would be very unlikely to vary more than 0.1 or 0.2 in magnitude for a given earthquake.

"The Richter magnitude scale was developed in the 1930s based on relatively nearby earthquakes in California, whereas the moment magnitude scale is better for earthquakes observed from a long way away and also for very large earthquakes," she said.

Professor Steacy described a 6.6 magnitude earthquake as a "very significant event".

She said while it was not outside the "realms of possibility; it would have 30 times the energy release of the 1989 Newcastle earthquake".

"It's a very serious earthquake in regions without strong building codes," she said.

"In general, the bigger the earthquake the more damage you would get. If construction standards were the same as 1989, it would do a lot more damage."

The 1989 Newcastle earthquake, that registered 5.4 on the moment magnitude scale, killed 13 people and injured more than 160.

It left a damage bill of more than $4 billion after shaking was felt up to 800km from Newcastle.

Damage to buildings and facilities occurred over 9000 square kilometres, equivalent to 160 times the size of the Sydney Harbour.

Mr Piper said the latest revelations about the discrepancy in the severity of earthquake used to assess risk to the ash dam comes as no surprise.

"As I've maintained from the start, the Office of Sport's decision to close Myuna Bay was breathtaking in its arrogance and was based on a report which was questionable at the very least," he said.

"It was more than a knee-jerk reaction from the department, and bordered on being farcical.

"I've always accepted that the Office of Sport has a duty of care to the people and children who are often accommodated at Myuna Bay, but I believe there's been a clear absence of common sense applied here."

Origin's spokesman said the ash dam must be engineered to the safety standards required by the dam safety guidelines and consistent with industry best practice.

"We're currently finalising detailed designs and procurement for works to strengthen foundations, buttresses and embankments around the ash dam and these works are expected to commence by the end of the year," he said.

According to Dr Pells, if the ash dam was hit by a major earthquake it would not necessarily cause the wall to collapse. He said it could take hours, or days, for the wall to be breached.

"The more likely scenario is that the embankment will settle like an unsuccessful souffle," he said. "But that does not necessarily mean it will be breached. It may, but it also may not."

He urged the government to look at the "whole picture" and not just focus on the risk to the sports centre.

He said the Mardi Dam - an off-river storage dam located near the Wyong River - would be at the same risk from a 6.6 magnitude earthquake.

The dam has a capacity of 7.4 billion litres, and is part of a system that supplies drinking water to almost 300,000 residents and businesses. "How many other places are just as vulnerable?" he asked. "Should we close them down also?"

Internal documents obtained by 1233 ABC Newcastle, via freedom of information laws, reveal Office of Sport went against the advice of its own experts when it suddenly closed Myuna.

NSW Dams Safety Committe head Chris Salkovic and NSW Public Works chief emergency engineer Martin Dwyer did not agree with the closure.

The Public Service Association said in July that it planned to refer the centre's closure to the Independent Commission Against Corruption.

Mr Piper said there was a risk that a 6.6 magnitude earthquake could demolish the Office of Sport headquarters.

"But I notice they haven't shut themselves down or evacuated," he said.

"We haven't stopped putting kids on school buses, or closed schools that could be destroyed by a catastrophic quake, because we know the risks are so very, very small. So why did they close Myuna Bay in a lightning raid?"

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