Related coverage: Mine stability ‘at risk’
A long awaited review into the catastrophic collapse of the Morwell River Diversion into the Yallourn coal mine last year has exposed an extensive list of likely faults in its ‘world class’ design process.
In what has been described as a collection of “systemic failures”, the Review of Failure of Morwell River Diversion report released last week has identified five key aspects considered to have cause the failure, targeting fundamental design flaws in the $250 million project.
The use of incorrect materials, a failure to fully integrate design aspects into risk assessments, and the sole reliance on a membrane seal in vital parts of the diversion were among three pages of dot-pointed failures identified in the report’s executive summary.
“Soil and water are natural enemies. The accepted philosophy of dam design is the inclusion of multiple layers of defence. Reliance on a single design feature to mitigate risks in un-conservative,” a report section titled ‘Lessons Learned or Reinforced’ stated.
“If a structure has to retain water, it should be designed as a water retaining structure.”
The MRD breached after heavy rainfall in the early hours of 6 June last year, sending billions of litres of water into the mine, crippling the power station’s generation capacity.
One year, and more than $150 million later, the diversion is still months away from a full repair.
The report also found issues in the MRD’s construction, which failed to achieve adequate compaction levels, while noting “conscientious” monitoring of the diversion’s integrity, including a delayed response to signs of “unexpected performance” which became evident soon after construction.
The MRD’s high-profile failure occurred despite the involvement of world-class engineer firms in the design process – who claimed the diversion could withstand a one-in-10,000-year flood – and regular ongoing monitoring by teams of experts.
Commissioned by the State Government and conducted by ATC Williams, the report has drawn “disbelief” from Monash University environmental engineering senior lecturer Gavin Mudd.
“The MRD failure already is a case study on ‘how not to do’ these types of projects; we use things like this in our lectures to instill the ‘fear of God’ into students that you cannot cut corners with this stuff,” Dr Mudd said.
“My personal reaction to this is its all very damning – it’s really damning – a lot of stuff in here you would have thought had been ticked off on by the design teams.”
A spokesperson for Yallourn Power Station owner operator EnergyAustralia said the report would provide the company and broader industry with “key lessons” which would minimise the risk of a similar event in the future.
“We have worked with the department throughout this process and ensured the findings from the report, as well as our own investigations, have been incorporated into the new designs as well as having the designs reviewed by a third party expert,” the spokesperson said.
However Dr Mudd, who gained his PhD researching groundwater issues in the Latrobe Valley, said the failure would entrench scepticism about the industry’s ability to safely manage their mine networks.
“They say they have got it right this time, but after all that’s happened – it’s hard to take them on their word now – they have lost our trust in such a spectacular way it’s not easy to regain it from this,” he said.
Environment Victoria safe climate campaign manager Victoria McKenzie-McHarg agreed.
“This report raises as many questions as it answers. Chief among them is can the community trust that this mine is safe and secure when this inquiry has identified five different problems that could have caused the collapse?”
Ms McHarg used the report’s release to criticise $4.2 million mine stability funding announced in the most recent state budget, which she said was an “extraordinary handout” to big coal companies to fix their own coal mines.
“These are privately owned mines, and if they’ve been mismanaged to the point that we’re seeing serious structural problems emerge then I think it’s fair to ask why are taxpayers paying to fix these problems rather than the coal companies?”
In releasing the report, Victorian energy and resources minister Nicholas Kotsiras said the review would held educate future regulatory decisions and minimise risks related to mine management and expansion.
“In Victoria we have got the strongest regulatory framework in place than any other state (but) time to time things do occur things go wrong – we have to learn from those mistakes and go forward, it is about minimising the risk into the future,” Mr Kotsiras said.