EnergyAustralia has three options to avert Yallourn mine collapse

EnergyAustralia says it hopes to have repaired the cracks in the Morwell River diversion wall at the Yallourn mine by the middle of next week, and will tonight deliver its proposal to the Victorian government on how it plans to divert the river while work is under way.

In a statement on Friday afternoon, EnergyAustralia said the extreme weather in Victoria last week had increased the water flow in that stretch of the river by nearly 40 times, putting extreme pressure on the embankments that keep the water from flowing into the Yallourn brown coal mine.

While those cracks are fixed, the river will likely need to be diverted. EnergyAustralia has not revealed the options under consideration to do that, but environmental groups believe there are three options on the table: divert the river into the disused western side of the Yallourn mine; divert it into the disused Hazelwood pit; or divert it straight into the larger Latrobe River. All three are problematic, they say.

The Morwell River diversion wall was built more than a decade ago when the Yallourn mine reached its western banks. It was built to allow mining to take place on the eastern side of the river, and it means the normal river course now runs straight through the mine.

EnergyAustralia said it would outline to the Victorian government “the options available to manage water flows to relieve pressure around the impacted area and enable longer term repairs”. It gave no further details.

“Yesterday’s declaration of an energy emergency will allow the government to evaluate and quickly provide a whole of government response to options to divert water flows,” energy executive Liz Wetcott said on Friday.

“These options, along with measures to seal the cracks, are particularly important to undertake in the event of further heavy rain.”

Nicholas Aberle, campaigns manager with Environment Victoria, and Bronya Lipski, an environmental lawyer with Environmental Justice Australia, agreed there were three clear options.

Aberle said the first two – which would see the river diverted either into the disused western Yallourn pit, or the disused Hazelwood pit that used to feed the decommissioned Hazelwood power plant – might be acceptable as an emergency short-term solution, but not in the longer term. He said both pits may contain toxic coal ash, which if mixed with water could contaminate ground water.

He said the third option, which is to divert the river into the Latrobe River, was the only acceptable long-term solution. The Morwell River merges with the Latrobe River downstream from the Yallourn mine, so diverting all that water into one of the two pits would disrupt the normal flow of the Latrobe River.

“If they’ve go to do it for a week, that’s one thing. But if it’s months and months, how do we make sure the river goes into Latrobe River?” he said.

On top of the coal ash risk, Lipski said there were “a whole bunch of stability issues with the Hazelwood mine floor, so any water that’s put in there needs to be done carefully”.

“It appears to me the environmental outcomes are not good either way. We’re not clear to what extent that part of the Yallorn mine has ben rehabilitated, and is ready for that water,” she said.

Meanwhile, she said diverting the water into the Latrobe River could add pollutants that would eventually flow to Lake Wellington in the Gippsland Lakes. This might have legal implications.

On Thursday, the Victorian government declared an “energy emergency” to allow it to approve environmental interventions without going through the normal regulatory processes. But because the Gippsland Lakes are protected under federal environmental laws, the state government’s special powers may not hold.

It’s the second time in less than a decade that the Morwell River diversion wall has been at risk of collapse. Last time, in 2012, the mine did flood, and the wall was not fully repaired for nearly two years, at a cost of $150 million.

Lipski and Aberle both said EnergyAustralia and the Victorian government would have to answer questions as to why it had been allowed to happen again.

“This was a one in 100 year rain event,” said Aberle. “So why did we have a piece of infrastructure that seems incapable of dealing with a one in 100 year event? There are lot of questions that need to be asked of the company and the regulator.”

The situation has forced EnergyAustralia to stop production in much of the mine, and dial down generation at the nearby Yallourn power plant, which is currently running only one of its four units. Yallourn supplies around 20 per cent of Victoria’s electricity, so the reduced generation takes around 15 per cent of the state’s capacity offline.

Despite this, Victoria’s wholesale electricity price rises over the past seven days have been relatively modest, rising to an average of around $132 a megawatt hour.

That is well above the last 12 month average of $50/MWh, but well below the big price jumps to $210/MWh in NSW over the last seven days – for no apparent reason that bidding practices by the major generators – and a jump to $241/MWh in Queensland after the explosion at Callide.

South Australia, with the biggest share of wind and solar in its grid, has had the lowest mainland prices over the past week of around $97/MWh.