The Hazelwood mine void will receive water rerouted from Yallourn in heavy flooding, as part of approvals granted to redirect water from the damaged Morwell River Diversion.
The state government has approved three of Yallourn operator EnergyAustralia’s water diversion proposals in order to carry out inspections and assess long term repairs on the diversion wall.
Under the approvals, EnergyAustralia will divert up to 3500 megalitres a day into the Latrobe River. This will dry the Morwell River Diversion for engineers to undertake repairs.
If the area receives heavy rain, larger flood flows may be diverted into Hazelwood – upstream of Yallourn – until flows return to normal.
In an emergency, the unused Township Field in the Yallourn mine can be used as a one-off storage for up to 3000 megalitres.
Construction and repairs are estimated to take up to 18 months to complete, and this will be closely monitored by the state government.
It comes after significant flooding in the Morwell River resulted in cracks in the diversion that threatened to inundate the Yallourn mine in the wake of a severe storm in June.
Short-term repairs have temporarily stabilised diversion, but it remains at risk in extreme heavy storms, meaning it could fail and the Morwell River could flood the mine.
EnergyAustralia chief operating officer Liz Westcott said the company would meet strict environmental conditions set by the state government and enforced by the Environment Protection Authority.
Ms Westcott said EnergyAustralia was undertaking extensive water monitoring, ramping up sampling to three times per week which will continue through the recovery program.
“We’ve held real fears since June that with a compromised structure and an unknown amount of damage in the low flow channel, we can’t confidently withstand further flood events,” Ms Westcott said.
“We commit to make public a summary of our monitoring data that’s being collected throughout the process later in the year, once it has been analysed.”
State Resources Minister Jaclyn Symes was in the Latrobe Valley on Friday and stated this would not affect Yallourn’s 2028 closure date as agreed upon with the state government.
She also said that the repair bill – which EnergyAustralia has previously estimated to be in the tens of millions of dollars – would be footed by the company.
“This agreement means these important long-term repairs to the MRD can keep going and allows us to maintain the structural integrity of the Yallourn mine and surrounding areas,” Ms Symes said.
ENGIE confirmed it was starting work to enable off-river water storage in Hazelwood to help mitigate the impact of surplus flows downstream and allow critical repairs at Yallourn.
“Water availability is an important element of our approach to mine fill – we’ve always planned to access water only when it’s plentiful and available,” ENGIE chief executive Augustin Honorat said.
Environment Victoria is watching the situation to ensure repairs will be done adequately with no cost-cutting by EnergyAustralia after the MRD had previously collapsed in 2012.
EV campaigns manager Nicholas Aberle said the state government assured the diversion plans were “not a backhand way of allowing Hazelwood to fill with water” before final mine rehabilitation is approved.
“The recent damage to the embankment is clear evidence that the repair job in 2012 was not done well enough, there are still questions that need answering,” Dr Aberle said.
“The design of the river diversion should have been able to withstand a rain event of the size we’ve just had.”