EnergyAustralia has been given the all-clear to divert up to 3,500 megalitres a day – equivalent to 1,400 olympic-sized pools – from the Morwell River so it can protect the Yallourn coal mine from the ongoing threat of inundation and collapse.
The Victorian government on Friday afternoon said it had come to an agreement with EnergyAustralia, the owner of the coal mine which is connected Yallourn Power Station, to allow for repairs it said were “necessary” to secure the state’s energy supply.
“This is the right approach that will protect Victoria’s electricity security, community safety, water entitlements and environmental impacts,” said state energy minister Lily D’Ambrosio.
The Yallourn power plant, which currently generates around 20 pert cent of Victoria’s electricity, was reduced to a quarter of its 1,480MW capacity for several days in late June when heavy rains threatened to inundate the brown coal mine that supplies it.
As RenewEconomy reported, the “one-in-100-years” weather event caused the Morwell River, which runs through the Yallourn mine, to swell to more than 30 times its usual flow.
This, in turn, caused cracks to form in an embankment created to protect the mine – called the Morwell River Diversion – raising the risk of flooding for the second time in less than a decade.
(In 2012, the $120 million river diversion – which had been supposedly built to last until 2032 and touted as capable of surviving a one-in-10,000 year flood – gave way in heavy rains and allowed an average of 500 million litres a day to flow into the mine, shutting it down for weeks.)
To avert immediate disaster, the Labor Andrews government on June 17 declared a state of “energy emergency” to allow for an immediate but temporary diversion of the Morwell River, with 232 megalitres per day shifted to the Latrobe River from the Township Field pond.
But a longer-term plan to divert most of the river flow into the Latrobe River was also flagged, to better assess the damage to the MRD and to properly protect the mine against any future threat of inundation.
In a statement on Friday, D’Ambrosio said the diversion of normal winter flows from the Morwell River around the damaged MRD and into the Latrobe River would dry out the MRD and allow engineers to undertake necessary repairs – an effort that is expected to take up to 18 months.
In the event of heavy rain, the agreement would also allow for flood flows to be diverted into the Hazelwood Mine Void, upstream of Yallourn, until flows returned to normal.
The unused Township Field at the Yallourn mine could also be used as a “one-off storage” for up to 3,000 megalitres in a case of emergency.
These last two measures have been flagged as highly undesirable by environmental groups, considering both the disused western part of the Yallourn mine and the abandoned Hazelwood pit are contaminated by toxic coal ash, and filling them with water would pollute ground water in the Latrobe Valley.
But local and green groups have so far given cautious approval to the agreement, with Environment Victoria describing it as “the best way out of a bad situation,” while warning regulators to “triple-check” that there was no cost-cutting by EnergyAustralia – particularly given the recently announced plans for Yallourn’s early retirement.
“We’ll be keeping a close eye on the quality of the repair job to the Morwell River Diversion. The public needs to have confidence that repair works will be done adequately,” said Environment Victoria campaigns manager Nicholas Aberle.
“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. The design of the river diversion should have been able to withstand a rain event of the size we’ve just had.
“The third attempt at building the Morwell River Diversion needs to last a lot longer than the first two,” he said.
Nonetheless the group said it was “pleased” that the parties had landed on a plan that had made the diversion of any water into the Hazelwood pit further upstream an action of last resort.
“We’ve received clear assurances from government that this is not a backhand way of allowing Hazelwood to fill with water before its final rehabilitation plan has been approved,” Aberle said.
These sentiments were echoed by the Friends of Latrobe Valley Water, which said on Facebook on Monday that the community would need “substantial assurance” that these repairs would be done to a standard that ensured safety to them and the local environment.
“Whilst we acknowledge the complexity in addressing this situation and the importance of averting further catastrophic events, we continue to assert that more transparency is needed, including community access to water monitoring and an investigation into how this event happened in the first place,” the group said.
In a statement from EnergyAustralia, COO Liz Westcott said the Victorian government approvals meant the company could proceed with relieving pressure around the Morwell River Diversion, understand the extent of damage and assess what longer-term repairs might be required.
“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,” she said.
Westcott also sought to assure the community that water diversion activities would continue to meet strict environmental conditions set by the state government and enforced by the Environment Protection Authority.
“Ensuring we continue to safeguard the surrounding environment, we have implemented an extensive monitoring regime of water properties with sampling frequency increased from weekly to three time per week, which will continue through the diversion recovery program.
“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,” she said.