The Morwell River's collapse into the Yallourn open cut coal mine has been labelled "catastrophic" by the state's mining and energy union, which says the State Government and TRUenergy have been playing down the severity of the situation.
Construction Forestry Mining and Energy Union mining and energy Victorian secretary Greg Hardy told The Express on Friday the river collapse was "by far a worse situation" than the 2007 landslip, when the Latrobe River spilled into the Yallourn mine for six days.
"You can't just build a little diversion around it like last time with the Latrobe (River), the Morwell River was already acting as an aqueduct," Mr Hardy said.
"This talk of the spill only occurring in a redundant part of the mine sounds like they are in denial; they are a long way off fixing this."
This comes as Yallourn Power Station and mine operator TRUenergy was able to redirect the Morwell River into an older and unused part of the Yallourn open cut mine, and away from coal supply conveyor belts over the weekend.
"Response teams are now working on clean up around sections of the conveyors and assessing what damage may have occurred in the coal conveyor tunnels," TRUenergy spokesperson Carl Kitchen said.
However he said it was still too early to respond to further questions regarding the severity, cost and duration of any long-term response to the damage.
"Our prime focus is still on supplying enough coal to ensure we can maintain generation from the unit that is currently operating, and gaining safe access to the conveyors," he said.
Water flowing into the mine from the nearby Latrobe River junction was plugged on Thursday; however, millions of litres of water continues to flow into the open cut today from the Morwell River after its levee collapsed early Wednesday morning, wiping out a coal supply conveyor belt and shutting down the remaining two.
"From the aerial photograph I've got here of the Morwell floodplain, it shows there's still an enormous amount of water yet to drain off, and even when it's gone there's still the regular flow to go in," Mr Hardy said.
The supply threat has forced the power station to reduce its output capacity to 25 per cent; with only one of four generator units operating, the rest of which are believed to be undergoing opportunistic maintenance.
After the 2007 landslip, TRUenergy managed to re-divert the Latrobe River through neighbouring farmland in a six-day round-the-clock operation;
however, Mr Hardy backed up earlier estimates made by the Gippsland Trades and Labour Council it would take at least six months before a permanent fix was in place.
The Morwell River was diverted through the mine on an embankment during a mine extension last decade, housing three conveyor belt supply tunnels plus an overburden tunnel underneath, in a $250 million construction project which won an Engineers Australia Victorian Division award in 2005.
However, Mr Hardy said the collapse had raised ongoing questions surrounding possible design and construction flaws.
“The people who designed or constructed these tunnels have made a mistake, and clearly have not allowed for these (flood) events to occur; these design awards they’ve won didn’t look closely enough at the design, which has clearly failed,” he said.
“It’s lucky nobody was in this tunnel when it failed; people were walking through those tunnels when they spotted the leak.”
A spokesperson for the Department of Primary Industries, the state’s mining industry regulator, said the construction project which was subject to an Environmental Effects Statement in 2005, was monitored by an independent panel of technical experts, and went through three stages of peer-reviewed assessments.
Federal Democratic Labor Party Senator for Victoria John Madigan called on the State Government to instigate a Royal Commission into the management of Victoria’s electricity industry, with a particular focus on the Yallourn mine, on Friday.