On average, 500 million litres a day is flowing through a collapsed bank of the diverted Morwell River into the ''eastfield'' mine - the primary source of coal for the power plant. Last week, about 400 million litres a day were being pumped into the Latrobe River from the neighbouring ''township'' mine. Water damage reduced the power plant's generation capacity to a quarter until last week, when the company was able to re-start a conveyer transporting coal from the mine. It is now operating at 50 per cent capacity. TRUenergy's owner, CLP Holdings, last week told the Hong Kong Stock Exchange that the partial shutdown of the plant would hit its earnings. Analysts estimated it could reduce revenue by $300 million. Steve Dodd, an organiser with the Australian Manufacturing Workers Union, said the flood had been an ''absolute disaster''.

''There is still more water going in than coming out,'' he said. ''They said they estimate it will be at least six months before they will be back to normal.'' A TRUenergy spokeswoman said it was expected a third generation unit would re-start this week, lifting generation capacity to 75 per cent. She said the plant would return to full generation ''when coal supplies allow'' and could not say when the company would finalise plans for a permanent repair to the collapsed riverbank, which gave way on June 6 following heavy rainfall. Before its collapse, the $120 million river diversion - approved to allow the expansion of the mine and give the plant access to coal to last until 2032 - won an award for engineering excellence and prompted claims it was capable of surviving a one-in-10,000 year flood. In the short-term, the company plans to divert the river out of the mine and into the Latrobe River through a 3.6-kilometre long pipe.

TRUenergy said the pipe would be able to carry the entire river by mid-August. ''Once this starts to come online we expect to be able to pump more water out of the mine than what is coming in,'' the spokeswoman said. ''However, it is dependent on the weather.'' Victoria McKenzie-McHarg of Environment Victoria said the collapse of the river diversion raised concerns about the state's management of mine sites. ''It's deeply worrying that we have this attitude that we can move rivers willy-nilly and there will be no consequences,'' she said. But a spokeswoman for Energy Minister Michael O'Brien said there had been an environment effects inquiry into the river diversion before it was approved in 2005. The Greens and Labor have called for a parliamentary inquiry into the flood. But Mr O'Brien's spokeswoman said the Department of Primary Industries had started an investigation and the government would shortly appoint an independent expert to help.

''This is standard practice after an incident of this nature and will help inform design of a long-term solution to the river diversion,'' she said. Experts have said a major disruption to the state's power supply is unlikely even if Yallourn is forced to completely shut. Electricity demand peaks on the hottest days of summer, and current demand is lower than recent years. Gippsland Trades and Labour Council secretary John Parker said there should be an independent inquiry, but was pleased TRUenergy had a long-term commitment to the site. ''If it had been a different owner they might have walked away,'' he said.