THE operator of the Ranger uranium mine expects to take drastic action to prevent radioactive water spilling into an Aboriginal community and Kakadu's World Heritage-listed wetlands.

More than 10 billion litres of highly contaminated water is trapped on the mine site 230 kilometres south-east of Darwin after near-record rainfalls.

 

Energy Resources of Australia, which is controlled by Rio Tinto, will be forced to pump water from the almost over-flowing dam into its operating open-cut mine known as Pit 3 if the Kakadu area receives about 100 millimetres more rain. With three weeks of the Top End's wet season remaining, more rain is likely.

 

This would delay for months, possibly years, the resumption of high-grade ore extraction in the pit that ERA relies on to supply 10 per cent of the world's uranium.

 

The company conceded this week it would be unable to resume production in the pit until the end of July at the earliest and that its ''ultimate contingency'' to protect the environment was to transfer water from the tailings dam.

 

But Pit 3, the only place available to put the water, already contains 3.6 billion litres of water that is sitting above high-grade ore deposits.

 

If forced to pump water containing heavy metals and radioactive material from the tailings dam into the pit, ERA would have to treat all of the water there as highly contaminated.

 

But sources at the mine said the treatment plants did not have the capacity to solve existing water management problems, despite recent upgrading of equipment.

 

For 30 years about 100,000 litres of contaminated water a day has been leaking from the tailings dam into fissures beneath Kakadu but an 18-month review completed last year failed to establish where the water had gone or whether it would damage the environment in the future.

 

Geoff Kyle, an industrial chemist and science officer working for the Mirarr Aboriginal traditional owners of Kakadu, said pumping water from the tailings dam was a last resort for ERA, which the company is trying to avoid by asking the mine's regulators to relax environmental standards.

 

Mr Kyle said the company had proposed ''deliberately allowing seepage into a local aquifer and has submitted detailed plans for remediating the damage it believes will be caused''.

 

''The height limit of the water in the tailings dam is 53 metres - it was 52.9 metres last Friday and there has been more rain since then so we believe the company will have to start pumping if we receive about 100 millimetres more rain.''

 

The Bureau of Meteorology has forecast showers and storms in the area over the next couple of days and unpredictable wet season weather for several weeks. Since ERA announced an initial three-month suspension of production at Ranger in January, the company's shares have fallen 45 per cent to $6.58 a share, a loss in value of $1 billion.

 

The crisis has thrown into doubt ERA's plans to expand its operation to include an underground mine and the use of a controversial acid heap leach processing technique to process low-grade ore.

 

The Ranger mine has had more than 150 leaks, spills and mishaps since it opened despite opposition from Kakadu's traditional owners in 1981.

 

Yvonne Margarula, a Mirarr senior traditional leader, said last week that her people were ''deeply saddened'' that uranium from their land at Ranger had been exported to Japanese nuclear power companies, including the one operating the stricken Fukushima plant.

 

This week the ERA chairman, David Klingner, publicly ruled out his company agreeing to give up the Jabiluka mineral lease, which contains known high-grade reserves of uranium worth more than $18 billion.