Plans to expand the Ranger uranium operations pose big dangers.

Inside Australia's largest national park lies one of the country's most controversial mines. Earlier this year it came close to a serious failure that would have contaminated Kakadu, effectively forever. Now, instead of heeding the warning signs, it wants to expand.

On January 28, 2011, halfway through a big Northern Territory wet season, Energy Resources of Australia shut down first the Ranger uranium mill then the mine. As the rain kept falling and the wet season entered the record books, process water levels in the tailings dam exceeded normal limits and fast approached the revised emergency level, and the tailings dam came close to overflowing uncontrollably. This is a classic industrial risk scenario: the probability is low but the consequences would be catastrophic. It would mean toxic-process water flowing down the Magela Creek and polluting Kakadu's unique wetlands and floodplains. The engineering remediation of such a failure would be extremely difficult and horrendously expensive. Such cavalier risk management for one of the natural and cultural jewels of Australia and the world would not satisfy Dad's Army or Sir Humphrey Appleby. It should have never come this close to the unforgivable precipice; little wonder that Ranger has been hammered by the market and described as Rio Tinto's ''major shame in this country''.

Any day now the ERA board, presumably with the support of its 68.4 per cent owner Rio Tinto, will decide on two possible expansions to Ranger: the acid heap leach project and the Ranger 3 Deeps underground project. Together these projects represent the most radical overhaul of Ranger in its 30-year history forcing massive changes to water and tailings management, increasing the area of major operational impacts and almost definitely delaying the start of comprehensive rehabilitation in 2021.

Acid heap leaching is rare in the global uranium industry but is being viewed as a means to allow the low-cost development of low-grade resources. Former heap leach mines such as Caetite (Brazil), Mecsek (Hungary) and Somair (Niger) have been small in scale but all have had major environmental impacts, including dust problems, spills and radioactive contamination. While heap leaching is widely used in the copper and gold sectors and the engineering designs and environmental performance have improved considerably from the initial dirt-cheap mines, the cold hard fact remains that no modern uranium mine has ever undertaken large-scale acid heap leaching let alone in the monsoonal tropics surrounded by a renowned World-Heritage site. The environmental impact statement on acid heap leaching at Ranger is (over)due to be released by ERA any day now for public comment and comment we must. ERA is allowed to develop a tunnel down to the Ranger 3 Deeps project and drill underground despite deep concerns about the extent of possible connection between the Magela Creek and groundwater and the potential for the delay in commencement of site rehabilitation. If a mine is eventually proposed, a whole new EIS would be required and we can expect further delays to Ranger and its rehabilitation.

The time has come for the Northern Territory regulator the Department of Resources and the Commonwealth adviser, the Office of the Supervising Scientist, to ensure that ERA and the Ranger site addresses the systemic failures in tailings and water management and ends the habit of unnecessary risk taking. Rather than allowing ERA to complete a revised study for treating process water, actual capacity must be built at Ranger which works and ERA must be held accountable until this is achieved. Indeed Ranger should not have been allowed to restart recently until ERA had active, working-process water treatment capacity to substantially reduce the volume of toxic soup held on site and allow progress towards the end goal of successful rehabilitation. Merely building the proverbial bathtub bigger every year only makes the problem bigger.

Kakadu is our largest National Park and a region of great environmental and cultural significance to the world. It deserves better treatment and protection than this. No expansion should be approved until the process water and tailings management debacles are demonstrably addressed to the satisfaction of all key stakeholders.