MAC: Mines and Communities

Human error likely cause of Ranger contamination

Published by MAC on 2004-03-30

Human error likely cause of Ranger contamination

Sarah Belfield,

Tuesday, March 30, 2004

A wrong connection between potable and process water systems may have been the cause of the water contamination incident last week at Energy Resources of Australia's Ranger uranium mine, according to the company.

ERA said the connection may have been made before Tuesday night last week, which was when a change in water supplies occurred, according to initial investigations. The company said records from routine water testing indicate no impact on drinking and washing water before Tuesday night.

Australian government supervising scientist Arthur Johnston has also been assessing the impact of a second, associated incident where process water leaked into a creek system nearby.

His understanding is that process water back-flowed into a header tank and then overflowed into the creek, probably occurring on Tuesday night or Wednesday morning.

Johnston announced yesterday that concentrations of all measured chemicals downstream from the mine in Magela Creek have remained within normal ranges, and that no adverse effects have been observed in monitored animals.

Magela Creek feeds a large wetland area, a spokeswoman for Johnston told

Johnston will discuss the incident today along with data results in meetings with traditional owners of the area and the broader Jabiru community.

"This problem in addition to the contamination of the potable water supply at the plant is not good enough," Johnston said on Friday.

Last week Johnston requested that ERA not resume Ranger operations until he has complete confidence that systems are in place to prevent a similar incident from happening again.

In April 2002, the federal government warned ERA to lift its game following a report by the supervising scientist into the mismanagement of a low-grade ore stockpile, which occurred in March that year.

From 1979 to January 2004, the supervising scientist assigned a "significant" status to two incidents reported at Ranger. One occurred in 1982 and involved the health and safety of two workers in the packing plant and another took place in 1995, involving a spill of diesel at the power station.

To extract uranium, ore is crushed and then pumped as a slurry to a thickener, where excess water is removed, before heading to leach tanks where sulphuric acid is added to dissolve uranium-bearing minerals.

Solids are removed from the uranium-rich solution and kerosene then selectively strips uranium from the solution. Ammonia precipitates the uranium, which then passes to a furnace where ammonia is driven off, allowing uranium oxide to form.

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