Interim Report: Investigation into the environmental impacts of the leach tank failure at Ranger uranium mine

Supervising Scientist, 2014

Supervising Scientist Report 206

Executive summary

At 00:54 on 7 December 2013 Leach Tank No. 1 at the Energy Resources of Australia Ltd Ranger uranium mine collapsed, spilling approximately 1400 m3 of slurry containing ground uranium ore, water and sulphuric acid into the processing area. The Supervising Scientist was advised of the incident at 06:20 on 7 December 2013, with Supervising Scientist Division staff onsite that morning to assess the scale of the incident and begin analysis of the potential environmental impacts.

No one was injured as a result of the incident and the spill remained within the processing area with an unknown quantity of slurry reporting to Retention Pond 2.

A joint Commonwealth/NT Government Taskforce, with representation from the Supervising Scientist, the Australian Government Department of Industry, Northern Territory Department of Mines and Energy, Northern Territory WorkSafe, Northern Land Council and the Gundjeihmi Aboriginal Corporation, was established to coordinate the various incident investigations.

The Supervising Scientist's investigation is confined to the assessment of the potential impacts on human health and the offsite environment, including Kakadu National Park, as a result of the incident. The Supervising Scientist's investigation does not consider the cause of the leach tank failure, nor does it consider issues related to the condition of the Ranger uranium mine processing facility, as this remains the subject of ongoing investigations by the Northern Territory Department of Mines and Energy and Northern Territory WorkSafe.

In assessing the environmental impacts from this incident, the Supervising Scientist undertook a comprehensive array of monitoring activities which included both onsite and offsite sampling and analysis of surface water, groundwater, radiation and soils. In addition Geoscience Australia was commissioned by the Supervising Scientist to investigate the potential impacts to groundwater as a result of the spill.

It is the conclusion of the Supervising Scientist that the leach tank failure has not resulted in any adverse impacts to human health or the surrounding environment, including Kakadu National Park.

Dose to workers involved in the cleanup activities was low and of no consequence to human health. No increase in airborne radionuclide concentrations as a result of the incident was detected at the Supervising Scientist monitoring stations in Jabiru town or at Jabiru East, indicating no impact to residents in the surrounding area.

Chemical and biological monitoring by the Supervising Scientist in Magela Creek did not detect any effects related to the incident. Limited groundwater data available in the area of the spill, and the six week timeframe for Energy Resources of Australia Ltd to commence the requested groundwater monitoring program, restricted the level of groundwater analysis which could be undertaken. Sufficient information was available, however, to conclude that due to the generally compacted nature of soils in the plant area only a small volume of contaminants may have entered the groundwater and this would not have any significant impact on groundwater quality in the offsite environment.

In response to the need for additional groundwater data in the Corridor Creek area, it is recommended that Energy Resources of Australia Ltd provide the Ranger Minesite Technical Committee with an implementation plan to address the recommendations of the Geoscience Australia report including;

  1. an increase in the frequency and density of routine groundwater monitoring in both the plant area and the Corridor Creek region;
  2. investigate the role of geological structures in groundwater movement to the east of the plant area, and
  3. continue the development and maintenance of a spatial database of groundwater data for the Ranger uranium mine.

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