Investigation into the environmental impacts of the leach tank failure at Ranger uranium mine, December 2013

Supervising Scientist, 2014

Supervising Scientist Report 207

Executive summary

At 00.54 am on 7 December 2013 Leach Tank 1 at the Energy Resources of Australia Ltd Ranger uranium mine collapsed, spilling approximately 1 400 m3 of slurry containing ground uranium ore, water and sulfuric acid into the processing area. The Supervising Scientist was advised of the incident at 06.20 am 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/Northern Territory Government Taskforce, with representation from the Supervising Scientist (Australian Government Department of the Environment), 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.

Radiological assessment of both the spill site and personal dosimeters show that additional radiation doses to workers involved in the cleanup activities were low and assessed to be of no concern 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.

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. However, sufficient information was available 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.

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.
  3. continue the development and maintenance of a spatial database of groundwater data for the Ranger uranium mine; and

It is recommended that soil contamination investigation works undertaken by Energy Resources of Australia Ltd in 2006 and 2007 be revisited to better inform site closure planning.

Related information