ISSN 0 158-4030
Supervising Scientist's overview
The Supervising Scientist plays an important role in the protection of the environment of the Alligator Rivers Region of the Northern Territory through the supervision, monitoring and audit of uranium mines, as well as research into the possible impact of uranium mining on the environment of the Region.
Ranger is currently the only operational uranium mine in the Region, and is owned and operated by Energy Resources of Australia Ltd (ERA). Production commenced at Ranger in August 1981, and current plans will see mining of the Ranger 3 deposit cease in 2012 with milling of stockpiled ore expected to continue through until 2020. A proposal to include a heap leach facility at Ranger was lodged in 2009 but was formally withdrawn by ERA in August 2011.
As the time of mine closure and rehabilitation draws closer, the work of the Supervising Scientist includes engagement with stakeholders in discussions and research activities associated with operations, rehabilitation and closure of the Ranger site.
Work has continued in developing improvements to the Supervising Scientist's surface water monitoring program. This program is relevant to both the operational and rehabilitation phases of mining.
During the year there were no reported incidents that resulted in any environmental impact off the immediate minesite. The extensive monitoring and research programs of the Supervising Scientist Division (SSD) confirm that the environment has remained protected through the period.
Monitoring programs by ERA, the NT Department of Resources and SSD continue to indicate that there is no evidence of seepage from the base of the Ranger tailings storage facility (TSF) impacting on Kakadu National Park. ERA has installed additional monitoring bores around the TSF at the request of stakeholders, including SSD. Installation and commissioning of monitoring bores in the vicinity of the TSF continues into 2011–12.
At Ranger mine the 2010–11 wet season was the third largest on record with rainfall of 2457 mm recorded. The high rainfall resulted in increased inventories of water accumulating on site. From 28 January until 15 June 2011 ERA ceased production at Ranger in order to restrict inputs to the process water system to only those attributable to incident rainfall. This initiative avoided the need to invoke a contingency response to transfer process water to the active mine pit, Ranger 3, in order to comply with authorised maximum operating levels in the process water system.
Delays in sourcing and commissioning an effective process water treatment facility mean that the process water inventory at the mine remains an acute focus. As an interim process water management strategy, raising of the walls of the tailings storage facility by four metres commenced in October 2010 and continued throughout the reporting period. Changes to the maximum operating level of the dam will require formal regulatory assessment and approval in order to make use of the increase in tailings and process water capacity created by this construction.
The SSD surface water quality monitoring program continues to be improved with refinements to the operation of continuous monitoring of pH, electrical conductivity (EC) and turbidity in Magela and Gulungul Creeks upstream and downstream of Ranger mine. The SSD monitoring stations are equipped with autosamplers that collect water samples triggered by in-stream events such as increases in EC or turbidity exceeding defined threshold levels. This event-based sampling has enhanced the capability of the monitoring program by allowing collection of samples outside of normal working hours or when conditions in the creeks are unsafe for manual grab sampling. SSD discontinued its routine surface water grab sampling program in the 2010–11 wet season in favour of the more conservative event-based program, although some manual grab samples were collected for research and quality assurance purposes. SSD's surface water monitoring results are posted weekly on the internet throughout the wet season.
The principal biologically-based toxicity monitoring approach for 2010–11 was in situ monitoring using freshwater snails, with test organisms deployed in containers floating in the creek water. This program was extended from Magela Creek to include Gulungul Creek during and since the 2009–10 wet season.
Determination of radionuclide levels in mussels from Mudginberri Billabong has been a continuing element of the SSD monitoring program downstream of Ranger. Results for samples collected in October 2010 contained above-average radium 226 content. This is attributed to lower soft body weights of the molluscs this season and not to mine related events. It is concluded that the levels of uranium and radium in mussels collected downstream of Ranger continue to pose no risk to human or ecological health.
Ecotoxicology research programs in progress include determination of responses for a variety of organisms to pulse exposures for a range of magnesium concentrations and durations. Previous work has confirmed a strong correlation between magnesium and EC in Magela Creek. Use of EC as a surrogate for magnesium has the obvious advantage of being suitable for direct measurement rather than relying on sampling and analysis at a remote laboratory. An eight hectare trial landform was constructed by ERA during late 2008 and early 2009 adjacent to the north-western wall of the tailings storage facility at Ranger mine. SSD is involved in erosion studies on the trial landform to assist in longer-term modelling of the performance of the ultimate landform created during rehabilitation of the site.
The Jabiluka project remains in long-term care and maintenance, and the next stage of the project is a matter for discussion between ERA and the area's traditional owners.
The Nabarlek mine in western Arnhem Land was decommissioned in 1995 and the rehabilitation of this site remains under ongoing assessment. During the year Uranium Equities Limited undertook exploration and rehabilitation activities at Nabarlek. SSD participated in stakeholder inspections and audits of these activities and there were no significant environmental issues identified.
Detailed research outcomes of the Environmental Research Institute of the Supervising Scientist (eriss) are published in journal and conference papers and in the Supervising Scientist and Internal Report series. Examples of this work are described in this annual report.
In May 2006, the Australian Government announced funding to undertake rehabilitation of former uranium mining sites in the South Alligator River Valley in the southern part of Kakadu National Park. This project has now been completed. SSD continues to provide advice and assistance to the Director of National Parks as the post works monitoring progresses.
The Alligator Rivers Region Technical Committee (ARRTC) continues to play a vital role in assessing the science used in making judgements about the protection of the environment from the impacts of uranium mining. Professor David Mulligan and Mr Andrew Johnston, with areas of expertise in plant ecology and rehabilitation and in radiation protection respectively were appointed in early 2010–11. Dr Terry Hillman and Mr Ray Evans resigned from the committee during the year, creating vacancies for independent members with expertise in freshwater ecology and hydrogeology respectively.
During the reporting period, SSD provided advice to the Approvals and Wildlife Division (AWD) of the department on referrals submitted in accordance with the EPBC Act for proposed new and expanding uranium mines and assisted AWD with compliance audits against approval conditions.
Funds were provided in the 2009–10 Federal Budget for a four-year program to progress and implement environmental maintenance activities, conduct appropriate environmental monitoring programs and develop contemporary site rehabilitation strategies at Rum Jungle under a national partnership agreement between the Northern Territory and the Australian Government. The Rum Jungle Technical Working Group (RJTWG) comprises representatives from the NT Department of Resources, NT Department of Natural Resources, Environment, the Arts and Sport, Australian Government Department of Resources, Energy and Tourism, the Northern Land Council and SSD. SSD has contributed to the work of the RJTWG during the reporting period.
I would like to offer my personal thanks to all the staff of the Supervising Scientist Division for their continued enthusiasm and efforts during the year. The commitment and professionalism of the division's staff remain vital factors in the division being able to fulfil its role in environmental protection.