Supervising Scientist, 2012
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 through the conduct of 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 open cut mining of the Ranger 3 deposit cease at the end of 2012, with milling of stockpiled ore expected to continue through until 2020. A proposal to develop a heap leach facility at Ranger was lodged in 2009 but was formally withdrawn by ERA in August 2011.
As the time for completion of mining operations draws closer, the work of the Supervising Scientist includes an increased level of engagement with stakeholders in discussions and research activities associated with rehabilitation and closure of the Ranger site. In particular, during the period ERA commenced a major Closure Pre-feasibility Assessment project. The timelines associated with acquiring the specific technical knowledge for this project has resulted in a re-prioritisation and refocusing of a number of the closure-related research projects being conducted by the Supervising Scientist.
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.
The 2011-12 wet season was close to average and this lower rainfall, combined with increased storage capacity in the tailings storage facility created by raising the dam wall in the 2011 dry season, meant that there was excess capacity available to ensure compliance with authorised maximum operating levels in the process water system. SSD reviewed three-dimensional groundwater flow and solute transport modelling provided as part of ERA’s application to raise the tailings storage facility walls and was satisfied that the increase in the maximum operating level will not produce increases in seepage that would adversely impact on the downstream environment of Kakadu National Park.
As this report is being prepared ERA is in the process of further raising the wall of the tailings storage facility to provide contingency capacity for the 2012/13 wet season. Changes to the maximum operating level of the facility 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. In June 2012 the Minesite Technical Committee agreed to revised wording of the maximum operating level requiring ERA to ensure that at all times there was sufficient freeboard and/or pumping capacity within the tailings storage facility to ensure that the relevant probable maximum precipitation event could be contained within the total available on site storage capacity.
Monitoring programs by ERA, the Northern Territory Department of Resources and SSD continue to indicate that there is no evidence of seepage from the base of the Ranger tailings storage facility impacting on Kakadu National Park. ERA has installed additional monitoring bores around the tailings storage facility at the request of stakeholders, including SSD. Installation and commissioning of monitoring bores in the vicinity of the tailings storage facility continued through 2011-12.
As reported previously, delays in sourcing and commissioning an effective process water treatment facility means that the process water inventory at the mine remains an acute focus. During 2011-12 ERA undertook pilot scale testing of its preferred brine concentrator technology for the treatment of process water. The positive conclusions from this test, including the findings from an ecotoxicological assessment conducted by the SSD (reported in Chapter 3), lead to the approval from ERA’s Board to install this technology on site. It is currently planned that the brine concentrator will be operational in the second half of 2013 with a treatment capacity of around 1.8 GL/y.
In April 2009 ERA submitted a referral for the proposed construction of an exploration decline to provide exploration access to mineralisation in the Ranger 3 deeps area. This proposal was deemed not to be a controlled action therefore not requiring further assessment under the Environment Protection and Biodiversity Conservation Act. The Ranger Minesite Technical Committee considered an application for construction of the decline from ERA. Satisfied that all aspects of this application had been adequately addressed by ERA, SSD advised the Northern Territory Government of its support for the approval of this application on 30 June 2011. Construction of the box cut for the exploration decline commenced on 1 May 2012, with the works expected to be completed in October 2012.
The 2011-12 wet season represents the second season for which continuous monitoring of pH, electrical conductivity (EC) and turbidity in Magela and Gulungul Creeks upstream and downstream of the Ranger mine has been the primary early warning monitoring method employed by the SSD. The 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. The SSD’s surface water monitoring results, together with explanatory notes, were posted weekly on the internet throughout the wet season. Overall, the water qualities measured in Magela and Gulungul Creeks for the 2011-12 wet season were comparable with previous wet seasons, with the results indicating that the aquatic environment in the creek has remained protected from mining activities.
In situ toxicity monitoring using fresh water snails in Magela and Gulungul Creeks upstream and downstream of the mine, with test organisms deployed in containers immersed in the creek water, is a biological-based method that complements the finding from the continuous monitoring. The measured responses of the snails during the 2011-12 wet season were consistent with that observed from past seasons. The results from monitoring of fish and macroinvertebrates conducted in the recessional flow period towards the end of the wet season continue to confirm that the downstream aquatic environment remains protected from the effects of the mining of uranium at Ranger.
Work is continuing on further enhancing interpretation of the results from the Supervising Scientist’s surface water monitoring program. It may be somewhat surprising to note that magnesium (Mg) is the solute most likely to approach or exceed its water quality trigger value in Magela Creek, based on many years of measurements. The aim has been to establish a quantitative relationship between the trigger value for Mg and exposure durations, such that the applicable trigger value can be derived for any given pulse duration and magnitude detected by the continuous water quality monitoring system. The final chapter of this story is presented in this report (Chapter 3), with the development of a functional Mg versus pulse duration relationship. It is anticipated that this fundamental work will pave the way for the development of a new compliance framework to assess conformance against Mg and electrical conductivity trigger values in Magela Ck.
Determination of radionuclide levels in mussels from Mudginberri Billabong has been a continuing element of the SSD assurance monitoring program downstream of Ranger. The results from the most recent sampling and analysis conducted in October 2011 show that the levels of uranium and radium in mussels collected downstream of Ranger continue to pose no risk to human or ecological health.
The Jabiluka project remains in long-term care and maintenance, with the next stage of the project being 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 limited exploration and rehabilitation activities at Nabarlek. SSD participated in stakeholder inspections and audits of these activities and there were no significant environmental issues identified.
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 on aspects relating to ongoing monitoring of the work.
The Alligator Rivers Region Technical Committee (ARRTC) continues to play a vital role in assessing the key knowledge required, and the robustness of the science used, to make judgements about the protection of the environment from the impacts of uranium mining. Professor Paul Boon (aquatic ecology) and Ms Jane Coram (hydrogeology) attended their first two meetings during the period. Their appointments bring back to full strength the range of science disciplines covered by the independent members of the committee.
Detailed outcomes from the Environmental Research Institute of the Supervising Scientist (eriss) research program are published in journal and conference papers and in the Supervising Scientist and Internal Report series. Highlights of this work are described in this annual report.
During the reporting period, SSD provided advice to the Environmental Approvals and Compliance Division of the Department on referrals submitted in accordance with the Environment Protection and Biodiversity Conservation Act for proposed new and expanding uranium mines.
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 Governments. The Rum Jungle Technical Working Group comprises representatives from the Northern Territory Department of Resources, Northern Territory Department of Natural Resources, Environment, the Arts and Sport, Australian Government Department of Resources, Energy and Tourism, the Northern Land Council and SSD. SSD contributed to the work of the Rum Jungle Technical Working Group during the reporting period, including reporting the findings from a major SSD project assessing the radiological status of the footprint of the former Rum Jungle South mine area.
In closing I 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.
Dr David Jones
Acting Supervising Scientist