Department of the Environment

About us | Contact us | Publications

About us header images - leftAbout us header images - centreAbout us header images - right

Publications archive - Annual reports

Disclaimer

Key departmental publications, e.g. annual reports, budget papers and program guidelines are available in our online archive.

Much of the material listed on these archived web pages has been superseded, or served a particular purpose at a particular time. It may contain references to activities or policies that have no current application. Many archived documents may link to web pages that have moved or no longer exist, or may refer to other documents that are no longer available.

Environment Australia Annual Report 1999-2000

Environment Australia, 2000
ISBN 0642450420
ISSN 1441-9335

Annual Report of the Supervising Scientist 1999-2000

Supervising Scientist's overview

The year 1999-2000 has been a year of change for the staff of the Supervising Scientist. It has been a successful year in which the work of the Supervising Scientist and his staff has received national and international recognition. It has also been a year in which the excellent record of environmental protection from the effects of uranium mining in the Alligator Rivers Region has continued.

Following my appointment to the position of Supervising Scientist in June 1999, the Minister for the Environment and Heritage, Senator the Hon Robert Hill, decided that the activities of the Supervising Scientist should, as far as possible, be located in the Northern Territory at Darwin and Jabiru. All positions in the Office of the Supervising Scientist (oss), with the exception of two liaison positions, were transferred from Canberra to Darwin. The Minister also approved the relocation of the Environmental Research Institute of the Supervising Scientist (eriss) from Jabiru to Darwin. By the end of the year, twelve eriss positions had been relocated to temporary accommodation in Darwin and the first stage of the tender process for the construction of new facilities in Darwin was underway. These changes were accompanied by a transfer of Canberra based Science Group programmes not associated with the core responsibilities of the Supervising Scientist to other Divisions of Environment Australia. I would like to congratulate my staff on the implementation of these changes in a productive manner that allowed our programmes to continue and to achieve our planned outcomes. I would also like to thank those former staff of the Supervising Scientist who were displaced in the change process for their outstanding contribution to the success of the organisation over the years.

The development of the uranium mine at Jabiluka has been the focus of public attention throughout the year. In July 1999, the World Heritage Committee considered the report of the Supervising Scientist on the Jabiluka Project, submitted to the Committee in April 1999, and the review of that report by the Independent Scientific Panel (ISP) of ICSU. The Committee also noted the Supervising Scientist's response to the ISP review in June 1999. The Committee decided not to inscribe Kakadu National Park on the List of World Heritage Properties in Danger but requested that the ISP be reconvened to consider the Supervising Scientist's response to its review. This process was incomplete by the end of the year but a highly successful visit by the ISP to Kakadu took place in early July 2000. The ISP will complete its report to the World Heritage Committee in September 2000.

Following the completion of the portal and decline development, Energy Resources of Australia (ERA) has, in line with its commitments to the World Heritage Committee, placed the Jabiluka mine on an environmental management and standby phase. Nevertheless, the oss supervisory and assessment programme for Jabiluka and the eriss research programme continued. These programmes demonstrated that developments to date at Jabiluka have not caused adverse impact on downstream ecosystems or given rise to radiological impact on people living in the region. For example, detailed measurements of suspended sediment loads in streams of the Swift Creek catchment revealed that any changes arising from construction of the facilities were very small and studies on the community structure of small aquatic animals demonstrated that these changes had no biological impact.

The principal issue that attracted public attention to operations at the Ranger mine during the year was the leak of tailings water (or process water) from the tailings water return pipeline in the bunded tailings corridor and the subsequent leak of some of this water to the external environment. This incident occurred during the 1999-2000 wet season, starting in February and continuing until early April, but it was not reported to the authorities until the end of April. The Minister for the Environment and Heritage and the Minister for Industry, Science and Resources requested that I prepare a report on the incident. This report was tabled in the Senate on 27 June 2000.

The principal conclusion of the report was that no adverse impact occurred on the ecosystems of Kakadu National Park as a result of the tailings water leak nor was there any significant radiological impact on members of the public, particularly local Aboriginal people living downstream from the mine. Nevertheless, a number of deficiencies were identified in ERA's management of the site, in its maintenance procedures, and in its communications with stakeholders. Deficiencies were also identified in the inspection programme of the Northern Territory Department of Mines and Energy and in the supervisory programme of the oss.

Seventeen recommendations were made to address these issues; all of these recommendations were accepted by the Commonwealth Government and by ERA. Of particular significance for my staff is the Government's decision that the role of the Supervising Scientist should be amended to include an on-site inspection and audit programme and a routine environmental monitoring programme. This decision was made in recognition of the public perception that such programmes are necessary to enhance the credibility in the eyes of the community of assurances provided by the Supervising Scientist.

Of significance for the future operation of the Ranger mine was the issue of a new Authority under Section 41 of the Atomic Energy Act, 1953. The new Authority was issued on 9 January 2000 and extends the period of mining for 26 years from that date. Incorporated within the Authority are revised Environmental Requirements (ERs) for the Ranger mine which had been developed through a consultative process involving the principal stakeholders. The new ERs are less prescriptive than their predecessors, focussing on environmental objectives and outcomes rather than detailed procedures and practices. For example, water at the mine site will, in future, be managed on the basis of quality rather than on the basis of source. In this way the new ERs place a greater onus on the mining company to demonstrate that it is meeting the Primary Environmental Objectives whilst providing more flexibility in the way in which these objectives can be met.

The principal issue at Nabarlek during 1999-2000 was an assessment of the extent to which revegetation of the site had progressed towards the issuing of a Revegetation Certificate. The operator applied for such a certificate in April 2000 following receipt of a report from an independent assessor whose appointment had been agreed by the site lessee and the Northern Land Council. The Supervising Scientist organised a workshop on this issue in April. It was agreed that the revegetation success demonstrated so far was not adequate for the issuing of a Revegetation Certificate and that further assessment of revegetation success using alternative techniques would be necessary. This will be implemented in 2000-2001.

The water quality in Kadjirrikamarnda Creek on the Nabarlek lease, affected in previous years by the slow ingress of water from a land irrigation site, continues to improve. Despite elevated concentrations of some chemical constituents, research on the community structure of fishes in the creek has demonstrated that biological impact has been very small. Research reported this year has provided some insight into the absence of adverse effects. It has shown that the concentrations of aluminium observed in the creek, in excess of Australian and New Zealand Environment and Conservation Council (ANZECC) water quality guidelines, do not cause adverse effects on biota because the presence of silica in the water ameliorates the toxicity of aluminium.

The regular inspection programme carried out by the Supervising Scientist at old mining and milling sites in the South Alligator River valley revealed, in August 1999, that tailings dispersed from the decommissioned South Alligator Mill had become exposed at the land surface adjacent to the Gunlom Road. Parks Australia North (PAN) was notified and a detailed radiation survey of the site was carried out by staff of the Supervising Scientist. A full report on the survey was submitted to PAN in February 2000. The report concluded that the radiological risks associated with the tailings are low. In particular, radiation exposure levels for tourists and PAN staff driving on the road are very small. Nevertheless, given the risk of dispersal of the tailings into the South Alligator River, the report recommended that rehabilitation works be carried out. The Director of National Parks considers this to be an issue requiring urgent attention and work will be undertaken to minimise dispersion of tailings during the 2000-2001 Wet season and to begin rehabilitation of the site.

The National Centre for Tropical Wetland Research (nctwr), an initiative of the Minister for the Environment and Heritage, was formally established through the signing of the Heads of Agreement on 16 December 1999. The Centre is a collaborative venture between eriss and three university partners; James Cook University, Northern Territory University and the University of Western Australia. The Centre conducts research and training to provide information and expertise that will assist managers and users of tropical wetlands in the sustainable use these valuable habitats.

The Hon Bob Collins was appointed Chair of the Board of the nctwr for a period of two years and Dr Max Finlayson, head of the eriss Wetland Ecology and Conservation Branch, was appointed Director of the Centre. We are currently establishing an Advisory Committee to provide advice on the issues considered of importance to stakeholders, to assist in the determination of research and training priorities and to provide ongoing review of the programme of the centre. The Advisory Committee is expected to meet in September 2000.

eriss contributions to the work of the Centre during 1999-2000 included: an assessment of the impact of paragrass, an exotic pasture grass, on the faunal biodiversity and ecosystem processes in the wetlands of Kakadu National Park; a review of the effects and appropriate management techniques for Mimosa pigra in Australia and south-east Asia; a review of environmental management of eleven major mining operations in Northern Australia, Papua New Guinea and Irian Jaya; and, in cooperation with Wetlands International Asia-Pacific, development of an Asia-wide wetland inventory based on protocols previously prepared by eriss under the Environment Australia Wetland R&D Programme. An assessment of the risks for the biota of Kakadu National Park arising from the expected arrival of cane toads is almost complete.

A milestone was reached in July 1999 with the release for public comment of the draft revised version of the Australian and New Zealand Guidelines for Fresh and Marine Water Quality. eriss has been managing the revision of the guidelines on behalf of ANZECC. Changes arising from the public comment stage were incorporated and the guidelines were forwarded to the Standing Committee for Environment Protection in May 2000. It is expected that the final Guidelines will be published in October 2000.

During 1999-2000, we built on our experience over the past two years in Aboriginal communications by establishing an Aboriginal Communications Unit, located at eriss. The unit was established to develop and implement communications programmes to ensure that all stakeholders, especially the local Aboriginal communities and associations, are kept informed on the programmes of the Supervising Scientist and, where possible, participate in those programmes. Substantial progress was made during the year. The traditional owners of the Ranger and Jabiluka lease areas, the Mirrar people, took part in biological monitoring programmes on their land and Murrumburr landowners collaborated with eriss staff at control sites on their land. Aboriginal people from Arnhem Land and adjacent areas worked with eriss staff and Mirrar people on billabongs in Arnhem Land. We all gained valuable experience from working in this cross-cultural environment. We also produced a bi-monthly newsletter, written in plain english, summarising the work of eriss and oss and distributed the newsletter to all Aboriginal stakeholder groups. Overall, the feedback we have received is positive; we appear to be bridging the gap between the Supervising Scientist and local people of the region. This complements the successful cooperation that has been established by staff of the Wetland Ecology and Conservation Branch with local community groups elsewhere.

Dr Arthur Johnston
Supervising Scientist


1. Introduction

The organisation of the Supervising Scientist consists of the Environmental Research Institute of the Supervising Scientist (eriss) and the Office of the Supervising Scientist (oss).To assist the Supervising Scientist in performing his role successfully, the oss carries out audit and policy functions, whilst eriss conducts vital research work into the impact of uranium mining on the environment and people of the Alligator Rivers Region. During the year the Supervising Scientist continued to ensure that the environment of the Alligator Rivers Region remained protected to a very high standard from the potential impacts of uranium mining. Well established processes are in place to assess the environmental management performance of mining companies in the region, including Environmental Performance Reviews and evaluation of monitoring data collected by the companies and the Northern Territory Supervising Authority. The Supervising Scientist provided high level technical advice to enhance environmental protection in the region through the Minesite Technical Committees and direct interaction with stakeholders.

The Supervising Scientist oversees the implementation of legislation relevant to uranium mining activities in the Alligator Rivers Region. The primary mechanism by which the Supervising Scientist meets this responsibility is through assessing applications made by mining companies for approvals under Northern Territory legislation. In providing comments on applications, the Supervising Scientist considers relevant Commonwealth legal instruments such as the Commonwealth's Environmental Requirements applicable to the mine site. New Environmental Requirements for the Ranger uranium mine were introduced under Commonwealth legislation in January 2000. The new Environmental Requirements improve upon the original ones which were drafted over 20 years ago, and will enhance environmental protection at Ranger.

eriss conducts research under two programmes: ‘Environmental Impact of Mining' and ‘Wetland Ecology and Conservation'. The Environmental Impact of Mining programme provides advice to the Supervising Scientist and other stakeholders on standards, practices and procedures to protect the environment of the Alligator Rivers Region from the effects of mining. In 1999-2000 the programme included some new areas of project work, particularly in relation to possible mine development at Jabiluka. The Wetlands Ecology and Conservation programme provides advice to stakeholders on the ecology and conservation of tropical wetlands. The programme takes into account international activities to further bridge the gap between wetland research and management practice by consulting with wetland owners, users and managers. eriss also carries out other research as required by the Australian government, such as the review of the Australian and New Zealand Guidelines for Fresh and Marine Water Quality and involvement in national research projects.

Keeping stakeholders, particularly Aboriginal communities, well informed about the status of environmental protection and the essential activities of the Supervising Scientist is achieved through the Alligator Rivers Region Advisory Committee and other forms of information dissemination including publications, newsletters and direct interaction with Aboriginal people.

The Supervising Scientist also provides advice to the Minister for the Environment and Heritage, the Department and the Australian community on uranium mining and nuclear issues and contributes to the development of national and international environmental policy on the nuclear fuel cycle.

The philosophy of the organisation is one that promotes continuous improvement in performance. As such the organisation's processes are open to review and enhancement.

1.1 Role of the Supervising Scientist

The primary role of the Supervising Scientist is to ensure, through research, assessment and the provision of technical advice, that the environment of the Alligator Rivers Region is protected from the effects of uranium mining to the very high standard required by the Commonwealth Government and the Australian people.

1.2 Functions of the Supervising Scientist

In summary, the functions of the Supervising Scientist, as specified in the Environment Protection (Alligator Rivers Region) Act, 1978, are to:

1.3 Performance outcomes

The Supervising Scientist developed and implemented strategies during 1999-2000 to ensure that the functions promulgated in the Environment Protection (Alligator Rivers Region) Act 1978 were successfully undertaken. Performance outcomes for each of those strategies are summarised below.

Apply mechanisms for environmental protection at uranium mines in the Alligator Rivers Region in a manner which meets the expectations of key stakeholders

The Supervising Scientist conducted Environmental Performance Reviews (EPRs) of the Ranger, Nabarlek and Jabiluka sites jointly with the Northern Territory Department of Mines and Energy. Ranger and Jabiluka are subject to two Environmental Performance Reviews per year whilst Nabarlek is subject to one plus a site inspection. Every Application for an approval under Northern Territory legislation made by the operators of Ranger, Jabiluka and Nabarlek was scrutinised by the Office of the Supervising Scientist (oss), and comments provided to the Northern Territory Department of Mines and Energy. In many cases, such applications were considered by the applicable Minesite Technical Committee (MTC) which includes representation of the mining company, Supervising Scientist, Northern Territory Department of Mines and Energy and Northern Land Council. All approvals issued by the Northern Territory Department of Mines and Energy adequately addressed the views of the oss. The MTCs also considered other issues of significance in relation to environmental protection, particularly water management at Ranger and Jabiluka, progress of rehabilitation at Nabarlek, and the implementation of the revised Commonwealth Environmental Requirements for the Ranger mine. The outcomes of the processes described above were discussed by key stakeholders at meetings of the Alligator Rivers Region Advisory Committee.

The Supervising Scientist completed an investigation into a tailings water leak which occurred on the Ranger site during the 1999-00 Wet season. The report, which was tabled in the Commonwealth Senate on 27 June 2000, made seventeen recommendations designed to improve environmental management at Ranger. The Commonwealth accepted each of these recommendations.

The value and effectiveness of the oss inspection regime for sites associated with historic uranium mining practices in the South Alligator River Valley was demonstrated when the August 1999 inspection revealed a deterioration in the stability of a site containing tailings. Appropriate follow-up investigations were completed with the assistance of eriss and recommendations made to rehabilitate the site as a matter of priority. Planning is underway in response to those recommendations.

The 1999-00 financial year saw the relocation of elements of the oss that were previously in Canberra to Darwin, intensifying the focus of the supervisory functions of the Supervising Scientist and facilitating a closer working relationship between oss and eriss. The use by oss of eriss expertise in completing its supervisory and assessment activities has increased significantly. The investigation of the tailings water leak at Ranger was a clear demonstration of the benefits of this closer liaison.

The mechanisms applied by the Supervising Scientist, in consultation with key stakeholders, succeeded in ensuring that there were no significant environmental impacts on Kakadu National Park as a result of operations at Ranger or the development of Jabiluka.

Conduct a collaborative programme of research on the impact of mining with other research providers which is relevant to environmental protection in the Alligator Rivers Region

Ecosystem Protection: To further develop a baseline for the Jabiluka mine development, investigations of macroinvertebrate and fish communities of Jabiluka streams were conducted. These data will be added to similar jointly collected data from 1998-99 and contribute to an accruing baseline that will be used to detect and assess any impact arising from mining. The macroinvertebrate work was carried out collaboratively with consultants engaged by Energy Resources of Australia (ERA). Biological monitoring continued in the vicinity of the Ranger minesite. These data add to the existing baseline that has been accumulated for the site and provide a broader perspective of the aquatic biodiversity in catchments in nearby locations within Kakadu National Park. A third year of monitoring data for chemical indicators was acquired from the Jabiluka lease area and a preliminary assessment undertaken and further sampling recommended. These programmes continue to demonstrate the absence of adverse biological impacts downstream of the Ranger and Jabiluka projects.

Erosion and Hydrology: Stream monitoring continued, in collaboration with external agencies, to obtain information on the hydrology and sediment movement in the catchment containing the Jabiluka minesite. This information will be used to develop models for proactive management of any mining related impacts and will assist with analysis of stream macro-invertebrate data collected by the Ecosystem Protection programme. A Geographic Information System that incorporates landform evolution modelling is being developed as one component of this work. Two years of data collected to date were used to estimate background stream sediment fluxes and conduct an impact assessment of erosion from proposed waste rock dumps on stream water quality. This assessment was presented to the United Nations Educational, Scientific and Cultural Organisation (UNESCO) Independent Scientific Panel (ISP). Following a review of rehabilitation progress at Nabarlek and a subsequent workshop, an assessment of erosion at the Nabarlek mine site was initiated and will assist with the development of a model of site stability to assess future impacts on downstream water quality. Projects assessing the effect of vegetation and ecosystem and soil development on mine site landform evolution are nearing completion. These effects can now be quantified, which is a significant advance in landform evolution modelling.

Environmental Radioactivity: Implementation of a regional network of radon/meteorological stations was completed. This network records data half-hourly and is designed to enable determination of the contribution of the Ranger and, eventually, Jabiluka mines to radon levels in the region. Measurement of the geographic variability of radon emanation rates over the site of the former Nabarlek uranium mine was undertaken collaboratively with the University of Adelaide. The application of airborne radiometrics to derive sediment discharge rates from the Nabarlek mine site also commenced with collaboration from the Rehabilitation of Minesites programme and Northern Territory University. These two projects form an important part of an overall programme to establish the radiological conditions of the site post-mining and to field-validate eriss models of radon and sediment transport.

Conduct a research programme for wetlands ecology and conservation

Wetland ecology and inventory: The impact of exotic weeds and herbicide control measures on the ecology of tropical wetlands was investigated in a collaborative project and the results publicly presented to stakeholders. A review of environmental management of some major mining operations in tropical Oceania and their risk for downstream wetlands was carried out to assist the World Wildlife Fund Australia in developing collaborative environmental programmes with local communities and mining companies. Work on remote sensing methods of mapping of wetland features using radar imagery as a basis for monitoring change in wetlands continued and will be extended. An inventory of wetlands in the Daly River Basin, Northern Territory, commenced and will provide the basis for a risk assessment to these habitats from existing use of groundwater and forecast future use. These tasks provided an extended base for developing a protocol for an Asian-wide wetland inventory and for providing advice to international conventions, governmental agencies and local community groups.

The National Centre for Tropical Wetland Research (nctwr) - a collaborative venture between eriss, the Northern Territory University, James Cook University and University of Western Australia - was formally established with the appointment of a Board and a Chairperson. Joint applications for research funding have been submitted through nctwr. Training of wetland managers continued with two courses held for wetland scientists and managers from Asian countries.

Risk Identification and Assessment: An assessment of the aquatic toxicity of aluminium and the potential ameliorating effect of silica was undertaken to help assess aluminium toxicity in relation to acid-mine drainage, natural fish kills and for rehabilitation of the Nabarlek uranium mine. The toxicity of uranium to a native freshwater cladoceran was assessed and the results used for deriving a revised site-specific trigger value for uranium in the Magela Creek catchment.

The ecology and control of the major wetland weed Mimosa pigra were investigated and used to assist wetland managers in Viet Nam develop a mimosa management plan. Along with a completed risk assessment of the herbicide Tebuthiuron, the information on mimosa is being used to undertake a management-oriented wetland risk assessment of the weed in northern Australia. A predictive risk assessment of the impacts of cane toads on Kakadu National Park commenced and will form an integral component of Parks Australia North's management strategy for cane toads in Kakadu. The results of an assessment of the vulnerability of two major wetlands in the Asia-Pacific region to climate change and sea level rise, undertaken in 1998-99, were published and distributed to a number of international agencies.

Develop and implement a programme to ensure a high level of communication with stakeholders especially Aboriginal people in the region

The Supervising Scientist formed the Aboriginal Communications Unit during the second half of the reporting year. The unit is responsible for developing and implementing communications programmes to ensure that all stakeholders especially the local Aboriginal communities and associations, are kept informed about work eriss and oss undertake in the region. It is also responsible for establishing an Aboriginal employment and training programme within eriss including implementation of an employment programme of traditional owners to assist with the collection and identification of fish and the recording of data in billabongs on and surrounding the ERA mining lease. Traditional owners of Kakadu National Park were involved in eriss research into the impact of cane toads through a survey that was conducted at Aboriginal communities in the Katherine region. Bi-monthly newsletters were produced to help keep the Aboriginal associations informed of the research work underway and that planned for the future. Information sessions were conducted for Aboriginal groups and associations on topical issues. An internal communications protocol to ensure that the methods and approach used to communicate with Aboriginal people and associations are appropriate and consistent was implemented and is part of the induction programme for new staff. Cross cultural training was provided for all staff.

Contribute to and support the achievement of the corporate objectives of Environment Australia

The Supervising Scientist Group was managed in accordance with Environment Australia corporate requirements and its work programmes were consistent with the Environment Australia vision and values. The Supervising Scientist worked with other areas of the Department to achieve corporate objectives.

In particular, the Supervising Scientist directed an extensive programme of work to assist Environment Australia to meet the needs of the World Heritage Committee in relation to scientific issues associated with the development of Jabiluka. A series of scientific investigations, information collation and logistical exercises were undertaken in preparation for the visit of the Independent Scientific Panel (ISP) convened by the International Council of Science Unions (ICSU) at the request of the World Heritage Committee. The ISP visited Kakadu National Park in the week of 3 to 7 July 2000. The role of the ISP is to review the response of the Supervising Scientist (June 1999) to the first report of the ISP (May 1999) and report back to the World Heritage Committee on scientific issues associated with the development of the Jabiluka project.

The Supervising Scientist Group actively participated in Environment Australia human resource, financial and information management initiatives including the implementation of the Investors in People programme, Output Pricing Review and redevelopment of the Environment Australia web site.

Report on performance of the Supervising Scientist Group in relation to outputs, contribution to outcomes, and performance targets set out in the Portfolio Budget Statement/Portfolio Additional Estimates Statement is provided in the Annual Report of the Department of the Environment and Heritage.

1.4 The Alligator Rivers Region and its uranium deposits

The Alligator Rivers Region is centred about 220 km east of Darwin in the Northern Territory of Australia. Comprising an area of about 28000 square kilometres, it includes the catchments of the West, South and East Alligator Rivers, extending into Arnhem Land and south into the Gimbat and Goodparla pastoral leases. The World Heritage listed Kakadu National Park is wholly enclosed within the Alligator Rivers Region.

There are four mineral leases within the Alligator Rivers Region that pre-date the proclamation of Kakadu National Park: Ranger, Jabiluka, Koongarra and Nabarlek (see fig 1.1). Ranger is currently the only operational uranium mine in the Alligator Rivers Region. Jabiluka is in the early development stage and mining of the orebody has not commenced. Koongarra is a significant uranium deposit but permission to develop a mine has not yet been sought. Mining at Nabarlek ceased in the late 1980s. The mine was decommissioned in 1995-96 and the performance of the rehabilitation and revegetation programme continues to be monitored prior to final close-out. There are also a number of former uranium mines in the South Alligator River Valley that date back to mining and milling activities in the 1950s and 1960s. These mines were subject to a hazard reduction programme in the early 1990s and the need for further rehabilitation is the subject of negotiations between Parks Australia North and the Jawoyn traditional owners.

Energy Resources of Australia (ERA) operates the Ranger mine, 8 km east of the township of Jabiru. The mine lies within the 78 sq km Ranger Project Area and is adjacent to Magela Creek, a tributary of the East Alligator River. The Ranger Project Area is surrounded by, but does not form part of, Kakadu National Park or the area inscribed on the World Heritage List. Ranger is an open cut mining operation and mining and commercial production of uranium concentrate have been under way since 1981. Orebody no.1 was exhausted in December 1994 and excavation of ore from Orebody no.3 began in May 1997.

Figure 1.1 The Alligator Rivers Region

Map of the region

 

Jabiluka is 20 km north of Ranger and, unlike the other deposits, lies beneath a cover of cliff-forming sandstone. It is in the East Alligator River catchment, adjacent to Swift Creek, which drains north to the Magela wetland. It is also in a mine lease area not included in, but surrounded by, Kakadu National Park and the World Heritage Area. The Commonwealth Government completed its assessment of ERA's Environmental Impact Statement, which provided for milling of Jabiluka ore at Ranger, on 22 August 1997. Since Traditional Owners have not agreed to the milling of Jabiluka ore at Ranger, ERA subsequently submitted a Public Environment Report (PER) based on a proposal to construct a new mill on the Jabiluka lease. The PER was accepted subject to a number of conditions. Construction of the portal, decline and ancillary facilities, elements common to both proposals, commenced on 15 June 1998 after the required approvals from the Commonwealth and Northern Territory Governments were granted. Stage 1 of the main decline was completed in June 1999, including a ventilation raise and associated surface facilities comprising workshops, offices and water management and erosion control structures. Development of Jabiluka ceased in September 1999 and the site has been in an environmental management and standby phase since then.

The Koongarra deposit is about 25 km south-west of Ranger, in the South Alligator River catchment. An Act providing for change of boundaries of the project (and thus the area of excision from Kakadu National Park) was passed in 1981 but was never proclaimed. The Koongarra deposit is owned by Cogema Ltd.


2. Environmental assessments of uranium mines in the Alligator Rivers Region

2.1 Ranger Mine

2.1.1 Tailings water leak

The incident

During the 1999-2000 Wet season, a leak occurred in the Tailings Water Return Pipeline at Ranger uranium mine. ERA reported the leak to the Office of the Supervising Scientist, the Northern Territory Department of Mines and Energy, the Northern Land Council and the Department of Industry Science and Resources on 28 April 2000. It was reported that approximately 2000 cubic metres of tailings water had leaked from the Tailings Water Return Pipeline located in the Tailings Dam Corridor between late December 1999 and 5 April 2000.

Further information provided by ERA indicated that some of the process water had entered the Very Low Grade Corridor Road Culvert (VLGCRC) built under the Tailings Dam Corridor and had thus escaped from the Tailings Dam Corridor which is designed to act as a secondary containment system. The VLGCRC flows into the constructed Corridor Creek Wetland filter, then into Corridor Creek, Georgetown Creek and finally Magela Creek. Figure 2.1 shows the site of the leak and the potential surface water pathway between the source of the tailings water leak at the Ranger mine and the entry point to Kakadu National Park.

Supervising Scientist investigation

The Minister for the Environment and Heritage and the Minister for Industry, Science and Resources requested that the Supervising Scientist investigate the incident and provide a report. The report produced was Supervising Scientist Report 153 Investigation of tailings water leak at the Ranger uranium mine, (Supervising Scientist, Environment Australia June 2000) and is available in hard copy and at www.environment.gov.au/ssg/ranger-leak. The investigation established that the volume of water that leaked from the Tailings Water Return Pipeline was about 2000 cubic metres. Of this, about 85 cubic metres entered the VLGCRC that flows into the Corridor Creek wetlands. The remaining water was collected in the Tailings Corridor Sump and returned to the water management system.

The Supervising Scientist conducted assessments of the possible radiological and ecological impact arising from the leak using both actual monitoring data and modelling.

Chemical monitoring data from the gauging stations on the Magela Creek upstream of the point at which the Creek enters Kakadu National Park and in Georgetown Billabong just downstream from the mine showed that no change occurred during 1999-2000 in the concentrations of principal constituents of concern compared to similar observations in previous years. The concentrations of all constituents were within the natural range observed previously. Similarly, biological monitoring at the gauging station and at a point upstream from the mine showed no difference in the response of animals exposed to water at the downstream and the upstream sites.

As chemical and biological monitoring failed to detect any impacts caused by the leak, a modelling approach was also employed. An assessment of the ecological impact of the leak was carried out by calculating the likely increase in concentrations of contaminants in Magela Creek caused by the leak upstream of the point where it enters Kakadu National Park.

The modelling supported the chemical and biological monitoring results. Even if it is assumed that all 2000 cubic metres of tailings water escaped the Tailings Dam Corridor, and the attenuation of contaminants such as uranium, manganese and radium in wetland systems on the Ranger Project Area is ignored, the calculated increase in the concentration of all constituents is small compared to the naturally observed concentrations at this point.

Figure 2.1 Site of the leak and the potential surface water pathway between the source of the tailings water leak at the Ranger mine and the entry point to Kakadu National Park

map of leak site

 

The radiological impact was assessed using the information derived in this study on the quantity of water released and the concentrations of radionuclides in tailings water together with the results of the past research programme of the Supervising Scientist on the dispersion of radionuclides in the surface water system and the uptake of radionuclides in animals and plants. The maximum conceivable dose received by members of the public as a result of the leak is lower than the public dose limit by more than a factor of 1000.

Findings

The overall conclusion reached from these assessments was that the leak of tailings water had a negligible impact on people and the environment.

The cause of the leak was determined to be corrosion and the subsequent failure of three bolts that secured the jointing of two flanges in the Tailings Water Return Pipeline. The principal cause of corrosion was burial of this section of pipe by silt. It is evident that the section of pipe may have been buried by silt for eighteen months. The silt would have been moist for up to six months of the year creating conditions conducive to corrosion. A contributing factor to the failure may have been the use of undersized bolts in the joint. Other contributing factors were the reduction in the standard of maintenance in the pipeline corridor carried out by ERA, the failure of Northern Territory Department of Mines and Energy's mine inspection programme to detect the gradual burial of the pipeline and, to a lesser extent, the failure of the oss to observe and require remediation of the buried section. It was also found that the leaked water reached the external environment as a result of the failure of the bunded corridor system. The cause of this failure was that the engineered structure between the roadway and a culvert that drains water from the nearby waste rock dump was not impermeable.

The statutory monitoring system was found to be deficient in two ways. Firstly, it has not been designed to include monitoring locations within secondary containment systems that would indicate the failure of primary containment systems. No statutory reporting of the quality of water in the tailings corridor sump is required under the Northern Territory Ranger General Authorisation. Secondly, there is no systematic monitoring programme designed to check the integrity of the secondary containment systems. If these monitoring systems had been in place, the leak could well have been identified and repaired much more quickly, and none of the tailings water would have escaped the Tailings Dam Corridor.

It was concluded that Commonwealth Environmental Requirement 3.4, which requires that process water be contained within a closed system, and Commonwealth Environmental Requirement 16.1, which requires ERA to report breaches or incidents which could be of concern to Aboriginal people or the broader public, were breached. From discussions with senior ERA staff, the Supervising Scientist was satisfied that there was no deliberate attempt to deceive the authorities.

Recommendations

Seventeen recommendations (see Appendix A) were made to address the deficiencies identified through the investigation, including reviewing and amending the Working Arrangements between the Commonwealth and the Northern Territory Governments.

Significantly there were recommendations to alter the role of the Supervising Scientist. It was recommended that the Supervising Scientist ensure that there is an adequate and independent on-site audit process concentrating on issues that have a potential to cause off-site impact, and that the Supervising Scientist should develop and implement a routine environmental monitoring programme with a focus on providing advice on the extent of protection of the people and ecosystems of Kakadu National Park.

Recommendations relating to the company included: that maintenance procedures in the Tailings Dam Corridor be improved; the efficacy of secondary containment of the Tailings Dam Corridor be reviewed; communication between ERA and its stakeholders be improved; and that environment protection staff at Ranger be upgraded. ERA accepted all recommendations and has commenced their implementation.

Recommendations directly involving the Northern Territory Supervising Authority were that the statutory monitoring programme should be extended to enhance its capacity to provide early warning of unplanned releases of contaminants, and that its site inspection regime should be reviewed and improved.

A recommendation was made to the Commonwealth Minister for Industry, Science and Resources to consider what action should be taken in response to the established breach of the Environmental Requirements taking into account the findings of the report.

Government Response

On 27 June 2000, the Minister for Industry, Science and Resources tabled the Supervising Scientist report on the incident in Parliament. The Commonwealth Government accepted the seventeen recommendations made in the report. The Minister for Industry, Science and Resources decided that the mining company, ERA, would not be prosecuted in this instance. The Government also stipulated that the Supervising Scientist should increase its on-site inspection role. The report was made available to the World Heritage Bureau at its June 2000 meeting in Paris.

2.1.2 Developments

A major development at Ranger during 1999-00 was the introduction of the new Commonwealth Environmental Requirements. The Ranger General Authorisation issued by the Northern Territory Department of Mines and Energy was amended extensively to account for the new Environmental Requirements. Section 6.2.3 contains more information on the revised Ranger Environmental Requirements.

Operational developments at Ranger included:

Revegetation of the capped low-grade ore stockpiles to the east of the tailings dam continued. Ground water intercepted prior to entering pit no. 3 was pumped onto the capped very low grade waste rock stockpiles and allowed to flow in an open drain to the constructed Corridor Creek Wetlands as part of a trial to determine the efficacy of these wetlands in removing contaminants from the water column. The trial was undertaken to provide data in relation to a proposal to discharge water from Retention Pond 2 in a similar manner. ERA intends to make an application to discharge Retention Pond 2 water to the constructed Corridor Creek Wetlands during 2000-2001.

2.1.3 Assessment methodology

The adequacy of environmental protection and the level of environmental impact arising from uranium mining at the Ranger site were measured through a number of mechanisms, mainly:

2.1.4 Environmental Performance Reviews

The environmental management performance of the mining company is assessed regularly through the Environmental Performance Review (EPR) process. This takes the form of bi-annual environmental audits, conducted jointly with the Northern Territory Department of Mines and Energy. Each review involves: development of a questionnaire seeking information on issues outstanding from the previous review; general environmental management performance; and special focus issues; interviews with senior mining company staff; an assessment of the company's responses to the questionnaire, and; a site visit to examine new developmental works and sites which may have been identified as problematic. The review team includes certified environmental auditors from oss and the Northern Territory Department of Mines and Energy. An Environmental Performance Review (no.12) was conducted for the Ranger mine on 9 December 2000 and the next review (no.13) is planned for 22 July 2000 as a consequence of some statutory reporting dates for environmental monitoring data and the timing of the next meeting of the Alligator Rivers Region Advisory Committee.

In December 1999 the Environmental Performance Review concentrated on matters arising from the previous review (no.11), general environmental management performance and the focus topics of water management and groundwater protection. In summary, the review team found that the environmental and water management systems at Ranger had been operating satisfactorily and that that there had been no adverse environmental impact away from the site during the period under review. It was noted that efforts continued to address the issue of reducing the inventory of excess process water on site. Also, tailings management options were under investigation, particularly the use of central deposition in pit no.1 and the potential to introduce thickened tailings technology to Ranger.

2.1.5 Water management

The introduction of the new Environmental Requirements in January 2000 has meant that the Restricted Release Zone concept is no longer applicable to minesite waters at Ranger. Instead water is to be managed on the basis of quality. Waters formerly in the Restricted Release Zone are still impounded and mechanisms and processes for release are formulated on the basis of water quality rather than origin. This will enable good quality waters to be managed in such a way as to ensure they will not be degraded through mixing with poorer quality water, as was sometimes the case under the previous Restricted Release Zone management programme.

Process water system

The water which is in direct contact with the ore during mineralogical processing is maintained in a closed circuit system. This comprises the mill, the tailings dam and the tailings repository in Pit 1, Retention Pond 3 and the pipelines joining these locations. Process waters may never be released from the site except by evaporation or after treatment in a manner and to a quality approved by the Supervising Scientist.

The succession of above average Wet seasons in recent years has resulted in the accumulation of an excess of water in the process circuit. At the end of the reporting period it was estimated that, assuming average Wet seasons and normal evaporation conditions, it would take approximately seven years for the system to return to balance. As this is an unacceptably long time, ERA has been investigating options for water disposal. A multiple effect evaporator has been tried in a number of configurations; however, none has proved satisfactory to date. Other enhanced evaporation options using irrigation of Pit 1 walls and a snow making machine which produces a very fine spray have also been examined. In addition to enhanced evaporation, ERA has investigated reverse osmosis as a technology which could be used to treat water to a standard suitable for release. The final solution is likely to be a combination of all or some of these components.

Restricted Release Zone

The water management system operated within a Restricted Release Zone until the introduction of the new Environmental Requirements in January 2000. Since that time water has been managed on the basis of its quality and not origin. In order to distinguish between the classes of water on site, waters which were previously part of the Restricted Release Zone have been given the preliminary title of Actively Managed Water. The quality of Actively Managed Water is such that it must be contained on site unless it has been treated in some manner, such as wetland filtration. No water from the former Restricted Release Zone was discharged from the site during the reporting period.

In the 1999 dry season, 327 ML (mega litres) of Retention Pond 2 water was treated by passing it through the Retention Pond 1 wetland filter before the water was irrigated in approved areas (total ~46 ha) to the west of Retention Pond 1. Relatively small volumes (71 ML) were also applied within the Magela Land Application Area at the end of the 1999 Dry season to assist with the balancing of the water inventory on site. Retention Pond 2 water was also treated through the Djalkmara wetland filter in the 1999 dry season with 171 ML being passed through the system prior to being applied to the 38 ha of irrigation area north of the access road.

The process of developing a release process and release criteria for Actively Managed Water in accord with the provisions of the new Environmental Requirements is an on-going item in meetings of the Ranger Minesite Technical Committee, and is due to be completed by December 2000.

Waters outside the Restricted Release Zone

Waters which were previously designated as non-Restricted Release Zone waters have been given the preliminary title of Passively Managed Water. Generally, Passively Managed Water may be released from the site subject to the implementation of sediment control measures. Throughout the 1999-2000 wet season Passively Managed Water was released from the Ranger site by three pathways:

The dewatering bore for pit no.1, MBL, also discharged about 285 ML over the reporting period. During the Dry season this water is used to maintain vegetation in the Corridor Creek wetland system; in the Wet season the water discharges via land application through the Corridor Creek system and Georgetown Billabong to Magela Creek.

Since Retention Pond 4 was decommissioned before the onset of the 1999-2000 Wet season, there was no release of water from that source. All references to Retention Pond 4 have now been withdrawn from the water management system and the General Authorisation.

There was a recurrence of abnormally high uranium (U) concentrations in Retention Pond 1 relative to background levels. An increase in U levels occurred suddenly in mid-January 2000 reaching a maximum of 40 g/L (micro grams per litre) in early February and falling in March 2000 to half that value. The uranium concentration at the end of the reporting period was 12 g/L, similar to that measured in early January 2000. Water from Retention Pond 1 spills into Coonjimba Creek and thence into the Magela system. Importantly, however, this episode has had no effect on water quality in the Magela system as monitored at the exit point from the Ranger lease (GS 821009).

The reason for the sudden increase in the concentration of uranium is unclear but follows a similar pattern to that observed during the 1998-1999 Wet season when uranium concentrations increased from background levels in late January 1999 to reach a maximum of 70 g/L in mid February 1999. At that time, the U entering Retention Pond 1 was sourced to waste rock. ERA responded to the problem by making changes to waste rock dumping methods and runoff retention and management. It may be that the latter requires further refinement but it is possible that the most recent increase in uranium concentrations in Retention Pond 1 may be linked to its release from sediment contained in the pond. Research is currently being conducted by ERA to determine the cause and, in support, research to elucidate why this episode occurred is to be undertaken by eriss who will examine the potential mobilisation of uranium from Retention Pond 1 sediment.

2.1.6 Water quality in Magela Creek

The primary mechanism by which operations at Ranger may impact upon the environment of Kakadu National Park or the health of Aboriginal people is via the transport of mine-derived contaminants in Magela Creek. These contaminants have the potential to adversely affect aquatic ecosystems. The radioactive contaminants may also deliver a radiation dose to Aboriginal people living downstream of the Ranger Mine who drink water or eat foods taken from the Magela system. Consequently, water quality in Magela Creek serves as a very important indicator of the extent to which the environment is protected from the potential impacts of mining at Ranger.

The Ranger General Authorisation issued by the Northern Territory Government sets water quality requirements that the company must meet downstream of Ranger. The company must ensure that the concentration of downstream contaminants does not exceed the concentration of upstream contaminants of Ranger by more than the Maximum Allowable Addition. Maximum Allowable Additions are set for uranium, heavy metals (copper, lead, zinc and manganese), calcium, magnesium, sulphate, nitrate, phosphate and turbidity, and are used in conjunction with additional annual load limits which refer principally to radionuclides.

Table 2.1 summarises the key water quality parameters upstream and downstream of Ranger for the 1999-2000 Wet season which are described as concentration medians and ranges. The median is preferred to the mean because the former provides a better description of the central point when data form part of a skewed distribution. Table 2.1 shows that there are minor increases in the concentration of most parameters in Magela Creek attributable to mining operations however these increases are well within the Maximum Allowable Additions and well below concentrations that may cause adverse environmental impacts.

Table 2.1: Summary of water quality parameters upstream and downstream
of the Ranger Uranium Mine over the 1999-2000 Wet season
- Median Range
Parameter Units Upstream Downstream Upstream Downstream
pH Units 6 6.10 3.97 - 6.75 4.8 - 6.8
EC (S/cm) 9.76 11.14 5.17 - 46.8 4.54 - 35.7
Turbidity (NTU) 3 3.62 1 - 21.1 1.5 - 9.61
Sulphate  (mg/L) 0.25 0.85 0.15 - 3.54 0.12 - 6.06
Nitrate  (mg/L) <0.02 <0.02 <0.02 - 0.20 <0.02 - 0.04
Magnesium  (mg/L) 0.49 0.68 0.29 - 0.93 0.30 - 1.99
Copper  (g/L) <0.2 <0.2 <0.2 - 0.33 <0.2 - 0.34
Manganese  (g/L) 4.29 4.44 <1 - 41.48 <1 - 32.16
Lead  (g/L) <0.1 <0.1 <0.1 - 0.45 <0.1 - 0.13
Uranium  (g/L) <0.1 <0.1 <0.1 - 0.22 <0.1 - 1.04
Zinc  (g/L) <2 <2 <2 - 13.46 <2 - 8.29
  Denotes dissolved constituent

The introduction of the new Commonwealth Environmental Requirements for the Ranger mine in January 2000 has initiated a review of water quality requirements. That review is described in section 6.2.3.

2.1.7 Tailings and waste rock management

Tailings from the Ranger mill continue to be routinely deposited into Pit 1. The pipeline to deposit tailings into the tailings dam was decommissioned during the year. The dam is now used as an evaporation pond to assist the balancing of the process water system. Tailings are pumped from the mill as a neutralised slurry and deposited in the pit via spigots located at several points around the pit perimeter. The tailings cascade down the walls and settle beneath the water in the pit below. From time to time beaches of tailings develop above the water level. This tends to give higher settled density for tailings around the edges of the pit and more dispersed mass in the centre. The Supervising Authorities require that the overall average density of tailings in the pit is greater than 1.2 tonnes/m3. ERA has achieved this target at each stage of filling the pit. Towards the end of the reporting period a trial using a floating pipeline to deposit tailings at the center of the pond in the pit was begun. There are no results available as yet. In the pit and in samples of tailings located within the mill area, trials are underway to assess the efficacy of wicks inserted into the tailings to speed up the settling process.

Waste rock continues to be dumped according to ore grade with materials containing greater than 0.02% U3O8 being managed within water control zones. Materials containing between 0.02 and 0.12% U3O8 are regarded as sub-economic and are generally being placed in final locations and then capped with clean waste rock. The site of the former Retention Pond 4 has been used as a dump for the next lowest grade of ore, which may be used for blending purposes in the mill. The waste rock capped sites in the former eastern corridor of the tailings dam are being progressively revegetated. The areas planted in the 1999 Dry season appear to be progressing well.

2.1.8 Radiological exposure to employees and the public

The Ranger mine is a potential source of radiological exposure to the local community and mine employees. There are three levels of radiation dose limits established in the Australian Code of Practice for the Mining and Milling of Radioactive Ores (1987) which specify the maximum allowable effective dose for:

These dose limits, in milli Sieverts (mSv), are based on the 1977 recommendations of the International Commission on Radiological Protection (ICRP 26). In 1990, the International Commission on Radiological Protection published ICRP 60, which significantly reduced the radiation dose limits for workers. The National Health and Medical Research Council (NHMRC) formally adopted the ICRP 60 limits into its recommendations in 1995. ERA applies the ICRP 60 limits (table 2.2), although they are not yet reflected in the Codes of Practice established under the Environment Protection (Nuclear Codes) Act 1978, which are currently under revision.

Table 2.2 indicates that radiation doses to workers and members of the public were below the applicable dose limits during 1999, and that they were less than during 1998. The reduction in dose compared with 1998 is primarily due to the adoption of dose conversion factors for ore dust and radon progeny which are based on the most recent recommendations of the International Commission on Radiological Protection. The dose conversion factors introduced at Ranger on 1 January 1999 are lower than those previously in use. The reduction in the collective dose to non-designated workers is due to a reduction, by approximately 50%, of the number of non-designated workers on site in 1999 compared with 1998.

Table 2.2: Radiation doses associated with the Ranger uranium mine
Subject group Radiation dose limits mSv per year Radiation doses for the 1999 calendar year
(Radiation doses for the 1998 calendar year)
  Australian Code of practice ICRP 60 & NH&MRC Average dose
mSv
Maximum dose
mSv
Collective dose
person Sv
Public 1 1 Adult-0.01
(Adult-0.03)
not calculated 1 not calculated
Non-designated worker 5 no provision 2 not calculated 3 1.3
(1.4)
0.7
(1.42)
Designated worker 50 20 averaged over 5 consecutive years with a maximum of 50 in any one year 2.2
(3.2)
7.6
(10.9)
0.37
(0.62)

1 Dosimetric modelling assumes all individuals in the critical group have the same characteristics. Thus all members of a critical group are ascribed the same dose, which is the average dose for the critical group. The concept of maximum dose has no application.

2 ICRP 60 does not provide for non-designated workers. If the ICRP 60 and NHMRC definition of occupational exposure is applied literally to non-designated workers, they would be subject to the 100 mSv per 5 year dose limit.

3 Radiation doses for non-designated workers are calculated using gamma exposure results from the Emergency Services Group, and radon progeny and radioactive dust concentrations measured at the Acid Plant. The dose thus calculated is highly conservative and would exceed actual doses received by any non-designated workers on site. Doses calculated for non-designated workers are hence considered to be maximum doses.

The most significant radiation exposure pathway for workers at the Ranger mine continues to be the inhalation of radioactive dust, followed by gamma ray exposure then inhalation of radon progeny. The inhalation of radon progeny is the principal contributor to radiation exposure of members of the public residing at Jabiru due to mining operations at Ranger. Radioactive dust and gamma ray exposures to members of the public attributable to mining operations at Ranger are negligible.

2.1.9 Minesite Technical Committee

Mine related technical issues are resolved by a Minesite Technical Committee (MTC) established for each site. Each MTC is made-up of representatives from the Supervising Scientist, Northern Territory Department of Mines and Energy, Northern Land Council and the mining company concerned. They are required to meet within eight weeks of Alligator Rivers Region Advisory Committee meetings to discuss technical issues arising from that meeting and the related Environmental Performance Review. The committees may co-opt other organisations or expertise from time to time as required. Additional MTC meetings are called as needed to discuss specific technical issues such as applications for changes to the Ranger General Authorisation, or to undertake an assessment of infringements. Meetings are chaired by the Northern Territory Department of Mines and Energy, but can be requested by any member. The Ranger MTC met six times during the year. Table 2.3 provides information on the meetings held and the major points of discussion during 1999-2000.

Table 2.3: Ranger Minesite Technical Committee Meetings
Date Significant Agenda Items
9 September 1999 Status of water quality in Retention Pond 1 (uranium levels), outlet modifications and bunding; tailings dam seepage characterisation; update on process water tailings density and water balance; Djalkmarra flood irrigation areas; toxicity testing protocols; quality control of water monitoring programmes; final land form design; quality assurance of soil analyses in Magela land application area; 1999 excision of wetland filters from the Restricted Release Zone.
29 October 1999 Final land form design.
3 November 1999 Status of studies on Retention Pond 1; Process water balance models; Djalkmarra flood irrigation area groundwater monitoring programme; soil radium data analyses for Magela land application area; tailings dam remedial work; new Commonwealth Environmental Requirements; monitoring philosophy; update on programme to reduce process water inventory; application to alter authorisation - redundant observation bore; access permit issues.
3 February 2000 Status of review of water quality parameters for Magela Creek in new Commonwealth Environmental Requirements; status of redraft of Ranger Authorisation; Retention Pond 2 water treatment trials; tailings dam seepage monitoring; progress on tailings paste trials; progress on rehabilitation, status of water quality in Retention Pond 1 (uranium levels).
25 February 2000 New Commonwealth Environmental Requirements; status of water quality in Retention Pond 1 (uranium levels); water management strategy review.
19 May 2000 Review of ERA interim investigation report into tailings water return pipeline leak.
21 June 2000 Review of water quality parameters and triggers for assessing impacts on Magela Creek; status of mining and milling manuals; status of draft explanatory notes on Best Practicable Technology definition; hazardous materials; research status into Retention Pond 1 (uranium levels); status and scope of water management sub-committee; draft guidelines on reporting thresholds; water management; waste rock stockpile; reverse osmosis trials, interpretation of environmental requirements relating to process water; Supervising Scientist report on tailings water leak.

2.1.10 Changes to the Ranger General Authorisation

The Ranger General Authorisation is issued under Section 13 of the Northern Territory Uranium Mining (Environmental Control) Act 1979. The Act provides for alterations to the authorisation to be issued by the Northern Territory Minister for Resource Development. A revised Ranger General Authorisation was issued on 13 March 2000 to account for the new Commonwealth Environmental Requirements.

The Authorisation requires that ERA seek approval for certain activities from the Northern Territory Supervising Authority. Depending upon the nature of the application, approvals may be issued by the Minister, the Director of Mines or a Mines Inspector.

Approvals issued under the Ranger General Authorisation during the reporting period

14 July 1999
Modification of the Restricted Release Zone boundary.

12 November 1999
Removal of observation bore OB(A) from the table of designated observation bores.

7 December 1999
Annual Water Management System Operations Manual accepted.

16 December 1999
Appointment of Statutory Radiation Officer.

13 March
Issue of a revised General Authorisation to account for a new set of Commonwealth Environmental Requirements

2.1.11 Incidents

During 1999-2000 there were five incidents. None was regarded as having a significant environmental impact. ERA is required to report breaches of the Commonwealth's Environmental Requirements or the Ranger General Authorisation and environmental mine related events which could be of concern to Aboriginal people in the region or the broader community.

5 August 1999
Retention Pond 2 water was used outside the Restricted Release Zone to fight a bush fire. It is estimated that less than five cubic metres of water was used. The fire damaged a joint in the tailings line allowing a small quantity of tailings to enter into the tailings corridor where it was contained. The area was cleaned and tailings were placed into the pit in accordance with accepted procedures.

7 October 1999
Four new, unused empty drums used by ERA to transport uranium were lost whilst in transit from Perth to Darwin.

2 February 2000
Reoccurrence of abnormally high dissolved uranium concentrations in Retention Pond 1. No effect from enhanced uranium in Retention Pond 1 was observed in water quality at downstream monitoring point (GS8210009) with no difference being demonstrated upstream or downstream from the mine.

28 April 2000
ERA reported that approximately 2000 cubic metres of tailings water (process water) had leaked from the tailings water return pipe during the 1999-2000 Wet season. This incident has been addressed in detail in section Section 2.1.1.

12 May 2000
A leak was discovered in ‘B' tails line between the processing plant and Pit 1. The failed spool piece was replaced and the rest of ‘B' line was inspected along with other lines in process water system to ensure their integrity. The total contents of the leak were contained within the secondary containment system.

15 May 2000
Weeping was detected between two pipe joints in the Tailings Water Return Pipeline. The line was shutdown and joints were disassembled, checked, reassembled and the complete line was pressure tested. The estimated volume of water lost was 5 litres.

2.2 Jabiluka Mine Project

2.2.1 World Heritage issues

At the request of the World Heritage Committee, the Supervising Scientist submitted a report to the Committee in April 1999 on the Jabiluka Project. This report was assessed by the Independent Science Panel (ISP) of ICSU in May 1999 and the Supervising Scientist provided a response to the ISP review to the World Heritage Committee in June 1999.

The World Heritage Committee met in Paris in July 1999 and resolved not to place Kakadu National Park on the list of World Heritage in Danger. In making its decision, the World Heritage Committee asked the Independent Scientific Panel (ISP) of the International Council for Science (ICSU) to continue to work with the Supervising Scientist and the International Union for the Conservation of Nature (IUCN) to resolve any remaining scientific issues and to provide a report on that work to the World Heritage Centre by April 2000. The role of the ISP is to review the response of the Supervising Scientist to the first report of the ISP and report back to the World Heritage Committee on scientific issues associated with the development of the Jabiluka project.

In April 2000, following a request from the Minister for the Environment and Heritage, the Minister for Industry, Science and Resources required that recommendations contained in Supervising Scientist Report and in the ISP review of that report be implemented (section 6.2.3 discusses these recommendations in detail).

Funding for the further work of the ISP was not made available by the World Heritage Committee until its November/December 1999 meeting. As such, the ISP had insufficient time to complete its deliberations and provide a final report to the World Heritage Centre by April 2000 as requested. Instead, the ISP reviewed the Supervising Scientist's response in May 2000 and provided a report on the progress of the ISP which was considered at the June 2000 meeting of the Bureau of the World Heritage Committee.

Since August 1999, the Supervising Scientist has worked with the World Heritage Centre to make arrangements for a visit of the ISP to Kakadu National Park, Jabiluka and Ranger. The planned visit was in response to concerns raised by the ISP in July 1999 that it had not had the opportunity to visit Jabiluka and that such a visit would greatly assist it in determining whether the development of Jabiluka posed a threat to the natural World Heritage values of Kakadu National Park. Those arrangements were finalised in June 2000.

The ISP visit occurred during the week of 3 to 7 July 2000. A representative of the IUCN accompanied the ISP. The programme for the visit, developed in consultation with the ISP, included tours of Ranger and Jabiluka, a flight over Ranger, Jabiluka and Kakadu National Park, and meetings with the Supervising Scientist and his staff, Energy Resources of Australia, Park Managers, and various Australian scientists. These meetings were structured to address particular scientific issues and allow the ISP to obtain additional information sufficient for it to report on whether the development of the Jabiluka uranium mine poses a threat to the natural World Heritage values of Kakadu National Park.

2.2.2 Developments

Over the past twelve months there has been little development of the Jabiluka project on site. The completion of stage 1 of the underground development was followed by the completion of a geotechnical borehole and some underground work in the vicinity of the ore body. Development work at Jabiluka ceased in September 1999 after which the site entered an environmental management and standby phase.

The major changes to environmental management systems and infrastructure undertaken at Jabiluka during the environmental management and standby phase have been the placing of an impermeable cover over the mineralised rock stockpile in November 1999, the reduction in area of the Total Containment Zone, the removal of redundant plant and buildings, the establishment of vegetation in areas formerly cleared but no longer required and the trialing of reverse osmosis as a potential water management strategy.

2.2.3 Assessment methodology

The adequacy of environmental protection and the level of environmental impact arising from uranium mining at the Jabiluka site were measured through a number of mechanisms, mainly:

2.2.4 Environmental Performance Reviews

The fourth Environmental Performance Review (EPR) for the Jabiluka Project was undertaken on 10 December 1999. The EPR followed the established format of an interview based on the audit protocol (described in 2.1.4), followed by a site inspection. The review considered matters arising from the previous EPR and the general environmental management performance of the site. In summary the team found that there were no unacceptable environmental impacts arising from operations at the site and that the environmental and water management systems were performing satisfactorily. The introduction of the stockpile cover, the erosion control works programme and the reduction in area of the Total Containment Zone were all noted as particularly significant events during the year. The next EPR is scheduled for 21 July 2000.

2.2.5 Water management

The Interim Water Retention Pond at Jabiluka was designed to contain runoff from the Total Containment Zone arising from a single Wet season with a return frequency of 1 in 10000 years. The permanent water retention structures were to have been constructed during the following Dry season as part of the ongoing development of Jabiluka. However, development at Jabiluka has not progressed. Consequently, the Interim Water Retention Pond has been in operation for two complete Wet seasons when it was originally designed for one.

ERA took action in the second half of 1999 to ensure that the Interim Water Retention Pond would continue to meet the 1 in 10000 year criterion throughout the 1999-2000 Wet season by reducing the catchment of the Interim Water Retention Pond. This was facilitated by the covering of the mineralised material stockpile. At the end of the 1999-00 Wet season, despite above average rainfall, the Interim Water Retention Pond continued to meet all regulatory requirements. However there is a significant risk that the Interim Water Retention Pond will fail to meet the 1 in 10 000 year criterion during the 2000-2001 Wet season unless its inventory of water is reduced.

In order to identify options for the disposal of water from the Interim Water Retention Pond, ERA trialled the use of a reverse osmosis plant at Jabiluka. The trial involved passing water from the Interim Water Retention Pond through the reverse osmosis plant and returning it to the Interim Water Retention Pond. The final results of the trial were not available at the end of June 2000 but preliminary results were very encouraging. If successful, the treated water would be of a very high quality, making various disposal options available for consideration.

2.2.6 Water quality in Swift Creek

The company is required to implement a water quality monitoring programme in Swift Creek to demonstrate that the development is not having an adverse impact on aquatic ecosystems downstream of Jabiluka. Table 2.4 summarises key water quality parameters upstream and downstream of Jabiluka over the 1999-2000 Wet season.

It is evident that the development of Jabiluka did not cause any changes in the water quality of Swift Creek that could be of ecological significance. Values of parameters upstream and downstream of the site, with the exception of turbidity, are not significantly different. It should be noted that variations in natural peak concentrations of some constituents are evident such as manganese, which exhibited a higher peak concentration upstream than downstream of the Jabiluka site. However, as the median values demonstrate, overall the concentrations of manganese upstream and downstream are not significantly different. Zinc exhibited a single data point peak downstream, however, the levels observed this Wet season are within the range documented in baseline data for Swift Creek.

Table 2.4: Summary of water quality parameters in Swift Creek upstream
and downstream of the Jabiluka Project area over the 1999-2000 wet season
- Median Range
Parameter Units Upstream Downstream Upstream Downstream
pH Units 4.92 5.2 4.31 - 5.46 4.33 - 6.45
EC (S/cm) 11.22 10.26 7.61 - 20.05 7.13 - 20
Turbidity (NTU) <1 1.4 <1 - 2.6 <1 - 5.69
TSS (mg/L) 2 3 <1 - 11 <1 - 13
Sulphate  (mg/L) 0.58 0.53 0.34 - 1.86 0.28 - 1.14
Nitrate  (mg/L) 0.52 0.12 <0.02 - 0.97 <0.02 - 0.36
Magnesium  (mg/L) 0.35 0.46 0.20 - 0.59 0.30 - 0.59
Copper  (g/L) <0.2 <0.2 <0.2 - 0.27 <0.2 - 0.57
Manganese  (g/L) 3.52 3.78 2.50 - 14.81 2.66 - 11.30
Lead  (g/L) <0.1 <0.1 - -
Uranium  (g/L) <0.1 <0.1 - <0.1 - 0.11
Zinc  (g/L) <2 <2 - <2 - 2.89
  Denotes dissolved constituent

eriss conducted research on sediment loads in Swift Creek that could be attributable to Jabiluka during the 1999-2000 Wet season. This work is described in section 3.1.2 of this report. The research found a small increase in the suspended sediment load in Swift Creek downstream of Jabiluka. However, the interpretation of the data is complicated by a fire that occurred in the catchment in 1998. Fires in a catchment are known to result in increased sediment transport and hence increased sediment loads in streams.

eriss also collected samples of benthic macroinvertebrates upstream and downstream of Jabiluka during the 1999-2000 Wet season. This work (described in section 3.1.4 of this report) did not reveal any significant difference between upstream and downstream macroinvertebrate communities indicating that the development of Jabiluka did not adversely affect the aquatic ecosystem downstream of Jabiluka.

2.2.7 Waste rock and mineralised material management

The waste rock arising from the stage one development is located in two main dumps dependent on the level of mineralisation present. Clean waste (below 0.02% U3O8) is essentially all sandstone and has been placed in a dump outside the Total Containment Zone to the south of tributary central but within the fenced area of the site. The runoff from this waste rock dump reports to drains equipped with silt fences and silt traps to restrict the movement of sediment off site. Based upon the water quality results presented in section 2.2.6, the performance of these features to date has been satisfactory.

Mineralised material containing uranium at concentrations exceeding 0.02% U3O8 was placed on a lined pad. Prior to the impermeable cover being placed over the mineralised material stockpile, rainfall runoff from it drained directly to the Interim Water Retention Pond. After it was covered, rainfall runoff from the mineralised material stockpile was diverted away from the Interim Water Retention Pond through sediment control structures to natural drainage lines. The mineralised material stockpile cover is designed to withstand 250 km/h winds and contingency plans are in place to divert rainfall runoff back to the Interim Water Retention Pond if the site is threatened by a cyclone of sufficient strength to damage the cover.

2.2.8 Radiological exposure to employees and the public

The Jabiluka project is a potential source of radiological exposure to mine employees and a potential source of exposure to the local community. As noted in section 2.1.8, there are three levels of radiation dose limits established in the Australian Code of Practice for the Mining and Milling of Radioactive Ores (1987), which specify the maximum allowable effective dose for the public, non-designated workers and designated workers.

The calendar year 1999 was the first full year for which radiation doses were calculated for employees at Jabiluka. Although development of the decline commenced in September 1998, material containing significantly elevated levels of uranium and other naturally occurring radioactive substances was not intersected until March 1999.

The development of the ore drive and footwall drive commenced on 3 June 1999 and ceased on 4 July 1999. The exposure of uranium ore in these drives allowed ERA to undertake investigations to determine by direct measurement parameters which significantly influence the radiation doses which workers could potentially receive, and consequently the radiation protection measures which are required. Those parameters are the gamma ray dose rate and the radon emanation rate as a function of ore grade. ERA also investigated the gamma ray shielding provided by shotcrete and by the cabins of mining equipment, and determined the average grade of the ore intersected to date. Table 2.5 lists the results of those investigations together with the values assumed in the Jabiluka Environmental Impact Statement (EIS).

Table 2.5: Comparison of measured radiation parameters
with estimated radiation parameters
Parameter Value assumed in EIS Value determined by Measurement

Average Ore Grade (%U3O8) intersected to date

0.74 in the first year 1.15
Gamma doserate factor (mSv/h/%U3O8) a 109 70
Radon emanation rate (Bq/m2/s/% U3O8 ) b 49 10-15
Shotcrete gamma shielding factor 57% for 60 mm 50% for 50 mm
Mining equipment gamma (shielding factor rate) 50% 40-65%

a Micro Sieverts per hour per percent U3O8
b Becquerels per square metre per second per percent U3O8

The average grade of the ore intersected to date is higher than that predicted in the EIS. However, both the gamma dose rate factor and radon emanation rate are significantly lower than predicted in the EIS. Also, the EIS assumed that the average concentration of radioactive dust in air throughout the mine would be 0.1 Bq/m3 (Becquerels per cubic metre). Personal monitoring results for underground workers at Jabiluka show that the average concentration of radioactive dust in drives being excavated in ore was 0.103 Bq/m3 and that average radioactive dust concentrations at other times and in other areas such as the decline were 0.01 to 0.025 Bq/m3. Hence measurements to date indicate that the average radioactive dust concentration throughout the mine will be less than was assumed in the EIS.

Caution must be applied in interpreting the data collected to date as underground development in ore has been minimal. However, if mining of uranium ore commences at Jabiluka, the results indicate that:

Table 2.6 records the results of the occupational radiological monitoring programme at Jabiluka for the 1999 calendar year. Radiation doses are well within recommended dose limits, as would be expected considering the minimal development in ore to date.

Table 2.6: Radiation doses associated with the Jabiluka Project
Subject group Radiation dose limits mSv per year Radiation doses for the
1999 calendar year
  Australian Code of practice ICRP 60 & NH&MRC Average dose
mSv
Maximum dose
mSv
Collective dose
person Sv
Non-designated worker 5 no provision 1 0.05 0.7 0.007
Designated worker 50 20 averaged over 5 consecutive years with a maximum of 50 in any one year 1.1 3.5 0.067

1 ICRP 60 does not provide for non-designated workers. If the ICRP 60 and NH&MRC definition of occupational exposure is applied literally to non-designated workers, they would be subject to the 100 mSv per 5 year dose limit.

ERA is required to ensure that radiation doses to members of the public from the operations at Jabiluka remain below dose limits and are as low as reasonably achievable. The critical group, that is the group of people who would receive the largest radiation dose, are the residents of Mudginberri, approximately 10 km south of the site. ERA has not been successful in obtaining permission from the Aboriginal traditional owners to undertake environmental radiological monitoring at Mudginberri. However the results of environmental radiological monitoring on the Jabiluka lease have been consistent with natural background levels.

The average radon progeny concentration (potential alpha energy concentration) and radioactive dust concentration (long lived alpha activity concentration) at Jabiluka Hill during 1999 were 0.036 mJ/m3 (micro Joules per cubic metre) and 120 madps/m3 (micro alpha disintegrations per second per cubic metre) respectively. Considering these results, no member of the public could have received a radiation dose due to operations at Jabiluka which was detectable above natural background radiation doses.

2.2.9 Minesite Technical Committee

As mentioned in section 2.1.9, mine related technical issues are resolved by a Minesite Technical Committee (MTC) established for each site. The Jabiluka Minesite Technical Committee met three times during the year. Table 2.7 provides information on the meetings held and the major points of discussion during 1999-2000.

2.2.10 Authorisations and Approvals

Authorisations and Approvals made by the Northern Territory Minister for Resource Development for Jabiluka during the reporting period are shown in table 2.8.

2.2.11 Incidents

There were no reported incidents during the year.

2.3 Nabarlek Mine

2.3.1 Developments

Throughout the year little has changed at the Nabarlek site. The revegetation assessment by the independent assessor, Adams Ecological Consultants, was finalised and submitted for evaluation by the Minesite Technical Committee in September 1999. No progress has been made on the removal of remnant infrastructure or debris from the site and revegetation proceeds slowly in some areas.

In April 2000, oss hosted a workshop to discuss the status of rehabilitation at the Nabarlek site (see section 2.3.6).

In April, the lessee, Pioneer Construction Materials Pty. Ltd., made an application to the Supervising Authorities to be released from the site but approval was not granted. At the end of the year discussions on the final site clean up and future management options were continuing.

2.3.2 Assessment methodology

The adequacy of environmental protection and the level of environmental impact arising from uranium mining at the Nabarlek site were measured through a number of mechanisms, mainly:

 

Table 2.7: Jabiluka Minesite Technical Committee Meetings
Date Significant Agenda Items
10 September 1999 Radiation monitoring site at Mudginberri; issues arising from EPR, Northern Territory Department of Mines and Energy check-monitoring programme; radiological management plan; general update
3 November 1999 Update of radiation monitoring site at Mudginberri; general update and status of additional studies; scope and terms of reference for aquatic surveys; silt trap monitoring, stockpile cover.
3 February 2000 Status report on performance of ore stockpile cover; future works programme; update of radiation monitoring site at Mudginberri; check-monitoring programme review/assessment; status of additional studies; water treatment.

 

Table 2.8 Authorisations and Approvals made by the NT Minister for Resource Development for Jabiluka
Date Approval
5 July 1999 Restricted Release Zone1 boundary extension to incorporate workshop area and fuel bay.
25 October 1999 Re-definition of Restricted Release Zone1 to exclude areas not required to be in Restricted Release Zone during the Standby, Environmental Management and Planning phase.
14 December 1999 Re-definition of Restricted Release Zone to provide for diversion of uncontaminated runoff from the covered ore stockpile to the sediment control zone.
Date Authorisation
1 October 1999 Modification of surface water monitoring - deletion of redundant section of authorisation and extension of creek monitoring programme.
1 The term ‘Restricted Release Zone' is used in the Jabiluka Authorisation issued by the Northern Territory Government. It is, however, a Total Containment Zone.

2.3.3 Environmental Performance Reviews

Environmental Performance Reviews for Nabarlek were adjusted to one per year with a mid-year inspection to check the impact of the Wet season. The ninth Environmental Performance Review for Nabarlek took place at the site on 8 December 1999. The early start to the Wet season prevented road access and so the team was obliged to fly in and walk around the site. This restricted the ability to study features away from the main area due to time limitations. However, the team did manage to visit most of the site in the time available and noted that a boring insect had attacked many of the trees at the pit and waste rock pile but this was regarded as a natural process. Over the remainder of the pond area, tree growth was still patchy and generally poorer than for the other areas. Some minor erosion features on the site were noted.

The team noted that there had been little change in conditions at the site since the previous inspection in mid-1999. It is understood that the Northern Land Council is trying to advance the issue of the removal of remaining infrastructure items by their purchasers. However, there are still likely to be considerable amounts of waste materials and debris to be dealt with before the site could be considered clear. This issue together with the final determination of the state of revegetation was carried forward to be discussed at the December 1999 Alligator Rivers Region Advisory Committee meeting and the workshop held in April 2000. The team agreed that there were no adverse environmental impacts arising from the site.

2.3.4 Minesite Technical Committee

As mentioned in section 2.1.9, mine related technical issues are resolved by a Minesite Technical Committee (MTC) established for each site. The Nabarlek MTC met once during the year. Table 2.9 provides information on the meeting and the major points of discussion.

Table 2.9: Nabarlek Minesite Technical Committee Meetings
Date Significant Agenda Items
8 September 1999 Remaining works required for final mine closeout; status and legal responsibility and stewardship after lease expiry; environmental monitoring; standards for final clean up; criteria for issue of revegetation certificate; assessment of revegetation; eriss radiological studies.

2.3.5 Incidents

There was one breach of the Authorisation relating to the requirements to make a photographic record of vegetation growth in May each year that is then submitted in an annual report. Photographs for the vegetation report were not taken in May 1999. Consequently, a report was compiled and submitted with photographs taken in December 1999.

2.3.6 Surface and groundwater quality

Surface and ground water quality continues to improve at Nabarlek. In the 1980s, irrigation of pond water resulted in the localised deterioration of groundwater quality as shown by the generation of acidity, and high electrical conductivity from elevated nitrate, sulphate and aluminium. Results from borehole sampling in 1999 indicate that the concentrations of these parameters continue to decline and that pH remains stable at around pH 4.1-4.4. Also, in the last few years, water quality in Kadjirrikamarnda Creek has recovered to near background values from the impact of pond water irrigation. Electrical conductivity and nitrate concentration remain slightly elevated (Table 2.10).

Table 2.10: Dry season water quality (dissolved constituents)
in Kadjirrikamarnda Creek at G1079 July 1986
Parameter July 1986 (Pre-impact) July 1989 (impact) August 1999
pH 6.2 4.7 5.0
EC (S/cm) 18 302 53
Sulphate (mg/L) - 68 11
Nitrate (mg/L) 0.03 45 0.30
Aluminium (g /L) 14 - 46
Uranium (g/L) <0.1 - <0.1

2.3.7 Rehabilitation workshop

The oss organised and chaired a workshop on the rehabilitation of the Nabarlek mine site in April 2000. Nabarlek is significant as it represents the first comprehensive rehabilitation of a modern uranium mine in Australia. All major stakeholders were invited as well as some outside experts. The workshop was an opportune time to examine the success of rehabilitation and focused on three principle issues:

The workshop was an open forum for discussion. The outcomes, including recommendations for the review or further development of plans for fire management and weed control, erosion control, site clean up, feral animal control and further research into revegetation will be presented to the Nabarlek Minesite Technical Committee.

2.4 Other activities in the Alligator Rivers Region

2.4.1 Exposed tailings adjacent to the Gunlom Road

In August 1999, oss undertook its annual inspection of sites associated with historic uranium mining activities in the South Alligator River Valley (figure 1.1). These annual inspections were initiated after the then Commonwealth Department of Primary Industries and Energy completed a programme of hazard reduction works at these sites in 1991. The goal of the hazard reduction programme was to significantly reduce the physical and radiological hazards at sites associated with uranium mining activities of the 1950s and 1960s.

Environmental protection requirements at the time operations ceased at these sites were very poor by today's standards and in many cases the sites were simply abandoned. The hazard reduction programme completed in 1991 involved activities to make the sites physically safe (such as sealing shafts) and also the collection and burial of material with elevated concentrations of radioactive substances.

During the August 1999 inspection, the oss noted that tailings had become exposed at the surface between the Gunlom road and the South Alligator River. At the time of the 1991 hazard reduction programme, these tailings were covered and not prone to dispersion in Wet seasons. Consequently, considering that the occupancy of the site by members of the public and therefore the radiological hazard to the public was extremely low, and also considering the disturbance to natural bushland that would be required to remove the tailings, no remedial action was taken in respect of this site as part of the hazard reduction programme.

However, the exposure of tailings at the surface due to erosion represented a significant change in the condition of the site compared with previous years. The oss immediately informed Parks Australia North of its observations and requested a comprehensive radiation survey of the site by eriss. This issue was also reported at the December 1999 meeting of the Alligator Rivers Region Advisory Committee. eriss undertook the survey in September 1999 and provided a final report to Parks Australia North in February 2000. The report recommended that the tailings be removed from the site.

The site could cause a person to receive a radiation dose in excess of the dose limit if that person resided continuously on the site for more than two weeks, or if a person disturbed the site in a manner which created significant amounts of airborne dust which was then inhaled. Based on the location and characteristics of the site, the probability of either of these scenarios occurring is extremely low.

The oss also considered the radiological hazard posed to people driving past the site. Potential exposure pathways are direct gamma irradiation from the tailings by the side of the road, and the inhalation of tailings dust generated by vehicles. The oss calculated that the dose received by a very regular user of the road due to the inhalation of tailings dust, such as a Parks Australia North employee, would be more than a factor of 100 below the background radiation dose received by Australians from natural sources every year. The dose due to direct gamma irradiation would be at least a factor of 20 lower again.

To confirm this calculation, direct measurements of dust concentrations were made in a vehicle with open windows driving past the tailings, following in the dust cloud created by another vehicle. This represented a worst case scenario. The dose calculated using the results of these measurements confirmed the earlier calculation.

Even though the radiological hazard presented by the tailings was extremely low, the Supervising Scientist was concerned that there should be no significant dispersion of the tailings into the South Alligator River. The site is inundated by water in the Wet season when the South Alligator River is in flood. Observations of the site indicate that there was no significant dispersion of tailings during the 1999-2000 Wet season, however, without appropriate action, there could be no guarantee that there would also be no significant dispersion of the tailings during the 2000-2001 Wet season.

Under the conditions of the lease between the Director of National Parks and the Aboriginal Traditional Owners of the area, Parks Australia North is responsible for establishing a rehabilitation plan for all the historic uranium mining sites in the South Alligator River Valley, including the tailings site, by the end of calendar year 2000. Parks Australia North then has 15 years to implement the rehabilitation plan. The Director of National Parks considers this to be an issue requiring urgent attention and work will be undertaken to prevent dispersion of tailings and to begin rehabilitation of the site during the 2000-2001 Wet season.

2.4.2 Exploration

During the Dry season of 1999 there were three exploration programmes related to uranium resources. All were continuations of programmes from previous years with the same operators and in the same general areas. No new exploration licences were granted during the year. oss visited all three operational areas during the exploration season to inspect the environmental management procedures in place, including the rehabilitation of drill sites and to check on progress of sites rehabilitated in previous years. In all three operational areas performance was found to be satisfactory with standards still improving as operators paid more attention to detail in dealing with environmental issues. The visits were undertaken jointly with an inspector from the Northern Territory Department of Mines and Energy so that operations were inconvenienced as little as possible. This joint programme also ensured that there was agreement on the level of performance between the two organisations. The issues raised were minor adjustments to some procedures for handling fuels and some Occupational Health and Safety issues raised by the Northern Territory Department of Mines and Energy mining engineer.

A significant change to the programme came during the early part of 2000 when it was announced that PNC would cease exploration as an operator and the continuing activity on their former exploration licences would be carried out under the management of Cameco (Australia) Limited.