Supervising Scientist, Darwin, 2003
ISBN 0 642 24383 2
ISSN 0 158-4030
2 - Environmental assessments of uranium mines (continued)
Mining continued throughout the year, although activity was interrupted during the late wet season through to late dry season when excess water was stored in the lower portion of Pit 3. The expansion of Pit 3 was continued to the east and north reaching to within 20 m of Djalkmara Billabong in places. The exploration drilling associated with this expansion required the construction of platforms out into Djalkmara Billabong as well as the redevelopment of the spectator viewing area on a new site at the north rim of the open cut. The level of water in Djalkmara Billabong was monitored and controlled carefully during the wet season as the lowest point of the rim of Pit 3 was adjacent to the billabong and less than two metres above the water level.
During 2002-03, ERA significantly upgraded key aspects of its water management infrastructure at Ranger, particularly in the Corridor Creek system, the Southern Stockpile area, and the upper catchment of Retention Pond 1. These are described in more detail later in this section.
Sediment control structures were constructed to enhance management of runoff from the unmineralised laterite stockpile to the north of the western stockpile. This system comprises semi-permeable bunds and a basin to remove sediment from runoff before the water runs to bushland.
Significant work on the tailings corridor drain to reduce its permeability and to rationalise pipework has also been undertaken. Toe loading of the south wall of the tailings dam and other minor works recommended following the annual inspection of the tailings dam were also completed. Toe loading is preventative maintenance involving the placement of waste rock at the outer base of the dam wall to ensure its continued structural integrity. During the 2002-03 wet season, runoff from the toe loading was directed to a sump where water flow and quality measurements were undertaken. Relatively high levels of uranium were recorded in the first flush, as anticipated, although flow volumes were very low. As a precaution, the first flush flow was collected and pumped back into the tailings dam.
ERA continued research into tailings deposition, process water management and treatment, and water treatment in wetland filters using the system established in the Corridor Creek catchment. A design for a process water treatment plant was commissioned and completed during the reporting period following the successful operation of the pilot plant reported in the Supervising Scientist's 2001-02 Annual report.
|Production (drummed tonnes of U3O8 )||1 188||1 419||1 245||1 460||5 312|
|Ore Treated (tonnes)||464 000||556 000||514 000||619 000||2 153 000|
Environmental Monitoring Programme Review
ERA undertook a comprehensive review of surface water and groundwater monitoring at the Ranger mine. Recent changes in NT legislation, ie the implementation of the Mining Management Act 2001 which necessitated changes to the Authorisation to Operate, and Recommendation 9 of the 'tailings water leak' report¹ - which specifically requires that a monitoring programme at Ranger has an in-built early warning capability - were key driving forces behind the review.
ERA proposed a new environmental monitoring framework and programme, based on scientific and risk perspectives, to provide optimum environmental protection. The revised programme was submitted to the MTC, which approved the programme and the presupposed changes to the Authorisation to Operate. The monitoring programme now consists of two parts, a statutory and an operational programme.
The statutory programme is based on the concept of surface and groundwater 'envelopes' around the mine site and solute movement from the innermost (source) to outermost (downstream) envelopes. Surface water is monitored weekly at ten sites and groundwater monitored quarterly at four sites. These sites are the inferred points of exit for solute movement in the three major mine subcatchments that enter Magela Creek. Key variables, defined by the Environmental Requirements for the Ranger mine, are monitored at these sites. Potable water quality monitoring is also included in the statutory programme. Data from these programmes are reported weekly to stakeholders during the wet season and annually in the wet season interpretive reports.
The operational monitoring programme is designed to provide specific information for ERA to manage and plan strategic and operational aspects of mining, milling and rehabilitation at Ranger, as well as giving early warning of changes in surface water quality at key locations that could potentially impact on the downstream environment. Impounded water other than RP1, bores in irrigation areas, and groundwater bores other than those statutory bores will be monitored under the operational monitoring programme. That programme will be set in consultation with the Ranger MTC, and will form part of the annual Mine Management Plans. Data from these operational programmes will be made available to the stakeholders on request or as part of specific or annual reports.
1 Supervising Scientist 2000. Investigation of tailings water leak at the Ranger uranium mine. Supervising Scientist Report 153, Supervising Scientist, Darwin.
In this section
- Letter of Transmittal
- Supervising Scientist's Overview
- 1 - Introduction
- 2 - Environmental Assessments of Uranium Mines
- 3 - Environmental Research and Monitoring
- 4 - Statutory Committees
- 5 - National Centre for Tropical Wetland Research
- 6 - Communication Liaison
- 7 - Administrative Arrangements
- Appendix 1 - List of Publications 2002-03
- Appendix 2 - Presentations to Conferences and Symposia
- List of Tables
- List of Figures