This report assesses the environmental impact of the proposal by Rustler's Roost Mining Pty Ltd to expand and upgrade the Rustler's Roost Gold Mine on the Old Mount Bundey Station, approximately 100 km south east of Darwin. The company currently operates an open pit, heap leach gold mine and proposes to deepen and join the existing pits, install a new treatment plant and construct a tailings dam.
The report reviews the draft Environmental Impact Statement (EIS) prepared by the proponent, comments from NT Government agencies on the draft EIS and the proponent's Supplement addressing these comments. No public comments were received as a result of the public review of the draft EIS.
Environmental impact assessment is the process of defining those elements of the environment which may be affected by a development proposal and of determining the significance, risks and consequences of the potential impacts of the proposal. Recommendations arising from the assessment address methods to mitigate these impacts.
Major issues
The major environmental issues identified with the proposed expansion and upgrade of the Rustler's Roost Gold Mine are:
- the use of new technology, Resin in Leach;
- the site for a tailings dam;
- waste rock characterisation and management; and
- water management including acid rock drainage.
Conclusion
It is considered that the environmental issues associated with the proposed expansion and upgrading at Rustler's Roost Gold Mine have been identified and that the proposal can proceed. Some of these issues have been resolved through the assessment process. However, the assessment has raised a number of matters that need to be further addressed before granting approval to proceed. These matters must be addressed in a Mine Environmental Management Plan that should be submitted to the Department of Mines and Energy for approval by that department and the Department of Lands, Planning and Environment.
Recommendations
It is acknowledged that during detailed implementation of proposals, flexibility is necessary and desirable to allow for minor and non-substantial changes to the design and specifications which have been examined as part of this assessment. It is considered that subsequent statutory approvals for this project could make provisions for such changes, where it can be shown that the changes are not likely to have a significant effect on the environment.
Subject to decisions which permit the expansion and upgrading of the Rustler's Roost Gold Mine (Stage 2 Mining) to proceed, the primary recommendation resulting from the assessment is:
Recommendation 1
The proponent shall ensure that the proposal is implemented in accordance with the environmental commitments and safeguards identified in the Rustler's Roost Mining Pty Ltd draft Environmental Impact Statement, or as modified in the Supplement to the draft EIS, this assessment report or an approved Mine Environmental Management Plan.
A. New Technology
Recommendation 2
It is recommended that the study into kerosene and its effect on the environment should include whether and how the kerosene breaks down in the tailings dam. Further, the study should commence prior to commissioning the plant. The proponent should also investigate the availability and effectiveness of microbial inocula that can be used to breakdown the kerosene.
B. Tailings Dam
Recommendation 3
It is recommended that either site 4 or site 6 be used for a tailings dam and if it is to be site 6 then the necessary investigations be carried out to determine its suitability. Further, only one tailings dam should be constructed and used for the proposed expansion and upgrade at the mine as described in the final EIS.
C. Waste Rock
Recommendation 4
It is recommended that further investigations be carried out to ascertain waste rock characteristics, the spatial distribution and quantities of the various waste rock components with potential for acid rock drainage, acid neutralising potential and the extent of non acid forming rock.
Recommendation 5
It is recommended that the design of the waste rock dump and the construction technique be reconsidered to ensure that it will be non-acid producing or alternatively the dump be redesigned and managed to minimise and control any acid that may be formed and leached from the dump.
D. Water Management
Recommendation 6
It is recommended that the water management system at the mine be further revised to take account of the need for storage of pit water, Annie Dam to be used for storage of clean surface water runoff and bore water only, the possibility of site 4 becoming available for a tailings dam, and the general mine layout.
E. Weed Management
Recommendation 7
It is recommended that weeds management at the mine be in accordance with the Department of Primary Industry and Fisheries recommendations to ensure the mine's operation does not cause the introduction or spread of weeds in the area.
F. Heritage
Recommendation 8
It is recommended that the archaeological survey referred to in the draft EIS (section 4.2.2) be completed and a report submitted to the Department of Lands, Planning and Environment for consideration.