4.0 Environmental Assessment
4.1 Water Management
Additional information was requested from Ashton Mining Limited in regard to their proposed water management plan and this was provided and assessed within the PER assessment period.
Key issues associated with the surface water runoff are erosion and sediment control, particularly during the initial pre-stripping and clearing for the dumps and pits and during dewatering of the mine pits. Sediment dams and erosion control structures will be constructed downslope of all waste dumps and mining pits to manage these issues.
Concerns relating to the mine water management system focus on containment of water from the mining and waste dump runoff and the potential effects on surface water.
Designs, schedules and monitoring proposals for the proposed water management systems will be required prior to the commencement of the project.
Recommendation 2
Ashton Mining Limited should prepare a water management plan which includes:
- site water balance;
- water storage design criteria;
- characterisation of discharge waters;
- a groundwater monitoring strategy; and
- monitoring of water quality/quantity prior to release/disposal.
This water management plan should be incorporated into the Environmental Management Plan and reviewed on a routine basis by the Department of Mines and Energy.
4.2 Weed and Feral Animal Management
The noxious weed Xanthium occidentale (Noogoora burr) occurs in the vicinity if the access road, particularly along watercourses. Appropriate management will be required to ensure that weed seeds are not transported during road construction and maintenance.
The project area itself has been relatively isolated due to its location and lack of access and as such safeguards need to be implemented to prevent the incursion of introduced and problem floral species into the area.
One of the prime ways of weeds entering a relatively weed-free area is on earth moving equipment, or in soil, fill, sand, gravel or other building materials. The disturbance occasioned by these activities also enable weed establishment and spread.
The cane toad, Chaunus marinus is found in numbers in the McArthur/Glyde Rivers region. Although the cane toad has become abundant in a range of habitats in the region appropriate management will be required to prevent the transportation of the toad to areas currently free from infestation.
Recommendation 3
In line with the Northern Territory Weed Management Strategy, 1996 - 2005, Ashton Mining Limited should design a weed management plan covering the mine site and access corridor to prevent the introduction and spread of weeds.
Ashton Mining Limited should implement a strict inspection program to prevent the transportation of cane toads from the area.
This information should be incorporated into the Environmental Management Plan and reviewed on a routine basis by the Department of Mines and Energy.
4.3 Rehabilitation
The PER identifies the construction and utilisation of two tailings dams for coarse and fine tailings respectively. There is the possibility that if the fine tailings are very fine, as is likely, these may be difficult to rehabilitate, and Ashton should investigate the possible need for discharge of thickened tailings. Additional information will be required prior to approvals being given for construction.
Recommendation 4
Ashton Mining Limited should prepare detailed tailings dam designs and tailings characterisation.
This information should be incorporated into the Environmental Management Plan and reviewed on a routine basis by the Department of Mines and Energy.
The rehabilitation strategy proposed in the PER is considered adequate at this time. During the development and operation of the mine, a detailed rehabilitation plan will be developed through rehabilitation trials and on-site experience.
Recommendation 5
Rehabilitation trials should be undertaken to develop a final rehabilitation strategy.
This information should be incorporated into the Environmental Management Plan and reviewed on a routine basis by the Department of Mines and Energy.
4.4 Heritage
A number of archaeological sites were identified near the proposed mine site and along the access road. The proposed development has the potential to impact on at least two of these, Catfish Hole 1 and Catfish Hole 2.
With respect to Catfish Hole 1 the preferred option is to realign the track and to construct a temporary fence to avoid damage by machinery operating in the area.
In regard to Catfish Hole 2 the PER identifies two protective strategies, these recommendations are supported and the proponent is strongly urged to adopt these measures.
Heavy machinery should be strictly prohibited from operating within the vicinity of archaeological sites.
Some form of fencing may be required to ensure that these sites are not inadvertently disturbed.
Recommendation 6
Ashton Mining Limited should, with respect to Catfish Hole 1, realign the access road and construct a temporary fence.
With respect to Catfish Hole 2, Ashton Mining Limited should fence the northern margin of the site and erect warning signs to prevent disturbance and damage.
This information should be incorporated into the Environmental Management Plan.
4.5 Environmental Monitoring
Ashton Mining Limited has outlined in the PER a proposed sampling and monitoring program. All components of the monitoring program will be implemented at the commencement of operations, including access road construction. Baseline surface water quality and groundwater level monitoring will be completed before the commencement of mining operations.
Recommendation 7
Ashton Mining Limited should complete and submit a baseline and operational monitoring programme, including identified parameters and thresholds, in an Environmental Management Plan.
Ashton Mining Limited should operate in accordance with the approved plans, with these plans being reviewed by the Department on a regular basis.
4.6 Other Issues
Social
The possibility of social impact on the township of Borroloola and surrounding area, by the construction and operational workforce, will be minimal. Given the isolation of the site, 130km by road, the fly in fly out staffing strategy and the accommodation of all construction and operational staff on-site (all employees and contractors will remain on site during their 14 day roster period).
Flora and Fauna
Several species of conservation significance were identified in both the project area and proposed access road corridor. The areal extent of the project, however, is small compared with the surrounding habitat, and if the proposed conservation measures are adhered to, there should not be a significant lasting effect on the local flora and fauna.
The Environmental Management Plan needs to consider measurers to manage flora and fauna of conservation significance. Additional surveys may be required to determine the relevant management strategies.