The Gove environment has a unique combination of bio-geographical, climatic and site specific features that are inappropriate for rehabilitation programs used elsewhere in the world.
When Alcan’s rehabilitation trials commenced in 1972 the team created a unique rehabilitation technique to suite the mine’s unique environment.
Under the rehabilitation program, seeds and plant species from the area to be mined are collected with the assistance of local indigenous community members, carefully cleaned, catalogued, and stored.
Tall trees are felled and the cleared areas are left for two or three years.
This allows the soil and plant species of the under-storey to propagate.
The topsoil is removed and retained for use in the rehabilitation process after bauxite ore is extracted.
The mined area is ‘deep-ripped’ to promote drainage, aeration and root penetration, and topsoil is re-laid over prepared areas.
This step, which is the nucleus of the regeneration program, preserves the micro-organisms in the soil and encourages plant regeneration.
Direct placement of the topsoil onto the area marked for rehabilitation provides the most cost-effective total mining solution.
Native plant species are spread onto the topsoil and fertilised before the start of the wet season.
Key native species targeted include Eucalyptus Tetrodonta, Eucalyptus Miniata, Grevillea Pfteridefolia, Acacia Leprocarpa and Acacia Aulacocarpa.
Germination and plant growth takes place during the wet season.
The only introduced species used in the rehabilitation process is Chloris gayana, commonly known as Rhodes Pioneer grass, which is used to prevent soil erosion and increase the stability of the soil during the early stages of rehabilitation.
This species is only evident in more recent rehabilitation and dies off after a few years having achieved its goal.
Specific weed management programs form part of Alcan’s overall rehabilitation program and are aimed at eradicating and controlling weed outbreaks.
Rehabilitated areas are protected from fire during early development until they are mature enough to withstand burning.
This also allows fire-sensitive monsoon and vine thicket plant species to spread through rehabilitated areas through bird dispersal.
Monitoring of rehabilitated areas is undertaken on an annual basis by external consultants, Government bodies and University researchers.
Assessment
Areas are assessed at six months post-seeding, 18 months post-seeding and at five year intervals thereafter.
The information gathered by this regular monitoring establishes parameters for further study and continuous improvement of rehabilitation processes.
Alcan is currently working on mine rehabilitation completion criteria that will evaluate the success of rehabilitation by implementing measurable criteria against which all rehabilitation areas can be assessed.
All information relating to the rehabilitation of the mining lease at Alcan’s Gove operations is documented to facilitate annual reviews and continuous improvement initiatives.
Achievements
Since rehabilitation commenced in 1972, more than 2,600 hectares of land has been regenerated by the rehabilitation team.
Studies undertaken in the late 1990s by the Australian Centre for Mining Environmental Research (ACMER) and the CSIRO indicate that the rehabilitated areas are as stable, if not more so, than the surrounding natural forests.
The long-term monitoring program undertaken annually by external consultants continues to provide information regarding the success of the rehabilitation process.
The Yirrkala Dhanbul Association and Laynhapuy Homelands expressed the potential for Indigenous employment opportunities collecting seeds from remote Indigenous homelands.
The local Indigenous community has been involved in elements of the rehabilitation process, strengthening the relationship between Alcan and the local community.
There have been three generations of Indigenous community members involved in the rehabilitation process over the past 30 years in the form of seed collection work and other rehabilitation tasks.
Ultimately the success of Alcan’s rehabilitation program on the Gove mining lease can be attributed to the commitment from Alcan, the local Indigenous community, consultants, and researchers, to an ongoing process of review, monitoring, and continuous improvement.
Highly commended
Lime Kiln Dust (LKD) has traditionally been treated as an undesirable waste in the cement industry, and has been stockpiled or land filled.
Cement Australia developed a solution to the problem of LKD that would render it suitable for re-use in the cement manufacturing process following simple processing.
For many years LKD from the Parkhurst Plant at Rockhampton had been stored on an old clay mine site next to the plant.
In 2005 there was about 20,000 tonnes of this material on-site.
With the cost of land filling the material at over $300 per tonne, the company was to save a significant amount of money by developing an alternative solution to the problem.
In consultation with the Environmental Protection Authority, employees, and the company’s Gladstone operation, Cement Australia assigned a value to LKD as raw material feed in the Gladstone cement manufacturing process.
Rather than land filling LKD, the company trucks the material to the East End mine for blending into the cement manufacturing process.
As a raw material, LKD becomes part of a useful product and removes the cost of transferring LKD into landfill, and also the cost of transporting the waste to an approved land fill site.
The re-use of LKD reduces carbon emissions from lime processing by reducing the amount of new lime required for manufacturing purposes.
The rehabilitation of the LKD storage site has been welcomed by the local government, and runoff, dust control, and visual problems have been resolved.