Land and biodiversity
AWAC has an aim of minimising environmental impacts and promote sustainable use of land mined.
Biodiversity management is a major part of the mine rehabilitation process. It is an essential practice for operations near regions where there are significant flora and fauna species (such as the jarrah forest Darling Range of Western Australia, and at Juruti near the Amazon in Brazil) areas recognised as sensitive eco-systems.
Decisions on future land use and preparation of rehabilitation plans are contingent on determining and maintaining the biodiversity of the area. In assessing the reconstruction of biodiversity in rehabilitated areas tree establishment and growth are regularly monitored. This includes reviewing the concentration of undergrowth and diversity. Regular reviews are also undertaken on establishment of birds, mammals, reptiles and insect life. Ground and surface water levels and quality is also monitored.
AWAC’s mining activities, although often limited to relatively small pits where bauxite exists, can affect a region because the pits must be connected by haul roads or conveyors. We work successfully to prevent the isolation of wildlife and the disruption of stream flows. We also maintain vegetation cover and the quality and quantity of both surface and groundwater. Our Western Australia operations have extensive programs around the management of soil erosion, weeds, feral animals, and forest pathogens to minimize impacts on biodiversity.
Alcoa have also committed to avoiding legally designated protected areas where strict nature conservation is the management objective. Prior to developing an area, Alcoa conducts extensive evaluations of the areas biodiversity to determine future rehabilitation programs. Evaluations include monitoring plant growth, density and diversity. A review is also conducted of birds, mammals, reptiles and including insects.
AWAC’s Western Australian mining operations, the Juruti mine in Brazil and the Portland aluminium smelter in Australia have developed and implemented biodiversity action plans that will serve as models for other locations.
Land disturbance and rehabilitation
In regards to mining operations, AWAC operates under the mandate that mining is a temporary use of the land and it supports returning mined land to a sustainable future. In most cases that means returning the land to its pre-mining condition with the same diversity of plant and animal species.
Bauxite mining, is done in relatively shallow pits, disturbs the land and disrupts its biodiversity. Mining accounts for the majority of land that is disturbed as a result of AWACs operations. As the joint venture is committed to minimising the disturbance of the original habitat and work closely with community and regulatory stakeholders to restore those lands we do impact to the most productive use possible, including, where feasible, re-establishing pre-operating conditions.
Some AWAC operations are within or adjacent to protected areas or sensitive bio diverse areas.
|OPERATIONAL SITE||SITE LOCATION & SIZE||POSITION||BIODIVERSITY VALUE|
|Huntly and Willowdale bauxite mines||Jarrah Forest, Western Australia - 712,900 hectares (1,761,614 acres)||Within protected area||Recognised by Conservation International as an international biodiversity hotpost; threatened species and ecological communities (International Union for Conservation of Nature - IUCN- and federal government listed)|
|Anglesea Power station (coal mine and power station closed in August 2015)||Anglesea, Victoria Australia - 787 hectares (1,945 acres)||Within and adjacent to protected area||Adjacent land zoned for conservation and listed on the National Estate Register; threatened species and ecological communities (IUCN and federal government listed)|
|Wagerup alumina refinery||Wagerup, Western Australia - 6,000 hectares (14,826 acres)||Contains portions of area of biodiversity value||Ramsar listed wetlands adjacent; threatened species and ecological communities (International Union for Conservation of Nature (IUCN) and federal government listed)|
|Portland aluminium smelter||Portland, Victoria Australia - 500 hectares (1,236 acres)||Adjacent to protected area||Threatened species and ecological communities (International Union for Conservation of Nature (IUCN) and federal government listed)|
|Juruti bauxite mine (railway and port facility)||Juruti, Brazil - 29,426 hectares (72,713 acres) that will be mined||Within protected area||Amazon rainforest and river; threatened species and ecological communities (IUCN listed)|
|Coermotibo (bauxite mine that ceased operation in October 2015)||Maroijne District Suriname 32,800 hectares (81,051 acres)||Adjacent to protected area||Adjacent to IUCN protected area; threatened species (IUCN listed)|
|Point Comfort alumina refinery (alumina refinery that was curtailed in 2016)||Point Comfort, Texas USA - 1,417 hectares (3,501 acres)||Adjacent to protected area||Native grassland and intertidal emergent marsh (protected under the Clean Water Act); threatened species (IUCN and federal government listed)|
Results and goals 2018
The goal going forward is to maintain a corporate-wide running five-year average ratio of 1:1 or better for active mining disturbance (excluding long-term infrastructure) to mine rehabilitation. This will manage net expansion in land disturbed.
The ratio for the 2014 to 2018 period was 1.02:1. It is expected the ratio to decrease as more areas at AWAC’s closed mines in Suriname are progressively returned to the Suriname government after rehabilitation.
Mining Land disturbed/Land Rehabilitated (hectares)
|Open mine area||13,863||14,371||13,702||14,155||14,380
|Area disturbed (annual)||1,169||1,235||1,086||977||1,123||1,195|
|Area rehabilitated (annual)||1,029||842||1,114||532||898
*expressed in hectares
The values in this table include some for Alcoa’s South American operations that do not form part of AWAC operations. However, the vast majority of disturbance and subsequent rehabilitation is the result of AWAC’s mining and infrastructure activities.
Area disturbed for mining and associated infrastructure (hectares)
Area disturbed means annual land used in each reported year for mining or for mining infrastructure (eg. roads, shops, crushing equipment, conveyors). In Brazil, the area disturbed increased in 2017 due to additional clearing necessary for long-term infrastructure associated with the expansion of our Juruti mine. In Australia, the small increase in 2017 was due to slightly higher clearing for active mine areas at both the Huntly and Willowdale mines.
Area rehabilitated (hectares)
*Annual figures. Area rehabilitated means annual land returned to natural conditions or to productive use (such as farming) after mining or decommissioning of mine infrastructure in each reported year. The reduction in area rehabilitated in 2016 was mainly due to a range of operational constraints at the Huntly mine in Australia and reduced areas returned to the Government of Suriname during 2016.
The Rehabilitation Process
Mining of the bauxite ore results in relatively shallow open pits and requires excavating through several layers of soil and sub-soil. The top soil which is rich with seed and nutrient reserves is removed and retained for return to the mined area to re-establish native vegetation.
The overburden is then removed to expose the bauxite ore. The overburden may also contain valuable nutrients and microbes necessary to assist with regeneration. Generally the overburden and any rock removed together with the topsoil is returned immediately to the mine pit (progressive rehabilitation) however in some cases that is not immediately possible or practical and those materials are stored for later use.
Also, the topsoil can be treated with specially grown seeds and nursery-grown vegetation or, where the plant species are not prone to produce a viable seed bank, to supplement with cuttings and tissue culture propagation.
The rehabilitation process also includes creating an environment for native wildlife to return. This may involve creating habitats from tree trunks and stumps that were removed during mining. These habitats provide protection and an area to recolonise.
Continual review and research is conducted at rehabilitation sites to judge the success of techniques and processes. Research conducted at the Western Australian sites discovered that the establishment and longer-term survival of some species could be improved by reducing the rate of fertiliser applied.
Different rehabilitation processes are also employed at specific sites due to local conditions. At the Juruti bauxite mine in Brazil a nucleation technique is used which relies on locally adapted plants and animals colonising micro-environments using small mounds of topsoil to create an undulating land scape. This technique is used to help trap surface water and control water runoff during the wet season (300mm of rainfall).