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Find out how Alcoa rehabilitated the Huntly and Willowdale mines

Industry News / Mining & Resources

Find out how Alcoa rehabilitated the Huntly and Willowdale mines

Key Facts:

  • Alcoa mines and rehabilitates approximately 600 hectares each year at its Huntly and Willowdale bauxite mining operations in the Darling Ranges in WA
  • Key objective is to restore 100% of the plant species that existed in the pre-mined jarrah forest within 15 months of rehabilitation
  • Alcoa has established it’s own nursery
  • Alcoa are working in collaboration with universities, government agencies and private researchers to understand the forest ecosystem

Alcoa’s Huntly and Willowdale mines in Western Australia produce 34 million tonnes (Mt) of bauxite per year, almost half of the 74Mt produced in Australia in 2011. The scale of the operations led to considerable deforestation since the mines began operation in 1963, and Alcoa has implemented an ambitious reforestation scheme to try to restore 100% of the plant species that were present in the Jarrah Forest before mining work began.

The company reached this target in 2001, as all of the plant species were reintroduced to the area, alongside new plants introduced to the region, leading to claims that Alcoa had achieved “101% of its goal”. The rehabilitation efforts have been spearheaded by the Marrinup Nursery at the mine, which provides a source of seeds and plants for the rehabilitation of mining land and enables scientists to conduct testing on new plant species that are being considered for introduction to the area. This is part of Alcoa’s aim to improve the biodiversity of the region and introduce plants that are more resilient and capable of surviving in Western Australia, which experiences an annual dry season.

The nursey is also equipped with a tissue culture laboratory to test a range of plant species, and is currently responsible for producing 50,000 plant cuttings a year.

Mine rehabilitation objective and process

Our key objective is to re-establish a self-sustaining jarrah forest ecosystem that fulfils forest land uses that include conservation, timber production, water catchment and recreation.

Our rehabilitation process, which has been developed and continually improved over decades, involves landscaping, pre-ripping, soil return, fauna habitat return, final contour ripping and seeding, recalcitrant planting, fertilising and ongoing monitoring and management.

We conduct annual monitoring of plant species richness to measure our performance. We first achieved our target of returning 100 per cent species richness to mined areas in 2001.

Alcoa is the recipient of numerous esteemed environmental awards including the Society for Ecological Restoration International Award for Outstanding Contribution to the Field of Ecological Restoration (2003).

Since mining commenced in 1963, we have mined less than four per cent of the jarrah forest within our Mineral Lease (ML1SA) which extends from Mundaring to Collie. Alcoa does not mine in old growth forest.

Bauxite residue management

Bauxite residue is a by-product of alumina refining and consists primarily of iron and silica minerals. The coarse sand fraction (red sand) comprises approximately 40 per cent of residue and approximately 60 per cent of fine silt fraction (red mud). Much of the sand is reused to construct residue drying areas which are eventually capped and revegetated.

Long Term Residue Management Strategy

Alcoa has a Long Term Residue Management Strategy (LTRMS) for each refinery. These are designed to inform both government and community about our long-term planning and management strategies including the location of future residue drying areas; current plans for closure and future land use options; and current research into residue management and reuse. LTRMS reports are available here.

Residue filtration

An innovative technology known as residue filtration commenced operation at Kwinana Alumina Refinery in 2016. With this technology, bauxite residue is forced through very large filters that squeeze the water from the mud, with the water being recycled in the refining process. As a result, the refinery will not need to construct another 30-hectare residue storage area for at least 20 years compared to every five years previously. The system also reduces freshwater use by more than one gigalitre annually. Pinjarra Alumina Refinery is currently constructing a similar residue filtration facility which will be commissioned in 2019.

Find out how mine rehabilitation legislation in Australia is changing in our FREE guide.

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FAQ:

What is mine rehabilitation?

According to the Department of Industry, Tourism and Resources, mine rehab (rehabilitation) is “the process used to repair the impacts of mining on the environment. Mine rehabilitation can also be referred to as coal mine rehabilitation, land rehabilitation, mine site rehabilitation or mine site restoration. The long-term objectives of rehabilitation can vary from simply converting an area to a safe and stable condition, to restoring the pre-mining conditions as closely as possible to support the future sustainability of the site”.

What are the different types of mine rehabilitation practices?

There are several types of mine rehabilitation practices including: - Hydrogeology - Flooding - Soil and capping material assessment - Water characterisation - Landform and cover design - Water management - Revegetation - Tailings storage facilities

Is my Progressive Rehabilitation and Closure Plan (PRCP) compliant?

Organisations carrying out mining activities in Queensland (QLD) are legally obligated to rehabilitate the land. A progressive rehabilitation and closure plan (PRC plan) is a critical element of the QLD Government’s Mined Land Rehabilitation Policy. When submitting a site-specific application for an Environmental Authority (EA) for a new mining activity relating to a mining lease, applicants are required to develop and submit a proposed PRC plan as part of their application. Download your free guide below to find out: https://www.decipher.com.au/MineRehabilitationGuideQLD


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