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Find out how Alcoa rehabilitated the Huntly and Willowdale mines

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Industry News / Mining & Resources

Find out how Alcoa rehabilitated the Huntly and Willowdale mines

Alcoa of Australia (Alcoa) is a recognised world leader in mine site rehabilitation.

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

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.

 

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