Alcoa of Australia Residue Management
 
Groundwater Protection
From the commencement of Alcoa of Australia’s operations in Western Australia, residue areas have been designed and constructed in accordance with contemporary accepted engineering standards. The need to contain the residue leachate has meant that the embankments were designed as water retaining structures that added further conservatism to their design. As such, their construction included base and embankment clay sealing layers.
 
In addition, the residue areas have dedicated water storage ponds to hold rainfall run-off, which is then recycled in the refinery. No run-off water is discharged from the residue areas into surface water bodies – it is all collected for internal recycling.
 
The introduction of dry stacking of the residue and the inclusion of base drainage layers in post-1980 residue areas has reduced the potential for release of residue leachate to the groundwater by reducing the water level within the deposit and decreasing the pressure on the base liners. All new residue storage areas are now built with a composite liner consisting of a clay layer and synthetic liner on top of the clay to further reduce the potential for seepage.
 
Alcoa of Australia has established and maintains an intensive groundwater monitoring network consisting of residue area perimeter bores and regional bores. The results are reported to Department of Environment and Conservation in accordance with licence conditions.