EXPANSION OF A BAUXITE RESIDUE DISPOSAL SYSTEM IN AN ENVIRONMENTALLY SENSITIVE LOCATION USING UPSTREAM EMBANKMENT CONCEPTS

Eurallumina SpA has been operating an alumina refinery facility in Sardinia since 1973. The refinery processes bauxite sourced from Weipa and Boké and produces some 0.85 million tonnes of alumina and has to dispose of approximately 0. 5 million tonnes of bauxite residue per year.

Bauxite residue is neutralised by seawater and pumped by low density slurry discharge methods to a discharge basin at Sa Foxi approximately 4 km from the plant. A high evaporation rate is beneficial to reducing retained surface water and promoting consolidation by drying of the red mud. The existing red mud basin which was approximately 110 ha in area with embankments approximately 8 m high was approaching maximum capacity and a decision had to be made in relation to future long term red mud disposal.

In 1992 investigations demonstrated that upstream raising was a viable cost effective means of increasing the storage capacity of the existing disposal basin, and the first stage of this has since been successfully implemented thereby removing any immediate need for additional disposal basin sites.

Studies have been carried out to demonstrate the minimal environmental impact of the disposal area on the surrounding area and groundwater regime. Upstream embankments are designed in 2 m stages to raise the basin at an overall slope of 1:8 with progressive rehabilitation and planting of external slopes. The result is a low maintenance, low impact disposal area at minimum disposal cost.

This paper reviews the planning and initiation of bauxite residue disposal methods which are environmentally proactive and cost effective.