Residue storage design delivers environmental and economic benefits
Golder has completed a detailed design for a bauxite residue storage facility for Emirates Global Aluminium’s new Al Taweelah alumina refinery.
An initial feasibility design prepared by another consultant, included a compacted clay liner and large earth fill perimeter embankments, requiring a large quantity of imported materials – clay and water – for construction.
The design proposed by Golder substantially reduced construction costs (by many millions of dollars), and greenhouse gas emissions associated with material transport, with no additional environmental impact. The Golder design utilised the geotechnical properties of the bauxite residue to create a stack on a lined base rather than a dam, and avoided the need to construct a perimeter embankment to contain the waste. This significantly reduced the volume of earthworks required to construct the facility and resulted in a much more efficient design. The optimised baseliner design was sympathetic to existing topography limiting the cut and fill required in construction. Materials found on site were used in the works, including dune sand as a drainage layer, rather than importing materials such as crushed rock.
A geosynthetic clay liner was incorporated in the design to avoid importing more than half a million cubic metres of clay, which would need to be hauled a significant distance (and possibly from another country), should a compacted clay liner had been constructed. Specialist accelerated durability testing was conducted on the proposed liner materials to ensure the liner system would perform satisfactorily under the anticipated exposure conditions, including a highly alkaline environment.
The stack has been designed to facilitate progressive rehabilitation, using site won materials, excavated to construct the baseliner of the facility. This has limited the exposed area of residue, and the associated risk of dust generation in the hot and dry environment. The design was prepared to enable waste liquid from the refinery to be used as a dust suppressant, reducing requirements to import fresh water during operations (an extremely precious resource in the local environment) and eliminates the need to dispose of this liquid elsewhere.
The storage facility is currently being constructed in accordance with the design proposed by Golder.