FOUNDATIONS FOR THE FUTURE: QAL’S DEVELOPMENT OF FOUNDATIONS FOR ITS FUTURE RESIDUE DISPOSAL AREA

Queensland Alumina Ltd (QAL) has developed and updated its Long Term Residue Disposal Strategy to address the challenge of providing additional red mud storage capacity beyond 2008 and remain on the existing footprint. Reviews of previous studies confirmed and updated early recommendations that a dedicated Neutralisation Facility be established along with a change from downstream to upstream raising of the dam embankments to satisfy long term storage requirements to 2046.

The design and construction of foundations within an existing residue disposal facility poses its own individual challenges. High groundwater levels, designing to protect and minimise impacts on habitat, liquefiable sands, un-neutralised residue, unknown foundation conditions and excavating 3 metres below sea level were all part of the considerations necessary in developing and constructing the future foundations for QAL’s upgraded residue disposal area. This paper describes the design issues that were addressed in developing the strategy and the challenges of constructing the first stage. Adequate foundation investigation and time for design development are keystones to success in conversion of brown field construction sites. Conditions can still change even with the most extensive investigation and consideration. The observational approach is being applied as a viable fall back position when the unexpected occurs.

In October 2007 QAL successfully completed the foundations for the first stage of the upgraded residue storage area.