Repurposing tailings storage facilities for development: experiences in mining and civil applications

Tailings being a waste product of mining and quarrying is highly compressible thus tailings dams and ponds are usually undesirable for development. However bigger picture issues such as sustainability and environmental considerations, and demand for land in urban or constrained areas, provide catalysts such that sites once thought of as undevelopable, are being considered for development. The question is, can a tailing storage facility (TSF) be used sustainably and productively after completion of mining? The aim of this paper is to show that it is not only possible, but perhaps now even desirable.

Several case studies of sustainable and productive end uses for TSFs are presented and discussed in this paper. A range of technical approaches are demonstrated in site investigations, characterisation of the tailings, and designing ground improvement works to allow reuse.

The first case history is a TSF in Western Sydney previously used as settlement ponds in a sand quarrying operation. Converting this TSF for industrial development involved ground treatment using a combination of wick drains and preload, as well as placement of engineered fill over the tailings. Another nearby TSF, is being developed as environmental wetlands which is a very different end use and thus the approach to its development is also very different. In mining, a case study is presented of construction of temporary mine infrastructure including crushing and screening plants, directly on top of an active tailings dam with ongoing settlements, a result of a geometrically highly constrained site. Some ground improvement was undertaken but because mine infrastructure has a relatively short design life and can be more tolerant to settlement, the improvement works were significantly optimised.

Collectively these case histories demonstrate a wide range of end uses for TSFs and the corresponding wide range of applicable ground improvement techniques and settlement criteria. The case histories emphasise that the geotechnical engineer needs to collaborate closely with the site owners and developers, and the designers of the future surface infrastructure, to allow TSFs to be repurposed with confidence and achieve sustainable outcomes. In particular we note the importance of all parties agreeing on practically achievable settlement criteria (as part of Landform Performance Requirements) and appropriate selection of the type of infrastructure, such that the repurposing is commensurate with the nature of the site.