Mega-everything: the world’s biggest open cut mine

The expansion of the Olympic Dam mine at Roxby Downs will see environment as the biggest loser. The draft Environmental Impact Statement (EIS), for which public comment closed early in August 2009, has serious deficiencies.

It has been stated, and indeed boasted, by both the proponents and the South Australian Government, that this expansion will result in the construction of an open-cut pit that will become the largest in the world. For those who know Adelaide, this is larger than the whole of the City of Adelaide, including North Adelaide.

There are no plans for filling it at the end of its life: the EIS states “The void created by the new open pit mine would remain as a permanent land feature”. The use of the word “feature” leaves one marvelling at the wonders of spin-doctoring.

Up to 350 metres of overburden weighing 44 billion tonnes will be removed from the pit to expose the ore. Thereafter up to 390 megatonnes of rock will be removed each year for the next 40 years. Most of this material would be dumped in what will be known as a rock storage facility (RSF). The EIS says it will be visible from a 30km distance, and “would be the most prominent feature in the local and regional landscape”. The proponents propose to shape it so that it will look like a natural feature of the landscape.

The RSF will cover 6,720 hectares to a height of 150m, but BHP Billiton advises that this figure is for the purposes of the EIS only. So it is not surprising to see their proposition of disposing of the extraordinary amount of 8,090 tonnes of vehicle tyres each year into the RSF! That alone must ensure a size increase. But more on the RSF later.

As would be expected from the creation of the world’s largest open cut mine, ore-processing will see the construction of the world’s largest tailings dam - one that will be deliberately designed to leak three megalitres of radioactive waste each year!

The environmental impacts of the expansion will be enormous - from climate change impacts to destruction of biodiversity. In particular, it appears that BHP Billiton has underestimated the amount of native vegetation it will destroy.

Native vegetation destruction and habitat loss

The habitat loss and resultant displacement of fauna would in all likelihood make this the single most environmentally destructive action ever deliberately considered by a South Australian government.

The EIS claims that the total area of vegetation clearance would be between 169 and 173 sq km. This is an aggregated area of more than 13km by 13km and includes the land for the new operations, residential areas and airport, land for the desalination plant, and clearance for pipe and transmission lines.

Yet based on the scale of the drawings in the EIS, the area of the new pit, the RSF, the tailings storage facility (TSF) and industrial area alone (without any roads connecting any of them) will cover 153 sq km. It is inconceivable then that no more than another 16-20 sq km of vegetation will be destroyed throughout the rest of the project.

Roads will be constructed in the new mining area between the various installations, storage areas will be set aside for vehicles, diesel fuel will be stockpiled etc. Along with the new mining area all of this construction will together account for 264 square km. This is much more than the area claimed for the total of the new developments in this project.

The EIS advises there will be stockpiles of assorted sands, limestone etc which clearly will enlarge the area of native vegetation destruction. Additionally, if the RSF increases in size - and remember the EIS leaves that option open - then still more vegetation would be destroyed. The figures provided by the proponent do not add up!