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

By Sandra Kanck - posted Monday, 24 August 2009

BHP Billiton has a Significant Environmental Benefit proposal (SEB) - a combination of a financial payout and like-for-like land to be set aside elsewhere -to cover the destruction of biodiversity.

Tens and maybe hundreds of thousands of trees and bushes will be destroyed. The SEB does not have regard to the age of the vegetation. A tree that is decades or even centuries old will not be easily replaced, regardless of whether it is a common species or not. Neither does the SEB appear to incorporate recognition of the fauna that is dependent on those trees and bushes. Whether or not they are common species, they are part of an ecosystem.

Energy use and associated climate change impact

The use of fossil fuels and associated climate change impact will be immense. While BHP Billiton claims the expansion will account for a not inconsiderable 9.8 per cent of South Australia’s CO2 emissions within just 11 years, the real figures may be closer to 14 per cent.


On-site diesel fuel usage will increase from the current 25 megalitres per annum to reach 454,000 kilolitres after 40 years (the mixed measurements are BHPB’s choice). Over the same time period, diesel for transporting material into and out of the site will increase from 16,000 to 36,500 kilolitres.

The EIS suggests potential conversion of haul trucks to run on LNG, resulting in the on-site construction of an LNG conversion facility. With peak oil impacts occurring early on in the expansion, the LNG conversion facility will no doubt need to be fast-tracked. LNG conversion of itself is a process which increase greenhouse gas emissions, yet it does not appear to be included in the climate change calculations.

BHP Billiton will source its electricity needs in the first instance from the current national electricity grid, which will result in the increased use of coal-fired electricity. The closest generators at Port Augusta produce power from relatively inefficient and polluting Leigh Creek coal, with associated greenhouse gas emissions (including the release of methane). At least one of the power-stations is half a century old and should have been decommissioned years ago.

Prodigious amounts of energy will be used in construction. For instance, to allow for the very large equipment that will be moved in, passing bays 30m wide and 250m long will be built between Port Augusta and Olympic Dam at roughly 17km intervals. This and other off-site construction will increase the use of fossil fuels and further blow out South Australia’s climate change targets, yet does not appear to be taken into account in the EIS.

Rock storage facility

The EIS envisages that, 40 years after digging has begun, the pit will be 1km deep. However, ore has been found at a depth of 2.5km, which begs the question of what happens after 40 years. If mining continues, obviously there will be still more rock to add to the RSF, yet this has not been taken into account in figures about its size.

When below-surface rock is removed its volume expands as a consequence of the removal of pressure and being broken-up. This can be given a mathematical value known as the expansion factor. The fine print of the EIS does not reveal any recognition of an expansion factor - it may not have been taken into account at all. Yet BHP Billiton previously informed the Natural Resources Committee of the SA Parliament that the expansion factor would be 1.7 - important information in calculating the size of the RSF.


The pit will be 4.1km x 3.5km x 1km deep, i.e. 14.35 cubic kilometres. If we very generously assume only 90 per cent of what will be taken out of the pit will go into the RSF, it will have a volume of almost 13 cubic kilometres. But with an expansion factor of 1.7 this becomes roughly 22 cubic kilometres.

So the RSF, if 1km high, would have a base of 22 sq km. In turn, if the RSF was to have a base three times that (66 sq km) the height could be reduced to 1/3 of a kilometre, i.e. 333 metres. This is still more than twice the 67 sq km by 150m size envisaged in the EIS.

This strongly suggests the proponents have not included an expansion factor in their calculations. With a 1.7 expansion factor, the RSF would have to be more than twice the ground size stated in the EIS to obtain a height of no more than 150m. But if the intention is to maintain the stated 6270 hectare base, then the height of the rock storage facility will be at least doubled. Which will it be?

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About the Author

Sandra Kanck is the former parliamentary leader of the South Australian Democrats. She is national president of Sustainable Population Australia, SA president of Friends of the ABC, President of the Australian Democrats (SA Division Inc.) and an Executive Member of the SA Council for Civil Liberties.

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