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Mt Coot-tha Quarry has since the 1990s prolonged its commercial life and continues to be an important source of high quality aggregate for Brisbane.
Mt Coot-tha Quarry has since the 1990s prolonged its commercial life and continues to be an important source of high quality aggregate for Brisbane.

The next 30 years – reflections and the future

“Double, double toil and trouble; Fire burn and cauldron bubble.”  The witches from Macbeth, you may ask? No, it’s Dugald Gray channelling the dark arts of forecasting to predict how quarrying may develop over the next 30 years.

In 1984, the birth year of Quarry magazine, I was engaged in my final year as a mining engineering student in Brisbane. As part of the curriculum, we had to complete two quarry-related assignments – one on Brisbane City Council’s Mt Coot-tha Quarry and the second on sand and gravel dredging from the tidal sections of the Brisbane River. For both extractive precincts, declining reserves and environmental impacts were the issues of the day.

Fast-forward 30 years and many would say not much has changed. However, while Brisbane River sand and gravel dredging is confined to history, the Mt Coot-tha Quarry is alive and well, albeit in the maturing phase of its life cycle.

TALE OF TWO PRECINCTS
The respective destinies or fortunes of these extractive resources in the heart of Brisbane is instructive in any examination of how the quarrying industry, its technologies and societal attitudes towards it have evolved over the past 30 years.

The principal driver of change has been community attitudes towards acceptable levels of environmental impact from quarrying, which since the 1970s have been increasingly reflected by legislation requiring incrementally lower levels of noise, dust, blast vibration, water contamination, visual impact, traffic dangers and ecological impacts.

To obtain or maintain their licences to operate, quarries have had little choice but to adopt technologies to mitigate environmental impacts. This has occurred in tandem with improvements in risk management, including adoption of automation and improved management systems to minimise risks to workers.

Those quarries (or resources) that have been willing to adopt, and able to adapt, have prolonged their commercial life, which is surely a goal of sustainability.

Mt Coot-tha Quarry is one such example. Focusing on high value aggregate production, regulating output and adopting a fully enclosed, noise-suppressed crushing and screening plant circuit in the 1990s, it has defied the odds and continued to be an important source of high quality aggregate for Brisbane City Council.

If we reflect on the demise of sand and gravel dredging in the Brisbane River in the 1990s, remaining resources were on the wane and the tide of public opinion was turning against dredging the river as a source of construction materials.

By the late 1990s the quarrying industry in southeast Queensland had largely switched to hard rock quarry production, with the most prominent “new” product being manufactured sand, which has largely replaced medium-coarse river sand as an aggregate in concrete.

Here we see the serendipitous nature of innovation driving product substitution. The invention of the Barmac crusher in New Zealand in the 1980s removed the very problems of deleterious particles and poor shape characteristics that had frustrated the widespread adoption of manufactured sand for use in concrete.

In terms of comminution technology, shaping rather than just sizing became a guaranteed and cost-effective option.

So the two drivers comprising i) reduced environmental impacts, led by public expectation and ii) adoption of new extraction, processing and transport technologies have driven extractive resource choice and availability over the past 30 years. But what
of the future?

Mt Coot-tha receives spoil from Brisbane’s Legacy Way tunnel project which is delivered by underground conveyor. The spoil is being used to rehabilitate disused sections of the quarry.
Mt Coot-tha receives spoil from Brisbane’s Legacy Way tunnel project which is delivered by underground conveyor. The spoil is being used to rehabilitate disused sections of the quarry.

PRACTISING THE DARK ARTS Here we enter the realm of the dark arts – forecasting!

Let’s assume that the level of community acceptance, reflected in legislation, along with innovation in technology and systems, will continue to remain key influences into the future. But note there are limits. For example, at present the limiting distance to sensitive receptors for production blasting is about 250m, provided certain blast designs, technologies (and flyrock control measures) are rigorously applied, and blasting experts say there’s little scope to go closer.

There is no doubt there is further scope for adoption of noise and dust suppression technologies, particularly as the costs of such technologies reduce. And innovations in transport, automation and materials technologies can be expected.

The relentless drive to reduce workers’ exposure to hazards, along with employment costs and difficulty of recruitment as people choose not to work in perceived “dirty” industries, will drive automation, but an autonomous quarry in Australia is not likely before Quarry’s 60th birthday.

Natural sand will remain a vital ingredient in any future mix of construction materials supply but uncertainty of tenure and continuity of supply will drive further innovation in fine sizing of shaped manufactured sands.

Resource scarcity from attrition and competing land use will continue to trend production to proven reserves worked by larger quarries with attendant economies of scale supporting a wider economic radius of distribution.

But not all quarries service large markets or areas. Perhaps two-thirds of Australia’s quarries (and more if gravel/borrow pits are included) are situated in regional Australia, with many worked only part-time.

Underpinning future supply, be it for city, town or rural community, will be a necessary increase in geological and geotechnical assessment, to ensure source rock properties are matched to needs and viable extractive footprints are designated before embarking on detailed design.

Increasingly, higher upfront evaluation costs will be the price to pay for planning scheme protection for greenfield sites and development approvals.

For impacts to be adequately known, the resource must be adequately known, so expect further innovations that lower the costs of geological assessments, inducing more quarries of all sizes to adopt a more scientific approach to initial resource delineation.

In terms of sustainability and its metrics, mining futurists1 foresee greater than 30 per cent reductions in energy use, waste, man hours worked per tonne, carbon emissions and transport costs over the next 30 years. It is certainly feasible that such reductions could be achieved across the extractive industries as a whole.

Recycling and substitute materials (eg spray-on roads, geopolymers) will play an increasing role, perhaps to 20 per cent or even 25 per cent of total demand. We can expect significant reductions in the generation of waste earth materials. But the majority of aggregate and roadbase demand will need to be met by conveniently located, hard rock quarries, where the “proximity principle” of local resources satisfying local needs will gain planning influence along with large but more distant hard rock quarry precincts.

In 1984, young mining engineering student Dugald Gray completed an assignment about the declining reserves and environmental impacts on the then 65-year old Mt Coot-tha Quarry.
In 1984, young mining engineering student Dugald Gray completed an assignment about the declining reserves and environmental impacts on the then 65-year old Mt Coot-tha Quarry.

Recycling and substitute materials (eg spray-on roads, geopolymers) will play an increasing role, perhaps to 20 per cent or even 25 per cent of total demand. We can expect significant reductions in the generation of waste earth materials. But the majority of aggregate and roadbase demand will need to be met by conveniently located, hard rock quarries, where the “proximity principle” of local resources satisfying local needs will gain planning influence along with large but more distant hard rock quarry precincts.

In its 2009 British aggregates industry scenarios, the Boston Consulting Group2 identified energy and economic climate as
the future “uncertainty generating factors” affecting the UK aggregates industry.

Its scenario matrix, with a distinct carbon flavour, featured “return on energy efficiency investment” and “demand/economic climate” as the key commercial drivers of the future. Certainly, neither can be left off any radar scanning the future of the extractive industry in Australia.

To venture further into the unknown (and I admit the crystal ball gets much cloudier), we might take a final look at geopolitical and global demographic scenarios and long-term trends. George Friedman, in his counterintuitive book The Next 100 Years, uses geopolitics and demographic trends3 to detect what Pierre Wack, the Yoda-like founder of scenario planning, called “weak signals”.

Friedman suggests we factor in a flattening in global population by 2030 as the Western rate of decline in the birth rate propagates globally, driven by rising living standards and, interestingly and quite perceptively, the achievement of gender equality on a near global scale.

By 2040 Friedman postulates that as population growth starts to plateau, countries will be actively competing to lure migrants as residents and workers.

If other countries offer greater incentives or Australia caps population because of fears of exceeding “carrying capacity”, then the day of a mature construction materials sector and its offspring, the Australian near-autonomous quarry, may draw nearer.

But let’s leave that for Quarry’s 60th birthday analysts. By then Mt Coot-tha Quarry will likely be a lake and botanic garden, its hornfels aggre



















Thursday, 24 January, 2019 09:18am
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