PART ONE: THE SCALE OF THE CRISIS

PART ONE: THE SCALE OF THE CRISIS

A worldwide mess

The safe disposal of tailings and other mine detritus (including overburden and waste rock) is acknowledged to be the most "problematic" technical challenge facing the mining industry - and one which is becoming more and more serious.

Each year, according to one estimate, some 15 billion tonnes of new tailings (sometimes mixed with "waste" rock and overburden, usually contaminated with chemical reagents and often with other detritus and pollutants) are deposited outside of metallic mine mills and other mineral extraction sites and open-pits. (If other solid and liquid wastes, especially from aggregates and coal mines were added to this figure, it would increase astronomically, probably by a factor of 300-400, ie. to around 5000 billion tonnes) 2

However, there is no international database of tailings sites. They are also rare at national level. There is not even a global figure of tailings dams, let alone their volume and physical and chemical composition.
Corporate irresponsibility

Many companies refuse - or are reluctant - to take responsibility for the massive legacy of toxic or acid-forming mine wastes already blighting our planet, even as they create additional ones .

The likely impact of ecospheric damage they cause can be gauged by a few examples. In the first eight years of operations at the Bougainville Copper mine (1968-1976) two hundred million tonnes of sediment clogged up the Kawerong and Jaba rivers, of which one third became deposited in the flood plains and the Jaba delta, thus "prograding" the Empress Augusta Bay by 30 metres [G Pickup and R J Higgins "Estimating sediment transport in a braided gravel channel - the Kawerong River, Bougainville, Papua New Guinea", Journal of Hydrology, Amsterdam, volume 40, 1979; see also L D Wright "Dispersal and deposition of river sediments in coastal seas: models from Asia and the tropics", Netherlands Journal of Sea Research, volume 23, 1989].

The Ok Tedi copper-gold mine in the highlands of Papua New Guinea has dumped 80,000 tonnes a day of tailings into the Ok Tedi/Fly river systems since 1989, causing a 90% fish kill in the lower Ok Tedi river and a current or eventual "die back" of vegetation and forests of at least 900 square kilometres. This devastation could increase to as much as 6,600 kilometres, if the entire catchment area were included ["Executive Summary, Assessment of Human Health and Ecological Risks for proposed mine waste mitigation options at the Ok Tedi Mine", OTML, Papua New Guinea, Detailed level risk assessment, August 6 1999].

But the world's worst "waster" is the Freeport/Rio Tinto-managed Grasberg mine across the border in West Papua (called Papua/Irian Jaya by Indonesia). Now the globe's biggest single gold producer and third biggest copper mine, Grasberg came on stream in 1973. By early 1999 it was casting no less than 200,000 tonnes of tailings each day into the Ajikwa river system.

Palliative responses

Growing international protests against tailings dam and "endemic" mine-waste disaster (occasional or regular leaching from thousands of mines worldwide) have prompted the mining industry to propose various "beneficial" uses of tailings or means to neutralise them. But only one of these - the reworking (often misnomered "reclamation") of tailings dumps (primarily in Asia and Africa) which still hold economic metallic values - promises to reduce heavy metal bio-availability, or acid drainage. And this still leaves behind virtually the same volume of wastes, along with the problem of neutralising the chemical reagents used in the "treatment" process, and ensuring longterm stability [see "Tailings retreatment in Northern Ontario" Engineering and Mining Journal (E&MJ) USA, September 1988 and E&MJ October 1989].
Theoretically, in-filling or backfilling, [treating and "replacing" tailings in old mine workings on closure] not only mitigates the toxicity of tailings, but can also stabilise treacherous underground shafts and help rehabilitate huge, ugly and dangerous open pits, suiting them for alternative use.

However, it requires impermeable, permanent linings and weather-resistant surface cover, as well as effective water run-off and collection systems, in order to stabilise metallic tailings over any length of time: this, along with the process of in-filling itself, can be prohibitively expensive. When pressed, some authorities have conceded that no lining, whether synthetic or natural (soil or clay) is impervious to leaking. This point is graphically illustrated by failures to deal adequately with higher acid (sulphide bearing) slag heaps at the huge Rio Tinto/BP Kaltim Prima coal mine in east Kalimantan [see MWAP/Nostromo Research, Kaltim Prima case study, London 1999].
Various "natural" methods of stabilising tailings, and attempts to neutralise them, have been proposed in the past 15 years. These include dry tailings disposal, the creation of wetlands to absorb heavy metals [see "Engineered wetlands and AMD" in Mining Environmental Management, London September 1993 and "Constructed wetlands - passive treatment of mine drainage" in Mining Journal supplement February 2 1991] and the addition of bacteria or algae to wastes [New Scientist May 25 1991]), along with recycling effluent discharges through a variety of collection points. Much of this sounds acceptable in theory. But practice (and costs) have a habit of jeopardising the best-laid plans of mines and men. For example, recycling and effluent treatment were judged unfeasible at the El Teniente copper mine in the Chilean Andes, where the dam was situated in a valley far below the mine workings, and 100,000 tonnes of waste water was daily being discharged at a powerful 1,500 litres per second. In 1991 siphoned the tailings onto cropland (sic) claiming this markedly increased agricultural productivity. The brains behind this scheme was Dames & Moore, which went on to win an Engineering Excellence Award (sic) for this effort, from the Utah-based Consulting Engineers Council [Financial Times, London June 6 1991].

Catastrophic costs?

The costs of "clean up" (another misnomer, since it implies not only effective detoxification but also removal which rarely, if ever, occurs) following disastrous "events", vary from site to site. None has come in at below US$100 million.

The prevailing definition of "costs" is often arbitrary and unacceptably narrow. It rarely includes paying adequate compensation to those whose health, goods, crops, land and drinking water quality have been directly degraded - or destroyed - by spills, leaks, or wholesale dam collapses, and the full costs of legal action in pursuit of these claims (if they ever reach court). The loss of income and benefits to mineworkers, the life-cycle replacement costs of degraded or depleted water are rarely evaluated.

Few companies go out of business as the result of the fines or compensation agreements imposed on them, or loss of confidence by shareholders, and some have devised methods by which to avoid financial liability or collapse.