Reprinted with permission of
Economic Geology, v.98:6, p. 1253-1254, Gustin, M.S., 2003.
Environmental Aspects of Mine Wastes. Short Course Series, Volume 31. J.L. JAMBOR, D.W. BLOWES, AND A.1.M, RITCHIE, EDS. 430 Pp. Mineralogical Association of Canada. 2003. Price US$50 outside Canada; CAN$50 in Canada; member price, US$40/CAN$40.
Mine wastes are the bane of the mining industry. In order to extract a mineral resource, a mining company is faced with determining how to deal with the waste material with the mining process. As environmental awareness has increased, this task has become increasingly arduous. Waste rock and tailings often contain high concentrations of metals and minerals that may produce acidic waters, which facilitate the release of contaminants to aquatic ecosystems. Although acid mine or rock drainage (ARD) is a major environmental issue facing the mining industry, W.A. Price points out in the first chapter of this book that this is only one of a multitude of issues facing those who manage mine wastes.
This volume is the result of a short course convened to assess the progress and new developments in the study of the environmental aspects of mine waste in the time since a similar short course was held almost a decade ago. The papers summarize the progress on understanding the geochemical processes that control the chemistry of the releases from mine waste, the methods applied for treatment of mine waste, and "real life" examples of environmental releases, management, and remediation. The well-written and carefully edited papers that make up this volume will be of value to any engineer, geologist, hydrologist, environmental scientist, and educator involved with opening, closing, and remediation of abandoned and active mine sites.
Preventing impact from mine waste materials is costly and some understanding of how to predict and mitigate impacts can help in initial resource evaluation, development, and mine closure. Improper actions can result in accrual of even greater costs; therefore, educated planning for dealing with wastes is the best management strategy. The 20 papers included in this symposium volume provide a foundation for making informed management decisions. As pointed out in the Preface, one of the major difficulties in assessing the environmental impacts of mine waste is that geochemical processes evolve over time. Therefore it is important that we can predict, using geochemical modeling and temporal field data, what those changes will be over time, given the environmental conditions. As temporal monitoring of releases continues and our database on the geochemistry of mine waste increases, our ability to implement sound remediation strategies will increase. This is demonstrated by the Rum Jungle uranium mine (northern Australia) story, described in this volume, and based on 30 years of data.
The first paper, by R.A. Price, nicely summarizes the challenges posed by metal leaching and ARD associated with mine wastes, and the approaches applied to address them. He points out that once the conditions conducive to ARD have been established, they are difficult to stop. We must, therefore, develop the tools to prevent ARD from initiating. He highlights the fact that if measures are to be implemented, they need to be designed so that they are operated and financed indefinitely. This may be difficult because there is little long-term operating experience in reducing releases.
The paper by Seal and Hammarstrom, which discusses geoenvironmental models, provides a great example of the type of mindset that is needed for an approach to mitigating environmental issues associated with specific types of ore deposits. This forward-looking paper demonstrates that the use of a geologic framework will facilitate implementing sound management practices to reduce environmental impacts. Development of a good geoenvironmental model based on already well-developed ore deposit models will provide a framework for responsible development, mining, processing, and closure.
Four papers address water and gas-driven transport processes within mine waste, and the geochemical" factors controlling the chemistry of the fluids being released from mine waste. Fluid and gas influx, as well as flow within waste piles, can be very difficult to characterize. The papers by Smith and Beckie, and by Ritchie, discuss the significance and the means of monitoring and reducing these flows. The chapter by Jambor provides a discussion of the changing mineralogy and chemistry of mine waste as it interacts with water and air over time-sort of a Bowen's Reaction series for the environmental geochemist. Jambor points out how we need to look beyond the acid-generating capacity of the waste to the neutralizing capacity, and the reactions associated with the gangue minerals.
Four papers discuss laboratory tests that have been applied to characterize mine wastes and the limitations of these tests. One of the explicit needs is to develop test data for representative rock types so that there will be a database of information that may be applied to a variety of deposit types.
Several chapters deal with the difficulties of characterizing the mineralogy of fine mine wastes and the importance of quantifying surface reactions within this material of high surface area. The chapters by Gould and Kapoor, and by Nordstrom, provide an educational discussion of how microbes may exacerbate and mitigate the environmental impacts of water released from mine waste.
Four chapters focus on the geochemistry of ARD and how to characterize and model potential formation. Over the past 10 years, significant advances have been made in incorporating key processes into models. The chapter by Ptacek and Blowes discusses the limitations and advances made in the application of geochemical models to natural and contaminated systems. They conclude that deficiencies in databases and field measurements continue to be the shortcoming for using models that predict geochemical processes. They describe recent improvements to model inputs-specifically, components that address the high concentrations of dissolved solids often observed in effluent and prediction of phases being precipitated. The paper by Mayer et al. discusses advances in modeling dealing with unsaturated flow and gas transport, and the fact that computational capabilities have significantly increased. The paper by Seal discusses applying stable isotopes for interpreting physical, chemical, and biological processes for generating acid waters, and the need to integrate data for multiple isotopes.
The last four chapters deal with methods of treatment and prevention of ARD, along with case studies. Treatment methods range from passive to development of permeable reactive boundaries to active treatment systems that will need to be maintained into perpetuity. These last chapters would give those assessing mine closure methods an awareness of the methods currently used, the successes and pitfalls, and most importantly, their longevity in protection of aquatic ecosystems. A detailed discussion by Ritchie and Bennett on remediation efforts at the Rum Jungle mine describes the implementation of a cover to reduce outputs of metals and ARD. The last chapter, by Alpers et al., summarizes the modeling results focused on development of a treatment system for the Iron Mountain massive sulfide deposits, a worst-case scenario in the generation of AMD.
There is a wealth of information within the covers of this book that can be used to assess the scope of environmental issues for waste derived from the mining of any metal deposit Despite the fact that we still do not have all the necessary tools for long-term prediction of releases, and that there are few inexpensive long-term solutions to control contamination, this book demonstrates that much progress has been made in our understanding of the environmental aspects of mine wastes over the past 10 years. This book also provides an impetus for us to adapt standard, well-developed, and researched geologic models, such as ore deposit models and rock weathering sequences, to reduce the environmental impacts of metal resource extraction.
MAE SEXAUER GUSTIN ASSOCIATE PROFESSOR
DEPARTMENT OF ENVIRONMENTAL AND RESOURCE SCIENCES
UNIVERSITY OF NEVADA
RENO, NEVADA 89557