Challenges in the characterization and prediction of the hydrogeology and geochemistry of mined ground

Abstract

Although mining is no longer a key industry in the UK, the international mining industry continues to expand. One of the principal legacies of past mining in Britain is water pollution emanating from abandoned mine voids and waste rock depositories. This has necessitated many expensive technical evaluations and remedial programmes in recent years, from which important lessons may be drawn for the still-growing mining industry overseas. Perhaps the single most important lesson is that there can never be too much information on mine hydrogeology and geochemistry available at the post-closure phase. As this phase is also the longest in the overall life cycle of any mine, it should be given appropriate consideration from the outset. The post-closure studies described in this paper and in this volume (as well as elsewhere) highlight the dearth of hydrological data that are usually available when compared with the wealth of geometric information available from mine abandonment plans. It is advocated that the collection of appropriate environmental data is built into the initial mine development plan and that monitoring commences from the green field site onwards. The uncertainties related to predictive modelling of mine water arisings are considerable, whilst those of predicting mine water quality are even greater. Numerous pointers towards robust mine water management strategies are identified, and a call for 'defensive mine planning' is made, in which relatively modest investments in hydrogeochemical control measures during the exploration and exploitation phases of the mine life cycle will yield dividends in the post-closure phase. With such measures in place, and enhanced monitoring data to hand, the conjunctive application of physical and geochemical evaluations will eventually provide much-needed predictive tools to inform site management decisions in the future.

Long‐term final void salinity prediction for a post‐mining landscape in the Hunter Valley, New South Wales, Australia

“…Also, catchment and landform dimensions need to be determined (Shevenell, 2000;Younger and Robins, 2002). This requires knowledge of the amount of overburden spoil resulting from mining, the final void dimensions and also the catchment area contributing to the final void.…”

“…The mine is typical of other opencast mines in the Hunter Coalfield, but differs from many other North American and European mines, in that the sulphide content of the coal and related strata is low and carbonate minerals are present; consequently, the chance of developing acid waters is low (URS, 2000;. The mine also lacks the high metal content prevalent in the overburden and groundwaters found in many other mines Younger and Robins, 2002). Nevertheless, the potential of generating a saline post-mining landscape at MAN is high (due to high sodium and chloride content in the groundwater and overburden), and it is important that methods for calculating post-mining salinity are available for mining companies, government departments and the local community.…”

“…This mining method is becoming increasingly common worldwide as advances in technology allow the economic handling of greater volumes of material (Bowell, 2002;Hartman and Mutmansky, 2002;Younger and Robins, 2002). This increased ability to handle larger volumes creates the potential for large final voids at the completion of mining, especially where stripping ratios are low.…”

“…This type of long-term study has not been undertaken before, and modelling is the only way to estimate the long-term risk from these lakes (Miller et al, 1996;Eary, 1999;Younger and Robins, 2002). Modelling also highlights deficiencies in existing input data and process knowledge.…”

Modelling the hydrogeochemical evolution of mine water in a decommissioned opencast coal mine

“…Various authors already studied the prediction of post-mining water quality in underground mines (Appelo and Postma, 2005;Banks, 1994;Gzyl and Banks, 2007;Wolkersdorfer, 1996;Younger, 2000Younger, , 2001Younger and Robins, 2002). Also the flooding scenario of opencast coal mines has been the focus of scientific studies (Ardejani et al, 2003;2007a;Dumpleton et al, 2001).…”