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By C A. Chaves

During most of its history, the metallurgical industry has been seen as a source of pollution for the environment. However, during the second half of the 20th century, as the world environmental legislation became more protective and the global environmental conscience consolidated, this landscape began to change. Metallurgical activities have become increasingly related to the social and environmental impacts caused by human activities. With the adoption of environmental management in steel plants, there has been a significant change in steel-related activities which have begun to introduce modern plants, managed with environmental, social and productive efficiency. More and more, steel companies search for a decrease in negative impacts of their industrial operations on the environment, fitting them to the current environmental legislation and even increasing productivity and profitability. The steel industry has started to become a clean and more efficient industry. This work presents a case study of a sustainable steel plant project, located in an environmental preservation area. The project includes treatment and reuse of industrial liquid effluents, air emissions control, noise control, recycling, recovery and adequate waste management. It also incorporates production processes using clean technologies, capable of coproducing energy resources which may be used in the plant showing how is it possible to produce steel with environmental and social responsibility and even increase the enterpriseÆs profitability.

Jan 1, 2009

By Hughes J. C

THE smelting plant consists of five large furnaces operating in the treatment of current flintered material, and one small furnace operating periodically in the treatment of copper dross and antimonial slag produced in the lead-refining process.he following table supplies the leading dimensions and details of the large furnaces:-(a) Crucible - Dimensions 17 ft. 2 in. long x 4 ft. wide x 2 ft. 3 in deep. Capacity - 30 tons lead. Class of lining - firebrick. No. firebricks required - 3000.(b) Crucible Tank - Dimensions 20 ft. 6in. long x 10 it. 6 in. Wide x 4 ft. 3 in. deep. Material - 1/2 in. mild steel.(0) Jackets - Dimensions 6 ft. long x 19 in. wide x 6in. thick. Material - Cast-iron. Average life - 2 years. Number per side - 11, with 13-in. bosh. Number per end - 3, with 9-in. bosh.

Jan 1, 1922

The Lane Cove Tunnel (LCT) is an important infrastructure link in New South Wales (NSW) and runs from the end of the Gore Hill Freeway at Artarmon at its eastern extremity, to the end of the M2 at North Ryde at its western extremity.  The LCT is 3.6 km long and generally consists of twin two/three lane unidirectional tunnels running largely under Epping Road from just east of Mowbray Road, west to the western end of the Gore Hill Freeway. The tunnel opened in early 2007. The presentation will provide a summary of the traffic and emission modelling performed for selected representative surface road sections in the vicinity of the Lane Cove Tunnel. An assessment of the predicted impact of vehicle emissions on ambient air quality in the corridor as a result of changed traffic conditions due to the tunnel opening will be presented. The traffic modelling and emission calculations were undertaken for the following two scenarios: Year 2006 û Lane Cove Tunnel no-build option, and Year 2006 û Lane Cove Tunnel build option. Vehicle emission calculations for the four main pollutants from vehicles: CO, VOC, NOx and PM10 on the surface roads in the vicinity of the Lane Cove Tunnel were performed using the predicted daily traffic for the two cases (no-build and build). The analyses indicated that the vehicle emissions for all pollutants are expected to significantly reduce in the corridor with the building of the Lane Cove Tunnel, including the areas in the vicinity of all tunnel portals, when compared to vehicle emissions for the no-build case.  As a result of the decreased vehicle emissions on the surface roads, the study concluded that the actual ambient air quality is expected to improve in the corridor including the tunnel portal areas after the Lane Cove Tunnel opening.

Jan 1, 2008

By J Cook

In this paper we present a case study of the challenges and opportunities associated with the development of cultural heritage management strategies at the Lihir gold mine in Papua New Guinea. We discuss the contextual drivers and constraints, and outline the ways in which Lihir Gold Limited is aiming to set new industry bench marks for the region through the development of values-based best practice cultural heritage management programs. This approach is largely based upon a compliance partnership with a local stakeholder group. We argue that such partnerships are a prudent means of mitigating company risk, while constituting a far more necessary tool for local people in the reconceptualisation and negotiation of the experiences of significant social change and modernisation experienced in the context of recent resource development.

Jan 1, 2009

By D S. Collins, Z Hosseini, I Pinnock, Y Toya

Microseismic monitoring is regularly used in the mining and geotechnical industries to provide detailed information about rock mass response to operational activities. This paper implements a variable 3D velocity model (VM) at a North American hard rock mine with the aim of further improving the accuracy of seismic event locations. A collapsing method is also used to help analyse two individual seismic event clusters at another North American hard rock mine. In the first case study, the location accuracy of events is shown to improve by moving from a conventional single VM to a variable 3D VM that accounts for voids and different geological domains. The modal average for the event location accuracy improved from 14 m to 5 m when the 3D VM was used. Additionally, the single VM failed to locate 26 per cent of the seismic events that were located by the 3D VM. In the second case study, the distribution of seismic events was further enhanced by using a collapsing method that highlighted planar structures. The collapsing method was performed on two large event sequences that occurred in close proximity and identified different seismic event distributions. One aftershock sequence aligned along a plane, suggesting an activated structure, while the other large event sequence had a more 3D distribution of events, suggesting a complex stress redistribution on smaller structures.CITATION:Pinnock, I, Collins, D S, Toya, Y and Hosseini, Z, 2016. Large event sequence analysis and 3D velocity models for seismic event location accuracy, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 879–884 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By Moeller T

The Bottle Creek mine, when opened next month, will consist of three open cuts, Emu, VB and Boags, feeding ore to a central mill. The open cuts cover a strike length of 4.5 kilometres which forms part of a linear structure, which can be traced geochemically for 26.0 kilometres. With the exception of a few small gossanous outcrops at Emu, the deposits are completely covered with insitu laterite and alluvial overburden. Since its discovery in 1984, the deposit has been subjected to three major reverse circulation (RC) drilling programmes which have successively closed up the drill spacing on the main mineralized zone to 25m horizontally and less than 25m vertically. All resource calculations have been based primarily on samples of RC drill cuttings from these programmes. Ore reserve calculations have been completed after each drilling phase. They began with a simple polygonal technique, progressed through two sectional half-distance calculations and are now being completed with a 3-D geostatistical technique. Because of the style of mineralization, Norgold personnel paid particular attention to assessing the variability of the mineralization by using repeat samples, repeat analysis and diamond drill vs RC comparisons. In addition, close attention has been paid to obtaining an accurate estimate of the global SG of the ore bodies. Particular care has been taken to obtain complete drill intersections of the orebody and to maximize wet sample recoveries. Extensive re-sampling and re-analysis of samples has confirmed that Bottle Creek is unusual for an oxidized gold deposit in that all the gold appears to be very fine grained, and evenly distributed within the mineralized zone.

Jan 1, 1987

By A H. Gray

Gekko Systems Pty Ltd engaged in the test work, design, manufacturing and commissioning of the pre-concentration plant at Silver Standard Resources Inc’s Pirquitas mine in the north western Jujuy province of Argentina. Testing of the ore at coarse feeds of between 2 and 12mm returned probable recoveries of up to a total of 95% silver into 50% of the mass fed to the InLine Pressure Jigs (IPJ’s). The plant has been designed and built based on the test results to include a preparation screen to bypass the fines that are naturally higher in grade and repulping of the coarse which is then pumped to three parallel trains of 2-stage IPJ roughing-scavenging. The target 50% yield to concentrate passes over a dewatering screen and the solids are returned back to the mill feed conveyor. The IPJ tails are transferred to a dewatering screen and solid rejects are stockpiled off the end of a transfer conveyor. All dewatered underflow products are processed via hydrocyclones to recover dirty water for use back into the IPJ circuit and return entrained fines to the fines bypass line.With the sulphide orebody being processed, the results from operations to date have shown that plant performance is matching the original laboratory sulphide ore testwork data. The objective of the pre-concentration step is to both reject gangue and achieve grades between 300-400g/t Ag to the float circuit as flotation recoveries are maximised within this range. The plant currently achieves overall upgrades of approximately 150% of feed grade with the IPJ only circuit producing an average 180% increase from calculated feed grade.

Aug 8, 2011

By K White, R Hardie, J Merritt, B Kirsch, R Lucas

Constructed stream diversions are a common element of mine sites across Australia. A review of constructed stream diversion performance in the Bowen Basin funded by the Australian Coal Association Research Program (ACARP) in 1999 found over 80 per cent of constructed stream diversions failed to meet regulator and operator expectations. Since that time, improvements have been made in the assessment, design, monitoring and management of constructed stream diversions. Fundamental to these improvements has been the development of a better understanding of the regional stream systems and efforts to replicate the natural stream processes in the function and operation of constructed stream diversions.This paper discusses the history of constructed stream diversions through the Bowen Basin in central Queensland recorded in the outcomes of a series of ACARP funded research projects. Further, the paper reports on the outcomes of a current ACARP funded project that has reviewed the success or otherwise of constructed stream diversions in the region. The assessment has compared the performance of diversions that have been designed to replicate and provide for ongoing stream geomorphic processes with those diversions that were designed and built prior to the development of these design improvements. Based on these investigations we have identified design and construction successes and issues requiring further research and management attention.CITATION:White, K, Lucas, R, Hardie, R, Merritt, J and Kirsch, B, 2013. Challenges and opportunities for constructed stream diversions in the Bowen Basin, Central Queensland, in Proceedings Water in Mining 2013 , pp 73-82 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 26, 2013

By M Aros, L Reilly

Iron ore is normally sold in bulk at certain specifications. These include iron grade and specific contaminant grades, typically silica, alumina, phosphorous and sulfur. These target grades are normally agreed between the mining company (producer) and the steelmaking company (customer).This study presents an alternative to traditional cut-off grade calculation, using linear programming that maximises the total ore inventories within a predefined mining envelope while meeting the specified targets. Providing a feasible mining sequence that maintains the target grade is not covered in this study.The method was applied to Fortescue’s operations. The complexity arising from differing ore quality within each mining horizon, variable yields and upgrades and the need to control iron and contaminant grades provided a good opportunity to test an alternative method of ore selection. The new method significantly reduced the time spent in cut-off selection and sensitivity analysis, and provided an optimised solution.CITATION:Aros, M and Reilly, L, 2014. Ore selection optimisation for an iron ore deposit using linear programming, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014, pp 345–350 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

The western Cordillera of North America, including more than 99% of Alaska, is made up of an agglomeration of litho-tectonic terranes, some of which have undergone large rotations and (or) translations. The larger terranes can be broadly grouped into a small number of composite terranes based on affinities in their lithology, structure, and tectonic evolution. The terranes reflect repeated episodes of marginal rifting as well as formation of marginal arcs, island arc chains, back-arc basins, and oceanic plateaus since late Proterozoic time. Accretion to the continental margin occurred mainly from Middle Triassic through Early Cretaceous time. Major northward dispersal of terranes was largely during the existence of the Kula plate from about 85-55 Ma. Major rotations are the mid-Cretaceous opening of the Arctic Ocean basin with counterclockwise rotation of Arctic Alaska and Laramide oroclinal bending of western Alaska. The present complex Cordilleran geology along the northeast Pacific rim is a sum of these earlier accretionary processes together with continued Cenozoic faulting and deformation that has been superimposed upon the agglomerated displaced terranes over a broad segment of the continental margin.

Jan 1, 1990

By Y Li

An ilmenite ore from the Murray Basin was initially characterised using combined X-ray Fluorescence Spectroscopy (XRF), X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Electron Probe Microanalysis (EPMA) techniques. XRF analysis showed the ilmenite sample contained 58.7 wt per cent TiO2 and 26.2 wt per cent Fe2O3. Major impurities included: Cr2O3 (4.5 wt per cent), Al2O3 (2.7 wt per cent), SiO2 (1.9 wt per cent), Mn3O4 (1.5 wt per cent) and MgO (1.1 wt per cent). Manganese and magnesium were present as solid solution components within the ilmenite lattice while the elevated Al2O3 and SiO2 levels were due to separate aluminosilicate gangue minerals. Chromium was associated with discrete chrome spinel gangue phases of variable composition, (Fe,Mg)(Cr,Al)2O4. Quantitative XRD analysis of the sample identified rutile (12 per cent), ilmenite (11 per cent), and pseudorutile (67 per cent) as the main titanium-containing phases and chrome-rich spinels (seven per cent) as the major impurity phase. Minor quartz, aluminosilicates, zircon and monazite were also present. The ilmenite was mixed with synthetic graphite, pressed into pellets and reduced carbothermally in nitrogen at 1200 and 1400°C with C/O molar ratio of 1.2. Titanium oxide in the ilmenite was converted to titanium oxycarbonitride. Iron oxides were reduced to metallic iron. The Changes of impurities as a result of reduction was examined by SEM and EPMA analyses. Iron and chromium oxides within Fe-rich chromite were reduced to form a Fe-Cr-C alloy. Mg-rich chrome spinels were partly reduced at 1200°C. Zircon particles were not reduced at 1200°C, but were significantly reduced at 1400°C, with the particles becoming porous and the silicon being removed.

Oct 5, 2011

A great range of contacting equipment is used in solvent extraction. However, a tower filled with a regular packing offers many advantages in the direct extraction from slurries. A study was made of the flow of a dense slurry through a packed tower in which the continuous phase was kerosene. The grid type packing, which was preferentially wetted by the slurry, had slats inclined at an angle of 30¦, to the horizontal. On the sur- face of the slats there were uniformly spaced longitudinal indentat- ions. These were of a height slightly less than the film thickness and divided the slurry discharging from the bottom of the slats into a number of uniform streams. When slurry entered the tower it was distributed by means of a troughs and weirs type of distributor. Because of the relatively high slurry velocities that occur at the entry region, it was necess- ary to have the distributor and the first two grids above the solvent level. The interface at the bottom of the tower was located at the mid-point of the bottom grid, so that the slurry entered the interface as a continuous film across the full width of the slats. Using the above system, stable flow with low entrainment was achieved at slurry flow rates of 3.4 mis/cm/sec. This would be equivalent to a flow rate of 177 gallons per minute through a tower of cross-section 4 ft 4 in. by 4 ft 10 in., or 1200 tons per day of solids of specific gravity 2.6 when the pulp density was 65 per cent. Previous tests indicated that a total tower height of about 30 ft would be required for a recovery of better than 99 per cent.

Jan 1, 1969

After some 50 years of worldwide research in relation to coal pillar mechanics and design as well as numerous workshops and technical papers related to these issues there is still some significant disagreement as to the approach one should adopt in the assessment and design of a coal pillar. Of course there are many different types of coal pillars that fulfil a wide range of roles at any particular mine and in this instance it is appropriate to have a 'tailored' approach for each pillar type in relation to the role it fulfils. However where it can become very difficult for the mine operators is when various researchers or consultants use or recommend significantly different approaches for the same type of pillar fulfilling the same role. By 1999 two pillar design techniques had been developed specifically for the Australian underground coal mining industry (ie The University of New South Wales Pillar Design Procedure, UNSW PDP and Analysis of Longwall Tailgate Serviceability, ALTS) and several other pillar design techniques were being practiced by individual consultants. The Australian industry hoped to resolve the issue of what technique to use for each pillar type and role, when it funded UNSW in 2000 to develop a 'Systems Approach to Pillar Design'. The findings of the abovementioned project were published in 2005 and while every attempt was made by UNSW to include the views of various local and overseas researchers and consultants it would be fair to say that a unified approach to pillar design in Australia was not adopted as a result of that project. This is the experience of one country where there has never been one central group solely undertaking such research in relation to pillar design (such as the Chamber of Mines in South Africa). This paper explores the Australian experience in terms of pillar research and what that experience may offer to researchers in Australia and other countries. At the First Australasian Ground Control in Mining Conference (2003) the first 'update' of the ALTS Design Methodology (ie ALTS II) was presented. In subsequent years the ALTS database was continually updated and significantly expanded such that it now includes detailed information in relation to both the tailgate (148 cases) and maingate belt road (58 cases). In addition to tailgate roof support and chain pillar design, the current version of ALTS (referred to as ALTS 2009) includes a maingate belt road roof support design module. This paper is also intended to update and summarise the development and application of the ALTS Design Methodology for longwall gateroad design over the last decade both directly and in the context of coal pillar research conducted in Australia over the last 15 years.

Nov 25, 2010

By S Lakemond, L I. Ku, J Vaughan

Conventional processing of poly-metallic gold containing flotation concentrates are challenging for a number of reasons. One reason is that substantial copper and zinc in the cyanide leach solution compete with gold and silver for carbon adsorption sites. In this study, metal-cyanide adsorption kinetics and equilibrium are measured on three samples of coconut derived activated carbon and one sample of synthetic carbon. Loading selectivity was confirmed to be in the order gold>silver>copper>zinc for all carbon samples. The synthetic carbon tested showed promising results in terms of loading kinetics and capacity for precious metals.CITATION:Lakemond, S, Ku, L I and Vaughan, J, 2013. Effect of carbon type on adsorption of Cu, Zn, Ag and Au from mixed cyanide solution, in Proceedings World Gold 2013 , pp 411-418 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 26, 2013

By Maidl B

A tunnel operations analyser is a new high technol- ogy instrument for use in underground work. By remotely sensing the acoustic emissions from operating machines and processes in a tunnel or shaft and by applying sophis- ticated computer processing to them individual process cycles and other detailed information about the operating processes can be collected. Detailed analyses and dissec- tions of the work in progress can be made and a variety of action oriented management reports produced. The pro- cess is fully automatic. Results of applying this device to two full scale tunnel projects are presented. The hardware and software that comprise the instrument are discussed in detail. Processes by which this device can be used to sub- stantially reduce tunnel costs are presented. It is concluded that this type of technology has great potential.

Jan 1, 1987

Since gold was first discovered, mining development in the West Australian goldfields has been heavily dependent on the location of groundwater both for potable and mineral processing supplies . The location of adequate and economic sources of water has been a constant challenge to both explorers and developers throughout the history of the goldfields. The provision of a piped supply from Mundaring in 1903 greatly alleviated pressure on scarce resources, lowered mining costs and permitted the orderly development of infrastructure. However, increases in the demand for water resulting from new mineral discoveries over the past three decades has led to renewed pressures for more local supplies to be established. Wide-ranging groundwater exploration took place in the late 1960's and early 1970's, also, more recently, in support of intensified gold exploration. The collation and interpretation of the hydrogeological data from the whole goldfields region indicates that despite a low mean annual rainfall of between 180 and 350 mm, quite marked differences exist between the rates of groundwater recharge in different parts of the area, In general, these can be shown to diminish in a southerly direction contrary to a trend towards increases in annual rainfall. Recharge rates are related mainly to differences in rock weathering pattern, geological structure and physiography. The same differences have controlled the pattern of groundwater salinity and the magnitude of groundwater storages associated with the palaeodrainages. In the vicinity of the northern and western watersheds with the Gascoyne, the superficial sediments tend to be thin, may have calcrete in the section and contain moderate storages of brackish or even fresh water. This contrasts with the lower regions of the palaeodrainages where calcrete is absent and deeper erosion has permitted the accumulation of relatively large thicknesses of fine-grained sediments which are saturated with hypersaline water and constitute substantial storages. Account must be taken of these characteristics if water supply sources are to be optimised to meet the growing demands for groundwater in the region.

Jan 1, 1988

By Hunter W. H, Wilson I. P, Craig R. W

In September 1988 the Imperial Smelting zinc - lead blast furnace at Avonmouth England, was uprated from its then 52 week annual rated capacity of 90 000 tonnes/year of furnace zinc to 110 000 tonnes. In order to provide sufficient extra feed the sinter plant was likewise uprated in April 1989 by increasing the blowing rate of the sinter/acid plants from 100 000 to 120 000 Nm3/h, effectively a 20 per cent increase. In the 12 months after the uprate zinc production was only 85 000 tonnes. Two years after the uprate zinc production had increased to 100 000 tonnes, but it was not until January 1992 that a rolling 12-month zinc production of 110 000 tonnes was consistently achieved. This paper describes the problems encountered with the uprate and how they have been or are being overcome. It deals chronologically with events starting with the restart of the ISF at the end of 1988 and covers the following issues and their resolution: 1. Initial shortages of sinter due to an offset in uprate timing. 2. Greater difficulties in operating the larger furnace particularly on start-up, the greater tendency for iron production and serious slagging problems. 3. Coincidental timing of deleterious trends in slag chemistry. 4. Refractory problems in the furnace shaft and condenser. 5. Shortages of sinter due to commissioning problems with the wet gas and sinter tip end fans, and difficulties in obtaining sufficient sinter hardness. 6. Unrealised full benefits of the sinter-acid uprate due to a late change in design to dispense with sinter gas recirculation, but offset by successful use of oxygen. In a planned maintenance stop in September 1992 further improvements to the furnace design were carried out to resolve the refractory problems, and with improvements to the sinter plant the furnace zinc output capacity is planned to rise to a rate of 120 000 tonnes/year within two years.

Jan 1, 1993

By M K. Singh

Mining is nothing but an art - besides being a science - of extracting valuable minerals from the womb of the mother earth. In this gigantic task, a large number of machinery and equipment are employed judiciously. Wire ropes play a vital role in lifting or hoisting men and materials under hostile/adverse working conditions and constitute a major item of investment on machinery/equipment. The economy of using a wire rope is a concern for engineers, users and the planners. The economic use of wire ropes for mining purposes largely depends on the following factors;Mechanical design considerations - which include tensile strength of wires, elasticity, resistance to abrasion and crushing, fatigue values, static and dynamic loads on wire ropes, factor of safety, fleet angle, etc. Metallurgical consideration - Composition and heat treatment of wire materials, defects like inclusions and voids, surface quality factor, lubrications, micro structural parameters. Operational consideration - Seizing and cutting of rope, storage, care and maintenance, cutting back, etc. Environmental consideration - Temperature and humidity, pit condition, dust, corrosive atmosphere, etc. In the present paper, an attempt will be made to suggest steps for achieving optimum economy while using the wire ropes for extraction of precious minerals and coal keeping in view the points noted earlier. Once technical viability is established, economy is the ultimate consideration for an industry for safe hoisting of men and material.

Jan 1, 2000

By H Zhang, A Lawrence

To accommodate the fast growing need for services in Singapore’s Marina Bay downtown area, Marina South, the construction of a common services tunnel (CST) was required. The CST includes various services such as telecom cables, power lines and water pipes. A deep excavation and temporary earth retaining system (TERS) was required to facilitate the construction of the tunnels. Marina Bay is reclaimed land over thick soft marine clay which is likely to be still consolidating. The deep soft marine clay poses a big challenge for deep excavations in downtown areas where highways and sensitive structures are close by. This paper presents a case study of part of the CST Phase 1B and 2 at Marina South, in particular a 26 m deep excavation supported by a 46 m diameter temporary caisson. The construction started in late 2006 and the basic structure was completed in early 2011. The caisson was formed by 1.0 m thick overlapping diaphragm wall panels with a capping beam and three ring beams at different depths. Two-dimensional finite element analyses were conducted to predict the ground settlement, lateral displacement, bending moment and hoop stresses in the diaphragm wall and ring beams during different excavation stages. A comprehensive instrumentation and monitoring scheme was established to verify the design predictions, control excavation safety and trigger the contingency plan to protect public safety. The impact of construction activity, unbalanced temporary stockpiles and adjacent deep excavation for a mole removal will be discussed.CITATION:Zhang, H and Lawrence, A, 2014. A case history of a deep excavation in a big circular shaft in Singapore marine clay, in Proceedings 15th Australasian Tunnelling Conference 2014, pp 581–588 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By P M. Ashley, M T. Costelloe

The Mary Kathleen tailings storage facility (TSF) contains 7.1 Mt of uranium mill tailings. This waste repository was rehabilitated in the mid-1980s using a multibarrier dry cover. At the time of mine closure, it was predicted that acid mine drainage (AMD) generation would not eventuate and that uranium, heavy metals and radionuclides would be adsorbed within the tailings and not seep from the TSF into the environment. This study reports on the environmental status of the TSF. Gamma-ray measurements indicate an intact dry cover of the waste repository. However, seepage (~0.5 L s-1) of acid (pH 5.71), saline (0.31 per cent), high conductivity (8.8 mS cm-1), slightly oxygenated (DO 2.6 mg L-1), radioactive waters occurs from the toe of the tailings dam into the former evaporation ponds and local drainage system. Seepage waters are calcium-magnesium-sulfate rich with elevated Fe, Mn, Ni, U and Zn values. Oxygenation of tailings seepages causes the precipitation of Fe and coprecipitation and adsorption of other metals (Pb, U, Y), metalloids (As), rare earth elements (Ce, La) and radionuclides (U-235, U-238, Th-227). In contrast, Ba, Ni, Sr, Mn, P, S, Ca, Mg, Na and K as well as Ra nuclides (Ra-226 and Ra-228) remain in solution until pH neutralisation and evaporation lead to their precipitation in efflorescences and sulfate-rich evaporative sediments further downstream. Dry capping of Mary Kathleen uranium mill tailings has resulted in physical containment of the wastes. The dry cover shows no signs of erosion and radiation levels are within acceptable limits. However, the flow rate of surface seepage from the TSF occurs at a much higher rate than predicted. Also, the neutralising potential and adsorption capacity of the tailings and underlying aquifer were overestimated at the time of mine closure. AMD has developed mobilising metals, metalloids, rare earth elements, alkalis, radionuclides and sulfate from the waste repository into surface water seepages.

Jan 1, 2003