Search Documents

By O. K. Mahabadi

The scope of this study is to simulate the behaviour of a layered rock sample under standard laboratory Brazilian Disc test using an innovative combined finite-discrete element method (FEM/DEM) research code. The influence of layering and the direction of loading on the samples behaviour are studied through various layering and loading configurations. A parametric study including the effect of loading rate on the tensile strength of samples has been carried out. This paper demonstrates the suitability of the numerical approach to explicitly model rock deformation and failure.

May 1, 2009

By Richard Maurice

RÉSUMÉ La restauration du site minier Poirier, à Joutel s?est déroulée entre 1998 et 2001. Le principal élément des travaux a été la restauration du parc à résidus et des zones d?épanchement qui totalisaient 4,5 millions tonnes de résidus répartis sur une superficie de 74 hectares. Les résidus sont fortement générateurs de drainage minier acide. La première partie de la présentation consiste en un bref rappel du concept de restauration suivi d?une description des principaux éléments de travaux avec l?emphase sur les leçons apprises de l?exécution des travaux. La deuxième partie de la présentation est axée sur les résultats du programme de suivi en cours depuis la fin des travaux en 2001. Les éléments de suivi se rapportent à la baisse du niveau de la nappe phréatique à l?intérieur de la cellule, au tassement des résidus dans la cellule, aux mesures de température et d?oxygène à l?intérieur de la cellule et finalement à l?amélioration dans la qualité de l?eau de surface. ABSTRACT The reclamation of Poirier Mine, in Joutel, was carried out between 1998 and 2001. The main component of the works has been the reclamation of the tailings basin and tailings spill area which contained a total of 4,5 million tonnes of tailings and occupied some 74 hectares of ground surface. The mine tailings are highly acid-generating. The first part of the presentation will deal with a brief review of the reclamation plan followed by a short description of the main work components laying emphasis on experience gained during construction. The second part of the presentation will deal with the results obtained from the environmental monitoring program still in progress since the end of reclamation work in 2001. The aspects discussed include the drawdown of pore water inside the covered tailing pile, the settlement of mine waste material, the monitoring of moisture, temperature and oxygen underneath the liner and finally, the reduction of loadings in surface water.

Nov 1, 2002

"The measurement of error in assays collected as part of a mineral exploration program or mining operation historically has been undertaken in a variety of ways. Different parameters have been used to describe the magnitude of relative error, and each of these parameters is related to the standard measure of relative error, the coefficient of variation. Calculation of the coefficient of variation can be undertaken in a variety of ways; however, only one produces unbiased estimates of measurement error: the root mean square coefficient of variation calculated from the individual coefficients of variation.Thompson and Howarth’s error analysis approach has also been used to describe measurement error. However, because this approach utilizes a regression line to describe error, it provides a substantially different measure of error than the root mean square coefficient of variation. Furthermore, because regression is used, Thompson and Howarth’s results should only be used for estimating error in individual samples, and not for describing the average error in a data set. As a result, Thompson and Howarth’s results should not be used to determine the magnitudes of component errors introduced during geochemical sampling, preparation, and analysis.Finally, the standard error on the coefficient of variation is derived, and it is shown that very poor estimates of relative error are obtained from duplicate data. As a result, geoscientists seeking to determine the average relative error in a data set should use a very large number of duplicate samples to make this estimate, particularly if the average relative error is large."

Jan 1, 2007

By Salvador Gómez, Rodolfo Espinosa, Jaime Bravo, Leopoldo Gallas

"Compañia Fresnillo, S.A. de C.V. - Proaño Mine, is owned by Industrias Peñoles S.A. de C.V. (Peñoles). The Proaño Mine, is one of the richest silver underground mines in the World, and for this reason, production capacity has always being expanded, based on generated reserves. Reserve generation has not being an easy task as this is a vein type deposit.This paper presents the growing stages at the Concentrator, for about the last twenty years; which can be listed as follows:1.,Increase in capacity from 1,000 to 4,500 tonnes per day, at several stages; on the same infrastructure, and without production interruptions.2.,Addition of a new flotation circuit to recover a zinc concentrate with a high silver content.3.,Installation of a semi-autogenous (SAG) mill, to replace a conventional crushing circuit. 4.,Modernization. Installation of an on stream analyser, an automatic reagent dosification system, 4500 ft3 unit cells, pressure filtration, a closed circuit video system to help process monitoring, an automatic ball addition system for SAG and ball mills, and on-line particle size analysers.5.,Silver recovery from old tailings, installing a 2,350 tonne per day treatment plant.INTRODUCTIONIndustrias Peñoles, S.A. de C.V. (Peñoles)Peñoles’ mission is to add sustainable value to non-renewable natural resources. Peñoles seeks to: build long-term shareholder value; provide customers with the highest quality product services; maintain productive long-term relationship with suppliers; develop and promote the capabilities of their personnel; foster mutually beneficial relationship with the communities in which operates; protect and preserve the environment."

Jan 1, 2002

By D. Gendzwill, N. Martin

"In early 1987, the Patience Lake potash mine near Saskatoon, Saskatchewan, was closed due to uncontrollable floodingWater inflows were first encountered during routine mining in 1975 at the south boundary of the mine lease. Underground grouting and construction of bulkheads limited the flo but did not completely stop it. Subsequent seismic surveys showed that the mine had approached the edge of a large collapse structure in which the salt and potash had been partly dissolved and removed by groundwater.In 1986, the small flow into the mine started to grow. Despite renewed grouting, the flood increased and outstripped pump capacity. The grouting program temporarily slowed the inflow but was unable to stop it. Eventually, from seismic and drilling evidence, it became clear that the water source was an extensive system of vertical fractures which would be impossible to seal by drilling and grouting from underground. A new plan to install 14 bulkheads underground would have sealed the water source from the rest of the mine but the construction program could not be completed before rapidly increasing inflow threatened to fill the mine. The underground mine was closed and a new solution mine started in 1988."

Jan 1, 1996

By H. M. Lewis

The current status of the international zinc market is summarized, and a supply /demand outlook is presented for the next five years. A number of technical problems facing the industry are outlined. Introduction ZINC has sometimes been called the unknown metal. Considering that on a world basis it ranks third among non-ferrous metals in production and consumption, zinc retains a certain modesty. It has no distinctive colour like copper, lacks the low density of aluminum or magnesium and is not always easy to identify as a product. The 'spangle' of galvanized steel is probably zinc's most distinguishing feature. The purpose of this article is to develop an over-all review of zinc. Starting with the current position of the metal, the major factors that will shape its future will be described so that an assessment of the outlook for zinc can be made.

Jan 1, 1978

By R. Sharon, P. M. Hawley, X. Ochoa

"Development of Barrick Gold’s Pierina gold mine in north-central Peru requires construction of a waste dump for disposal of nonore grade materials stripped from the open pit to expose the ore. The waste dump site is located near the open pit in a U-shaped valley that is underlain by thin colluvial and morainal soils with locally thick peats and glaciolacustrine deposits. Bedrock underlying the site consists of variably weathered volcanics. The site is subject to moderately high seasonal rainfall and significant seismicity. The geotechnical quality of the waste rock is highly variable, ranging from low-quality, degradable, soil-like materials containing appreciable quantities of silt and clay, to high-quality, hard, durable, blocky waste rock.A hybrid dump design concept was developed that requires in-pit segregation of highand low-quality waste, and selective placement of materials in the dump to maximize stability and enhance internal and subsurface drainage. The design includes a rock drain beneath the dump along the axis of the valley and a series of connected finger drains. Extensive peripheral diversions and stormwater control measures to inhibit infiltration of precipitation are also included.This paper discusses the unique challenges presented by the site and waste materials, the design methodology and stability analyses, and planned monitoring systems."

Jan 1, 2003

By M. Holm

Coal is an important fuel for energy generation, and since there are no adequate alternatives it will also be for the next decades. The deep lying hard coal is important in particular because of its high energy content. Automation of underground mining has led to major improvements in productivity and safety. A fully mechanized longwall shearer workface has already reached a high degree of automation and provides a high productivity for example utilizing the memory cut. Current researches and developments in longwall mining are focused on extending this method by adaptive cutting drum height adjustment. The so-called horizon control is often based on memory cut methods. Horizon control in this way requires information of the environment, which can be provided by models (seam model, cut model) and coal interface detection (CID). Available CID systems only provide an optimal output under specific conditions. The authors propose the shield-data-based horizon control (SDHC) system as an alternative approach. SDHC does not require information from a CID system or an environmental model. All necessary information is provided by roof supports, shearer and process monitoring. The SDHC system was tested in simulation under different seam conditions and yielded promising results which will be presented in this paper. In cooperation with the German mining company RAG the SDHC has already reached an experimental stage. A test assembly was built up at the surface and the SDHC system was implemented on real mining equipment. To make the test scenario as realistic as possible, the SDHC system was only connected to the monitoring system, not to the simulation model. The aim of these tests was to establish the cooperation between all subsystems, find appropriate controller parameters, locate and address safety critical aspects and finally to achieve an automatic cutting drum height adjustment. An introduction of SDHC for shearer guidance is given in this paper. The experimental tests are described and the control results of the realized SDHC system on the test assembly are shown.

Aug 1, 2013

By D. Mark Richards

Highland Valley Copper (HVC) is a large open pit copper mine in the southern interior of British Columbia. Machine guidance technology using GPS has been utilized at the mine since 1996 for blast hole drill navigation and since 2000 for shovel and dozer navigation. Since 1997, rock recognition has been part of the drilling process. This allowed the mine to develop a Mine to Mill strategy using the rock hardness information from drill monitoring systems to both refine drilling and blasting parameters as well as downstream crushing and grinding strategies. Although this preliminary effort has been very successful at HVC, the current intent is to gain further benefits through better use of existing information while also deriving an enhanced data set from monitoring production drills. In the latter case, the objective is to acquire and process drill variables in such a manner as to permit more detailed definition of rock mass characteristics. The subsequent focus will be to use the derived geotechnical and geological information as part of a practical process to more prescriptively blast the rock mass. Through the definition of domains based on drill monitored derived rock mass properties, the intent will be to enhance blast outcomes that lead to optimized downstream (from blasting through to concentration) processes in a more proactive and timely manner. This paper examines a proposed approach to be able to derive more accurate and consistent rock mass properties from production drilling. In addition, the discussion will identify potential benefits to be gained from process improvements that result in enhanced productivities, and crushing and grinding optimisation due to blasting strategies that are more closely matched to identify rock mass characteristics.

May 1, 2007

By P. Radziszewski

"The comminution energy curve is a profoundly simple graphical technique that displays detailed operating efficiency information for industrial comminution processes. The database underlying the methodology has recently more than doubled, to now contain a substantial fraction of the international comminution output (1.7 billion tonnes of rock per year) across more than 8 major commodities. This increase has deepened the analytical capabilities and effectiveness for assessing comminution circuit performance in relation to comparable operating mines. This paper will explore how the energy curve methodology can be used to examine the ability of stirred mill technologies to increase efficiency.Specifically, this paper explores how the energy curves methodology can be used to present energy efficiency gains achieved at three mines employing a stirred mill technology under different duties. The first of these cases studies was conducted by Rosa (2014) who compared the performance of two ball mills operating in parallel with a Vertimill in the regrinding circuit at the Samarco Iron project in South East Brazil. The Vertimill was found to achieve the same product specification while consuming 40% less energy. Brissette (2010) investigated the impact of grinding media on the performance of both ball mills and Vertimills. The energy savings achieved varied from 10% to 40% for the ball mills and 30% to 60% for the Vertimills. Lastly, Bergerman (2012) investigated the operating conditions of the Sossego regrind circuit from 2006 to 2011 against design specifications and laboratory testing. The operating work index of this circuit varied from 5.2 kWh/t to 44 kWh/t over this 5 year period. The full suite of energy curves"

Jan 1, 2016

By K. Swedburg, M. Samuels

"The New Afton concentrator was commissioned in June 2012, reaching the design milling rate in September 2012. By late 2013, through a campaign of optimization and de-bottlenecking, it was recognized that the installed plant was capable of greatly exceeding the design throughput of 11,700 tpd. Because the value of the metal contained (by increasing the plant feed rate) exceeded the offsetting losses of copper and gold recovery (as the operation moved to a coarser grind), the concentrator feed rate was strategically increased with support of New Gold, while the operations team was given a mandate to evaluate, and then implement, flow sheet options that could re-establish the original design criterion grind target and achieve the corresponding improved recovery. Broadly, the two options implemented were the addition of a tertiary grinding stage consisting of Metso Vertimill® prior to rougher flotation (in order to address the grinding required at increasing throughput by increasing the power), and the addition of three Woodgrove Staged Flotation Reactors (SFR) added to the cleaner circuit after regrind of the rougher concentrate (to address the increased mineral loading to the cleaner circuit). Through test work, it was anticipated that the SFRs would be capable of achieving final concentrate grade in a single pass without the integration of recirculating loads, a strategy sometimes referred to pre-cleaning. This paper describes the expectations generated for the Woodgrove SFR unit operation through pilot plant testing on site, and compares those results with the performance of the expanded circuit that exceeded the original design criterion of P80 160 µm, which was commissioned in the second quarter of 2015.INTRODUCTIONThe New Afton concentrator, located near Kamloops, BC Canada, commenced operation in June 2012. The mill achieved the design throughput of 11,000 tonnes per day average during the month of September 2012 and, following various operational optimization efforts (O’Hara et al, 2015), achieved the design p80 grind size of 160 µm at the design milling rate in July 2013.During August 2013, trials were carried out to determine the throughput rate limits of the mill circuits and to evaluate mill metallurgical performance at higher rates. Milling rates up to 15,500 dmt per 24 hours were achieved during this trial, demonstrating potential capability for sustained milling rates exceeding the nominal design capacity. As was expected, the higher milling rates resulted in a coarsening of the grinding circuit product size, and resulted in marginally lower recoveries in the rougher flotation circuit. Despite the lower recoveries, the higher milling rates resulted in higher metal production and the financial analysis favored running at rates of at least 13,000 tonnes per operating day, with the higher cash flow in the near term offsetting the value of metal production loss at the end of the mine life (due to the short term increase in the rate of reserve depletion). Milling rates were sustained above 13,000 tonnes per day through the second half of 2013, and increased above 14,000 tonnes per day by mid-2014 (Figure 1)."

Jan 1, 2016

By G. Belzil, F. Robichaud, M. Fullam

"The Goldex mining and milling complex is operated by Agnico-Eagle Mines Ltd. and is located in the Abitibi greenstone belt of Northwest Quebec, Canada. The mill operates presently at a throughput of 8,250 tpd with gold grade varying between 1.8 and 2.2 g/t. The ore is very high in gravity recoverable gold (GRG) at about 92% and as such a significant emphasis was placed on the gravity circuit. Commercial production started in 2008. Average gold recovery is 93.5% with about 68% of gold recovery coming from the gravity circuit. Over the course of the first several years of production, several gravity audits were carried out. In 2009, a complete gravity audit was completed, including ore, classification, Knelson Concentrators, and the gold room. In 2011, an audit was undertaken of the flotation circuit to determine the efficiency by which GRG is floated. Large samples of flotation feed and tails were collected and process for GRG content. This allowed a link between gravity and overall recovery to be made. This paper presents results of the audits and the development of a model linking gravity and overall gold"

Jan 1, 2012

By Manqiu Xu, Songtao Yang, Zongfu Dai, Robert Pelton

"Hydrophobic polystyrene nanoparticle suspensions were evaluated as potential flotation collectors for pentlandite. Experiments involving both clean model mineral suspensions and complex ultramafic nickel ores confirmed that conventional water-soluble molecular flotation collectors such as xanthate could be partially or completely replaced by hydrophobic nanoparticle flotation collectors. The ability of nanoparticles to induce flotation was demonstrated by floating hydrophilic, negatively charged glass beads with cationic polystyrene nanoparticle collectors. Electrostatic attraction promoted the spontaneous deposition of the nanoparticles on the glass surfaces raising the effective contact angle sufficiently high to promote the adhesion of beads to air bubbles. As little as 10% coverage of the bead surfaces with our most effective nanoparticles could promote high flotation efficiencies, whereas conventional small molecular flotation collector requires ~ 20% or higher coverage for a good recovery. Surface functionalized nanoparticles enhanced the ability for nanoparticle collectors to selectively deposit onto surfaces of the desired mineral particles in the presence of gangue. For example, poly (styrene-co-vinylimidazole) nanoparticles were designed to selectively deposit onto nickel mineral (pentlandite) in the presence of Mg/Si slime. Flotation tests of ultramafic nickel ores at Vale with these nanoparticle collectors have shown improvements in both pentlandite recovery and selectivity. On-going work includes attempts to identify specific applications where nanoparticle flotation collectors might be cost effective.INTRODUCTION Most mineral processing operations include multiple stages of froth flotation to concentrate and isolate the desired product. Before flotation, chemical collectors are routinely added to ground ore slurries, selectively binding to mineral-rich particles, increasing their hydrophobicity thus promoting selective flotation. (Fuerstenau, Jameson, & Yoon, 2007) Conventional collectors are surfactants with a short hydrocarbon tail and a head group, such as xanthate. A typical conventional collector is potassium amyl xanthate (PAX), which is a small molecule with an extended molecular length of about 1 nm. Critical characteristics of a good collector include the ability to selectively adsorb onto desired mineral surfaces and to lower the water/mineral surface energy. Despite the extensive role of flotation in mineral processing, some ores are difficult to process by flotation. For example, ultramafic nickel sulfide ore containing both valuable pentlandite and large quantities of unwanted Mg/Si slime [primarily serpentine, (MgFe)3Si2O5(OH)4] responds poorly to flotation. (Mani, Xu, Quinn, & Stratton-Crawley, 1997) Fibrous hydrophilic Mg/Si slime usually masks the surface of pentlandite (known as “slime coating”) due to electrostatic interaction (Edwards, Kipkie, & Agar, 1980) and dramatically depresses pentlandite flotation. Consequently, new approaches are required for processing these difficult ores."

Jan 1, 2012

By T. Bhambhani, D. R. Nagaraj

"Ultramafic Ni ores present significant challenges in processing in that both recoveries and grades are not satisfactory, due to the presence of Mg silicates in large amounts. Significant quantities of xanthates and CMCs are generally used for their recovery by flotation. Additionally, given that some of these ores are processed under acidic conditions, CS2 generation due to xanthate decomposition presents some safety hazards. Technology to replace xanthate has been developed for which the safety and health issues are absent. Collector S-10294 shows significant improvements in Ni and overall S recovery at a dosing rate of one half that of xanthate. New polymeric modifiers have also been developed that help reduce the Mg content of the concentrates at very low dosages. The reagents are custom designed for use in normal or hypersaline water, and acid or alkaline conditions.INTRODUCTION The use of xanthates in sulfide mineral flotation is reported to have started as early as 1925 (Nagaraj 2005). The reagent is now ubiquitous in the mining industry, accounting for 40-50% of total collector consumption. In recent years, the development of more selective reagents has rendered xanthates largely obsolete in Cu flotation. However, xanthates continue to be sold in large amounts in the Au, PGM and Ni flotation industry, where bulk sulfide flotation is required. The low cost and easy availability is the largest driver for the use of xanthates in the minerals industry. Of particular interest to this study is the use of xanthates in the flotation of Ni sulfide ores. About 60% of the world’s annual nickel output is obtained from sulfide Ni ores (Hoatson, 2006). A strategically important category of these ores is the ultramafic hosted sulfides, such as those of Western Australia and Canada. These ores are characterized by low Ni grades (<1%), with the Ni minerals being pentlandite, violarite, millerite and mackinawite, and gangue minerals comprising an array of altered Mg silicates, mostly serpentines. The challenges associated with treating these ores are well documented (Eltham et al. 1973; Claridge et al. 1975). One challenge is that Ni recoveries from these ores are lower. This has been attributed to the increased pulp viscosity, as discussed in detail by Vasudevan et al., 2010. Additionally, Mg silicates tend to report to the concentrate in large quantities, which is problematic for two reasons: a) concentrate dilution, and b) the high melting point of Mg silicates tends accelerate wear on the refractory lining of smelters. This has been attributed to network transport to the froth phase via bubble flux and entrainment (Patra et al, 2010)."

Jan 1, 2012

By H. B. Sahu, N. M. Mishra, D. C. Panigrahi

The paper presents the development of a spontaneous heating liability index (SHLI) of coal based on a mathematical approach. The parameters for the calculation of this index have been determined by differential scanning calorimetric studies. Thirty-one coal samples representing both fiery and non-fiery coal seams of different ranks have been collected from different Indian coalfields and their SHLI values have been determined. In addition, the susceptibility of these samples to spontaneous combustion has been ascertained by standard crossing-point temperature measurement. The moisture percentage of all the samples has been obtained by proximate analysis. A comparative study between SHLI and crossing-point temperature, along with moisture percentage, indicates that SHLI predicts the proneness of coal to spontaneous heating more accurately.

Jan 1, 2008

By Turgut Yalcin

"Recent years have seen a resurgence of interest in flotation cell design, and one of the areas where attention is being focused is flotation in centrifugal fields which aims at increasing the flotation rates by forced bubble-particle contact.A new cycloflotation device was developed at Laurentian University and tested on the nickel ore of Falconbridge Limited in Sudbury. In comparison with conventional flotation, cycloflotation yielded at least seven times faster flotation rates in terms of the mass of solids floated per unit time per unit flotation volume, while producing concentrate grades similar to those of conventional flotation. These results, which were obtained with a bench-scale ""cyclofloat cell,"" suggest that cycloflotation has the potential of setting a new direction in flotation technology.IntroductionFroth flotation is no doubt the dominant separation technique in the mineral processing industry. Since its inception early in this century, much research effort has been and is still being expended on this process. Until recent years, emphasis seems to have been placed on the chemical aspects of flotation, but there is now an increased awareness for the need to improve flotation machine performance and more and more attention is being directed towards this area. In a 1982 article on ""Flotation Machines"" (Young 1982) it is stated that "" ... by now the design of the machines used would have reached a high level of perfection, ... In fact, this is not the case ... "".The process of flotation in a flotation device may be considered to take place in several distinct stages as follows:"

Jan 1, 1994

By Michael Stuart Parsons

The haulage cycle is the sequence which a haulage vehicle must first arrive at the loading area, then turn around and reverse into position. Once it is loaded, the vehicle leaves and travels to the unloading area, where again it must turn around and back up to unload. The cycle is repeated over and over again. The Vector Neutral truck is a rubbertired, self-propelled hauling vehicle designed such that it eliminates the requirement to turn around and back-up to either load or unload. Vector Neutral Truck Cycle: 1.) Travel from the load station to the dump station. 2.) Stop and dump load. 3.) Travel from the dump station to the load station. 4.) Stop and load. The Advantage is in the Difference: 1.) Shorter distance traveled. 2.) Fewer brake and steering actuations. 3.) Easier to automate. 4.) Easier to adapt for remote control operation.

May 1, 2003

By P. M. May, V. Gella

The deportment and speciation of trace elements during mining and minerals processing is becoming an area of increasing concern with regards to potential health and environment risks. The use of chemical modelling can enhance our basic understanding of the deportment and speciation of trace metals under conditions present in gold processing solutions, and assist in laboratory and field investigations. In this paper, we report the results of chemical speciation modelling using the JESS software package for the trace toxic elements Pb, Cd, Hg, Se and Te in cyanidation solutions of varying salinity and relate the models to experimental data. The speciation of mercury is examined in detail.

Jan 1, 2011

By R. D. Lindsay

"Pamour Porcupine Mines, Limited is involved in the mining, milling and primary refining of various gold, gold - copper and refractory gold ores. Pamour operates five mines in the Porcupine Mining District of Ontario, and two 2,550 t/d milling facilities.Both metallurgical facilities use conventional cyanidation technology including zinc cementation for precipitation of gold and silver from solution. The precipitation process, as applied to clarified leach solutions (less than 1 ppm suspended solids) at Pamour is called the Merrill - Crowe process. Precipitates from both milling operations are treated at Pamour's Area Refinery. Schumacher precipitates, unlike Pamour No. 1, require an ''Acid Treatment Stage"" prior to refining to remove the high contained copper. This is accomplished by leaching the precipitates initiallv with sulphuric acid to remove zinc and then with sulphuric acid and manganese dioxide to dissolve copper. Refining procedures after ''Acid Treatment"" are essentially the same for both precipitates.The following considerations highlight the basic principals applied to refining cyanidation precipitates at Pamour, including:"

Jan 1, 1986

On the 26th of June 2000 a hydraulic fill retaining barricade failed at the Bronzewing mine in Western Australia. The barricade failure resulted in the release of 19,000 m3 of saturated hydraulic fill into the mine and caused the deaths of three miners. Following this tragic accident, the practices and procedures of mines using hydraulic fills came under intense scrutiny by regulatory bodies and mining companies. At this time, the use of hydraulic fill at Normandy?s zinc/copper Scuddles mine was suspended and waste rock became the sole backfill material in use underground. By 2003, development of the adjacent Gossan Hill mine had progressed to a point where a self supporting fill material was required to enable full recovery of high grade ore. Cemented hydraulic fill (CHF) was identified as the optimal fill type and work began on designing appropriate management procedures and controls to ensure the safe implementation. This work included definition of the fill properties, plant design and construction, reticulation system design, design of stope barricades and drainage systems and fill placement control and monitoring practices. CHF placement began on 16th July 2004 and has continued to date. Significant operational experience has since been gained in areas including plant performance, fill product quality assurance, barricade construction, stope drainage and in-situ performance.

May 1, 2007