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By G Le Juge, K Waldock

The current suite of bulk mining explosives has been available to the industry for over 20 years. The flexibility and performance of ammonium nitrate based emulsion blend explosives were accepted by the mining industry in the early 1980s. These water resistant explosives rapidly displaced the water gels and slurries developed during the previous two decades. However, since the 1980s there has been no equivalent step change to the basic formulation or application of bulk explosives, although there has been a continuous process of refinement with respect to stability, handling characteristics and most significantly, cost. In the 1980s explosives supply contracts were awarded based on technical evaluations, usually accompanied by field trials. Technical personnel from both mining companies and explosives suppliers dominated the negotiations and there was a strong focus on explosive energy and blasting requirements. Today, explosives from alternative suppliers are difficult to differentiate on the basis of energy so the focus has shifted to aspects of service and price û bulk mining explosives are now largely treated as a commodity and the negotiations are dominated by commercial personnel. Commercial pressures from large mining companies have seen a substantial reduction in the real price of explosives. However, this has come at a cost. In order to reduce manufacturing costs, emulsion formulations have changed. In general they are not only cheaper, but also less energetic. Powder factors have had to increase to achieve the same blasting results, especially in hard ground. It is debatable whether the mining companies have achieved all of the economies they were seeking. This paper discusses these issues and argues that the mining industry would benefit from taking a more technically driven approach to meeting their blasting requirements. Recent trends towards more open contracts between the mining companies and their suppliers can be extended to explosives. To achieve this, mining companies will need to acquire sufficient technical knowledge to take a more pro-active approach to specify the characteristics of the explosives required to maximise the economic performance of their operations.

Jan 1, 2004

By C Hoffmann

Given that each year, 30–40 per cent of mining industry deaths are attributable to failures of vehicle interaction controls (EMESRT, 2023), the mining industry is now armed with a growing body of knowledge from EMESRT (Earth Moving Equipment Safety Round Table) and ICMM (International Council on Mining and Metals) global vehicle interaction initiatives over the past years, that enables mining companies, OEM’s and technology providers to work together to develop and implement more effective controls and drive the adoption of capable solutions. Leveraging 20 years of experience as a global technology provider of Proximity Detection System (PDS) and Collision Avoidance System (CAS) solutions for surface mining operations, Wabtec Digital Mine Technology shares key insights for ensuring the effective selection, implementation and integration of these technologies into existing mine site controls and mining operations for effectively reducing vehicle interaction risk enabling mines to drive towards ‘zero-harm’ objectives. Topics covered include: alignment with industry best practice for controlling vehicle interaction risk by EMESRT and ICMM, importance of the maturity of EMESRT levels 1–7 vehicle interaction (VI) control framework, managing expectations that PDS/CAS is a ‘silver bullet’, alignment with industry functional – performance – technical requirements, proximity detection versus collision avoidance, sensor performance and fusion and limitations, rules engine intelligence critical to mitigating nuisance alarms during normal operations, system health monitoring and reporting, human factors engineering and operator acceptance, implementation strategy, installation standards and quality control, change management program, training programs, reporting and data analytics with actionable insights and maintenance strategies. Insights will also be provided on the challenges moving from EMESRT levels 7 (operator awareness) and 8 (advisory controls) to level 9 (intervention controls) as it’s a journey not an out-of-box solution, the growing demand for coexistence of CAS and Autonomous Haulage Solutions (AHS), functional safety approach, value added systems integration and the applicability of new emerging technologies.

Apr 16, 2024

By I R. F MacCulloch, K Jones

Pintail Systems, Inc, a Colorado USA based company has developed and commercially applied bioremediation processes for biological detoxification of cyanide compounds in mine waste. Site-specific microorganisms are isolated from spent ore, tailings or process solutions and augmented in the laboratory for cyanide oxidation, denitrification and metal biomineralisation. Biological processes typically treat complex contaminants (cyanide compounds, soluble metals and nitrates) in a fraction of the time of conventional remediation processes. Cyanide is used in microbial metabolic processes as a carbon or a nitrogen source. Biological detoxification processes applied at the end of mine life can end long-term liability and perpetual monitoring and containment. Case studies from commercial application and demonstration programs for the US Environmental Protection Agency will be presented in this paper.

Jan 1, 2004

By A McCallum, J Abols, G Patrick, G Johansen

The authors challenge the traditional thinking that whole ore cyanidation followed by Carbon in Pulp (CIP) or Carbon in Leach (CIL) should be applied as a standard process in the majority of gold processing flow sheets. The concept of whole ore leaching by using cyanide can result in unnecessary environmental and capital risk. Alternative, currently available technologies can be used to provide the desired level of gold recovery at a much lower installed cost and less impact on the environment. Gravity concentration, alone or in conjunction with flotation, can produce a gold bearing concentrate that can then be fed directly to a batch or continuous intensive cyanidation unit. The In-line Leach Reactor (ILR) is an intensive cyanidation unit developed by Gekko Systems of Australia. Advantages of this technology include significantly reduced capital outlays for greenfield plants or plant upgrades and increased investor returns. Reduction of onsite cyanide and carbon inventories improves plant safety, materials handling and site security. By using direct electrowinning to treat the gold bearing solutions produced by the ILR, the need for a conventional carbon stripping circuit is removed. Potential also exists to increase grind size û saving energy, further reducing capital and operating costs and decreasing the environmental impact of a mill. Detoxification of cyanide before the release of solution to the tailings dam can minimise tailings disposal and containment requirements. When used in the right application the proposed process will have little or no impact on gold recovery and may actually increase recovery for complex ores. Areas applicable to this type of treatment include: plants in environmentally sensitive regions, lower tonnage higher grade deposits, coarse gold deposits, and preg robbing ores û some of which may not currently be economically feasible using standard processes and flow sheets. We have provided two examples of such projects, where an alternative to whole ore leach and CIP or CIL has the potential to deliver these benefits.

Jan 1, 2004

Tunnels are being built around the world using TBMs and prefabricated segments or in situ concrete as linings. Clients demand high quality of these linings to guarantee a long-term stability and density of the tunnels. This paper describes the development and the use of segmental lining systems, including joints, important design criteria, installation procedures, possible mistakes and consequences, repair works and final results for different sites in Europe and around the world. The experience on these sites shows that damages may occur, if some essential aspects are not considered. These aspects include:parameters of the TBMs and back-up equipment such as fixation of jacking rams, movement of the back-up on the lining or ring reformer;parameters of the segments such as quality of moulds, quantity of reinforcement or structure of the joints; andparameters of the tunnel drive such as advance rate, ring-gap grouting or experience of the tunnel crew.All these aspects have to be considered very carefully in detail to get a good lining accepted in total.

Jan 1, 1999

By J Seppelt, B Akerstrom, J Bubnich, D Seaman, T Waters

The Cadia Hill concentrator at Newcrest’s Cadia Operations has undergone several modifications and upgrades to treat an increased throughput rate of harder ore from the Cadia East block cave mine.Subsequent to the commissioning of the expanded circuit, the flotation cleaner block has undergone a systematic optimisation programme tackling all facets of circuit operation. This included debottlenecking circuit constraints and installation of Jameson cell technology to enhance copper and gold recovery while rejecting fluorine and gangue from the concentrate.This paper outlines the improvements over the course of the project and results obtained from the implemented actions.CITATION:Akerstrom, B, Seppelt, J, Waters, T, Bubnich, J and Seaman, D, 2018. Cleaner circuit optimisation at Cadia Operations, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 457–476 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By P Cesare, S Munro, D Wandel, R A. Bearman

Consideration of the processing plant operational envelope is a key factor in production scheduling,and therefore mine planning, for any mining operation. In many cases hard-wired or regressionbased tonnage-grade-recovery relationships are used as mine planning constraints and as a means of valuing the system output. In extensions of this type of approach, various regressions can be used to describe throughput limits, based on a number of global metallurgical parameters.The ultimate position for the optimisation of a mine plan and production schedule is to have a full process plant model running as an integrated part of the mine planning exercise. A plant model suitable for this needs to have all the required sensitivities to input parameters such asfragmentation, grade, mineralogy, strength and hardness. The model then needs to convert these to performance measures for the plant, which include recovery, throughput, product size distributions, energy consumption, water use and operating cost.In this paper an approach is outlined that takes this view and then goes beyond it to provide a full, time-based bottleneck identifi cation and valuation tool.Using such an approach it becomes possible to run mine plans and production schedules in windows of days, weeks, months and over the life-of-mine with a time-enabled process model acting as the active constraint. In this way virtual bottlenecks can be identifi ed for various mine plans and schedules well ahead of time. The value of de-bottlenecking can be defi ned, not just at a plant scale, but in terms of the overall mining operation, and the data can be used as the basis for capital investment decisions.CITATION:Bearman, R A, Cesare, P, Munro, S and Wandel, D, 2014. Incorporation of a full process plant model as an active constraint for mine planning and production scheduling, in Proceedings Orebody Modelling and Strategic Mine Planning Symposium 2014 , pp 121–128 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 24, 2014

By R Carreau

The results of a detailed acid rock drainage (ARD) prediction program were used to revise the waste rock segregation criteria at the Restigouche open pit mine. Waste rock at the site was predominately derived from altered volcanic rocks that hosted a massive sulfide lead/zinc orebody. The program assessed the five years of drainage chemistry from both the potentially acid generating and the non-acid generating waste rock storage facilities in addition to laboratory-based kinetic test results. Material-specific leaching characteristics including relative metal-release rates and neutralisation potential depletion rates were determined from 12 laboratory-based kinetic tests. Solid-phase analyses indicated that, although pyrite was typically the most abundant sulfide mineral in the waste rock, its abundance varied significantly as documented by total sulfur contents ranging from 4.0 per cent. Kinetic test results were used to establish revised waste rock segregation criteria based on total sulfur content and neutralisation potential. The revised criteria maintain that waste material with a total sulfur content 4.0 per cent as potentially acid generating. When present in sufficient quantities, ankerite provided an effective source of neutralisation potential for the range of observed sulfide oxidation rates. Kinetic testing documented that up to 6 kg CaCO3/t was ineffective at neutralising acidity in samples that contained >4 per cent S. The carbonate molar ratio measured from the humidity cells was adjusted to reflect the stoichiometry of the ankerite and applied as an NP/AP criteria for waste rock containing 0.1 <S per cent <4.0.

Jan 1, 2003

By T Berryman, C Adams, L Griesel, C Buxton

The Kalgoorlie Consolidated Gold Mines (KCGM) schedule model is used for short- to medium-term planning and scheduling at the Fimiston Open Pit Mine (the Superpit). The model bridges the gap between grade control models, which are generated one to seven days prior to mining, and the annual Resource and Reserve model update that is used for budget and life-of-mine plans. The schedule model uses close-spaced grade control data (up to 20 000 m drilled each month) as well as resource definition drilling to estimate production volumes three to six months ahead of current mining. From this, a rolling 12 week mining and processing schedule is generated on a monthly basis. As the KCGM operation is mill and sulfur constrained, the schedule model needs to be an accurate predictor of ounces as well as tonnes, gold and sulfur grades. The process must also be time efficient in order to meet monthly planning and reporting deadlines. Due to the large amount of new data generated each month, model updates using conventional interpretation and estimation techniques have proven to be impractical and too time consuming. This paper will examine the evolution of the Superpit schedule model process over time, recent improvements and the effect of different model outcomes on short- and medium-term mine planning.CITATION:Griesel, L, Buxton, C, Adams, C and Berryman, T, 2014. The superpit schedule model – A time-efficient data-driven estimation for short- and medium-term planning, in Proceedings Ninth International Mining Geology Conference 2014 , pp 397–410 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By X Hu, Z Pokrajcic, R Embry, P C. Stewart, J Carpenter, E Jones

Whilst the value of Pit to Plant and Mine to Mill optimisation has been proven since the 1990s, sustaining the productivity and efficiency gains typically requires ongoing test work, blast trials, plant surveys, and model calibration services. In contrast, the input to digital twin Pit to Plant or Mine to Mill optimisation is tens to hundreds of millions of tonnes of standard mine operating data. This paper presents a series of digital twin case studies from across the mine value chain, including machine learning testing methodology, model accuracy statistics and the application of Shapley Additive Explanations (SHAP) for model interpretation. These case studies demonstrate how machine learning and data fusion ore tracking connects hundreds of millions of tonnes of downstream performance data to produce digital twin models (operating models that are continuously updated and integrated into the wider Mine to Mill/Pit to Plant ore tracking system). Digital twin modelling software has been used to add block model variables for dig-rate, crusher and mill throughput, recovery (tailings grade), lump yield, product grade and product quality, fines yield and fines in lump. Block-by-block predictions are added to the geological resource and grade control block models as new block model variables. These new block model variables are used across all mine planning time horizons from life-of-mine planning to daily schedules. In addition to the materials handling and geometallurgical prediction case studies, the paper also presents digital twin case studies for drill and blast simulation and plant set point optimisation. The case studies show how digital twin simulation enables drill and blast engineers to simulate the effect of different blast designs in different blast domains using the mines operating data. Plant set point optimisation applies mathematical optimisation algorithms to the machine learning model to provide live operational decision support to metallurgists and plant operators. The digital twin machine learning case studies demonstrate a digital and sustainable paradigm for Mine to Mill and Pit to Plant optimisation.

Jun 22, 2022

By P J. Vardon, L A. van Paassen, Y Yao, A F. van Tol

Thin-lift atmospheric fine drying (AFD) is a technique used to dewater mine and oil sand tailings, which utilises both self-weight consolidation and atmospheric evaporation. The disposed layers undergo a cyclic drying and rewetting process due to precipitation and deposition of additional lifts on top of the dried layer. The current research aims to optimise the deposition process via use of a numerical model and realistic atmospheric conditions, including both periods of drying and wetting. The model is based upon water balance and includes large strain considerations. A number of material behaviours are characterised using empirical fitting curves based upon laboratory measurement of material characteristics, including both the shrinkage and water retention curves for drying and rewetting. The model is able to model multiple lifts, simulating field scale and realistic climatic conditions within timescales suitable for engineering practice (eg seconds or minutes). The model has been previously validated against controlled laboratory experiments and utilised to simulate field tests. A series of simulations are presented to illustrate the ability of the model to be used as a practical tool for the optimisation of a tailings deposition strategy.CITATION:Vardon, P J, Yao, Y, van Paassen, L A and van Tol, A F, 2015. The use of a large-strain drying and consolidation model to optimise multilift tailing deposits, in Proceedings Tailings and Mine Waste Management for the 21st Century , pp 263–270 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 27, 2015

By K Sommerville, J Parkinson

"Open pit mines today have more technology and data available. The challenge is to effectively use resources to analyse and identify mine productivity improvements. AMC Consultants Pty Ltd (AMC) has completed more than 100 benchmarking studies worldwide. In the process of gathering cost and productivity data, insights have been gained on how mines are using data to drive productivity. This paper aims to share good practice on using data, what benchmarks operations should be aiming for, where mines are currently sitting, high value areas to target, and how to best prioritise improvement to meet operational goals.A key purpose of data is to assist in managing and improving operations. Key information is used to drive meetings, decisions, budget estimates and reports. Safety, equipment productivity, available stocks, grade and spatial reconciliation are examples of where data is important for management systems. The key is to keep reporting simple whilst maintaining access to source data for troubleshooting and analysis.Some operations still have paper-based reporting systems. Some operations collect data directly off machines and instruments, use cameras and have off-site control centres. The level of technology is a fit-for-purpose choice.Comparisons of productivity assumptions commonly used in feasibility studies with good practice productivity numbers sourced from AMC’s benchmarking database will be shared in this paper. A typical activity mining cost breakdown will highlight where the high value areas for productivity improvement sit.In addition to examining the productivity of each mining step it is also important to examine the impact on the mine plan. Equipment numbers, strip ratio, grade and material hardness can impact the results of bottleneck analysis. A bottleneck example case study will highlight how productivity and other factors can be used to identify and prioritise improvement opportunities.Keep it simple. Use only the critical data for meetings, decision-making, reports and plans. Knowing and communicating the key performance indicators (KPIs) you are striving for aligns the operation and prioritises improvement plans.Citation:Parkinson, J and Sommerville, K, 2016. Getting the Most Out of Technology to Drive Mine Productivity Improvements, in Proceedings Ninth AusIMM Open Pit Operators' Conference 2016, pp 84–93 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 15, 2016

By B Taylor, S Evans

Bulk explosive technology for underground mining has not seen any significant technological advances since the widespread transition from ammonium nitrate fuel oil (ANFO) to ammonium nitrate emulsions (ANE) commencing in the 1980s. The in-hole energy profile that conventional ANE systems deliver is limited by the physics of chemical gassing and simple control systems. This compromises the range, precision, and accuracy of energy delivery into the blasthole, and in some cases limits the length of charge that can be delivered. Orica’s 4D™ bulk system removes many of these constraints, enabling better blasting performance across all underground mining methods. This paper reviews work completed at three mining operations across Australia, the United States, and Chile with a focus on how this system can improve mining operations and deliver sustained commercial and productivity benefits into the future. These benefits include improved ore recovery, reduced dilution from waste rock, and reduced overall explosives consumption. This paper also reviews how this new technology can be applied for planning future mining operations.

Sep 1, 2024

By M Berndt

Four siltite-argillite rock samples were characterised (particle size, chemistry, mineralogy) and subjected to laboratory dissolution testing for 36 to 298 weeks. In two samples sulfur (0.99, 1.69 wt per cent) occurred largely as pyrite, and in the other two samples sulfur (0.96, 1.93 wt per cent) occurred predominately as potassium jarosite. The observed rate of sulfate release from the pyritic samples was one to two orders of magnitude greater than that from samples containing potassium jarosite. Drainage pH values from the pyritic samples were one to two units lower and acidities were ten to 70 times higher than associated values from the potassium jarosite samples. Geochemical modelling supported the hypothesis that pH and concentrations of sulfate and potassium in drainage from the potassium jarosite samples were controlled by the limited solubility of potassium jarosite. This dissolution produced an iron-dominated mineral phase, but iron concentrations in the drainage were well below those predicted by ferrihydrite solubility.

Jan 1, 2003

By Bawden WF, Paynter JT

This investigation involves laboratory testing and stability analysis of paste fill at the Golden Giant Mine. Site-cast samples are tested in unconfined, confined, and consolidated-undrained triaxial compression. Pore pressures during shear and consolidation characteristics are measured to determine both drained and undrained shear strength parameters and assess the potential for undrained loading. Liquefaction potential is also considered. A limit equilibrium solution is used to obtain factors of safety against failure of the fill during mining of adjacent stopcs

Jan 1, 1998

By D J. Brake

Most mine ventilation engineers are involved in ventilation planning and design in some capacity. Ventilation modelling software used by a competent experienced ventilation engineer is extremely useful in developing good ventilation designs by allowing assessment of a wide range of potential options. Unfortunately, ventilation modelling undertaken by persons who do not have sufficient experience or knowledge usually results in a façade that covers up a fundamentally unsatisfactory design. Ventilation models are produced for a wide variety of purposes including: fault-finding of a problem area in a mine and options analysis for resolution of such problems; a complete review or optimisation exercise of an entire mine’s ventilation system; or a much longer life-of-mine type of study. Models can be intended as the basis for studies with diverse purposes such as primary shaft or airway sizing, primary fan specification, examining re-entry times after blasting, resolving leakage or recirculation, or investigating the impact of fires or underground climate or cooling requirements. The concepts of ‘materiality’ and ‘fitness for purpose’ are essential to developing or using a ventilation model and serious mistakes have been made in wrongly using a ventilation model for purposes for which it was never intended, often because it is simply the most recent model on the mine site. Mistakes at this level often translate into faulty ventilation strategies and inefficient or ineffective use of scarce capital for ventilation projects. Validating a ventilation model is a time-consuming and expensive process and not every model must (or even should) be fully validated to meet the objectives at that time. This paper discusses the application of quality assurance in ventilation planning with particular respect to the ‘basis of design’ (BOD) as well as the standards for validating a ventilation model. It also provides a recommended way of dealing with non-conformances in measured versus modelled values of critical parameters in the model.CITATION:Brake, D J, 2015. Quality assurance standards for mine ventilation models and ventilation planning, in Proceedings The Australian Mine Ventilation Conference, pp 221–228 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 31, 2015

By B D. Burford

High intensity stirred milling using the IsaMill has been the enabling technology for many projects by transforming the economics of fine grinding and simplifying circuit design. IsaMill grinding technology was originally developed for large-scale grinding to P80 sizings of 7 ¦m. The IsaMill is a high throughput, high efficiency mill that produces sharp product size distributions in open circuit configuration. The ability to grind in an inert environment, using a wide variety of media types, can give further metallurgical and economic benefits. The high energy intensity results in a small footprint that enhances the ability to distribute grinding power throughout the circuit, applying grinding energy to the minerals that need it. Recent scale up developments in IsaMill technology have enabled the benefits to be extended to large-scale conventional grind sizes, until now the domain of ball and tower mills. This paper will examine the crossover of IsaMill technology from ultrafine applications into the more conventional grinding area (P80 20 - 150 ¦m). Scale-up developments in IsaMill technology that have enabled this are reviewed. The upcoming commissioning of a 3.0 MW M10,000 IsaMill, the most powerful to date, grinding to P80 55 ¦m at PPL in South Africa will be discussed, as will the recent commissioning of a 2.6 MW M10,000 IsaMill at Kumtor. Recent testwork at McArthur River, where an IsaMill is being considered as an addition to the primary grinding circuit to replace the current tower mill will be reviewed. The potential combination of HPGR and IsaMill to transform concentrator grinding economics will also be discussed. Large-scale IsaMill technology has the ability to transform circuit design and energy efficiency for both coarse and fine grinding.

Jan 1, 2006

By F Shi, W Huang, D Seaman, K Runge

High Voltage Pulse (HVP) technology is a novel process that could potentially be the step-change needed in ore processability in the mining industry. The propensity of high voltage pulses towards mineral-enriched ore particles during treatment makes this technology selective and has the potential to enable ore pre-concentration by size separation. In this study, the potential for pre-concentration of a low grade copper-gold ore sample subjected to HVP pretreatment is investigated and compared to that achievable after mechanical breakage in JKMRC’s rotary breakage tester (JKRBT). The data show that a better pre-concentration result can be achieved after HVP processing than conventional breakage. The gold pre-concentration potential is much better than that observed for copper. 4D HVP pre-concentration characteristic curves were produced to assess the metallurgical performance possible as a function of energy input. The case study shows that when targeting a nominal metal recovery of 90 per cent for gold, the HVP pre-concentration technique can split the low grade ore (0.9 ppm gold and 0.28 per cent copper in the feed size 26.5-37.5 mm) into two components – a low grade oversize material (0.3 ppm gold and 0.15 per cent copper) and a high grade undersize material (1.0 ppm gold and 0.3 per cent copper). The mass split to the low grade is 23 per cent. Under this mass split scenario, gold recovery to screen undersize is 90 per cent and copper recovery is 85 per cent. The HVP treatment of this feed size requires a specific energy (spark) of 2.8 kWh/t.There is further research that would be required before industrial uptake of the HVP pre-concentration technology would be possible. This paper also outlines the research challenges that need to be overcome.CITATION:Huang, W, Shi, F, Antonio, C, Runge, K and Seaman, D, 2018. High-voltage pulse pre-concentration study using a low-grade copper-gold ore, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 327–338 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By T E. Hayward, D H. English, S J. Smith

Gold mineralisation at Bendigo is exclusively associated with quartz reefs, commonly found within or near anticlinal fold hinges. The gold is typically coarse grained (0.5 mm to 5 mm), free milling and displays a complex, nuggetty distribution within the veins. This ore is highly amenable to gravity recovery processes. As the Bendigo operation is not permitted to treat whole ore by a cyanide leach/CIL circuit, the flow sheet is more complex than conventional gold recovery circuits. Primary gold recovery is from a gravity circuit closing the grinding circuit to a bulk gravity concentrate and from a flotation circuit treating cyclone overflow to a bulk float concentrate. The plant capacity is relatively low by current gold industry standards at 600 000 tpa. Re-establishing gold production at Bendigo has presented several challenging, and sometimes competing, issues in process design and operation. The mine, process plant, associated services and infrastructure are at Kangaroo Flat, a low density, semi-rural zone in the southern urbanisation of the Bendigo metropolitan area. One of the main processing challenges during the design was the competing comminution requirement to avoid over-grinding, which would flatten or smear the characteristic nugget gold and hinder effective gravity gold recovery, whilst also providing sufficiently well liberated particles that would respond well to flotation. Important, non-metallurgical challenges were to minimise impacts on the local community from noise, dust, air emissions, visual impact, water egress and off-site traffic.

Jan 1, 2007

By M Ind, B Usher

Environmental regulators are increasingly adopting risk-based approaches to protect aquatic ecosystems. The Australian and New Zealand Environment and Conservation Council (ANZECC) and the Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ) (2000) introduced a risk-based approach to water quality guidelines that use decision frameworks to adapt water quality guidelines to local environmental conditions. Environmental quality objectives are no longer a simple ‘pass or fail’ number such as restricting total suspended solids (TSS) concentration to a specified limit for a particular rainfall event. This approach ignores spatial and temporal variability and the complexity of aquatic ecosystems. The risk-based approach establishes levels where adverse effects may occur. If these objectives are not met, further risk-based investigation is undertaken to assess the potential impact to the ecosystem. Klohn Crippen Berger (KCB) developed a dynamic simulation to predict the variability of sediment discharges, which is applicable for risk-based impact assessment of aquatic ecosystems. The application of the methodology over the life of a mine site is illustrated using a proposed South Pacific mine.The site location is in extremely rugged terrain with a high annual rainfall of approximately 4.7 m. There were two major sediment ponds proposed to reduce sediment discharges. A sediment and hydrology model was developed in Goldsim to provide daily estimates of run-off flows and sediment concentrations. A modified algorithm based on the Australian water balance model was created and incorporated into the Goldsim model and calibrated using recorded field data.The sediment module was developed based on a Revised Universal Soil Loss Equation (RUSLE) assessment, an annual prediction of soil loss over a catchment. A land-use type erosion vector was developed for different land-use types and for each of the subcatchments, a subcatchment erodibility vector was calculated. This vector and the daily rainfall erosivity factor were used to estimate the daily soil loss. The estimated soil loss and the modelled run-off yielded predictions of daily sediment concentrations. Finally, a sediment settling module was used to predict the daily efficiency of the sediment ponds and hence discharged sediment concentrations.The results of this modelling form the first part of a quantitative risk-based assessment into suspended solids impacts. The second part is the assessment of the effects of these predicted TSS concentrations on aquatic ecology. As part of the feedback-loop required in a risk management framework, if the environmental quality objectives are not met then further management decisions and actions may be required to reduce the risks presented by suspended solids. This may include modifications to: the mine-development plan; construction techniques and scheduling; processing techniques; rehabilitation strategies; or hard-engineering solutions such as sediment basins or flocculation.The Goldsim water-balance model provides a quick and efficient method of testing potential remedial actions on predicted sediment loads and concentrations. In combination with a cost-benefit assessment, options for reducing sediment releases from the mine site can be effectively and quantitatively compared thereby providing mine operators with a basis for decision-making. Regulators can also be satisfied that potential impacts to aquatic ecology have been comprehensively assessed and the necessary management decisions have been initiated to limit risk to the environment.CITATION:Ind, M and Usher, B, ?2014. A dynamic sediment simulation to predict the variability of suspended solids concentrations over life-of-mine for application to a risk-based environmental assessment, in Proceedings Life-of-Mine 2014 , pp 191–204 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014