Search Documents

By Iwu GO, Almond DP, Joasoo _

The gravimetric integral Knudsen effusion method was used to measure cadmium activity values in binary liquid In-Cd alloys in the range 523 to 573 K. The activity measurements together with other studies from the literature indicate that special bonding conditions exist in the melts near a composition corresponding to InCd3. Sound velocities in In-Cd melts were also measured using a precision pulse-echo over- lap method in the range 404 to 953 K. The frac- tional deviation of experimental and ideal isentropic compressibilities at 623K shows a functional dependence on composition with a pronounced maximum near the composition 75 at.%.

Jan 1, 1980

By T N. Little

This paper is concerned with the influence of engineering geology on design of Wall Control Blasts. In the Introduction, the Blast Management Framework and the Blast Design Requirements classification system (previously developed by the author) is drawn upon to set the context. Blasting objective for all wall control blasts involves both profile and damage control. Four classes of approaches for blast design are outlined and briefly discussed. Five distinct wall control blasting techniques are summarised. The general relationship between geology and blast design is explored in the paper. Influence of geology on pre-split and post-split design and blasting direction is highlighted. Wall damage modelling from the closest row of blastholes is also introduced using the Analytical Damage Model (ADM). The relationship of rock properties and explosive selection and in particular the Mach wave generation is introduced to assist blast designer in this regard. Finally a Conceptual Model that relates vibration, damage and rock mass condition has been presented along with some applications that have been undertaken by the developer. Eight conclusions have been formulated based on extensive work in this area and the current study.

Jun 22, 2022

By C L. McIntosh

The west coast of New Zealand’s south island is host to a large number of placer goldfields that stretch from the Westport area in the north to Gillespies Beach in the south and inland to the foothills of the Southern Alps. This area is host to a large number of alluvial, glacial and strand line deposits ageing in range from Recent to Tertiary. In recent years exploration models have been developed for off shore placer deposits on the continental shelf.Gold mining on the west coast has exploited placer gold resources from the 1860s to present, and with the recent surge in the gold price the industry is currently undergoing a resurgence. The current increase in mining is dominated by small-scale mechanical operations usually involving one to two people at each site; a few larger operations also exist such as the Grey River Dredge.Mining methods range from using floating bucket dredges to small diggers. Some of the mining technologies used are similar to those employed during the great gold rushes of the 19th century. Exploration and grade control techniques can be very rudimentary often relying on previous sampling programs or wide spaced bulk sample drill holes. Some bulk sample drilling is used on the larger operations as a form of grade control, most of the small operations tend not to use any ore control sampling prior to mining. Extraction techniques relying on simple gravity based designs with riffle tables or spirals are the most commonly used. Environmental standards are very high within New Zealand and require operators to return mined areas to preagreed to landforms. The high rainfall experienced on the west coast causes challenges to operators in regard to water quality. Technical issues combined with often limited capital provide for challenges to the operations.

Aug 22, 2011

By M R. Lane, M L. Cramer, N P. Wines

Increasing attention is being focused by regulators and industry on the residual environmental liabilities associated with mining projects following site relinquishment (termed surrender in Queensland). Even sites that have been rehabilitated to a high standard and to the satisfaction of the regulator are not completely risk free and may require some degree of ongoing management. As well as ongoing monitoring and maintenance costs, considerations should include how costs associated with potential risk event occurrence can be quantified and, if considered material, how provisioning should be undertaken to minimise the risk to the state and to taxpayers. In Queensland for example, once a resource site is fully rehabilitated and meets its environmental authority conditions or rehabilitation completion criteria, the tenure and environmental authority can be surrendered. During the surrender process any ‘residual risks’ resulting from the use of the site for the resource activity must be considered, and, if requested, a payment given to the government to cover any ongoing management and risk costs. Accent Environmental, in conjunction with Lane Associates, was engaged by the Queensland Government as part of the government’s financial assurance framework reforms to develop an innovative, ‘one-size fits most’ Residual Risk Calculator for the Queensland resources industry. The calculator is an Excel-based tool that uses detailed user inputs to estimate post-surrender management requirements and liability at resource sites. If residual environmental risks associated with rehabilitated mine sites can be identified, quantified and managed through pragmatic regulatory tools and effective provisioning, site relinquishment/surrender can be achieved without compromising environmental and social outcomes or exposing the state to unreasonable financial risk. The effective management of residual risk can also help facilitate operations as well as relinquishment/surrender of sites where a ‘walkaway’ solution may not be otherwise technically feasible.

Aug 2, 2023

By B Green

With a focus on safe productive tonnes, there has been an ongoing drive to increase the productivity of the mining fleet across BHP Billiton. In response, a team from the Iron Ore business was formed to review all aspects of the end-to-end drill and blast process and to challenge conventional practices that limit production efficiency. As a result of the outcomes of this work, a number of initiatives were identified to improve operational practices that have also delivered significant cost savings.One such initiative was to increase pattern size to a minimum of 1 Mt where practicable, thereby creating ‘megablast’ as a new standard across all mines. To achieve blasts of this size, the team had to overcome the complex problem of integrating wall control into the megablasts.With traditional blasting techniques, the key strategy, which is also historically inefficient but was thought to be integral to having stable, safe walls, was to utilise the trim blasting/modified production blasts technique (ie narrow blasts along the pit wall designed to ‘peel off’ the material while minimising the effects of vibration and charge confinement on wall integrity).Small traditional trim patterns comprise three to four rows of production holes and one or two rows of batter/buffer holes of reduced diameter that require the firing face to be completely exposed before blasting. This is an extremely slow process that requires a lot of resources for very little tonnage while adding additional expense to the final cost per tonne.This paper will show how the megablast approach was developed to control damaging vibration and confinement effects, flyrock and fragmentation while having the largest possible blast that includes wall control. The new practice is based on a theory that involves the initiation point and control row being the second row of holes from the pit wall itself. Adjusted charges in vented batter and buffer holes help to achieve an optimal toe design, and at the same time create a zone of broken ground that absorbs damaging vibrations formed by the attached production blast of any size, whether it is a straight wall or a multi-angled complex pit shell design.Using the new style of blasting has allowed an increase in the size of the patterns from an average of 300 kt to over 1 Mt whilst maintaining pit wall integrity. Case studies will be presented showing drill, charge and tie-in designs with the presentation having additional blast videos, including overall shots of blasts and in-close footage of what happens behind the blast at the crest of the planned catchment berm.The paper will also demonstrate the flow-on effect of using this style of blasting to reduce operational costs associated with other downstream processes, such as the reduced requirements for pattern preparation, an increase in productive digging, reduced maintenance costs and a decrease in fuel burn for equipment.CITATION:Green, B, 2015. Megablasts – enabling technologies in BHP Billiton Iron Ore, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 599–606 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

This presentation is a 20 minute snippet of my professional career, and my progression in the mining industry, from a lazy uni student to an up-and-coming blast engineer in the middle of a mining boom.My name is Daniel Hepburn and I am a blasting engineer for Orica Mining Services. I graduated from Royal Melbourne Institute of Technology (RMIT), in Melbourne in 2003. I completed both of my final year projects with Orica Quarry Services and was offered an assistant shotfiring job, which I accepted and worked for eight months. Having missed the cut-off date for the Orica graduate program, I planned to work with Quarry Services until the following year where I hoped my marks and the experiences I had gained would secure a graduate position. I didnÆt have to wait long, as in August of that year, I was offered (and I accepted) a graduate position in Perth as a technical services engineer for Orica Mining Services. The Orica graduate program is based over two years, and consists of real roles from day one; however, there is also opportunity to fast track the program for high performers. There is a structured rotation, from site to site, interstate or even international if you are so inclined. This includes the backpacker program, which allows graduates to experience the Orica culture in countries of their choice. There are also opportunities to try cross-functional roles in the different Market segments within Orica. I was lucky in that I knew what I wanted to do and where I wanted to work, so I stayed in Perth for my entire graduate program. I was also lucky enough to be fast tracked and finished my graduate program in 15 months. At the end of 2005 I accepted a position as an open cut blasting engineer based in Perth and even in such a short period of time I have already completed a number of major accomplishments. Some of these accomplishments are described below. This paper is available as a PowerPoint presentation only.

Jan 1, 2006

By C D. Pocock

Maintaining catch berm capacity in open pit mines through controlled blasting prevents production delays associated with managing risks associated with wall instability. A method has been developed to quantify the drill hole deviation of presplit holes at Century Mine. Different controlled blasting techniques are used to control wall quality and decrease the risk. The performance of presplit drilling, in terms of deviation from design has been investigated. A methodology has been developed to quantify the drill hole deviation in three dimensions. This methodology was converted into a series of algorithms capable of handling an extensive range of data. The methodology was applied to a case study at Century Mine to evaluate the performance of drilling on two presplit blasts. Overall, 67 drill holes were investigated in the case study. The drill hole deviation was quantified in terms of three parameters: skewness, linearity and drill hole deviation parameter. Methods for quantifying each parameter were developed. Skewness, a measure of the amount of curvature and linearity, was defined as the measure of the consistency of the gradient of the drill hole. Drill hole deviation parameter is defined as the average measured deviation of the surveyed drill hole position from the design position. Acceptable drill hole deviation tolerances for each of the defined parameters were developed by analysing drill hole deviation parameters with respect to implications to catch berm capacity. Verification of the methodology was confirmed through the comparing of the completed drill hole deviation results using both visual inspection and cross analysis for each of the three methods. Holes with an R squared value of less than 0.97 for skewed deviation were classified as having skewed deviation, while holes with a difference in gradient of 3.5 were classified as having linear deviation. The results show that 76 per cent of the drill holes had deviation. Of this, 19 per cent were skewed, 57 per cent had linearity and 12 per cent contained both skewed and linearity deviation.

Nov 8, 2011

By J Wu

Swirl Flow Technology (SFT), a novel approach for agitation in large industrial slurry tanks, was jointly developed and patented by CSIRO and Queensland Alumina Ltd (QAL). Currently, SFT is used in 16 alumina precipitation tanks at QAL, with the first installation in January 1997. This paper provides insight to the underlying fluid dynamics, which were investigated through pilot-scale experiments. A key finding was that SFT produces tank wall velocities approximately four times that of conventional draft tube agitator systems for the same power input, whilst for solids suspension, much less power is needed. SFT is energy efficient and practical in scaling suppression as demonstrated by the full-scale experience at QAL.

Aug 8, 2011

By M G. Millad, M Zammit

The Kipoi Central (KPC) copper project is located in the Katanga Province in the Democratic Republic of the Congo and is presented here as an example of an operating mine where the Mineral Resource was initially estimated by uniform conditioning (UC) and subsequently updated to localised uniform conditioning (LUC). This paper discusses the implementation of an estimate run using LUC and compares the results based on resource definition drilling to those obtained by close spaced grade control drilling and actual mill production.UC is a nonlinear geostatistical technique designed for recoverable resource estimation, typically using wide spaced exploration and resource definition drilling. The primary output of UC is the grade, tonnage and metal above a series of user-defined cut-off grades for a particular selective mining unit (SMU) block size. The UC approach is considered to provide a more accurate representation of the recoverable grade and tonnage at SMU support for non-zero grade cut-offs than would typically be achieved by a traditional linear estimator such as Ordinary Kriging. LUC is a relatively new approach involving the post-processing of a UC estimate and is used to spatially present the grade distribution predicted by UC at the SMU scale.This study demonstrates that the calculation of a more accurate and realistic grade-tonnage relationship for small SMU sized blocks is possible at the exploration stage using LUC, provided that the necessary theoretical and practical conditions for implementation of this technique exist.CITATION:Millad, M G and Zammit, M, 2014. Implementation of localised uniform conditioning for recoverable resource estimation at the Kipoi Copper Project, Democratic Republic of the Congo, in Proceedings Ninth International Mining Geology Conference 2014 , pp 207–214 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By N Kojola, A Vickerfält, J Huss

The possibility of using an acidic autogenous hydrogen direct reduced iron (H-DRI) slag as a basis for vanadium extraction is investigated. For a raw material to be suitable for producing high-quality FeV, the vanadium oxide content should be sufficiently high and the phosphorus oxide content in a tolerable range. Therefore, the feasibility for vanadium extraction relies on fulfilling two demands: the predominate partitioning of phosphorus to the metal and vanadium to the slag. Correspondingly, the behaviours of phosphorus and vanadium in the Al2O3-SiO2-FeOx-VyOz-P2O5-Fe system were studied experimentally. Slag, 10 g, was put in contact with liquid iron, 30 g, for different durations (2–24 hrs) in closed alumina crucibles at 1873 K. The slag composition was varied between 33.1– 49.3 wt per cent Al2O3, 27.1–46.7 wt per cent SiO2, 16.6–30.1 wt per cent FeOx, and 2.5– 8.8 wt per cent V2O3. The equilibrium phosphorus distribution was 0.42, while the vanadium distribution ranged from 7.6 to 43.4, increasing with the Al2O3- and the FeOx-content.

Jun 19, 2024

By I C. Carrasco, V G. Mirada, J F. D Domingo, F S. Leite

This paper investigates ore loss and dilution produced by rock movement in bench blasting. A total of four blasts, in which electronic detonators have been used, were monitored in Cobre Las Cruces Open Pit Mine (FQM Ltd) in Gerena (Sevilla, Spain). Rock motion has been obtained in 137 points of the free face and 6 points inside the block. Multiple liner regression has been applied to predict rock motion and estimate ore dilution as a function of hole coordinates, rock contacts, powder factor/hole, amount of explosive per blasthole, burden, spacing, hole length, stemming length, explosive energy, hole row, subdrilling, blast sequence, stiffness ratio, blasthole distance to free face, rock density and Young’s modulus. The model is statistically significant with a determination coefficient over 0.8. Rock motion measurements in 31 more points have been used to validate the model and to show a reduction in ore dilution.CITATION:Domingo, J F D, Leite, F S, Mirada, V G and Carrasco, I C, 2015. Dilution, ore grade and blast movement calculation model, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 71–78 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

The basic make-up of the majority of currently produced bulk explosives has changed little in the last 20 years. These explosives would be described as mature in a life cycle analysis. Therefore these explosive products and the practical rules for their use are well understood and well established. In recent years there has been interest in low density explosives, predominantly due to ammonium nitrate shortages and the associated increase in the cost of explosives. In the use of low density explosives some of the practical rules for the more commonly used bulk explosives do not apply. Therefore a shift in the thinking among users is required. At a number of mines low density explosives have been trialled or are being used, utilising the practical rules that apply to bulk explosive products. This has led to poor blast results in many situations. These poor blast results have often then led to a reduction in the use of low density explosives at the mine. This reduction does not acknowledge the advantages that can be gained from this product in the area of reduced cost of mining. This paper looks at low density explosives and discusses how and why these products work. Included in the paper are some practical ideas and examples of how low density explosives can be effectively used at the mine site.

Jan 1, 2007

By J E. Moffatt, N A. Spooner, T J. de Prinse, D J. Ottaway, E Klantsataya, L d. S Teixeira, B W. Smith, T B. Payten, G Tsiminis

Single wavelength fluorescence sensing has been used in the preconcentration of ores for many years in situations where it is typically specific to the mineral of interest. Examples of fluorescence sensing include the sorting of diamonds in diamond mines and the sorting of scheelite in tungsten ores. However, the number of minerals that show useful single wavelength fluorescence properties in the visible spectrum is relatively small, so the application of fluorescence sensing is currently limited to niche application in the minerals industry. Recent developments at the University of Adelaide have focussed upon extending fluorescence signal measurements into the infrared spectrum, as well as investigating multi-wavelength fluorescence known as up-conversion fluorescence. These techniques may not only significantly increase the number of minerals that exhibit fluorescence properties suitable for both identification and sensor-based sorting, but also provide mineral-specific signatures of higher quality than previously attainable. This paper details the research work carried out by the University of Adelaide and funded by CRC ORE to develop a mineral-specific fluorescence sensor. The sensor targets two fluorine bearing minerals, fluorite and fluorapatite, that are common in many base metal ores such as porphyry copper ores and silver/lead/zinc ores. Fluorine is a known penalty element in mineral products derived from these ores, so mining companies need to monitor and control the amount of fluorine in their final product to keep it below commercially agreed specifications. Currently there is no real time sensor capable of monitoring fluorine in the ore feed so monitoring and control is carried out using time-consuming standard sampling and off-line laboratory measurements. The development and application of a real time fluorine sensor will enable the mining companies to monitor and control fluorine levels in the plant, greatly reducing the time and cost associated with producing their mineral concentrates within the prescribed specifications.

Nov 10, 2020

By K Seddon

Segregation of tailings on deposition can occur as a result of a) sub-aqueous deposition, and b) sub-aerial deposition at lower solids concentrations (i.e. when the solids concentration is less than the segregation threshold). The effects are likely to be more pronounced in the case of subaqueous deposition.This paper presents the results of an investigation of a sub-aqueous tailings facility.Data from the investigation show extreme variations in particle size and density compared to test results for non-segregated ‘all-in” tailings. The results indicate that on segregation both the fine and coarse splits tend towards a well sorted (poorly graded) mix, and both have significantly lower consolidated density than the all in tailings. This result is reasonably well known for the case of the segregated fines (“slimes ponds”) but less appreciated for the coarse fraction. The results suggest that if the effects of segregation are not allowed for, the overall density of the deposit can be seriously over-estimated at the design stage. Also the quantity of water retained in the tailings can significantly influence water recovery and water balance results.CITATION:Seddon, K, 2018. Segregating tailings – effects on density and water retention, in Proceedings Mine Waste and Tailings Stewardship Conference 2018, pp 299–308 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 23, 2018

By K T. Broekman, R L. Koenig

"The Braemar Iron Formation is atypical ore when compared to the current magnetite ores being processed. In attempting to process and economically recover the vast quantities of iron ore stored within the Braemar Iron Formation, æshifting the paradigmÆ is required. The formation has a low Davis tube recovery (DTR) grade of 15 - 20 per cent, which is much lower than magnetite ores processed in Australia. Despite this, by thoroughly testing and understanding the ore characteristics, it is found that the Braemar ores have significant advantages to processing than the harder banded iron formation (BIF) and taconite resources.The Hawsons magnetite iron ore resource has been known from the early 1960s when CRA explored the area. The grade was low and the Pilbara region discovery lead to the development of high-grade direct shipping hematite ores. Carpentaria Exploration (CAP) rediscovered the magnetite whilst undertaking multi-commodity exploration in the Broken Hill district during 2009. Shifting the paradigm away from grade the advantages of processing this ore are achieved by having an extremely low waste to ore ratio, lower Bond work index, lower abrasion levels and high-grade magnetite concentrates with little impurities other than silica. While developing the Hawsons Iron Project (HIP) it became more apparent that a positive business case is achievable when the following factors are exploited: very large resource - the resource is contained within one pit the rock fractures easily along grain boundaries - ideal for cheap impact crushing of the ore the ore is extremely soft, with a Bond work index of 6.3 - 8.0 kWh/t all major infrastructure required is readily available - rail, power, access and port the mine is in close proximity to Broken Hill - rich mining history and skill set available the resource contains many billions of tonnes of magnetite mineralisation.Shifting the paradigm by selecting equipment suitable for processing soft ores and not hard BIF or taconite ores and taking locality and available infrastructure into account may change the way people approach new low-grade resources in future.CITATION:Koenig, R L and Broekman, K T, 2013. Understanding ore characteristics and equipment selection, in Proceedings Iron Ore 2013, pp 403-410 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Aug 12, 2013

By X Li, W McKeague, M S. Powell

This paper explores the importance of operators in the overall efficiency of mineral processing plants. With the potential of future control configurations becoming more remote, it is time to review the implementation of control and utilisation of operators. This paper is based on a preliminary review of operators and control room operations and clearly shows that, in the minerals industry, operations are typically run in a reactive mode (with a focus on ensuring equipment operation), rather than in a proactive mode (with a focus on optimising the process performance). The primary reason for this misguided approach is the short sighted thinking applied to the challenges of designing technology and organisational tools capable of addressing the essential operational needs: an approach which inevitably results in a disconnect between people and technology. Contrary to the popular approach of replacing operators with expert systems, the thesis of this paper is that the shift to more complex circuits, with higher demands on processing capability and control, will require the actual upskilling of operators. Experience in mineral processing and other industries indicates that expert systems cope well with small changes but are typically unable to respond to major changes in feed material and this is where the expert operator becomes crucial. Providing operators with ongoing high level training in process understanding, and restructuring how they interact with the plant and interface with the control system is the approach being proposed here - an approach surprisingly underutilised and often absent in the minerals industry today.CITATION:Li, X, Powell, M S and McKeague, W, 2012. Unlocking processing potential by empowering our operators, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 333-340 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By A Suokas

Boliden Tara Mines Ltd, located in County Meath Ireland, produce in excess of 2.5 million tonnes per annum of ore from the underground resource located 40 miles north west of Dublin. The zinc-lead ore is mined using long hole open stoping techniques, with ore treated on site. The operation is continually searching for new ways to improve productivities at the mine, and have employed a detailed data acquisition and reporting system on site to provide feedback around performance. One area where both Boliden Tara Mines Ltd and Orica Mining Services believed improvements could be made was in the application of bulk emulsion technology through an Orica supplied but Tara operated Maxipump Delivery System for all production and development blasting at the mine. Both parties committed to the evaluation of this technology at the mine, however the capital cost and technical and economic changes meant the project needed to be diligently investigated and any improvements documented. The first stage of this project was for Orica Mining Services personnel to visit the operation, and conduct a detailed analysis of the operationÆs performance over the past 12 months. The next step in moving forward was then to commission and utilise the customer operated emulsion system at the mine. This was then followed with the collation and analysis of data from the demonstration period to examine and document the benefits of the system. This paper is a summary of the observations made during the site inspection and the data analysed to date, and has been used in determining operational and financial improvements in the comparison between a Maxipump Emulsion Service and the current ANFO loading systems.

Jan 1, 2005

By C Beal, S Singh

Sensor-based bulk ore sorting is a form of preconcentration that autonomously measures and physically separates discrete bulk ‘pods’ of run of mine (‘ROM’) or primary crushed material. This case study examines the results of a full scale bulk ore sorting trial undertaken at Cozamin mine in Zacatecas, Mexico in 2019. The bulk ore sorting plant comprised primarily of a mobile jaw crusher, fixed conveyor, MR analyser, and diverter gate. Results of the trial demonstrate that bulk ore sorting could deliver a net improvement in copper metal fed to the processing plant of 6-8 per cent within an equal gross tonnage of ore. Copper metal increases were the result of improvements in mining recovery, where valuable mineralisation is recovered from marginal or sub-grade material that would otherwise be discarded as waste or stockpiled as low-grade. The increase in mining recovery more than compensates for metal losses suffered in the bulk ore sorting plant.

Nov 10, 2020

By M S. Tuohy

Since the independent review of fatal accidents in the mining industry carried out by Dr Sean Brady (the ‘Brady Review’), High Reliability Organisations (HROs) and their operating principles have been discussed across the Queensland mining sector. HROs are organisations said to consistently avoid serious failures, reliably delivering their organisational objectives despite operating in environments characterised by high levels of inherent risk and/or operational complexity. HRO concepts have previously found application in other similarly hazardous industries to mining. However, as Hopkins (2009) pointed out, HROs ‘are very elusive creatures that inhabit the realm of theory more than the real world’. The Queensland Resources Council (QRC) with support from the Commissioner for Resources Safety and Health initiated a review of how HRO principles can be translated to the mining industry. The review was conducted by Noetic, an Australian management consulting company that specialises in hazardous industries, including mining and metals, and has prior experience applying HRO theory.

May 5, 2022

By M L, G Maddocks, A Ferrier, ers, A Forbes

Evolution’s Mount Rawdon Operation (MRO) produces gold and silver through open pit mining methods. The mining operations are scheduled to be completed in FY24 (Financial Year 2024), after which low-grade stockpiles will be processed until the end of FY27. As part of MRO’s Progressive Rehabilitation and Closure Plan (PRCP), RGS Environmental Consultants (RGS) and Deswik were engaged to develop the final landform surface and a whole of site probabilistic water balance/water quality (WB/WQ) model to evaluate the viability of several closure options with respect to water quality in the various site water storages, particularly the final void which will form a pit lake. This case study details the closure option which included (amongst other things) covering the final landforms and directing water toward or away from the final void post closure. Closure and rehabilitation for MRO had previously been planned and evaluated on a ‘domain’ basis. Furthermore, the rehabilitation plans and final water management plans for the Tailings Storage Facility (TSF), Waste Rock Storage Facility (WRSF) and other domains were not coordinated, possibly resulting in competitive rehabilitation material requirements at the commencement of closure activities. An assumption was that a legacy non-acid forming (NAF) stockpile would provide sufficient material to both supplement ex-pit material for the construction of the TSF embankment raises and to complete all closure activities, but the volumes available and the volumes required to complete the closure activities had not been quantified.

Aug 2, 2023