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David Piccolo, Gareth Swarbrick, Garry Mostyn, Bruce Hutchison, Rodd Brinkmann
Hillgrove Resources owns and operates Kanmantoo copper mine some 44 km southeast of Adelaide.
An important feature of the mine is its tailings storage facility (TSF) which is fully lined with HDPE, and double lined at the base, fully under drained, has a secondary underdrainage system for leak detection and a multi-staged centralised decant system. This onerous design of the TSF was developed in consultation with DMITRE between 2007 and 2010 amid concerns of groundwater protection and effective water management.
The Authors were approached in 2010, following construction of the initial stage of the TSF, and charged with developing the design to increase storage from 13 to 20 million tonnes, as well as optimising the design and construction of future stages.
This paper presents the more interesting aspects of the design and construction optimisation between 2010 and 2016 including:
- Optimisation of the:
o extent of the double liner and underdrainage system,
o protection layer below the liner, and
o quality control process adopted during construction. - Design, construction and operational responses to the challenges arising from the raising the TSF including the effect of increased tailings height on the decant structure, buried pipes, and the double liner.
The design and construction approaches have been scrutinised and accepted by regulatory authorities, and implemented by the mine operator over a period of 6 years. The paper includes lessons learnt during the implementation process.
Now showing 1–12 of 14 search results:
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2016 Papers
2016 – Kanmantoo Tailings Storage Facility (TSF) – Optimising the Design, Construction and Operation of a Fully HDPE Lined Tailings Storage Facility
Learn moreDavid Piccolo, Gareth Swarbrick, Garry Mostyn, Bruce Hutchison, Rodd Brinkmann
Hillgrove Resources owns and operates Kanmantoo copper mine some 44 km southeast of Adelaide.
An important feature of the mine is its tailings storage facility (TSF) which is fully lined with HDPE, and double lined at the base, fully under drained, has a secondary underdrainage system for leak detection and a multi-staged centralised decant system. This onerous design of the TSF was developed in consultation with DMITRE between 2007 and 2010 amid concerns of groundwater protection and effective water management.
The Authors were approached in 2010, following construction of the initial stage of the TSF, and charged with developing the design to increase storage from 13 to 20 million tonnes, as well as optimising the design and construction of future stages.
This paper presents the more interesting aspects of the design and construction optimisation between 2010 and 2016 including:
- Optimisation of the:
o extent of the double liner and underdrainage system,
o protection layer below the liner, and
o quality control process adopted during construction. - Design, construction and operational responses to the challenges arising from the raising the TSF including the effect of increased tailings height on the decant structure, buried pipes, and the double liner.
The design and construction approaches have been scrutinised and accepted by regulatory authorities, and implemented by the mine operator over a period of 6 years. The paper includes lessons learnt during the implementation process.
Learn more - Optimisation of the:
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2017 Papers
2017 – A Unique Experience with Liquefaction Assessment of Impounded Brown Coal Ash
Learn moreRadin Espandar, Mark Locke and James Faithful
Brown coal ash has the potential to be a hazard to the environment and local communities if its storage is not well managed. The risk of releasing contained ash from an ash tailings dam due to earthquake induced liquefaction is a concern for mining lease holders, mining regulators and the community.Ash tailings dams are typically raised by excavating and compacting reclaimed ash to form new embankments over slurry deposited ash, relying on drying consolidation and minor cementation for stability. Understanding the post-earthquake behaviour of the brown coal ash is necessary to assess the overall stability of an ash tailings dam during and after seismic loading events.A particular concern is the seismic motion may break cementation bonds within the ash resulting in a large reduction in shear strength (i.e. sensitive soil behaviour) and potential instability. There is limited information available for black coal ash however, brown coal ash has different properties to black coal ash and no known work has been carried out to date in this area.The dynamic and post-earthquake behaviour, including liquefaction susceptibility, of the brown coal ash was studied, specifically for Hazelwood Ash Pond No. 4 Raise (HAP4A) in Latrobe Valley, Victoria. In this study, different well-known methods for liquefaction susceptibility, including the methods based on the index parameters, the cone penetration test (CPT) and the cyclic triaxial testing, were used and the results were compared.It was found that the impounded brown coal ash is susceptible to liquefaction and /or cyclic softening. Triggering of the liquefaction or softening was assessed based on the results of cyclic triaxial test.In this methodology, the relationship among axial strain(εa), Cyclic Stress Ratio (CSR) and number of uniform cycles (Nequ) was determined based on the triaxial test results. Then, asite-specific CSR was determined using the ground response analysis. The CSR and number of uniform cycles (Nequ) for each ash layer was calculated and added to the εa-CSR-Nequgraph to determine the expected axial strain during an MCE event. It was found that the calculated axial strain for the ash embankment and ash deposits during site specific Maximum Credible Earthquake (MCE) are less than the axial strain of the ash material required for triggering of liquefaction and the brown coal ash in HAP4A does not liquefy and/or soften the material during an MCE event. Also it was found that the insitu tests which break the cementation between particles(such as CPT)does not provide accurate results on triggering or sensitivity.
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2017 Papers
2017 – Tailing Dams – How Do We Make Them Safer?
Learn moreDr Andy Hughes
Tailings dams continue to undergo failures at an unacceptable rate compared to water storage dams, including failures at operations owned by high profile mining companies.Tailings dams have often a different form and method of construction than water storage dams in that tailings dams continue to be raised over time as part of the mine operations and rise to considerable heights. These failures are often the result of a combination of design, construction and operations actions that are controlled by humans and must be better coordinated and managed in the future. The consequence of failure can be widespread flows of tailings and water over the landscape and water courses. This can have extreme consequences in terms of life loss, environmental damage, social license to operate, company value, and mining industry sustainability. Therefore,it is necessary that the mining industry strive for zero failures of tailings facilities. Any additional technology and information that enables an owner of a tailings dam to be more certain of its condition and thereby reduce the risk of failure is of tremendous value to reliable tailings and mine water management.The Willowstick method uses low voltage, low amperage, and alternating electrical current to directly energise the groundwater by way of electrodes placed in wells or in contact with seepage or leaks. This approach has been successfully used to identify water flow paths through, under and around tailings dam in plan and elevation.The Willowstick technology provides additional information to supplement the geological, geotechnical and hydrological, evaluations analyses and designs, and to further improve tailings dam safety by more robust designs if necessary. This paper, using several tailings dam case studies, illustrates the procedure, findings, and the benefits of the Willowstick methodology. The findings of many Willowstick surveys range from tailings dams where the methodology has confirmed the design evaluations, to tailings dams where new groundwater and leakage flow paths were identified. In the latter case, the dam designers were able to update the designs, based on the new information,to mitigate the identified risks and to improve the overall safety of the tailings dams in accordance with the goal of zero failure.
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2018 Papers
2018 – Numerical modelling of embankments built on tailings with advanced soil models
Learn moreSimon Tan
Two tailings storage cells were raised by constructing new embankments upstream of the existing
embankment walls. The performance of the new embankments was mainly dictated by the underlying tailings that consisted of a thick layer of very soft to soft fine tailings. The fine tailings in one cell was capped by a layer of sand for more than 30 years hence the tailings had mostly consolidated under the load of the capping. The fine tailings in the other cell was under consolidated because the cell had only been capped for about 18 months before the construction of the new embankment. The capping material was sand extracted from the tailings.Stratification of the tailings was determined by CPT. Undisturbed samples of fine tailings were obtained by a piston sampler for CIU and oedometer testing to obtain parameters required for advanced soil models SHANSEP and Soft Soil (SS) models. These models were incorporated in full 2-D FE models to analyse the stability and settlement of the new embankments at various locations.
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The application of advanced soil models such as SHANSEP and Soft Soil by hand calculation and
conventional slope stability analysis is considered cumbersome and labour intensive. This paper
demonstrates that with the help of FE software (PLAXIS in this case), it is practical to implement such advanced soil models to simulate the behaviours of soft fine tailings with reasonable accuracy. A similar approach could be used to model other fine tailings and soft clays. One should be reminded that the reliability of any analysis method relies on validation of the analysis model and parameters adopted. -
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2020 Papers
2020 – Challenges in applying new guidelines to existing tailings dams projects
Learn moreMichael Ashley, John Phillips
New guidance and publications relating to tailings dams have been released recently by many jurisdictions across the world as an initial response to recent, well-documented, catastrophic tailings dam failures. The application of new guidelines retrospectively to existing tailings projects can introduce complex challenges, especially for sites with a long and often not well documented history. Challenges can be difficult to overcome while balancing time, cost and risk objectives.
This paper explores the impacts of changes between the 2012 and 2019 revisions of the ANCOLD Guidelines on Tailings Dams and potential implications for existing facilities.
The most significant update between the 2012 and 2019 revisions of the guidelines relating to design practices is the additional detail and guidance on seismic stability analyses and static liquefaction. Guidance on the application of new guidelines for tailings dam designers, owners and regulators is required to provide a consistent approach to manage the risk.
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2020 Papers
2020 – Increasing risks: The unintended effect of our TSF Standards and Guidelines
Learn moreRyan Singh, Jiri Herza, James Thorp
Recent and continual failures of tailings storage facilities (TSFs), often resulting in catastrophic consequences, has led to calls for action from the industry, stakeholders and the public at large. Several standards and guidelines are being prepared at the time of writing, most notably a Global Industry Standard on Tailings Management (GISTM), with the overall objective to reduce the rate of TSF failures globally. While better guidelines are certainly necessary, there are requirements that must be carefully followed in developing a document that has the ambition to become a standard. If such requirements are not fulfilled, the document can become ineffective or potentially have the opposite result to that which was intended. This paper discusses whether or not the GISTM meets the requirements of the standards and analyses the potentially negative impacts of its implementation on the industry and wider society. Based on this analysis, this paper provides several recommendations for improvements that should be considered by the GISTM panel and other working groups preparing standards and guidelines.
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2020 Papers
2020 – When the bottom-line impacts dam safety: Case studies of commercial realities leading to increased risks
Learn moreJames Thorp, Ryan Singh, Jiri Herza
Responsible management and operation of tailings and water storage facilities comprises a series of activities and projects that must be delivered within the commercial realities of the organisation and operation context of the facility owner. All projects are constrained by several variables, which are commonly represented by the Project Management Triangle of Scope, Time, and Cost. These variables are often finite and mutually exclusive, and delivery of the required outcome is accomplished by successfully managing each variable. The activities (variables) associated with the long-term dam safety are sometimes omitted to meet the immediate project requirements. In addition, the commercial realities, such as a selected project delivery model, can have a significant impact on dam safety risks through the allocation of risk, ability of the key decision makers, and the undue commercial pressures applied by each project delivery model. This paper presents several case studies where the project and commercial realities have led to decision making that impacted dam safety and increased the risk presented by the storage facility. While the immediate impact of these decisions may appear to be minimal, all stages of a tailings or water storage facility’s life span are impacted. This paper presents learnt lessons with the aim to prompt both owners and consultants to reconsider their commercial processes and project delivery strategies and limit unforeseen risks to the safety of tailings or water dams.
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2021 Papers
2021 – Accounting for brittleness in tailings storage facilities
Learn moreJiri Herza, Kyle Smith, Ryan Singh
Following the failures of Samarco and Feijão dams, brittle failure has become a frequently discussed topic within the geotechnical community. The post-failure review of the Feijão Dam identified that the sudden failure of the dam was caused in part by tailings exhibiting brittle behaviour. Brittle failure has also been identified to be a contributing factor in many previous tailings storage facilities failures. Of concern to the tailings community was the finding that there were no apparent signs of distress prior to the failures, which characterises brittle failure.
The industry’s concern regarding the presence of brittle materials within tailings storage facilities, particularly when featuring upstream raises is evident in the requirements of the newly published Global Industry Standard on Tailings Management, which includes a requirement to “Identify and address brittle failure modes with conservative design criteria…”. This is also reflected in ANCOLD Guideline on Tailings Dams, which provides recommendations for conservative design assumptions if materials are found to be susceptible to static liquefaction which is noted to be a brittle subset of contractive materials. The ICMM’s Good Practice Guide for tailings management uses the term
brittle on numerous occasions and even refers to “credible brittle failure modes” when discussing the performance based approach. Despite its frequent use, the term brittle failure has not been defined in any of the listed references and the authors of this paper are not aware of the any clear geotechnical definition for brittle embankment failure in literature.Brittleness, on the other hand, is a well-known geotechnical parameter that describes the degree of reduction of the soil shear resistance after reaching the peak strength. Bishop (1967) described the soil brittleness in the context of progressive failure of clays by means of a brittleness index, which is the ratio of the shear resistance loss to the peak shear strength. In recent years, the brittleness index has become a common soil parameter that is used as an indicator for tailings susceptibility to liquefaction. The brittleness index does not consider the rate at which the soil resistance reduces, and it ignores the stress strain relationship. As a result, the same brittleness index can be calculated for a soil that collapses over a very small strain range and a soil that gradually reduces its shear resistance over extensive strain levels as long as both soils have similar peak and residual shear strengths.
This paper discusses the root causes of brittle behaviour of tailings, summarises the current approach for brittleness assessment and recommends considerations and methods to assess and deal with potentially brittle soils within TSFs.
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2021 Papers
2021 – Emergency Preparedness for Tailings Dams
Learn moreOlle Wennstrom, Andrew White
Over the last few years tailings dams have come under increased scrutiny, partly due to two highly publicised TSF failures in South America, but also because of several other incidents in Australia and elsewhere in the world. As investors came under pressure to positively impact the projects they financed, the Global Industry Standard on Tailings Management (GISTM) was released in August 2020.
Topic 5 of GISTM, “Emergency response and long-term recovery”, comprises Principle 13: “Prepare for emergency response to tailings facility failures” and Principle 14: “Prepare for long-term recovery in the event of catastrophic failure”. The topic further introduces the term “Emergency Preparedness and Response Plan” (EPRP).
This paper explains what the term “Emergency Preparedness” means and how the owner/operator of a mine can achieve it. The paper also delivers a concept for long-term recovery planning.
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2021 Papers
2021 – The Critical Link between Risk Assessments and Critical Controls
Learn moreRyan Singh, Jiri Herza, James Thorp, Michael Ashley
Performance-based risk-informed decision making is an underlying principle of the Global Industry
Standard on Tailings Management (GISTM). While owners make significant efforts to align with this
principle, commonly used risk assessment and management practices in the mining industry have largely been based on the HSE principles, which consider more frequent, lower consequence incidents.As a result, the existing risk assessment frameworks do not provide the owners with a comprehensive understanding of the risk profiles of their tailings storage facilities (TSFs). Without the understanding of a facility’s risk profile, the owners cannot appreciate how changes to their facility, processes and operational activities may impact the risk profile. A large step-change in thinking is therefore required in risk assessment practices for the owner to align their TSF management with GISTM requirements.
Beyond risk assessments, the mining industry has other valuable concepts to manage the safety of their tailings management practices, such as Critical Controls, however, commonly used risk assessment and management practices do not incorporate these concepts.
This paper explores commonly used risk assessment practices and the concepts of Critical Controls. It proposes how these concepts can be linked, with Critical Controls being embedded in the risk assessment process. The outcomes of linking these concepts result in an estimation of the effectiveness of the Critical Controls and how they can be improved to demonstrably reduce the risk presented by a TSF. A case study has been included to demonstrate the benefits of linking risk assessment with Critical Controls and how owners can readily identify deficiencies and efficiently manage the risk profiles of their facilities.
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2012 Papers
2012 – Gördes Dam – A Turkish Delight
Learn moreDr. Mark Locke, Jiri Herza
Gördes Dam is a nickel and cobalt mine tailings dam situated in a seismically active zone in Manisa Province, Western Turkey. The dam is a conventional cross valley earthfill structure with a fully lined storage basin. The starter embankment with a maximum height of 50 m will be raised in downstream lifts to an ultimate height of 90 m. The total storage capacity is 19 million m3. Construction of the starter embankment is planned to commence in late 2012 and the dam will be commissioned in June 2013.
The tailings will be discharged from the dam crest and return water will be collected by a floating decant pump at the opposite site of the storage. Decant water has high calcium sulphate levels and will require treatment before re-use in the plant or release. The tailings contain about 33 % of solids and are classified as high plasticity silts and clays with more than 90 % of particles passing the 0.075 mm sieve.
The dam is founded on a complex formation of altered sedimentary and metamorphic rocks including mudstones, siltstones, limestones and serpentines. The mudstone blocks, the predominant foundation materials, are juxtaposed with siltstones and serpentines via a complex arrangement of faults. Where exposed, the mudstones are highly to completely weathered with a well-developed structure of smooth bedding surfaces leading to anisotropic strength characteristics. Several landslides, likely associated with the anisotropic character of the mudstones, were identified within the area including a significant landslide under the upstream shoulder of the dam.
Mining development in Turkey has a complex legislative environment. There is also standard practice which is not legislated but expected, this can be considerably different to normal design practice in Australia. The Turkish legislation is based on waste management guidelines and may be more appropriate to landfills than large tailings storages. The legislation is very prescriptive in some aspects and silent in others, with little consideration of risk or consequence based design.
This paper discusses the design difficulties associated with the challenging foundation conditions, which have been magnified by the requirements and limitations embedded in the approval documentation and the legislative environment in Turkey. It will also address some of the key differences between the design philosophy in Australia and in Turkey with a focus on the major risk elements of the design.
Keywords: Tailings, Turkey, Liner, HDPE, Nickel laterite
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2008 Papers
2008 – “When is a dam not a dam?”- Design of mine tailings storage facilities for closure
Learn moreDavid Brett, Ben Hanslow. Rob Longey
Abstract: Mine tailings storages are among the largest man made structures in the world and often pose a considerable risk to the aquatic environment due to the nature of the stored materials. In particular, sulphide minerals are prone to oxidation when brought into contact with air and water. This leads to the formation of acidic conditions within the storages leading to dissolution of toxic metals, with seepage from these structures being known as Acid Rock Drainage (ARD). ARD is responsible for pollution of natural waterways in many areas of the world with some significant examples in Australia. Current practice in the mining industry is to attempt to exclude oxygen or water from tailings storages in order to prevent the oxidation process taking place. This involves capping of the storages with sophisticated soil covers or, where sufficient water is available, leaving a permanent water cover.
Mining operations have a relatively short life, usually around 5 to 10 years, although some can operate for over 100 years, as has the Mount Lyell Mine. Normal practice has been for companies to relinquish the mining lease on the cessation of mining, however governments are now realising the extent of liability involved with the “ownership” of large waste storage facilities. Bonds are placed by mining companies during operations, intended to cover the cost of “closure” of the mine. Often the major item covered by the bond is for the “closure” of the tailings storage facility. Following “closure”, the intention is that ownership of the lease, including waste storages, reverts to the State. State governments are now more aware of the potential liabilities in accepting the relinquishment of these leases and need to address the issues of their long-term management.
In Tasmania, Dam Safety legislation covers both water and also soil covered tailings storages, with the legislation requiring each type to meet various ANCOLD guidelines. In other jurisdictions this could well also be the case through common law requirements to meet common best practice. However, the current ANCOLD Guidelines are generally written around water storage dams and interpretation to include a waste storage facility is often not straightforward. As an example a tailings dam during operations with a water storage component is clearly a dam. Due to the environmental impact of failure it could well have a Significant or High-C hazard rating, which would require design for extreme floods and earthquakes. After closure, with say a soil cover and water diverted away, is it still a dam within an ANCOLD definition? Are ANCOLD guidelines relevant? The current ANCOLD (1998) Guidelines on Tailings Dam Design, Construction and Operation does not give specific guidance on these issues.
This paper explores these questions and suggests ways that ANCOLD could provide assistance with more guidance on the long term management aspect of tailings storages to assist designers, owners and regulators consider the closure phase.
Keywords: tailings, acid drainage, mine closure
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2009 Papers
2009 – Why should ANCOLD produce tailings guidelines?
Learn moreJohn Phillips
There are many international guidelines, state regulations and technical standards relating to tailings disposal. In addition, the larger mining companies have their own in-house standards and design rules with competent personnel in charge of their operations. Sound embankment design methods can be used by most designers familiar with earth dam design.
The paper gives a listing of many of the current sources of information and guidance available, with some comments by the author on their perceived relevance to the Australian mining industry. Despite the availability of a number of other guidelines at the time, the need for Australian Guidelines was recognised in the mid 1990s and the reasons for the development of the 1999 ANCOLD Tailings Guideline are explained.
Perhaps the best recognition of the need for the original ANCOLD guideline is the degree to which it has been adopted since publishing the 1999 edition. It is in almost universal use in the Australian mining industry and is recognised as providing appropriate and acceptable standards by all state governments. Its use is recognised and sometimes even specified by a number of neighbouring countries and it is also recognised internationally when used by Australian companies with overseas operations.
The reasons for this wide acceptance are described. However, there are some areas where more recent developments have led to the Guidelines becoming dated and improved international guidelines have been published since 1999. The need for a revised ANCOLD guideline and its elevance is then described.
Keywords: Tailings, dams, mining, guidelines
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2010 Papers
2010 – Hidden Valley – Design and Construction of Highland Papua New Guinea First Tailings Dams
Learn moreRick Friedel, Len Murray, Gerrad Suter, James Penman, James Watt, Hendra Jitno
The Hidden Valley tailings storage facility (TSF) has set a new precedent in environmental management of tailings in Papua New Guinea (PNG). Modern mining in PNG arguably began with the development of Bougainville Copper in the late 1960s, and continued through to Ok Tedi, Porgera, Lihir, Misima (and others). These mines have proceeded with deep sea or riverine tailings deposition, rather than construction of a tailings dam to retain the mine waste within an impoundment; as is the practice throughout the majority of the mining industry.
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The Hidden Valley TSF is comprised of two large earth and rock fill dams, raised by the downstream method. Starter dam construction was completed in 2009. At final height the Main Dam will be one of the highest tailings dams in the world. The dams are constructed of pit waste and therefore have the dual function of storing tailings and waste rock.
Construction of the starter dams and subsequent raises is complicated by conditions at the site. Water management was, and remains, the dominant issue. High rainfall, weak erosive soils, material availability, dense vegetation and remoteness of the site provide constant challenges to construction. The Observational Approach to construction was recommended by the designers and adopted by the mine operator. This involves a knowledgeable pre-assessment of what is likely to change and having contingency plans to deal with possible major issues. This approach allows changes to the design during construction so the “as-built” product is suited for the site, fit for purpose, and remains consistent with the overall intent of the design.
The TSF has been in operation since August 2009 and monitoring data of the structures has been collected during construction and operation. This data is reviewed to confirm design assumptions and assess dam performance.
Personnel involved with this project combined their experiences working in the PNG environment and dam building from other locations. This process led to close interaction between the mine operators, designers and construction teams. Team work and diligent construction practices were and will continue to be necessary to construct and operate the pioneering TSF in PNG.