Credit: INAP Covers Report – Illustrator Derrill Shuttleworth
Over the years, INAP has instigated and funded a number of key Acid and Metalliferous Drainage (AMD) research projects to fill knowledge gaps. Cutting-edge technologies are studied, AMD measures at specific sites are examined, and literature reviews are undertaken to summarise AMD state-of-the-art.
Current and Ongoing INAP Projects
Updates to Global Acid Rock Drainage Guide (GARD Guide)
The GARD Guide, first published in 2009, was intended from the start to be a state-of-practice summary of the leading practices for the prevention and mitigation of acid and metalliferous drainage (AMD). The GARD Guide is a living document and requires periodic updates. A detailed review was completed in 2017; gaps were identified and chapters prioritized requiring updating. Chapter 7, Treatment, was the first to be addressed and was completed in July 2021. The project was a collaboration between Klohn Crippen Berger and Golder, and the updated Chapter 7 can be downloaded here.
Since the creation of the GARD Guide in 2009, mine closure became much more visible and is seen as a strategic issue. The addition of a mine closure chapter (Chapter 11) that addresses the implications of ARD for achieving effective and sustainable mine closure was completed in July 2024 by WSP-Golder and can be downloaded here. This chapter will significantly raise the profile of this area and provide a more focussed and holistic view for stakeholders and users of the Guide.
Work on the updates continues with Chapter 6 - Prevention and Mitigation currently in draft. More are planned with Chapter 8 Monitoring being the next chapter to be updated. Plans are to launch a new GARD Guide website to accommodate these updates. Please consult the GARD Guide web page for complete project details.
Pit Lake Database
The time interval between the prediction of pit lake water quality and the measurement of pit lake water quality following pit lake filling can be decades to centuries. This presents a significant challenge to pit lake modelers, mining companies, and other stakeholders who wish to validate pit lake water quality predictions.
To address this challenge, the International Network for Acid Prevention (INAP) has been working diligently on the development of its Pit Lake Database. This work began in 2010. This comprehensive resource now represents a centralized record of water quality data for pit lakes across a range of ore body types, host rocks, and climatic conditions over time. With over 2,600 water quality observations from 271 pit lakes and 25 ore body types, the database is a significant achievement. All the information has been collated from publicly available sources, such as publications and government records, and can be fully referenced. The Pit Lake Database is expected to be a powerful tool for mining companies, consultants, and researchers. Its applications include validating pit lake models using data from similar ore bodies and climates, supporting better outcomes for water quality prediction, and advancing sustainable practices in mine water management.
A paper titled an “Update to the INAP Pit Lakes," presented at ICARD 2024 can be downloaded here. Also available here is a flyer on the Pit Lake Database that lists the pit lakes that can be found in the database. INAP encourages stakeholders to share additional public water quality data to further enhance this valuable resource.
INAP is pleased to announce that access to the Pit Lake Database is now available for research and project work. INAP is committed to ensuring this valuable asset is widely utilized. Interested parties can request access through the INAP Technical Manager.
By making this resource accessible, INAP hopes to support industry efforts in achieving better water quality outcomes while fostering collaboration and innovation across the mining sector.
A new study was awarded in late 2024 which aims to provide insights into the data contained within the pit lake database and to review modelling and predictive approaches that can be supported by this extensive resource comparing predicted pit lake water chemistry and observed pit lake water chemistry from the same lake. By leveraging the data, this study seeks to refine predictive methods and enhance understanding of water quality dynamics in pit lakes.
Develop an Industry Guidance Framework to Support Assessment of Tailings Stability Risks Arising from Geochemical Reactivity
In 2024, a collaborative project that consists of the preparation of a guidance document that focuses on the geochemical processes influencing the geotechnical stability of tailings and mine waste materials, including, but not limited to, embankment materials, waste rock, conventional slurry deposited tailings, and filtered tailings was initiated. This ia a collaborative project between the Mine Environment Neutral Drainage (MEND) program and INAP with SRK as the contractor.
Phase I Summary Report: Geochemical Processes of Geotechnical Significance, is now completed can be downloaded here. The report highlights how geochemical processes can influence the long-term physical behaviour of tailings storage facilities (TSFs). Understanding these processes supports safer designs, better monitoring and more resilient closure planning.
Phase 2 is planned in 2026 and will consist of assessing the plausibility of these processes/risks through development of a screening-level risk assessment tool that identifies key factors influencing a facility’s susceptibility to geochemically induced stability risks.
Working with University to Develop Educational Games
Since 2023, INAP is working with Queensland University of Technology (QUT) students in Brisbane to develop educational mining games that have ESG and AMD learnings. The goal of these interactive games/education packages is to teach students at the high school and university levels the importance of AMD and the environment. It could also apply to the mining community as a whole. The innovative work by the students to date is impressive.
Several games have been developed, including one called Sul Fury. The key objective of the game, is to avoid environmental issues (e.g., AMD) while mining but it also aims, to build interest and capacity in our industry.
In addition to Sul Fury, a series of mini-games was developed by 2nd year QUT students. There were 28 students that formed 6 different teams. Teams were tasked to develop mini games that teach AMD concepts in a fun way. One of the teams developed a game for the android phone where the player needs to move their phone left and right to enable a water drop to pass through obstacles, avoiding the pyrite mineral each time (downloadable from: https://witchofendor.itch.io/rock-bottom). In 2025 a contract was awarded to further develop accessibility to the Rock Bottom game and make it available on the Google play store for everyone to download on their mobile phone.
Demonstration of other games developed at QUT are also available from https://www.linkedin.com/feed/update/urn:li:activity:7288031681104527360. And INAP plans to continue to work with QUT in 2026 to develop the educational games further.
Completed Research Projects
- Phase I Summary Report: Geochemical Processes of Geotechnical Significance
- Tool for Acid Rock Drainage and Metal Leaching Prevention and Management (Excel-based Tool Here)
- AMD ARD/AMD Source Control for Mine Rock Stockpiles Phase 3
- GARD Guide Chapter 11 – Sustainable Mine Closure
- GARD Guide Updated Chapter 7 - Treatment
- Rock Placement Strategies to Enhance Operational and Closure Performance of Mine Rock Stockpiles – Phase 1
- Global Cover System Design – Technical Guidance Document
- Store and Release Covers – The Role of Vegetation (Stage 2)
- Evaluation of the Long Term Performance of Dry Covers
- Waste Rock Dump Characterization
- Treatment of Sulfate in Mine Effluents
- Rum Jungle Waste Rock Cover
- Diffusive Gradients in Thin-films
- Co-Mixed Tailings Waste Rock and Slag
More information, including project reports and presentations, can be made available by contacting the Technical Manager, Gilles Tremblay.
Tool for Acid Rock Drainage and Metal Leaching Prevention and Management
Proactive management of Acid Rock Drainage and Metal Leaching (ARD/ML) is a fundamental aspect of integrated mine closure planning. By addressing ARD/ML early and systematically, mines can significantly reduce the potential for long-term environmental degradation such as water contamination and ecosystem destruction. This approach not only helps to safeguard local biodiversity and water resources but also ensures that mining operations meet regulatory standards and avoid costly remediation efforts in the future.
In 2024, a collaborative project between ICMM and INAP developed the ‘Tool for Acid Rock Drainage and Metal Leaching Prevention and Management’ to support mining companies with the proactive management of ARD/ML. This Tool provides a comprehensive framework to improve how mining companies manage materials throughout the mining lifecycle that aims to safeguard water quality while reducing long-term remediation costs, supporting more sustainable practices across the industry.
Designed to complement INAP's Global Acid Rock Drainage (GARD) Guide, the Tool makes its technical content more accessible to non-specialist audiences working both at operational mine sites and at a corporate level. An additional Excel-based function allows users to quickly navigate and filter through a large volume of technical information, delivering relevant outputs on a single page tailored to specific lifecycle stages and practice areas.
The Final Report and the Excel-based tool can be downloaded from both the ICMM and INAP website.
ARD/AMD Source Control for Mine Rock Stockpiles Phase 3
Preventing mine leaching through source control has become a major focus for INAP. “Source control” refers to any mine waste management approach that limits release of constituents from the mine waste itself as opposed to external removal approaches (e.g., water treatment). It can also be thought of as potentially removing the spectre of perpetual water treatment as the only solution to the issues of AMD. INAP has been working towards improving both mining and mine rock placement strategies to reduce water quality risks during operations through into closure for mine rock stockpiles.
One key area of work has been in improved mine rock stockpile construction and management. A phased program was initiated to look at how MRS construction could be altered to provide a much different outcome in terms of performance. Phase I identified opportunities to incorporate improved mine rock placement and management strategies to limit re-supply of oxygen into MRS’s.
Phase III of this project, completed in 2024, has advanced the development of these concepts by posing the question “What value does constructing an MRS with a focus on source control provide in respect of reducing asset liability to an acceptable level of residual risk?”.
A key component for Phase III was the development of a decision-making framework, or tool to evaluate the benefits of including methods to enable source control measures within the mine rock stockpiles during construction. The tool outlines how the level of uncertainty can be managed through different mitigations and controls to ultimately reduce probability of unrecognized and underfunded liability for sites through operations and closure. The information provided within the tool is not a replacement for a site-specific study and engineering required for MRS design. It is a means of facilitating conceptualization to help focus further investigation and design and to form realistic expectations for MRS performance at early stages of strategic mine planning. The tool can be used to evaluate and guide informed decision making on whether conventional MRS construction practice will achieve the desired, or required, closure outcomes.
The framework aims to capture decades of lessons learned in industry experience and provide new users guidance in asking the right questions in evaluating source control strategies as part of their mine development and closure plan. Two case studies were referenced to demonstrate utility of the decision tool. These case studies have been put forward to support development of the tool and provide credibility to the process by illustrating the benefit of incorporating source control within MRSs despite vastly different climate zones and physical settings. The decision tool directs users to ask critical questions and consider site-specific conditions to determine how best to increase mine life cycle value through incorporating MRS source control to reduce asset liability to an acceptable level of residual risk.
The Final Report can be downloaded here.
A communication approach, consisting of two webinars, was developed to broadcast the findings of the source control project. The webinars, titled "Prioritizing ARD/AMD Source Control: Responsible Practices for Building Mine Rock Stockpiles" presented the Phase I for context and the Phase III findings. Both webinars can be viewed: Webinar 1 and / or Webinar 2.
Rock Placement Strategies to Enhance Operational and Closure Performance of Mine Rock Stockpiles – Phase 1 (Earth Systems and O’Kane)
The mining sector worldwide is experiencing significant increases in closure costs and is accumulating a growing number of stranded liabilities due to poor closure outcomes. Direct and indirect measurement of acidity loads from various mine site domains at more than 40 sites over the past 25 years has revealed that disposed mine rock materials are responsible for the majority of AMD/ARD pollution (60-80%) at most mine sites.
Conventional mine rock stockpile (MRS) construction typically involves disposal of well sorted, relatively dry rock materials from the back of tip-trucks down angle-of-repose slopes of previously disposed material with wide particle size distributions. This method minimises costs associated with loading, hauling and placing rock, while maintaining geotechnical stability of the MRS. However, it also optimises sulfide oxidation and minimises acid neutralisation; the approach is therefore largely responsible for long-lived water quality impacts post-closure.
Improved construction methods are available and new approaches are emerging. These are principally focused on improved control of gas transport within MRSs, both during and post construction of the MRS, which can be influenced by transport disruption layers / trafficked layers, encapsulation of high-risk materials, decreasing tip head heights, and paddock dumping in thin compacted layers from the base up. Strategic placement of oxygen consuming and pyrite passivating materials can also lower acidity production. Each of these construction methods perform differently under different physical and chemical conditions (e.g. topography, climate, geochemistry) and can also be combined to lead to improved outcomes. Ideal construction methods are highly likely to be site-specific.
This report, Phase I of a multi-phase project, focused on the geochemical benefits of the various construction methods. Numerical modelling was also conducted to demonstrate how the performance of conventional end-dumped MRSs can be compared with some of the improved MRS construction methods, in terms of a percentage reduction in kilograms of acidity produced per tonne of waste rock placed (kg H2SO4/tonne). A failure modes and effects analysis was conducted to demonstrate that risks associated with MRS construction can be progressively lowered (or adaptively managed) by adopting a combination of the improved construction methods. It also provides the groundwork for additional phases, or ‘next steps’, for building improved MRSs.
→ Click here for the final report (5.4 MB)
→ Click here for the Webinar Presentation by Dr. Jeff Taylor, Earth Systems (June 9, 2020)
→ Click here for the Webinar Presentation by Mike O’Kane, Okane (June 9, 2020)
→ Click here for the Webinar Presentation Slides
Global Cover System Design – Technical Guidance Document (November 2017)
The Global Cover System Guidance Document, like the GARD Guide, is intended as a best practice summary to assist mine operators, designers, and regulators to address issues where cover systems can be employed. This document builds on previous technical guidance documents on cover system design, construction, and performance monitoring. The Global Cover System Guidance Document will be of interest to individuals who are seeking more detailed information than what is outlined in Section 6.6.6 of the GARD Guide - Engineered Barriers.
A holistic framework for management of reactive materials during operations and at closure is the pillar of the document. The framework for cover system design is presented at a high level, suitable for readers with minimal technical background. It is presented at a conceptual level, using a hierarchy of climate, geology and materials, and topography, leading to an understanding of the patterns of water movement on a specific landscape. Ultimately, these elements will govern how cover systems perform, and it is up to designers to manipulate them to achieve desired performance.
This document presents a conceptual model of how cover system designs might affect contaminant and acidity loading. This model attempts to determine when the varying roles of the cover system design (e.g. control of net percolation or oxygen ingress), might influence loadings. Acknowledgment of these unique relationships provides an opportunity to optimize ML/ARD management in a cost-effective manner. Other key concepts discussed within the document are the role cover systems play over the life of the mine from early conceptualization to long-term performance monitoring considerations.
Application of the holistic framework is achieved through the use of a cover system design tool that walks users through relevant climatic factors to optimize cover system design alternative for a desired performance design criteria. This allows users to understand what a realistic objective is when developing cover system design alternatives based on site-specific climate conditions. Additionally, the tool refers to specific elements integral to the design where an in text commentary is provided. The tool helps identify where potential for management exists on the site, leading to the selection of the most appropriate form of prevention.
The information provided within the tool is not a replacement for site-specific classification and engineering required for cover system design. However, the tool is a means of beginning early conceptualization to help focus further investigation at a site level and to begin to form realistic expectations for cover system performance at an early stage of a project.
→ Click here for the final report (12.4 MB)
Designing Effective Store - Release Covers for the Long–Term Containment of Mine Waste - The Role of Vegetation (Stage 2)
The former Australian Centre for Minerals Extension and Research (ACMER) research project, managed by the Centre for Mined Land Rehabilitation at The University of Queensland, addressed the following objectives: (1) to use water balance data for vegetated store-release covers to assess the performance of existing covers, and contribute to recommendations of future covers, (2) provide a workable model that links into existing cover water balance models, and effectively describes annual water use as a function of weather, leaf area index, changes in root zone properties and cover construction technique, and (3) facilitate significant improvement in the capacity of existing water balance models to describe hydrological processes in waste storage facilities. The work included quantifying and modeling the water uptake processes of different soil and vegetation community combinations which were (or are being) used as store-release covers at two established sites with differences in climate, vegetation, geology and soils from western and eastern regions of Australia.
In addition to the project report, a list of publications originating from research within this project is available.
→ Click here for the final report (3.3 MB)
→ Click here for a copy of the list of publications (699 KB)
A study to improve our ability to accurately predict the long-term performance of dry covers
Dry cover systems are one of the most common preventative measures used to control acid drainage. Accurately predicting the long-term performance of covers is a vital part of minimising the mining industry’s AD legacy issues. With this objective a study on the long-term stability of dry covers was commissioned to O’Kane Consultants Inc.
The study:
- Identified and defined factors that affect long-term performance.
- Evaluated state-of-the-art tools for modelling dry cover systems.
- Provided recommendations for improving and validating existing models.
→ Click here for the final report (1674 KB)
A characterization study of the geo-chemical and hydrological nature of 2 waste rock dumps that were being dismantled by member companies.
In 2000, waste rock dumps from the Rio Tinto Kennecott Ridgeway Mine and the Inco Whistle Mine needed to be relocated. The opportunity was seized to study the geochemical and hydrological nature of the waste rock dumps and the extent of oxidation zones within them. The project generated much interest and was jointly funded by INAP, NSERC, and R&D Start Funds. Dr. Ward Wilson from UBC, Maree and Stuart Miller from EGi, and David Williams from the University of Queensland lead the study. The findings from the work link the hydrological and geo-chemical nature of the dumps, which contain complex hydrological pathways that dictate the geo-chemistry of the released drainage. There is an indication that many of the layers within the dumps contain large amounts of stored oxidation products and soluble metals. The layers may not have an adequate degree of saturation to allow water to flow through them, thus reducing final drainage concentrations.
→ Click here for the final report (806 KB)
A review of sulphate treatment practices and a discussion of legislation trends "Treatment of Sulphate in Mine Effluents".
Very little research has been undertaken on the treatment of sulphate in mine effluents. INAP members saw the need to fund a literature review of state-of-the-art sulphate treatment processes including regulations and guidelines from governments and agencies around the world. Lorax Environmental (the consultant) carried out the study, which describes methods for removing sulphate and metals from mine effluents and associated operating costs. Case studies of successful operations are also documented.
→ Click here for the final report (3416 KB).
A case study on the deteriorating performance of the 18 year-old Rum Jungle dry cover system in Northern Territory, Australia.
The 18 year old cover Rum Jungle in Northern Territory, Australia is one of the oldest cover systems for which the design, construction, and continuous monitoring date are well documented. Water infiltration through the covers increased significantly in the last few years and this project was designed to use the data history to understand the reasons for the deterioration performance. The Australian Nuclear Science and Technology Organisation (ANSTO) and the Commonwealth Scientific and Industrial Research Organisation (CSIRO) were contracted to undertake the work. The study found that the cover materials no longer met the original design specifications –particularly for permeability which increased by several orders of magnitude. Findings from the study indicated that the increased permeability may be attributed to:
- A shortage of cover material during construction resulting in bare patches;
- A combination of biological and physical process - galleries formed by termites and ants, root growth from
- the pasture grasses and the few volunteer trees, and an extensive system of shrinkage/dessication cracks.
→ Click here for the final report (2224 KB)
A study to use Diffusive Gradient in Thin-films (DGT) technology (or gel samplers), which allows for in situ determinations of free-ion activity of metals in mine water and provides a more accurate representation of biological impacts than measurements of total or dissolved metal concentrations.
Conventional water quality analysis is restricted to measuring total and dissolved metals in discrete water samples. Lorax (the consultant) was commissioned to undertake a study on the use of diffusive gradients in thin-films (DGT) - or gel samplers as this technology can provide a more accurate estimation of metal toxicity in water.
The project findings indicated that the use of DGT provides a measure of metal bioavilability, and hence a more representative measure of metal toxicity in water. This is mainly due to the fact that DGT detect free or weakly complexed metal species without measuring constituents that are not bio-available. The use of DGT also has the advantage of being an in-situ measure and can provide a time-integrated estimation over a deployment interval. This is especially beneficial when dealing with highly variable water quality, as is usually the case when measuring mining effluents discharged into natural watercourses. The use of DGT is, however, limited to a certain pH range (5-9 for most metals, 2-11 for Cu) and is not effective in waters of very low cation concentration. The study concluded that the DGT technique can be applied to various aspects of environmental chemistry, however more work is required to validate the use of DGT in mining-impacted waters.
→ Click here for the final report (1587 KB)
A review of the potential use of co-disposed waste rock and tailings for the construction of covers on mine waste dumps as a practical, low cost AD prevention method.
Following a literature review on the application of co-disposed tailings and waste rock to construct covers, this project was designed to examine the stability and hydraulic conductivity of a number of co-mixtures with varying ratios of tailings, waste rock and slag. Klohn Crippen in association with Dr. Wilson from the University of British Columbia, were commissioned to undertake the study.
The findings of the work can be summarized briefly as follows:
- Well-graded materials provide the best performance for the construction of soil cover systems with high resistance to erosion, frost, and desiccation. The co-mixtures of slag, waste rock and tailings provided a material that showed both excellent geotechnical characteristics and varying degrees of hydraulic conductivity.
- In-situ mixing of tailings and waste rock is feasible for semi-competent rock types and has low costs. However, this method provides poor cover performance on dump slopes. Layering tailings and waste rock results in good covers and involves low costs, but is also difficult to apply on slopes. Mechanically placing engineered mixtures of tailings and rock provides the most flexible cover option for flat and sloping surfaces. Waste rock would optimally be crushed to 50-75 mm minus size to have the right grading, however this method involves double the cost of the other methods.
- When bentonite was added to the co-mix the conductivity decreased, indicating that once the characteristics had been determined it would be possible to blend mixes with varying properties to meet the needs of the cover being designed.
- Estimates of cost indicated that the covers would be potentially expensive and future focus would have to include an examination of means to provide these mixes in a cost effective manner. Bentonite addition particularly added considerable costs to the overall cost per area of co-mix covers.
→ Click here for the final report (202 KB)