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By T. Lupek, M. Buxton, A. de Jong

"With regard to the EU funded project ‘Real-Time Mining’ a sensor-based acquisition, collection and transmission of data for the resource extraction process will be developed. The key concept promotes the change in paradigm from a discontinuous to a continuous process monitoring. Especially concerning material characterization, machine performance and underground positioning ‘Real-Time Mining’ will provide sensor solutions as well as the interfaces for integration, management and visualization of the collected data for a permanent updating process of the resource model with the aim of near real-time optimization of decisions. On the basis of ‘Real-Time Mining’-Output a permanent monitoring of costs can be performed as well in both, the installation and the production process of a mine. Due to the collected data in terms of machine performance connected with the underground positioning information added with personnel tracking and mine surveys a comprehensive overview of process performance is available. By evaluating those information in a specific manner costs per unit will arise for monitoring and possibly controlling actions. INTRODUCTION By having a look into the future of mineral extraction projects, a new challenge for the Ore Mining Industry will arise in the short and medium term. Due to the depletion of currently mined mineral reserves in addition to the persistently high demand of mineral raw materials, the extraction of complex reserves will be necessary. By characterizing such deposits as not constantly graded and geometrically varying, the extraction process, especially concerning the requirement of a minimized zero-value material handling, will become economically ineffective by utilizing the traditional mineral resource management methods. Regarding the state-of-the-art mineral resource management process along the mining value chain, an intermitted, discontinuous sequence of actions is applied (Figure 1). Recently data will be collected from drill hole cores. These rock samples are analyzed in a laboratory. Based on those analyses a resource model is created whereby unknown data between drill holes is interpolated. This resource model is the basis for all mine planning actions including the selection of the mining method, extraction sequencing and the prediction of the expected performance. With the start of the production, real conditions (concentrations of elements, hardness, stability, etc.) can be observed and measured. As the production process is running accordingly to the above described mine plan, the verification of the initial assumptions happens at the earliest after processing of the extracted material. Even if deviations between the predicted and the actual performance are now recognized, the execution of corrective actions is not possible anymore."

Jan 1, 2016

By M. U. Khan, A. D. S. Gillies

"Diesel exhaust is a major cause of large number of occupational diseases. Acute and continuous exposure to Diesel Particulate Matter (DPM) can cause numerous health issues including respiratory disease, reduced lung capacity, heart disease etc. The National Institute of Occupational Safety and Health (NIOSH) and the International Agency for Research on Cancer (IARC) consider diesel engine exhaust as carcinogenic. In large underground metal and nonmetal mining operations, regulatory compliance regarding miner’s exposure to airborne particles especially DPM is a big challenge. Complex mine networks add more difficulties in controlling DPM. MSHA relies on the NIOSH 5040 method for DPM compliance. The NIOSH 5040 method is a shift average based method which inherits some limitations. Due to these inherent limitations of the NIOSH 5040 method the concept of real-time DPM monitoring is promoted in the mining industry. Several real-time DPM monitors have been used by the researchers and efforts still continues to improve their measuring techniques and understanding. Real-time monitoring of DPM is vital to gain understanding of rapid changes in the mine atmosphere. The current study highlights the advancement in real-time DPM monitoring and mainly covers a review of several studies in which DPM concentrations were measured by utilizing real-time DPM monitors. INTRODUCTION Ventilation of underground mines is an important aspect of mining operations. Mining is a continuous activity and the ventilation networks in modern mines change with extended developments. Proper understanding of the ventilation network is a key design factor of an optimum mine ventilation plan. An important task of underground mine ventilation engineers is to provide clean air with sufficient quantity to the underground miners (Khan M. U. and Gillies A.D.S. 2015). The amount of fresh air supplied to the mine should be adequate to dilute the concentrations of contaminants present in the mine atmosphere. In the United States it is estimated that diesel powered equipment is used in thousands of mining operations (Stephenson D. J. et al. 2006). Use of diesel powered equipment is an attractive option in underground mines due to its several advantages over other available alternates. Diesel engines are rugged, dependable and fuel efficient (McKinnon 1999). It is common for diesel engines in heavy duty trucks to have a life of 1.6 million kilometers (McKinnon 1999). Looking at the developments in other energy alternatives, it can be assumed that the underground mining industry will maintain its reliance on diesel powered equipment (Anon 2001). DPM is an important source of mine air contamination in many non-gassy underground mines (Khan M. U. and Gillies A.D.S. 2015). Diesel exhaust is harmful for humans. Acute and continuous exposure to diesel exhaust concentrations can cause several health issues. Some of the health diseases caused by DPM exposure are respiratory diseases, reduced lung capacity, heart disease, and lung cancer (National Research Council. 1981, Mine Safety. 2005). In addition, NIOSH regards diesel exhaust as “potential carcinogen” (Centers for Disease Control 1988) and IARC has declared that “diesel engine exhaust is carcinogenic to humans” (IARC 2012). NIOSH has also declared that the reductions in DPM exposure would reduce cancer risks (Centers for Disease Control 1988)."

Jan 1, 2016

By Milan Yekich, Emanuele Cauda, Justin Patts, Cody Wolfe

This study presents the application of low-cost dust monitors (LCDMs) for real-time monitoring of respirable dust in a mining environment. LCDMs significantly enhance data collection by providing continuous, granular and cost-effective dust concentration readings. This case study demonstrates that by deploying LCDMs, mining operators can respond quickly to changes in dust levels, improving occupational safety and air quality management. The results show how such monitoring technologies can be integrated into routine operations to reduce dust exposure and prevent health hazards such as silicosis, especially when coupled with appropriate mitigation strategies.

Nov 1, 2024

By Milan Yekich, Emanuele Cauda, Justin Patts, Cody Wolfe

A worker’s personal exposure to respirable dust in occupational environments has traditionally been monitored using established methodologies which entail the collection of an 8-hour representative sample that is sent away for laboratory analysis. While these methods are very accurate, they only provide information on the average exposure during a specific time period, generally a worker’s shift. The availability of relatively inexpensive aerosol sensors can allow researchers and practitioners to generate real-time data with unprecedented spatial and temporal granularity. Low-cost dust monitors (LCDM) were developed and marketed for air pollution monitoring and are mostly being used to help communities understand their local and even hyper-local air quality. Most of these integrated sensing packages cost less than $300 per unit, in contrast to wearable or area dust monitors specifically built for mining applications which have been around for decades but still average around $5,000 each. At the National Institute for Occupational Safety and Health (NIOSH), we are leveraging the power of high-volume data collection from networks of LCDM to establish baseline respirable hazard levels and to monitor for changes on a seasonal basis as well as following any application of control technologies. We have seen the effective use and advantages of monitoring live data before, during, and after events like shift changes, operational changes, ventilation upgrades, adverse weather events, and machine maintenance. However, many factors have prevented a systematic adoption of LCDMs for exposure monitoring: concern for their analytical performance, the complexity of use, and lack of understanding of their value are some factors. This contribution outlines a one-year case study at a mine in Wisconsin USA, covering the installation, maintenance, data visualizations, and collaboration between NIOSH researchers and the industrial hygiene professionals at the mine.

Feb 1, 2024

By J. A. Herbst

It is widely recognized that Semiautogenous Grinding (SAG) circuits require the use of effective process control techniques to achieve their full processing potential and to protect them from the harmful effects of overloads and grind-outs. This requirement is even more essential as the variability of the ore being processed increases. The new Chino Mines Company concentrator located near Santa Rita, New Mexico started operation in June of 1982. At least eight major rock types are mined and milled. Ore hardness, feed size, and specific gravity are quite variable. Typical feed rates per grinding line are 850-900 tph but extremes of 260-1200 tph have been encountered. Normal feed rate variations of between 400 and 1100 tph are encountered on a weekly and sometimes daily basis. Feed size varies with rock type from a maximum of eight inches for the harder ores to two inches for the softer ores. One somewhat unique characteristic of the Santa Rita ore body among major copper mines is the wide variation in ore specific gravity. Specific gravities of the major rock types range between 2.7 and 3.6. The specific gravity variations are due to large changes in magnetite concentration throughout the pit. The result of this is large variations in SAG mill throughput which can have a harmful effect on downstream ball milling and flotation performance. Due to these wide fluctuations in ore characteristics, it was recognized soon after startup that successful operation of the grinding circuit and the plant at large was dependent upon the development of an effective automatic grinding control strategy. Research at the University of Utah has suggested that control based upon critical but difficult or costly to measure variables would improve automatic control performance. A project team made up of the Chino process control staff, Kennecott's Process Control department and the University of Utah Metallurgy Department was established to assess these concepts at Chino. This paper describes the development and on-line plant implementation of an Extended Kalman Filter that uses simple models of the SAG milling process, to predict the volumetric loading, the rock mass, the water mass, and the ball mass within the SAG mills at Chino. The on-line estimation of these parameters is the first step in the development of an integrated SAG mill/ball mill control strategy which is hoped to L eventually maintain the grinding circuit at its maximum capacity, while balancing the grinding load between the SAG and ball mills. Examples of long term estimation with the models and filter are shown for typical operating conditions as well as a SAG mill overload and grind-out.

Jan 1, 1983

By R. Spring

Artificial intelligence, and especially expert systems, are currently receiving considerable attention. Of interest to the control engineer is the utilization of these tools for real-time process control applications. To evaluate this technology, a real-time expert control system was implemented in one of the grinding circuits at Brenda Mines Ltd. The performance of this micro computer based expert system compared satisfactorily to the proven supervisory control system currently in use. The study confirmed the expectations that expert systems have potential for real-time, supervisory control of mineral processing operations.

Jan 1, 1989

By M. Buxton

"Advanced data acquisition and process modelling technology provides online data and decision support about different aspects of the resource extraction process. Real-time approaches have recently been applied to utilize the value of this information for improved production control in mineral resource extraction in different operational set ups including coal, polymetallic ore and gold deposits. The key concept of these approaches promotes the change in paradigm from discontinuous intermittent process monitoring to a continuous process and quality management system in the resource extraction process. The framework includes a real-time feedback control loop that rapidly links online material characteristics data acquired during extraction at the mining face, during material handling and processing with a sequentially up-datable resource model. This will allow near real-time optimization of decisions related to long-term planning, short-term sequencing and production control. The contribution reviews recent developments in the three main constituents sensor based material characterisation, rapid updating of grade control models and simulation based optimization for improved production control. Technological readiness is assessed and critical gaps for further technology development are identified. The value added is illustrated by means of selected case studies. INTRODUCTION With the depletion of known and established mineral reserves, the decrease in head grades and the continuing demand of mineral raw materials by the modern society, future exploitation will move towards extraction of deposits under geologically more complex conditions. Complex deposits are characterized by a low continuity in grade, presence of deleterious elements such as arsenic and high irregularity in the geometry of the ore boundaries. The profitable exploitation of such deposits becomes significantly more challenging. To be able to better utilize such unconventional mineral resources of the future, smart autonomous mining systems are needed, which integrate local exploration of spatially varying material characteristics in–situ and have the ability to follow and extract the pay zones in the ore body while minimizing dilution (Buxton and Benndorf, 2013). The main barriers to overcome for the successful economic exploitation are: • effective grade control which will maximize resource potential along the whole value chain, • minimization of handling zero-value material introduced by dilution, thus • reducing unnecessary expenditure of energy and financial resources and • management and control of the geological uncertainty due to limited information available,"

Jan 1, 2017

By W. P. Arnott

This paper presents real time photoacoustic measurements of diesel-soot black-carbon (BC or EC) and Dusttrak nephelometer total carbon (TC) concentrations in a Nevada gold mine. Comparisons with time-integrated filter-based measurements of EC and TC accomplished using the NIOSH 5040 method were found to be 50% smaller than the integrated real time measurements. This work was initiated primarily as a demonstration project for the usefulness of photoacoustic instruments in measuring BC in the mine environment. Real time black carbon measurements are very useful for determining miner exposure, for providing feedback in mine ventilation systems, and for quantifying machine specific emission rates to understand the operating conditions for specific machines that produce greatest black carbon concentrations. This paper reports real time measurements of DPM from a loaded and empty hauler as it is operated in a drift with a 12% grade. The photoacoustic instruments were demonstrated to be satisfactory for BC measurements in the mine environment.

Jan 1, 2009

By J. P. McDonald

Exposure to particulates containing metals and metal fumes (PCMMF) is a potential concern in ore refining and smelting. Some metals of primary interest are arsenic, cadmium, copper and lead, which have been linked to various adverse health effects. The current National Institute for Occupational Safety and Health (NIOSH) sampling method for metals in particulates requires the use of a filter, precision airflow pump and laboratory analysis. A major concern with this method is the one-to-two weeks? wait before laboratory results are available for use in determining if additional controls are needed to assure adequate exposure protection for workers. Particulates containing these metals were sampled during sixteen sampling events at a copper smelter using the traditional NIOSH methods. Monitoring of particulates was simultaneously conducted using a TSI 8520 Dust-Trak real-time aerosol monitor with a 10-µm-cutpoint sampling inlet. NIOSH analytical methods related to particulates and metals (methods 0500, 0600 and 7300) were used to determine particulate mass and individual mass contributions of metals on sample filters. Linear regressions with y-intercepts forced to zero were developed to determine the relationship between the PM10 measurements recorded by the DustTrak and laboratory-reported total particulate mass, PM10 and respirable arsenic, cadmium, copper and lead concentrations. These linear regressions yielded correction factors that can be applied to DustTrak readings to obtain total particulate mass, PM10 and respirable concentration estimates for each of the four metals. The R2 (coefficient of determination) values from the linear regressions ranged from 0.65 for total lead to 0.91 for total copper. These results suggest that the DustTrak may produce real-time data useful in providing estimates for airborne concentrations of arsenic, cadmium, copper and lead in copper smelter particulates.

Jan 1, 2011

By S. Frimpong

Cable shovel requires continuous monitoring through excavation to achieve reliability, longevity and economic usage. The operating environment and the stress and deformation fields on the front-end assembly must continually be monitored to avoid random fatigue failure. In this paper, the authors advance frontiers of cable shovel reliability through real-time stress and deformation monitoring during excavation. Cable shovel boom stress and deformation analysis are developed using a combination of flexible and rigid body approach. A virtual prototype is developed to simulate the cable shovel excavation in oil sands and to examine the motion, stress and local deformation of the boom. A numerical example is used examine cable shovel boom durability using stress and deformation fields simulation. The results show that stress and deformation are large around the joint between the upper body and the boom. The simulation of the effect of material properties on boom deformation shows that the deformation is larger in hard formation than in soft formation. The study provides a solid foundation for further study of failure life analysis of the cable shovel components.

Jan 1, 2006

By C. L. Karr

Establishing suitable control of pH, a requirement in a number of mineral and chemical industries, poses a difficult problem because of inherent nonlinearities and frequently changing process dynamics. Researchers at the U.S. Bureau of Mines have developed a technique for effectively controlling such systems. This technique successfully combines the process control capabilities of fuzzy logic and the search capabilities of genetic algorithms. Fuzzy logic offers an effective mechanism for handling nonlinearities, while genetic algorithms can provide fuzzy logic controllers with real-time adaptive capabilities. This Bureau-developed technique is applied to a laboratory acid-base neutralization experiment. Nonlinearities in the laboratory system are associated with the logarithmic pH scale and the changing process dynamics are due to alterations in pH and buffering capacity input solutions. Results indicate fuzzy logic controllers augmented with genetic algorithms offer a powerful alternative to conventional process control techniques in such nonlinear, rapidly changing systems.

Jan 1, 1992

By Lynn B. Hales, Randy A. Yncbausti, Rick Smith

Object oriented programming has been developed to model the way we think about the world. It allows higher levels of abstraction, generalization and classification than many other programming techniques. Some tools of object oriented design and programming are encapsulation, classes, inheritance, modularity and reusability. Expert systems have been used for years to implement process control strategies in the minerals industry. Expert systems allow process control knowledge to be expressed in linguistic rules that are processed by an inference engine. Expert systems which employ object oriented design and programming provide new opportunities for real- time process control. The concepts of object oriented programming and an example object oriented expert system are discussed in this paper.

Jan 1, 1992

By C. L. Karr

Researchers at the U. S. Bureau of Mines have developed a technique for producing adaptive control systems using fuzzy logic and genetic algorithms. These controllers can be used to efficiently manipulate complex systems in real-time. Furthermore, they can achieve an acceptable level of control despite limited feedback in the problem environment. The control systems that result from the implementation of the Bureau-developed technique are able to recognize when changes have occurred in the problem environment, evaluate the magnitude of these changes, and alter the strategy being used to control the problem environment. Fuzzy logic is used to provide the controller with a rule-base that mimics the "rule-of-thumb" approach generally adopted by humans in the area of process control. Genetic algorithms are used to provide the controller with the adaptive capabilities necessary for the control of complex time-varying processes popular in the minerals processing industry. The effectiveness of this technique is demonstrated on a laboratory pH titration system. The pH system includes a changing setpoint, titrants with varying concentrations, and the possible addition of a buffering solution.

Jan 1, 1993

By M. K. McCarter

A unique telemetry system was developed to monitor potentially unstable natural slopes above a residential area. Continuous interpretation of data transmitted from remote movement-sensitive devices and immediate communication of signficant changes to emergency personnel were made possible by a readily available "home" computer. Even though the computer based system was originally developed for a non- mining application, it could be used with little or no modification to monitor ground control instrumentation in open pit and underground situations.

Jan 1, 1985

By A. W. Laughlin, C. R. Mansfield, M. J. Ferris, D. A. Cremers

Laser-Induced Breakdown Spectroscopy or LIBS can be used to provide exploration companies with precise and accurate chemical analyses in the field, in real-time, resulting in major time and cost savings. Using a Field-Portable Analyzer(FPA), anomalies can be followed up immediately while crews are still in the field. Lower limits of detection (LLDs) are element dependent, but many are sufficiently low to be useful in exploration. LLDs in ppm for selected elements of interest are: Be-2, Cu-3, Zn-20, As-200, Sb-500, Pb-30, Ag4,Mo-100, B-33, Ti-500, V-350, and Cr-l. LIBS analyses require little or no sample preparation.

Jan 1, 1999

By A. W. Laughlin

Laser-Induced Breakdown Spectroscopy or LIBS can be used to provide exploration companies with precise and accurate chemical analyses in the field, in real-time, resulting in major time and cost savings. Using a Field-Portable Analyzer (FPA), anomalies can be followed up immediately while crews are still in the field. Lower limits of detection (LLDs) are element dependent, but many are sufficiently low to be useful in exploration. LLDs in ppm for selected elements of interest are: Be-2, Cu-3, Zn-20, As-200, Sb-500, Pb-30, Ag4, Mo-100, B-33, Ti-500, V-350, and Cr-1. LIBS analyses require little or no sample preparation.

Jan 1, 1999

By C. Anderson, B. Schug, C. Cristoffanini, S. Nazari

The Haile Gold Mine in South Carolina is increasing the automation level of their processing plant in order to improve operational stability. One step towards this goal is the application of a Digital Twin concept to provide Virtual Instruments. Haile has engaged ANDRITZ to implement Virtual Instruments at their grinding area hydrocyclones and at their tailing thickener underflow pump. These virtual instruments provide density values in a traditionally difficult location for reliable slurry density measurement. The Digital Twin is a first principles IDEAS1 ™ simulation model, connected in real time to the control system. Results have been promising, with the virtual instrument values matching the physical instrument under normal operating conditions, and showing better prediction under upset conditions. Haile plans to use the virtual instruments as optional process control parameters. INTRODUCTION OceanaGold’s Haile Gold Mine is located near Kershaw, South Carolina, about 50 miles southeast of Charlotte, North Carolina. This location was first mined in 1827, and has produced gold through several operating periods since then, including a heap leaching operation from 1985 through 1992. In October, 2015, OceanaGold acquired Romarco Minerals, the previous owner of the Haile Operation. The current operation began in 2017 as an open pit mine with additional underground resources. The nameplate throughput is 6,350 tpd ore, and 2017 production was 118k oz gold, with 140 to 155k oz gold expected in 2018. Proven and Probable reserves exceed 3 Moz. The process, as shown in Figure 1, includes a primary jaw crusher, comminution with a Semi-Autonomous Grinding (SAG) mill and ball mill circuit, flash flotation, rougher flotation, regrinding, pre-aeration, carbon in leach (CIL) leaching, carbon elution and regeneration, cyanide recovery, electrowinning and refining. The Haile Operation’s inaugural gold pour took place January 20, 2017. Mine life is expected through at least the year 2030. Based partially on prior experience of some key OceanaGold personnel with automation services from ANDRITZ on other projects, OceanaGold decided to include ANDRITZ on the Haile project. The scope of these services for Haile included design and supply of the process control application software, an ANDRITZ dynamic process simulator for operator training, and ANDRITZ Advanced Control Expert (ACE) ®2 systems for the SAG mill, ball mill, and rougher flotation areas. Since startup, ANDRITZ has continued to provide services for the site, particularly related to PLC and HMI equipment, programming and support, ACE system expansion, and the implementation of Virtual Instrumentation. The implementation of this new Virtual Instrumentation technology at Haile is consistent with Haile goals: increased automation, a change in the role of the operator from interactor to monitor, and improved stability by removing human error.

Jan 1, 2019

By Richard Newcomb

It is four years since the seminal study of demand for rapid excavation by the National Academies of Sciences (NAS) and Engineering outlined this technology's opportunities, requirements and significance to the challenges of urbanization and natural resource conservation. The demand study was quite simple. Opportunities were valued at market while requirements to produce new technologies were valued at cost. The significance of new technology in economic terms was measured by the net discounted gains to users over time. The Academy view in 1968 was that these gains, even most modestly estimated, appeared large enough to justify the bill for research proposed by that Committee (1). In 1970 the question of demands became international in what is recognized as the first international experiment in technological policy analysis, terminating in the Advisory Conference on Tunneling of the Organization for Economic Cooperation and Development (OECD)(2). A monumental demand survey formed the basis for its economic assessment. The twenty-two OECD nations also made an impressive attempt to measure the magnitude of existing research and development efforts. In their recommendations periodical statistical demand forecasting and collection of demand data (Recommendation 1) was given central importance for public planning (Recommendation 2), the financing of public construction (Recommendation 3) and the encouragement of technological advance (Recommendation 4). Their program for international cooperation led to OECD's establishment of a Directorate for Environmental Affairs, and influenced the organization of the World Environmental Conference meetings now held in Stockholm under United Nations auspices. The OECD Conference was the first example of "an attempt to apply the concept of technological policy analysis to a 'civilian' technology having potentially

Jan 1, 1997

Global mining company achieves significant productivity gains with three-dimensional (3D) mine models developed with Abaqus finite element analysis software. In a steep change beyond traditional processes, Abaqus finite element analysis (FEA) software from Simulia (the Dassault Systèmes? brand for realistic simulation), is being used to enhance mine design and engineering simulation at a number of major mines around the world. In North and South America, Africa and Australia some of the world?s biggest mining companies are applying FEA technology to evaluate safety and improve design planning, implementation and operations. Beck Arndt Engineering (BAE), a Sydney-based international consultancy, is a pioneer in the commercial development of engineering solutions for the mining industry. The consultancy has worked closely with engineers at Simulia Australia to expand the use of Abaqus FEA simulation software for mining applications. Among the early adoptors of mine-ready FEA technology is the world?s largest miner, BHP Billiton. With BAE?s help, BHP has already applied this technology to evaluate mines in Canada and Australia. At the BHP Billiton Nickel West Perserverance Deeps Project in Western Australia, Abaqus FEA software is now being used to help engineer the safety and productivity of planned deep-mining operations. To achieve this goal in the deep-mining environment significant technological innovation is required. Using measurements of site deformation and seismicity, Abaqus FEA models have been calibrated and, in a single day, used to simulate a full, 3D, inelastic analysis of a mine?s life cycle. In recent years, similar applications at Debswana?s Jwaneng Mine in Botswana, the Newcrest Mining Ridge-way Deeps Project in New South Wales, Australia and Rio Tinto?s Argyle Diamond mine in Western Australia have also established Abaqus FEA analysis as the lead-ing technology for multi scale, simulation-aided mining engineering. Joop Nagtegaal, a pioneer of FEA and a Dassault Systèmes Corporate Fellow, said that Abaqus FEA software is unique in its capabilities to enable mining engineers to investigate design innovations from the drawing board to full production. ?In the design stage, Abaqus models, which include rockmass volumes spanning several kilo-meters around the ore body and down to excavations just a few meters across, are used to compare and optimize engineering options,? Nagtegaal said. ?Then, as the mine goes into production, large volumes of data from the field are incorporated with the analysis models to allow them to be calibrated to a precision not previously available to the mining industry.?

Jan 1, 2009

By J. J. Gusek

Passive treatment of mine drainage using constructed wetlands has been employed on coal and metal mine sites since about 1985. The technology has advanced significantly since then; there are currently over 600 of these systems treating coal mine drainage in the Eastern U.S. at flow rates of hundreds of liters per minute. Passive treatment performance at three metal mines discussed in this paper has been positive for a wide variety of flows, water chemistry, and climates. The sites include a high-altitude underground copper mine, acidic seepage from a gold heap leach pad, and pumped effluent from an active underground lead mine in Missouri.

Jan 1, 2000