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By M. R. Hieb, J. R. Britt, S. P. Harteis, M. J. Sapko, E. S. Weiss, R. K. Zipf

The design requirements for mine ventilation seals have undergone a radical transformation in recent years, and these revisions have greatly increased the cost of the seal designs and their construction. For example, in the past two years, new federal regulations have increased the minimum design requirement to withstand explosion pressures from 138 kPa (20 psig) to 345 kPa (50 psig) or 827 kPa (120 psig), depending on whether the sealed mine volume is monitored continuously or not. Moreover, there is still a possibility that under certain conditions (such as detonations), even higher pressure requirements may be necessary. The ability of a monolithic, stand-alone mine seal to reliably withstand the full range of possible explosion pressures is becoming increasingly difficult and expensive. In an effort to develop a practical alternative, the West Virginia Office of Miners’ Health Safety and Training (WVOMHST) and the National Institute for Occupational Safety and Health (NIOSH) have collaborated in a research effort to develop a practical, economic and safe mine sealing technique that can enable mine seals to meet the full range of new explosion pressure design requirements. The basic idea is to use a barrier of common mine gob and rubble, in combination with a conventional mine seal, so that the pressure resulting from a gas explosion is reflected, absorbed and attenuated, and the pressure on the ventilation seal is reduced. This paper discusses some concepts and preliminary test results for a “passive mine blast attenuator” (PMBA) that can provide a useful alternative to increasingly larger and stronger stand-alone mine seals. Numerical models and full-scale experiments conducted at the NIOSH Lake Lynn Laboratory Experimental Mine (LLEM) show that the use of a PMBA can signficantly reduce the blast pressure and impulse on conventional ventilation seals.

Jan 1, 2009

By Dean D. Turner

Exploration geochemistry requires computer processing for quick and efficient reduction and interpretation. An easy to use microcomputer based geologic workstation fulfills this need and allows the geologist to independently process geochemical data. Functions necessary for geochemical data processing are: 1)Digitizing; 2)Communications; 3)Data base management; 4)Statistical analysis; 5)Mapping analysis; and 6)General purpose applications (ie: word processing). A geologic workstation that can perform these tasks will yield significant advantages in processing and interpreting geochemical data.

Jan 1, 1987

By George E. Peacock

Campbell Red Lake Mine is situated at Balmertown, in the Red Lake District of Northwestern Ontario, Canada. This area is some 120 miles north of the Trans Canada Highway and is some 160 miles Northeast of Winnipeg, Manitoba. The majority of our 300 employees live in Balmertown, which is a community of some 1,200 people, situated adjacent to the mine proper. The mine is serviced by a single shaft 4,300 feet deep. There are 27 levels at 150 ft. intervals. Stoping is being carried out down to the 20th level with only preliminary development having been done on the bottom 6 levels. The majority of our mill feed of 825 tons per calendar day comes from above the 10th level. Gold occurs as specks and streaks in bluish-grey to white quartz carbonate veins. It is extremely fine grained and most is invisible to the unaided eye. In addition to Gold the veins carry varying amounts of sulphides such as, Arsenopyrite, Stibnite, Pyrite, Pyrrhotite and Sphalerite. A minor amount of silver occurs as an impurity in the gold. Arsenopyrite is a marker for the gold ore at Campbell. The average grade of the mill feed is 0.7 oz. of gold per ton. The ore is dumped into an underground ore pass that feeds to a jaw crusher on the 20th level that reduces the rock to a maximum size of 4". This material is hoisted by skips to an ore bin in the head frame.

Jan 1, 1975

By H. Janas

In a gas/coal outburst the gas plays an active, driving part. The proneness of coal to outbursts can be determined by means of its gas emission properties, since coal that is liable to outbursts differs from coal with normal gas emission properties in that it liberates its gas from the sorptive bond more quickly. There is a risk of outburst when the flow of metha¬ne originally desorbed by the coal is sufficient to move the loosened coal which has been broken suddenly. The violence of a gas/coal outburst can be evaluated from the distance of projection of the mass of coal. It depends on the gas pressure and on the liability to outburst of the coal at the original centre of the outburst. Both factors are complementary in their effects so that the same work is done in a gas/coal outburst when there is a high gas pressure and low proneness to outburst as when there is a low gas pressure and a higher proneness to outburst. The gas pressure in the coal increases with its gas content. Consequently it is possible to deduce the gas pressure of a coal seam from its gas content. In the Federal Republic of Germany the risk of a gas/coal outburst is thought to exist when the desorbable gas content of the coal reaches or exceeds the value of 9 m3/ton and if the specific limit value of the proneness to outburst is exeeded. The Mine Ventilation Testing Station of the Westfalische Berggewerkschaftskasse has developed a new method for determining the risk of gas outbursts immediately after taking the samples at the coal face (1), (2).

Jan 1, 1980

By Roger C. Wilmoth

The most common method of treating mine drainage to prevent water pollution consists of neutralization and aeration. This process removes the acidity, iron, aluminum, and some other heavy metals, but does not render a water suitable for domestic or industrial use because of the high dissolved solids, hardness, and sulfate in the treated water. The Environmental Protection Agency (EPA), has been sponsoring and conducting research since 1966 on the use of reverse osmosis (R.O.) for the treatment of mine drainage. This process has been found to be highly effective in the removal of nearly all the dissolved solids. In addition, since R.O. is a concentrating process, potentials for recovery of valuable heavy metals are possible. This paper is a review of the state-of-the-art on the treatment of mine drainage by reverse osmosis.

Jan 1, 1972

By M. Paul

"INTRODUCTION In 1990, the uranium production of SDAG Wismut in East Germany was stopped. 45 years of inconsiderate destructive exploitation had scarred both landscape and nature. With the “Wismut law” which came into force in December 1991, the Federal Republic took responsibility of the remediation of the legacies from former uranium ore mining and milling in Saxony and Thuringia. A unique opportunity turned out in order to remove environmental damage, to enhance the life quality of the local population, to shape new landscapes and to advance the economic restart. (1) The results of nearly 25 years of remediation activity are evidence that this opportunity was used at all former SDAG (Sowjetisch-Deutsche Aktien-gesellschaft) Wismut sites. The reference project “Wismut“ has evolved into a joint project of all parties involved and radiates beyond the affected regions. This is particularly reflected by the Know-how transfer starting from Wismut and the increasing activities for third parties abroad.WATER MANAGEMENT AT WISMUT REHABILITATION Within the Wismut project, water management and conventional technical water treatment are by far the most cost-intensive long-term tasks of the remediation programme. Over the medium term, there is no viable alternative to the operation of active systems to catch and treat contaminated mine waters at the Ronneburg, Schlema, Königstein, Pöhla, Seelingstädt and Helmsdorf sites. Based on the status quo, this paper outlines the key issues of the Wismut GmbH water management strategy over the medium and long term. It is focused primarily on achieving protection goals for potentially impacted water bodies in the surroundings of Wismut sites and on optimising associated remediation expenditures as well as on creating the prerequisites for achieving low post-remedial care and maintenance or walk-away system status over the long term. (2) The applied mining practices during the active SDAG Wismut period have not been up to the high standards of modern mining operations and their requirement to leave former production premises and deposited residues in a condition that was not only physically but also chemically stable. Rather the emission of mine and seepage waters laden with high acidity, metal and salt content is a frequent corollary and difficult legacy of historic mining and processing operations (4, 5). As a consequence, the control or mitigation, respectively, of environmental impacts associated with contaminated mine waters ties up enormous public resources worldwide (6, 7)."

Jan 1, 2016

By N. S. Tanious

Three water-spray ventilation systems were tested to determine their effectiveness in diluting methane at a room and pillar coal mine face. These systems were: the shrouded nozzle, the spray fan, and the conventional nozzle system that is normally supplied with continuous miners. The testing was carried out in two stages. The air-moving capacities of the nozzles were first evaluated in a duct. The duct tests showed that: (1) the volume of air moved by the nozzle is controlled by the type of nozzle, the space around it, and its location relative to the duct wall; (2) the spray fan nozzles or the shrouded nozzles are both capable of moving air quantities up to 6400 cfm (3.02 m3/s); and (3) when the shroud was removed from around the shrouded nozzle, its bare nozzle moved between 9 and 65 percent more air. In the second stage of testing, a full-scale evaluation of the three systems was conducted. The three spray systems were mounted on a continuous miner which was positioned in an aboveground simulated mine entry. The simulated face tests gave the following results: (1) the standard nozzle system, which is mounted on the front end of the miner, is inadequate for diluting methane; (2) under the best testing conditions (lowest methane emission rate, highest primary ventilation airflow, and closest brattice set back), the slight improvement given by either the shrouded system or the spray fan is the same; and (3) under the worst testing conditions (highest methane emission rate, least primary ventilation airflow, and farthest brattice set back), the spray fan gave superior performance.

Jan 1, 1987

By B. K. Mishra, R. K. Rajamani, R. Venugopal, P. Songfack

Millsoft is a computer-simulation software that predicts the performance of large industrial grinding mills. This software surpasses all other tumbling-mill analysis techniques available today because it is based on fundamental laws of physics instead of empirical correlations. Graphical user interface (GUI) forms simplify the specification of the following design and operating parameters: mill diameter, length, speed, charge density and size distribution, lifter material and geometry. All of these parameters are taken into account in the discrete element numerical technique that constitutes the essence of the simulation software. In turn, the software produces a visual animation of grinding-charge motion, predicts mill power and gives the distribution of impact energy. In this paper, a case study of an 8.5-m-(28 ft-) diam SAG mill is used to illustrate the application of Millsoft for mill design and trouble shooting.

Jan 1, 2000

By Todd S. Webster, Matthew J. Pierce, Brad D. Krumel

With the Working Shafts and Starter Tunnel under way, it became apparent this 4.7-mile, 19-foot diameter wet weather tunnel was going to live up to its name. The shaft’s pre-excavation grouting was completed, and ground water inflows were slowing project progress. As the tunnel drive was approaching 50% complete a cooperative effort was underway between the owner, engineer, and contractor to raise the base of the Retrieval Shaft by 65 feet to avoid ground water infiltration construction challenges. The tunnel alignment needed to be raised in kind. The project was behind schedule and rethinking the cast-in-place adit work was next on the agenda due to the very wet environment in the tunnel. The race was on to finish the project within the owner’s time constraints while completing multiple redesign aspects of the tunnel alignment and associated adit construction. This paper will evaluate original design criteria and actual in-route design modifications and change management to meet the owner’s just-in-time schedule needs.

Dec 1, 2022

By William S. Brack

The mining industry is very capital intensive. Competition for shareholder investment has never been greater. Among our challenges is the need to meet shareholder expectations (return on investment), and one area of focus lies in our ability to deliver value on our capital investments. Our ability to meet project expectations affects not only the economics associated with the immediate project but also directly influences our ability to finance future projects. Moreover, our ability as individual companies to attract investor capital is influenced by how we have done overall as an industry, and our industry track record has not been that stellar. With safety, scope, cost, schedule, and quality as guiding principles, our project managers today must address high expectations on every project. This paper examines some items that should be on today's project management checklist. PROJECT ENGINEERING Herbert Hoover, himself a mining engineer, said Engineering is a great profession. There is the fascination of watching a figment of the imagination emerge through the aid of science to a plan on paper. Then it moves to realization in stone or metal or energy. Then it brings jobs and homes to men. Then it elevates the standards of living and adds to the comforts of life. That is the engineer's high privilege.

Jan 1, 2004

By John Neale, Robert Huberts, Tony Pinches

A major R&D programme for the application of bacterial oxidation to the pretreatment of refractory sulphide gold ores was started at Mintek in the early 1980s. This arose from an established expertise base in the bacterial leaching of base-metal sulphide ores. The refractory gold programme has been supported by a number of South African gold-mining companies, but major support has been provided by the Anglo American Corporation of South Africa (AAC) and the AAC Vaal Reefs Exploration and Mining Company Limited · (Vaal Reefs). The Mintek-AAC collaboration has been formalized as a joint-venture technology agreement for the comme;cialization, as well as continued development and improvement, of the bacterial oxidation process (MINBAC). From a process standpoint, bacterial oxidation involves the contacting of slurries of finely ground sulphide concentrate with suitable strains of iron-sulphur oxidizing bacteria, which act as the catalyst to promote sulphide·· oxidation by oxygen from air. Process engineering is simplified in that this reaction is carried out at low temperatures and ambient pressures. The view was taken that the successful development and implementation of the MINBAC technology should be based on parallel R&D aimed at an understanding of the process fundamentals, the process engineering and scale-up requirements, as well as the ancillary requirements for the gold recovery-processes and environmental management. This has represented a major R&D effort at a total cost to date of around US $10 million.

Jan 1, 1993

By Sheldon P. Wimpfen

Under the Wilderness Act of 1964 and the accompanying House Conference Report, the Geological Survey and Bureau of Mines are charged with the responsibility of making recurring mineral studies of wilderness and wilderness candidate areas in national forests within and proposed for the National Wilderness Preservation System. The Wilderness Act, a major shift from the multiple-use concept of national forests, identified for the first time the value of mineral resource information in decisions for single-use designation of public lands. This concept was further realized when the Secretary of the Interior in May 1974 recommended that mineral studies be made prior to wilderness recommendations for five large Interior-managed game ranges and the Glacier Bay National Monument aggregating 7.8 million acres. Presently, our studies have been completed on 126 wilderness and proposed wilderness areas totaling 15.4 million acres in the national forests. In 1973, 1 year in advance of the act's 10-year review deadline, we completed the 34 primitive areas, originally the only potential additions considered by the 1964 Act.

Jan 1, 1975

By Mortimer J. Richardson

Dredging can be traced to early times where it may have been derived by the Phoenicians prior to the 4th century B.C. The first tangible design drawings of a bucket ladder (BL) dredge can be found in the collections of Leonardo da Vinci (1452-1519), which he produced when he was attempting to create better methods of channel and port dredging. The perfection of the system did not commence until after the invention of the steam engine in the early 1800's; providing the impetus to progress from man-powered mud mills, horse drawn along polders or dikes in the Netherlands, England, France and Germany, to steam-driven. In the 1860's following the various gold rushes in the U.S., Australia, New Zealand, Siberia and South America, with placers in particular, efforts were begun to apply mechanization to achieve deeper digging. There is a recording of a dredge being installed to mine gold in Montana in the 1860's but did not include a processing system. Then in the 1880's in New Zealand, some practical engineers developed a system that is said to be the first bucket ladder mining (BL/M) dredge for mining gold placers. In studies of the New Zealand gold dredging experience, it is estimated that some 500 dredges were built to mine gold between the 1880's and 1942. A careful analysis of the data, however, shows that very few were profitable. The technology appeared to stagnate in the early part of the century. Two of the BL/M dredge design engineers left New

Jan 1, 1992

By C. Garcia, J. J. Opazo, A. Potulsha, T. Comi

"Sierra Gorda SCM is a joint venture partnership of KGHM International (owned by KGHM SA, Poland), Sumitomo Metal Mining and Sumitomo Corp. (Japan) operating in northern Chile. The Sierra Gorda openpit mine and coppermolybdenum processing plant will become one of the largest mines in the world. The need for optimum production efficiency and sustainability has driven the creation of the most modern, wellinstrumented mine in Chile. This article contains a general review of the project including geology and history.This was a fast-track project going from greenfield site acquisition to mill startup in 10 years. Highly experienced and motivated engineers and technical staff have overcome many significant challenges resulting in a rapid ramp-up of production capacity. A potential expansion to double the production rate in the fourth year of operation has also been intensely studied.The Sierra Gorda property is located in the Atacama Desert of northern Chile, in the District of Sierra Gorda, Region II of Antofagasta, Chile (Fig. 1). There is almost no precipitation in this area. The mine site is generally flat with some rolling hills. The project is located about 5 km (3 miles) from the village of Sierra Gorda at an elevation of approximately 1,700 m (5,600 ft) above mean sea level. The village is near a highway and railway line. The city of Calama, home of the famous Chuquicamata Mine, is located about 60 km (37 miles) northeast of Sierra Gorda. In addition, the SG mine is in the midst of numerous other mines including Spence, Esperanza, Mantos Blancos, El Tesoro, Lomas Bayas, Gabriela Mistral, El Abra, Radomiro Tomic and Escondida, to name a few.The primary organizational value at Sierra Gorda is "Zero Harm." This includes employees, contractors, the environment, the community, plant facilities and mine equipment. A cornerstone of this program is called 5X5S (five by five S), which combines the lean principles of 5S with the safety model of taking five steps back and thinking about the task at hand for five seconds, five minutes, the time it takes to assess and manage the risk. "People caring about people" promotes proactive engagement in the safety of coworkers and others at work and at home."

Jan 1, 2014

By Changshou Sun

The Leeville underground mine has been in operation since 2006 and currently produces 3,175 t (3,500 st) of ore per day with an average gold grade of 12.6 g/t (0.4 opst). The mine has a large horizontal extent of 762 by 152 m (2,500 by 500 ft) and a vertical extent of 6 to 61 m (20 to 200 ft). Based on the characteristics of the ore bodies, the deposits are divided into several mining zones. The geotechnical properties of mining zones are also different from one zone to another. A successful geotechnical collection system is very important for mining design and operation in the Leeville underground mine. Three methods are used to collect the geotechnical data in the Leeville underground mine: • Core logging. Most geotechnical data are collected by this method, which is based on exploratory drills and estimates parameters for rock quality designation (RQD), fracture frequency (FF), compressive strength and rock mass rate (RMR). • Site investigation. This method collects more detailed geotechnical data and geostructural data from work done in the underground drifts and stopes. Parameters of RQD, FF, compressive strength, RMR, rock tunneling quality index (Q) and geostructural data are estimated. • Data collected from drill holes made for the critical infrastructure facilities. This method provides the best detailed geotechnical information for areas in which the critical infrastructure located. A complete geotechnical database has been constructed using this geotechnical data collection system. The database can be used for the design of ground support, stopes and stope blasts, among other critical applications.

Jan 1, 2010

By Larry Snyder, Levent Ozdemir, Charles Fishman, Fun-Den Wang

Tunnel Boring Machine Instrumentation A 9.17 m. diameter tunnel boring machine presently in operation in Chicago, Illinois, has been instrumented to continuously monitor and record machine thrust, torque and penetration rate during boring. A micro-processor-based data logger capable of monitoring up to 60 channels of data digitizes and converts into appropriate engineering units the signals from various transducers mounted on the machine. The output from the data logger is sent to a teleprinter, providing a permanent record of measured data. The program control enables the data logger to scan all data channels at desired time intervals. Data obtained to date have been analyzed to determine the interrelationships of the parameters measured. Penetration rate was found to increase linearly with machine thrust with a unit increase in thrust causing more than a unit increase in penetration rate. For low thrust levels corresponding to the initial stages of a boring cycle, the penetration rate was observed to behave erratically until the thrust pressure was sufficiently high for the cutters to establish full contact with the tunnel face. Torque showed a curvilinear increase with machine thrust, reaching the design rating at about 70% of maximum available thrust. No-load torque was approximately 20% of the machine's rated torque capacity. Overall, the trends observed in measured machine parameters correlated closely with those predicted from experimental and theoretical boreability studies. In summary, the instrumentation system has mett two basic goals. First, it provided extensive and accurate boring data and secondly, it has proven that an automatic data acquisition system can be installed on a TBM and can function under adverse environment.

Jan 1, 1979

By J. Helton, J. L. Bellanca, M. McNinch, L. R. Swanson

DISCLAIMER The findings and conclusions in this paper are those of the authors and do not necessarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. Mention of company names or products does not constitute endorsement by NIOSH. ABSTRACT Accident data indicates that mobile haulage poses a significant pinning, crushing, and striking risk. Proximity detection systems (PDSs) have the potential to protect mineworkers from these risks. However, unintended consequences of mobile PDSs can undermine the safety benefit they provide. Soliciting iterative user input can improve the design process. Users help provide a critical understanding of how mobile PDSs may hinder normal operation and endanger mineworkers. Researchers explored users’ perspectives by conducting interviews with mineworkers from seven mines that have installed mobile PDSs on some of their haulage equipment. Mineworkers reported that mobile PDSs affect loading, tramming, section setup, maintenance, and general work on the section. Mineworkers discussed the operational effects and increased burden, exposure, and risk. Mineworkers also suggested that improved task compatibility, training, logistics, and PDS performance might help address some of these identified issues. This paper also gives additional insights into mobile PDS design and implementation. INTRODUCTION Pinning, crushing, and striking accidents are a large problem in underground coal mines, especially for mobile haulage. Between 1984 and 2014 there were 179 non-fatal and 42 fatal pinning, crushing, and striking accidents involving mobile haulage vehicles, including coal hauling machines and scoops [1]. Proximity detection systems (PDSs)—automated systems that decelerate and stop a vehicle in order to prevent a collision—have the potential to protect mineworkers in these situations. In fact, PDSs are now required on all place change continuous mining machines as of March 16, 2018, as a result of the final rule published in January 2015 (30 CFR 75.1732) [2]. To address mobile haulage, later in 2015 the Mine Safety and Health Administration (MSHA) also proposed a new rule that would require PDSs on mobile haulage vehicles [3]. Though there has been no additional actions related to the proposed rule and it is not currently required, mobile PDS can still help to save lives. MSHA estimates that the adoption of mobile PDSs could prevent approximately 70 injuries and 15 fatalities over the next 10 years [4]. As of June 2015, the underground coal industry had already equipped 155 of the 2,116 mobile haulage vehicles in use [1]. In order to capitalize on the projected safety gains afforded by PDSs, it is important that the systems are designed and implemented effectively. Along with others, researchers at the National Institute for Occupational Safety and Health (NIOSH) have been exploring PDSs for more than two decades [5-7]. Throughout this time, NIOSH has also held several stakeholder meetings (2010, 2014, 2016, and 2017) in order to disseminate information and provide an opportunity to discuss on ongoing issues and concerns. Despite some progress, human factors remain a key concern. Previous research examined mineworkers’ attitudes towards PDSs on continuous mining machines [8] as well as how continuous miner operators’ perceptions of risk have changed as a result of PDSs [7]. However, stakeholders have still expressed a need to better understand how mobile PDSs affect the mining process, the mineworker, and whether and how they may present previously unidentified risks.

Jan 1, 2019

By C. W. Lockhart

Strength evaluation programs, based on sub- jecting a number of 5-718 inch (0.15 m) diameter core samples from highly fractured or poorly consolidated rock, to triaxial compression tests, have been successfully completed. An innovative approach was required since con- ventional methods with similar materials had not produced reliable results. Drilling methods were modified, and specially designed transparent core barrels were used. Sample preparation was successfully accomplished by using speciallydesignedtools and unorthodox hand- ling methods. Initial tests were carried out on weathered oxides from an open pit copper mine. The technique was later used successfully where the test material was weak, friable coal. The procedures used offer a practical method of testing weak materials where conventional methods would not be successful.

Jan 1, 1980

By Thomas Schultheis, William Heron, Paul Watson, Colin Warren

This paper describes the geology and geotechnics associated with construction of the Thames Tunnel, part of the UK’s Channel Tunnel Rail Link (CTRL). The 2.5km long twin tunnels run beneath the river Thames at depths of up to 40m and are currently under construction. They pass through varying geology comprising alluvium, terrace gravels and chalk with flints and are currently being bored using Herrenknecht mixshield slurry tunnel boring machines (TBM’s). This paper outlines the lithology and engineering properties of each geological formation and describes the geotechnical processes, potential hazards and difficulties experienced in the works. A summary is given into the extent of the investigative work in terms of route selection, tunnel design, TBM optimisation and further details are provided on the geotechnical aspects associated with the construction of the tunnel approach structures and the tunnels.

Jan 1, 2003

By Rich Perry

HARRY HINDS: Our second speaker today is Rich Perry. Rich is the manager of leach and dewatering at Newmont Gold Company's Carlin operations. He has been the operator of Newmont's refractory leach development program for the past three years. Prior to joining Newmont in 1994, he was plant superintendent at the Big Springs and Jerritt Canyon Roasting Mills for Independence Mining Company. He graduated from the University of Nevada's Mackay School of Mines, and has lived with his wife and three children in Elko, Nevada, for the past 12 years. Please welcome Rich as he presents "New Facility Design Engineering: On-Site Versus Engineering Companies' Offices." RICH PERRY: Newmont Gold Company has been mining and processing gold ore at its Carlin, Nevada, operations since 1965. Processing is done using oxide milling, heap leaching, and whole ore roasting methods. Newmont began development of refractory leach processing technology at its research and development facility in 1988. The R&D staff focused on developing processing methods for low-grade refractory gold resources at Carlin that could not be economically processed by refractory milling methods. The term refractory ore refers to those ores that contain quantities of sulfides and/or organic carbon that result in low recoveries using conventional cyanide leaching. The R&D staff developed two potential processes deemed worthy of further testing: heap biooxidation to liberate gold occluded by sulfides and ammonium thiosulfate leaching for gold recovery from carbonaceous preg-robbing ores. These were piloted in small heaps by the staff of the R&D and Carlin metallurgical labs from 1990 through 1994. By 1994, Newmont's R&D and metallurgical staffs had unlocked the chemistry and kinetics of the two processes, and it was decided that the operations group would be brought in to begin development of a commercial plant. A project manager at Newmont's Denver office was assigned to the project. Scale-up issues such as biooxidation leach pad design; on/off heap heights; handling of various ore types during stacking and reclaiming; operating costs; and environmental, health, and hygiene concerns using a new process chemistry remained unanswered.

Jan 1, 1998