Search Documents

By Rahul Bhaduri

Mercury levels in Twin Creeks Vista pit ore (previously Chimney Creek, North pit ore) increased substantially since plant start-up in November 1987. Consequently, modifications were necessary to minimize industrial hygiene hazards and potential operational problems. The original plant design included mercury control measures. With progressive increases in mercury levels, the issue had to be re-addressed. Modifications to operational practice, industrial hygiene and management philosophy will be discussed. Additionally, a detailed examination of the mercury vapor suppression system currently employed at Twin Creeks will be presented.

Jan 1, 1994

By D. C. Sisti

A paper was presented during the 1970 SME Fall Meeting on the Stinson Preparation Facilities by representatives of Beaver Creek Consolidated Cool Company and Heyl & Patterson, Inc. This paper summarized a combined approach to development of a flow diagram and selection of cleaning equipment required to produce a uniform metallurgical coal at maximum recovery with special emphasis on sulphur reduction. These facilities were located in the Elkhorn. Coal Fields of eastern Kentucky and, in particular, the area of Wayland, Knott County, Kentucky, where approximately forty-five- million tons of Elkhorn No. 3 coal could he recovered. The facilities incorporated a Bradford Breaker for reduction of the ROM coal to minus 1-1/2 x 0, 6000 ton-raw coal storage, preparation plant, water clarification and thermal drying facilities, clean coal storage and a 4000 TPH unit train loading facility.

Jan 1, 1973

By Erik Sundström, Magnus Nygren

The study explores the influence and consequences of safety initiatives on the development of safety cultures in the Swedish mining industry. It involves interviews with experts from four mining organizations, highlighting themes such as organizational structures, safety leadership, feedback, and communication.

Nov 1, 2023

By S. K. Kawatra, K. J. Shoop, T. C. Rao, T. C. Eisele

This study investigates the use of a horizontally- baffled column (7.6 cm inside diameter by 344.2 cm high) to reduce the ash content of a high ash bituminous coal. Tests were carried out to determine how the baffled column responded to changes in feedrate, reagent dosage, and feed quality, and to compare its performance with a conventional column installation in an operating plant. In this paper, the results of this investigation will be reviewed and discussed.

Feb 24, 1997

Minerals are fundamental to the U.S. economy, contributing to the real gross domestic product (GDP) at several levels?mining, processing and manufacturing finished products. The estimated growth rate for the real GDP of the United States was 2.1 percent and the nominal GDP was about $13.8 trillion in 2007 (Table 1). The prime interest rate decreased to 7.25 percent in December from 8.25 percent at the beginning of 2007, reflecting actions taken by the Federal Reserve Board to counter financial difficulties surrounding subprime mort-gages. Delinquencies on subprime mortgages increased throughout the year, affecting not only the delinquent home owners but also financial instruments invested in mortgage-backed securities. The average contract mortgage rate for the purchase of previously occupied homes in the United States was 6.35 percent in November; a slight decrease from 6.37 percent in January but still greater than 5.34 percent reported in July 2003, the lowest rate in the past five years. With the tightening of credit, the seasonally adjusted annualized rate for new privately owned housing starts declined 27 percent from December 2006 to November 2007. The loss in the residential market was balanced by a 9-percent increase in nonresidential construction between January and August 2007, during which slight increases occurred in nearly all

Jan 1, 2008

By K. Burke, K. L. Myers, R. Espell

Barrick Goldstrike’s (Goldstrike) AA Heap Leach Pad is an HDPE lined facility used for gold recovery from low grade ores using conventional cyanide heap leach technology, operated from 1987 through 1999. Goldstrike prepared a unique reclamation plan for the AA Leach Pad Facility to provide for a cost-effective, environmentally sound facility closure and to fulfill the State of Nevada’s closure requirements. Traditional Nevada leach pad closure has involved rinsing to reduce cyanide concentration to an acceptable level, followed by reclamation. However, certain metals and compounds are not typically reduced by rinsing and some constituents may increase in concentration with rinsing. A closure scenario to effect limited infiltration through installation of a capillary cover for the leach pad was developed. The capillary cover was constructed by placing a fine-grained layer above the coarse-grained spent leach material to create a capillary break. In an arid climate such as Nevada, the fine-grained layer will rarely reach full saturation and the cover will be able to store water during precipitation and allow removal of water through evaporation and transpiration (ET) during the growing season. A 1.22 m (4 ft) cover thickness was selected as the optimum design cover thickness. The drainage network on the surface of the re-contoured AA Heap Leach Pad was specifically designed to enhance the revegetation, reclamation, and sediment yield control aspects of the AA Heap Leach Pad closure, while resulting in a natural looking surface, compatible with the surrounding topography. Adjacent natural topographic features were used to establish target design parameters for re-contouring and erosion control design.

Jan 1, 2001

By A. B. Cecala

Video technology coupled with data logging exposure monitors have been used to evaluate worker exposure to different types of contaminants. However, previous application of this technology used a stationary video camera to record the worker?s activity while the worker wore some type of contaminant monitor. These techniques are not applicable to mobile workers in the mining industry because of their need to move around the operation while performing their duties and tasks. The Helmet-CAM is a recently developed exposure assessment tool that integrates a person-wearable video recorder with a data logging dust monitor that are worn by a miner in a backpack, safety belt, or safety vest to identify areas or job tasks of elevated exposure. After a miner performs his or her job while wearing the unit, the video and dust exposure data files are downloaded to a computer and then merged together through a NIOSH-developed computer software program called EVADE (Enhanced Video Analysis of Dust Exposure). By providing synchronized playback of the merged video footage and dust exposure data, the EVADE software allows for the assessment and identification of key work areas and processes, as well as work tasks that significantly impact a worker?s personal respirable dust exposure. The Helmet-CAM technology has been tested at a number of metal/nonmetal mining operations and has proven to be a very valuable assessment tool. Mining companies wishing to use this technique can purchase a commercially available video camera and an instantaneous dust monitor to obtain the necessary data, and the NIOSH-developed EVADE software will be available for download at no cost on the NIOSH website.

Feb 27, 2013

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 Steve Meador

West Virginia's basic coal mining regulatory programs are not unique when compared to Federally approved programs implemented by other coal producing states. In fact, the language in The West Virginia Energy Act governing subsidence mirrors that written in the Federal Surface Mining Control and Reclamation Act as well as other states' statutes. Certain legal and administrative issues, how¬ever, combine to make West Virginia's regulation of surface subsidence a singular approach.

Jan 1, 1986

By Raymond Sandiford, Kenneth Xu, Taehyun Moon

Tunnel approach structures situated in slow moving earth flows are subjected to significant earth pressures. The authors have developed a system, utilizing collapsible concrete columns, that limits such loading. The system uses an array of collapsible concrete columns in front of the structure to absorb downslope movement and limit-imposed loads. This concept has been modelled using 3D FEM analyses and a rudimental lab test. For implementation, the collapsible columns would be prefabricated in strengths to mimic the soil strength profile. This concept has merit, and analytical results demonstrate that collapsible columns are a viable means to limit loading.

Jun 23, 2024

By Edward J. Zeigler, John T. Miller

INTRODUCTION Construction of Phase I, Section A, of the Baltimore Region Rapid Transit System required that six underground stations be built using a cut and cover excavation technique. For five of these stations, soldier piles, used as support of excavation, were installed with tip elevations well below the bottom of the excavation. However, in the case of the sixth subway station, the Mondawmin Station, soldier piles were installed only through soil and decomposed rock, with the tips of the piles being stopped well above the bottom of the excavation in partially decomposed rock. Below the tips of the soldier piles, and below a cut slope where piles were not installed, the sides of the excavation consisted of partially weathered and fresh rock and were supported by a combination of rock bolts, wire mesh and shotcrete. An extensive installation of geotechnical instrumentation permitted detailed monitoring of horizontal and vertical movements of the soldier piles and the walls of the excavation. Preliminary studies indicated that the excavation support system selected for the Mondawmin Station would have several advantages over a conventional system consisting of soldier piles extending to the bottom of the excavation, braced with prestressed struts. These advantages included lower cost of installation, a decreased time required for installation, and a more open excavation for the contractor during construction of the station. The Mondawmin Station is situated in the northwestern quadrant of Baltimore City, approximately 6.4 km (4 miles) from the center of the City. The station lies midway in a project 12.9 km (8 miles) long identified as Phase I, Section A, of the Baltimore Region Rapid Transit

Jan 1, 1981

By A. Davaliev, K. Hrkovic, V. Pavlovic

On the territory of Macedonia in South Yugoslavia primary and dory gold occurences were known since ancient times. Remnants of numerous goafs and remainders of washaries on river terraces and alluviums date right back to the times of Phillip II and his son Alexander of Macedonia and from Roman times, as well as from the Middle Ages witness exploitation of primary and secondary gold. More recent explorations on primary and secondary gold occurrences date from the period between two World Wars. Over that period a number of private companies, each on their own jointly, carried out gold exploration, particularly of alluvial occurrences on rivers emptying into River Vardar, starting from Skopje to the Greek frontier. The latest gold explorations carried out In the alluvium of River Konjska date back in 1976, and in 1978 old terraces of River Konjska were explored. The Visibility Study was prepared on possibilities of exploitation of gold from River Konjska alluvium. In the paper are collected the basic date an all known primary and secondary occurrences of gold, the results of the latest explorations, and the study itself. To-date geological explorations and analyses show very interesting potentionality of River Konjska and River Vardar alluvium, which proves continuing of he further explorations. For the moment, it is necessary to re-explore more complete view of the deposit. After that it will be possible to make complete techno-economical estimation of the auriferious alluviums and the conditions of the evaluations of the alluvial gold. 1. REVIEW OF PRIMARY AND SECONDARY GOLD DEPOSITS IN MAOEDONIA,YUGOSLAVIA 1.1. Primary deposits Scarse data are available for primary gold deposits in Macedonia` being unadequate for clear

Jan 1, 1988

By I. E. Perera

Experiments were conducted to evaluate the response characteristics of commercially available gas, smoke, and flame sensors to fires of common combustible mine materials. The experiments were conducted in the large-scale Fire gallery located at the National Institute for Occupational Safety and Health (NIOSH) Lake Lynn Laboratory (LLL) in Fairchance, PA, using Ponderosa Pine, Red Oak, Douglas-fir, high and low volatile coals, PVC and SBR conveyor belt, No. 2 diesel fuel, and diesel exhaust. All the experiments (except those using No. 2 diesel fuel and the diesel exhaust tests) were conducted in a similar manner, with combustible materials heated rapidly by electrical strip heaters producing smoldering fires that quickly transitioned into flaming fires. The sensors included a diffusion-type carbon monoxide (CO) sensor, photoelectric- and ionization-type smoke sensors, a video smoke/flame detector, and an optical flame detector. Simultaneous measurements were obtained for average gas concentrations, smoke mass concentrations, and smoke optical densities in order to quantify the levels of combustion products at the alert and alarm times of the sensors. Because the required sensor alarm levels are 10 ppm and 0.044 m-1 optical density for CO and smoke sensors, respectively, the different sensor alarms are compared to the time at which the CO and smoke reached these alarm levels (1). In addition, the potential impact of using smoke sensors that have met the performance standards from accredited testing laboratories is also evaluated using the response of an Underwriters? Laboratory (UL)-approved combination photoelectric/ionization smoke detector. The results are discussed relative to fire sensor needs that can have a positive impact on mine fire safety.

Jan 1, 2012

By Tony Treasure, Ian Ewart

The EMEW® cell has been developed to overcome a number of inherent limitations in conventional electrowinning technology, particularly the high cost and restricted process windows characteristic of conventional hardware. The EMEW technology has been widely demonstrated to achieve high performance for various metals under chemical conditions well outside the limits required for efficient operation of conventional cells. In particular application of the EMEW cell for recovery of silver offers significant operating and capital cost advantages over conventional Merrill Crowe technology used for cyanide based solutions. The cell also offers process advantages for direct silver recovery from nitric acid solutions. The performance of the EMEW® cell on silver cyanide solutions, producing high grade silver metal in a single step, is accomplished by providing a physical mechanism which presents metal ions to the cathode on a highly efficient and continuous basis. The simplicity of design and operation of the EMEW cell offers the following advantages for silver recovery from cyanide or nitrate based solutions: • High grade product in a single step. • Selective for silver over other metals in the electrolyte. • Wide operating concentration range (100,000 - 5ppm). • Ability of the cell to operated in a variety of acid or alkaline electrolytes. (Cyanide, Nitrate). • Simple liquor reticulation. • No pretreatment required - Clarification, deaeration or zinc dust. • High cmTent density and current efficiency compared to conventional electrowinning cell. • Modular design allows for flexible operation and production rate. • Pilot plant results using full scale cell result in accurate scale up design. • Easy/fast installation - cell banks are delivered pre configured with piping and wiring. • Enclosed cell minimizes corrosive vapor and liquid losses in the circuit.

Jan 1, 2000

By R. V. Johnson

The review of mineral activities in Minnesota arrived too late to appear in the May issue. Minnesota continued to lead the nation in iron ore production in 1989 with more than 70% of the market. At no time in the past 50 years has Minnesota's iron ore market share fallen below 50%. 1989 production was provided by six iron ore pellet operations and one high-grade iron ore mine. Most American steel companies are represented in these operations through whole or partial ownerships in Minntac (USS), Minorca (Inland), Eveleth Mines (Armco and Rouge), Hibbing Taconite (Bethlehem), and LTV Steel and National Steel Pellet. A seventh iron ore pellet producer started up in 1989 when Cyprus Minerals acquired the assets of bankrupt Reserve Mining Co. This operation, with first production scheduled for 1990, will be the only non-steel company captive operation in Minnesota. Encouraging minerals development In an attempt to stimulate further and additional mineral development in Minnesota, the state's legislature established a Minerals Coordinating Committee (MCC). This committee is comprised of the Department of Natural Resources-Division of Minerals, the Minnesota Geological Survey, the Natural Resources Research Institute, and the Mineral Resources Research Center. The Committee has sponsored and coordinated various projects. Among these MCC-sponsored projects are glacial drift geochemistry with an emphasis on gold and indicator minerals, accelerated geologic mapping, continued aeromagnetic surveying of Minnesota, greenstone geochemistry, structure and stratigraphy of the Duluth complex, and drill core and exploration data acquisition from past exploration programs. Regarding drill core, the Division of Natural Resources completed construction of its third core library building in Hibbing. These data and core are available for public examination.

Jan 1, 1990

By John J. Rhodes

I welcome this opportunity to give a Congressman's birdseye view of a subject which I believe holds great potential for the future in helping meet the needs of people, with minimal adverse impact on the environment. All mankind, not just the people in this great nation, faces the need for additional usable space. In some parts of the United States the problem arises from rapid urbanization of the surface and little utilization of the subsurface. Everywhere there is an increasing problem of insufficient space arising out of the increasing population crush and growing demands for open space, housing, water, transportation, communication, and social service. You are the technicians to whom we look for assistance in finding answers. We look to you also to provide guidance for broad policy decisions concerning underground space. I prepared for a career practicing law, but since 1952 I have been a member of the House of Representatives. In this latter capacity I deal with programs designed to help solve all kinds of problems. But, naturally, I am especially interested in the water scarcity and other environmental problems of my home state of Arizona and the arid and semi-arid areas in the West. This North American Rapid Excavation and Tunneling Conference has as its theme: "Tomorrow's Tunneling Technology Today." I have a very great interest in this potential of our underground space resource. The Central Arizona Project now getting underway in my state will consist in part of tunnels and underground pipelines to convey life-sustaining water from the Colorado River to people and lands across Arizona to the Phoenix and Tucson areas.

Jan 1, 1997

By Henry Antwi

The decade of the 1990s promises to be one of increasing internationalization for domestic minerals producers as they scramble to enhance relative positions in highly competitive, international minerals markets. This "international mining rush" is fueled by developing countries seeking international investment capital to explore for, develop and exploit sizable mineral endowments in an attempt to support the increasingly popular, but expensive, wave of democracy and selfdetermination sweeping the world. This "fuel" typically takes the form of revised mining codes and, often, lucrative investment incentives. These incentives include favorable tax rates, royalty provisions, relaxation of import/ export constraints, depreciation schedules, profit repatriation and other variables that can positively impact mineral investment decision making. Concomitantly, in their attempts to address real and perceived short- and long-term woes associated with enhancing competitive positions internationally, many domestic explorers and producers are attracted to the prospect of finding high-grade deposits in relatively virgin areas. Combined with the investment incentives provided by foreign governments, these high-grade deposits promise lucrative potential returns from projects having short payback periods. Classic examples of this mutual desire to intensify international mining efforts by domestic producers are illustrated by activity levels in countries like Chile, Bolivia and Venezuela in Latin America and, more recently, in Eastern Europe and select locations in the former Soviet Union. As US corporations scurry to send fact-finding, technical, evaluation and financial teams to these presently popular locations, one area of the world has received little attention - Subsaharan Africa. Specifically, the country of Ghana (formerly the Gold Coast) deserves more attention than it appears to be receiving from North American mining companies.

Jan 1, 1992

By P. Schiavi

A trend towards the independent verification of sustainable development reporting and assessment using third party certification can be discerned in the global minerals industry. Various codes that provide for the third party assessment and certification of performance against a range of externally developed sustainability indicators are being adopted by minerals companies, and there is also considerable activity in the broader area of third party assurance. Using a sociological approach, this paper examines the reasons why third party certification schemes are appearing in the minerals industry to address sustainable development imperatives in preference to other forms of regulation, and considers the broader implications of this trend. Data are drawn from a series of qualitative, in-depth interviews conducted with some of the key players in the development and adoption of certification schemes in the minerals industry, with executive managers of a range of large mining corporations, with representatives of global non-governmental organizations that are active in mining issues, and with government officers responsible for the regulation of mining corporations in Australia. Factors responsible for the emergence of the new certification schemes include: increasing demands from stakeholders for greater credibility in reporting against sustainable development indicators; broader contextual factors including globalization and neoliberal policies; and issues relating to trust and risk. Using insights from our research, and the work of others in this field, we identify some of the critical features of a credible third party certification scheme, and note some of the challenges for the design and implementation of such schemes. We conclude by discussing some of the broader implications of third party certification as an emerging form of regulation in the minerals industry.

Jan 1, 2007

By Liu Cheng-si

Basing on a brief assessment of the conventional theory of ventilating air distribution, its methods of calculation and practical application, this paper makes an approach to the controllability of different aircourses of a ventilation network and further points out that it is possible for the positions of control to extent into the natural distribution subnetwork of the ventilation network, which was been long considered as a restricted zone. This important discovery makes the regulation of the ventilation system more flexible and diversified, thus attaining quantitative distribution of ventilating air as well as a cost benefit. Because it has been impossible to solve the problem mentioned above by conventional theory and its relevant methods of calculation, the author, based on applying graph theory on the structure, characteristics, and requirements of controllability of the ventilation network, presents a new controllable subgraph concept and the means for determining the rational quantity for control devices of the ventilation network. The solution of all the control alternatives and methods of obtaining all the parameters for the solution of various alternatives have been derived. The economic benefit and the optional positions of the control devices have also been approached. Specific calculation examples are a1 so included in this paper. Along with the conventional theory and its methods, it can be seen that the new theory presented makes a great change in the control aspects of the ventilation network, with the number of possible alternatives increasing in an astonishing manner. Among the alternatives, some may be safer, more economical or technologically superior than those obtained from conventional theory. Thus, the new theory may provide an immense improvement in the choice of a ventilation system.

Jan 1, 1987

By Kenneth L. Myers

The net balance of the inflow and outflow of water in a tailings storage facility has major economic implications in any large mining and milling operation. In a net precipitation environment it can control the ultimate size and storage capacity of a facility or dictate the need for an expensive treatment and discharge program. In a net evaporation environment it can control the extent of the water rights acquisitions required for makeup water and dictate the number and size of expensive wells and pumping and delivery systems. The elements considered in a water balance analysis include the anticipated production rate, the water content of the slurry used to deliver the tailings, inflow from precipitation and snowmelt, and losses from evaporation and seepage. The mine can exert significant control over only one of these elements: the production rate. All others are subject to considerable uncertainty from month to month and year to year. The traditional approach is to analyze in a spreadsheet environment by making simplifying assumptions and using monthly mean or "average" values for precipitation inflows and evaporation losses. Often the analysis will be repeated with values subjectively assigned to represent a "wet" year or "dry'' year. The probabilistic approach uses the same basic spreadsheet model in conjunction with a probabilistic simulation add-in program allowing probability distributions to be substituted for any of the deterministic variables. The resulting analysis shows the full range of variation possible for each parameter of interest (i.e., available return water, makeup water required, storage, seepage losses) and estimates the exceedance probabilities for each. The potential uses and advantages of the probabilistic approach are discussed.

Jan 1, 1992