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By M. P. Valoski

In the United States, the occurrence of underground mine fires/explosions continue to decrease; however, they pose great danger to the miners and any subsequent mine rescue teams and/or fire brigades. Tragically, 19 coal miners lost their lives in 2006 at fires or explosions. Fires/explosions can devastate a mine and cause its permanent closure. It is vitally important to obtain accurate information on the gas content (concentration and composition) of the mine atmosphere after the event so that appropriate action can be instituted to rescue any trapped miners while not exposing the mine rescue teams to unnecessary hazards. Additionally, the fire fighting techniques (spraying water, sealing, etc.) will be dictated by the gas content. Finally, the gas content will determine when it is safe to recover the mine. The gas content of the air can be determined using detector tubes, handheld instruments, portable instruments, or gas chromatographs. No single instrument is suitable for all analyses. Each type of instrument has its advantages and disadvantages. This paper discusses these attributes.

Jan 1, 2010

By C. N. Bensley, S. K. Nicol, R. Lamb, G. W. Kidd

Flotation circuits in the metalliferous industry recover high value concentrates from very fine (minus 0.lmm), low grade, slow-floating feeds. Flotation columns acting as final cleaners within these circuits offer the benefits of higher grade concentrates, reduced circuit complexity, improved control and reduced power consumption. By contrast, in the coal industry, these benefits have not been realised, principally because columns are not well suited to the treatment of conventional coal flotation feeds (minus 0.5m). However, this does not imply that columns do not have a place within the coal industry, rather that they must be applied in a role where all the unique advantages of column flotation can be of benefit. The development of a commercial scale column to recover discarded ultrafines from the Riverside preparation plant of BHP-Utah Coal Limited is discussed. Particular emphasis is placed on the column design features pertinent to the recovery of ultrafine coal. Pilot and commercial scale column performances are compared. The results of the commercial scale testwork indicate that a full installation at the 5.5 MTPA Riverside plant would annually recover additional coal worth $US 6.6M.

Jan 1, 1988

By George C. Hawley

Historically, mica usage has been low because of limited availability; as a by-product of many small processors, who have lacked motivation for extensive R & D. The discovery of a 30 million ton deposit of 85-90% pure phlogopite, when existing markets are only 300,000 tonnes annually, forced the search for large volume new markets. Increasing costs of energy, petrochemicals, plastics and glass fibers, and environmental constraints on asbestos usage, have led to new opportunities for mica as a reinforcing filler. Extensive research and developments; in beneficiating, processing and treating mica, has been necessary to satisfy these new markets.

Jan 1, 1981

By Rafael Moure

On April 21, 1980 the Oil, Chemical and Atomic Workers Union (OCAW) submitted a petition urging the revision of the Mine Safety and Health Administration (MSHA) permissible exposure limit to radon daughters in underground mines. This petition asks for: 1. Annual worker exposure to be lowered from the current 4 WLM/year to 0.7 WLM/year; 2. Full economic protection for workers whose exposure exceeds the proposed 0.7 WLM/ year; and 3. The primary means of lowering workers' radiation exposures shall be environmental controls. I will present the scientific rationale for the lower standard requested in our petition to the Department of Labor. [1. Radiation Exposures to Uranium Miners] Two types of radiation exposures are present in the environment of uranium mines: A. [External Exposure] to gamma sources which until 1978 was considered as negligible compared with internal alpha radiation. R. E. Utting (1), in an investigation of three Canadian uranium mines, found levels of exposures adding to an annual dose equivalent of 3 rems (30 mSv)/year. He concluded that gamma dosages may be a major fraction of the maximum permissible dose for many individual miners. The U.S. experience has shown that there is significant gamma exposure in U.S. uranium mines and, therefore, it could contribute to the total radiation exposure to the lungs in combination with internal alpha radiation. Before ventilation improvements in uranium mines, the contribution of external radiation to total lung dosage was relatively small. After improvements in ventilation, the reduction in internal radiation exposure appears to be in 1980 as low as 1/10 of the 1950 dosages. However, ventilation improvements do not affect external gamma radiation. Gamma radiation remains at the same 1950's level, and it represents today a higher proportion of the total radiation burden to the miner's lungs. MSHA regulations (57.5-47) state that if gamma exposure is below 2.0 milliroentgens per hour, then workers are not required to wear gamma dosimeters and cummulative gamma radiation records need not be kept. Assuming an exposure of 1.9 milliroentgens per hour per 173 hours/month for 12 months,a miner would accumulate a dose from external radiation of 3.9 rems/ year. This dosage would, of course, go unrecorded. MSHA, therefore, should consider a downward revision of the external radiation permissible exposure limit of 2.0 milliroentgens/hour. MSHA should make clear that this exposure level, when added to the internal exposure, does not make for sound health physics -even though the measured current levels do not approach 2.0 milliroentgens/hour. B. [Internal Exposure] to alpha radiation is still the larger contributor to lung irradiation in uranium miners. The target organ is still the lung. The parameters to be considered in determining the biological radiation load appear in Table I for radon daughters present in the upper respiratory tract (URT). TABLE I RADIATION DOSE PARAMETERS IN THE URT OF URANIUM MINERS Parameter Uranium Underground Mining [1. Quantity of the Absorbed Radon daughters (Po-218, Nuclide Pb-214, Bi-214) deposit in bronchial and lung tissue. (Measured by air concentration, Working Levels) 2. Type of Radiation Emitted Alpha Particles 3. Energy of Radiation High-Linear Energy Transfer 4. Half-life of the Nuclide Ra 222, 3.8 days in the Organ Po-218 (RaA), T1/2 = 3.1 minutes Pb-214 (RaB), T1/2 = 26.8 minutes Bi-264 (RaC), Vi = 19.7 minutes 5. Selection Factor of the Direct inhalation with mine Organ dust to be deposited in the tipper Respiratory Tract 6. Mass and Form of the Organ Especially cancer sensitive, tracheobronchial region and bronchi* 7. Distribution of the Activity Dependent on deposited dust in the Organ distribution in the Upper Respiratory Tract 8. Chemical Nature of All compounds (RaA, RaB, RaC) Incorporated Substance biologically insoluble. (Only localized, irradiation) *See Reference (2)] The parameters of Table I depend, in turn, on the demography of the exposed population, especially: 1. Age 2. Sex 3. Health Status 4. Genetic Constitution 5. Lifestyle (Smoking, Diet) Some of these demographic characteristics of uran-

Jan 1, 1981

By M. R. Haibach, M. L. Shema, J. M. Silvis

"Since 2005, longwall coal mine operators in Pennsylvania (US) have been required to collect extensive hydrologic and biological data to document pre- and post-mining conditions of aquatic resources (streams and wetlands) overlying the subsidence control plan areas. Continued operation of the longwall mine is dependent upon empirical data demonstrating that the undermined aquatic resources have either been maintained or restored to an accepted range of pre-mining conditions. This study used quantitative hydrologic methods and comparative biological metrics to examine response of aquatic resources to longwall subsidence at the Bailey Mine located in Greene County, Pennsylvania. This study analyzed data from over 25 miles of streams and over 8 acres of wetlands that traverse the 4,779-acre study area. Hydrologic analysis of flow intermittency suggested that there are variable degrees of change to headwater streams immediately following mining; however, the majority of the effects are reversible through streamflow mitigation measures. Furthermore, the post-mining discharge from streams can be restored to within the range of pre-mining conditions the majority of the time. Biological assessments showed that greater than 95% of assessed stream length has maintained its ability to support benthic macroinvertebrate communities following mining and intervention (i.e., mitigation). Comparative metrics of the benthic macroinvertebrate communities showed that the biological community in 48 of the 50 sample sites is being maintained or restored across both high- and low-gradient streams. The effectiveness of intervention was further substantiated by the similarity in recovery times between streams having no intervention (median = 2.1 years, 95th percentile = 4.9 years) and streams with intervention, when recovery times were measured from the date of the intervention (median = 1.7 years, 95th percentile = 4.7 years). Changes to individual wetlands were observed between the pre- and post-mining assessments, but cumulatively a net gain of 7% in wetland acreage was realized. Hydrologic assessments were used to infer whether there was a potential that streams had been affected by mining; however, the ultimate test of stream recovery is based on biological metrics that establish the relative quality of the biological communities following mining. Overall, the hydrologic balance is being protected and the aquatic life use of streams is being maintained within the Bailey Mine’s subsidence control plan areas."

Jan 1, 2017

By H. Colijn

Vibratory or oscillatory conveyors can be found in all types of industry, handling virtually any granular bulk material, often at elevated temperatures. These conveyors can be combined with other process functions, such as screening, cooling, drying and dewatering, while conveying. Although construction and installation is relatively simple, the engineering and design analysis of the vibratory mechanics is fairly complex. This paper will discuss the basic types of vibratory conveyors and the analysis of the material movement along the carrying trough.

Jan 1, 1985

By B. C. Lewis

The mining industry has experienced a general trend toward an increasing number of longwall operations, an increasing percentage of underground coal being mined by longwalls, and increasing productivity from the longwalls. Longwall operators have not yet reached a state of mining euphoria. Competitiveness both within the industry and from alternate fuel sources is forcing continued pursuit of higher productivities and lower costs. The following graphics present trends in the industry. Longwall mines, as defined for this presentation, are those reportedly having longwall installations in each of the respective years. Production from both the continuous miner and longwall units is included in the longwall mines. Non-Longwall mines are all other underground mines. Productivity calculations are based on total employee-hours associated with the operation.

Jan 1, 1990

By J. V. Thompson

The Powderhorn complex as a source of perovskite (calcium titanate) containing about 1.5% rare earths has been examined in several recent feasibility studies. Much promising exploration and process research has been done in recent years. This paper is presented with cautious optimism and with the acknowledgment that there may be some technical and economic areas yet to be explored. The Powderhorn carbonatite and alkalic stock in Gunnison County, Colorado, lies about 203 airlines km southwest of Denver at an elevation of 2450 to 2750 m (see Figures land 2). All of the mineable ore bodies are owned by Buttes Resources Company of Houston, Texas.

Jan 1, 1990

By Russell L. Cook

Stringent environmental regulations, which have limited the use of sludge ponds, coupled with the economic incentive to clean more 'coal or to add fine coal cleaning additions to existing preparation plants have increased the use of static thickeners in preparation plants. The Lamella Gravity Settler, sometimes de signated Lamella Thickener, is a shallow depth sedimentation device which has been applied in a variety of industrial process and wastewater control projects in place of the conventional raked thickeners. This paper presents the theory and design of the La-mella Thickener, as well as describing the operating results from several full scale installations in a variety of Appalachian preparation plants.

Jan 1, 1977

By R. A. Williams

Surface and electrochemical techniques have been used to describe the surface chemistry of ferrosilicon powders, as a function of pH and electrochemical potential, for conditions typical of operating DHS plants. The practical consequences on the likely corrosion behaviour and associated electro- kinetic particle-particle interactions (which affect stability to sedimentation) in the suspension, are discussed.

Jan 1, 1987

By P. G. Martin

"As the speed of business has continued to increase over the last decade, the focus on real-time control of the performance of both stationary and mobile assets has become an increasing priority. Traditionally the maintenance team has been focused on the management of the availability of assets while the operations team has been focused on the throughput of those same assets. Typically operations and maintenance teams worked almost independently in spite of the fact that they were both working with the same assets. Part of the problem has been their traditional performance measures which have often been diametrically opposed. Recent advancements in the area of real-time performance measures and decision support have helped to drive higher levels of collaboration between operations and maintenance leading to real-time asset performance control and higher levels of business performance. This paper will explore the forces driving the need for changes, present an effective approach to the definition of the most appropriate business performance measures, and examine the effectiveness of contextualized real-time decision support resulting in asset performance control. TRADITIONAL APPROACHES TO ASSET PERFORMANCE MANAGEMENT In most industrial operations the phrase asset performance management is synonymous with maintenance of the industrial assets. This is the way industry has viewed asset management and asset performance management for decades. This is a very limited perspective that is serving to constrain the profitability of industrial operations. As industrial organizations began to form following the Industrial Revolution, the complexity of the operations forced an organizational design based on specialization. No single person could understand all of the aspects of an industrialized operation. This was particularly true at the plant floor level where the operation and maintenance of the industrial equipment required very different skillsets and training. To accommodate the vast differences most industrial organizations set up operations teams to run the equipment and maintenance teams to keep the equipment available to the operation. Both teams were dealing with the same industrial equipment but from very different perspectives and with very different performance measures. Typically the operations team was measured on maximizing the output of the equipment – or throughput. On the other hand the maintenance team was measured on the uptime – or availability of the equipment."

Jan 1, 2015

By S. Veeramasuneni

The recent nonequilibrium electrophoretic mobility measurements by laser-Doppler electrophoresis coupled with the stability and prevalence of collector colloids in soluble-salt flotation systems suggest that the selective flotation of alkali halides is due to the adsorption of oppositely charged collector colloids by heterocoagulation. Previously reported flotation results confirm this surface charge/collector colloid adsorption model. These results also indicate that the sign of the surface charge has a significant effect on the extent of particle dispersion/aggregation. In this regard, the nature of such particle interaction forces at high ionic strengths are examined to improve our understanding of these systems. Atomic force microscopy (AFM) is now being used to directly measure the interaction forces responsible for the stability of these alkali halide aggregates observed in optical microscopy studies. Results from this study indicate that, while repulsive hydration forces exist between similarly charged hydrophilic particles, attractive forces exist between oppositely charged hydrophilic particles in high ionic strength solutions.

Jan 1, 1999

By J. P. Hanten, G. Ramadorai

This paper presents laboratory and pilot plant data on the removal of heavy metals and molybdenum from mining-milling waste water. Molybdenum is removed as an Fe-Mo precipitate by proper addition of ferric sulfate. Heavy metals are lowered by lime treatment. Solid-liquid separation was achieved in both cases by flotation techniques. The Lectroclear electrocoagulation-electroflotation process was used to achieve the desired degree of metals removal. Good correlation was obtained on the laboratory and pilot plant scales. A two-step process consisting of the sequential removal of molybdenum and heavy metals was tested successfully using a mobile pilot plant. Preliminary data on sludge characteristics was obtained and the feasibility of recycling the iron sludge for iron and molybdenum recovery was established on the laboratory scale.

Jan 1, 1987

By D. J. Lachel, Douglas E. Hansen, Bruce Kennedy

The very high cost of exploration and development for new mines requires that a carefully planned, complete, and technically competent geotechnical evaluation be applied to the ore body and the surrounding rock. The ground conditions must be predetermined sufficiently so that, during the development and exploitation stages, unexpected conditions will be of minor consequence. Ground conditions are a major factor affecting the cost of excavated items such as shafts and inclines. For example, shafts cost less to sink in tight dry ground than in highly pervious ground below the water table, with all other factors being equal. The proper mining methods also is dependent upon the ground conditions. Bad ground for room-and-pillar mining may be ideal for caving methods; whereas, ideal ground for room-and-pillar mining would be extremely difficult for a caving operation. To do a proper engineering design, the parameters of strength, deformability, and permeability must be determined, in addition to the loads that will be applied as a result of the mining activity. The required degree of accuracy for each parameter depends upon the individual case. For example, the strength of massive rock in which openings of small cross-sectional area are to be driven at shallow depths needs to be resolved only within several thousand kilopascals (pounds per square inch). Under such conditions, the rock strength is not likely to be of great economic importance unless the rock is very weak. Large openings at great depths require a much more accurate appraisal of rock strength and deformation characteristics. Ground water conditions are important at any depth. Today, a number of techniques exist for evaluating conditions before opening up the ground for development. These techniques and their applications are described in more detail later in this text. The evaluation of ore body ground conditions should start at an early stage, as soon as the deposit has been proven viable for a mine. Economic geology investigations mainly serve to define the value and limits of the ore deposit. To do this properly, the geology of the site is determined in at least as much detail as is necessary to define the "controls" for the ore body. The ground-condition evaluation must determine the engineering properties of the ore body and the surrounding material. This includes the structural geology as it relates to rock strength; i.e., the frequency, extent, and orientation of discontinuities such as faults, joints, bedding, etc. Ground water conditions also must be determined. It is important that the detailed geology of the site be determined at an early date. Reasonable geotechnical parameters must be established during this time period, so they can be used in mining model studies that include both physical and mathematical models. The ultimate goal bf-the geotechnical evaluation is to predict the ground behavior as the excavations are made and how the ground behavior will affect the safety and economic well-being of the mine. The formulation of a ground-condition evaluation program should be planned carefully to determine the particular geotechnical parameters only in as great a detail as will have a bearing on the mine design. For instance, it is not necessary to make numerous triaxial tests in strong rock when the mining will be conducted within a few meters (feet) of the surface in a regime of gravity loading and an absence of tectonic stresses. Similarly, it is not necessary to invest large amounts of time and effort in the determination of joint strengths if the orientations of the joints are such that the failure could not occur along them. Generally, the determination of ore body ground conditions can be divided into four main steps: 1) The general and structural geology of the site must be determined; this is determined primarily during the economic evaluation. 2) The material behavior characteristics of the deposit and the vicinity must be determined. 3) The ground water hydrology of the deposit and the vicinity must be determined. 4) Miscellaneous ground support considerations must be established. Gross features are defined first, followed by a series of increasingly detailed investigations. Specifically, the geology study should start by utilizing techniques such as remote sensing, topographic map interpretation, geologic mapping, etc. After the gross features, such as major faults, have been delineated, the studies are directed toward defining the more detailed elements of jointing, rock strength, ground water hydrology, and other characteristics. This information is used to formulate an assessment of the strength of the ore body and the surrounding rock. Finally, all of the gathered information is integrated to make an assessment of the rock behavior in relation to the types of openings, the excavation methods, the support requirements, etc., that should be used for the rock conditions that are present. The mine design and the geotechnical assessment should be an iterative process. General conclusions about the rock conditions will dictate a type of mine plan. The specific mine plan then should be modified by specific geotechnical considerations. For example, an initial assessment may conclude that the ore body is strong and that a strong rock unit is present over the ore body. Thus, one definite possibility is to mine the deposit by room-and-pillar methods. However, subsequent investigations may reveal faults through the deposit, requiring relocation of the mine openings so that pillars and other structures are in sound rock. In other words, the final mine plan should be compatible with the geotechnical aspects of the ore body.

Jan 1, 1982

By Keith A. Yarborough

INTRODUCTION The National Park Service (NPS) conducted a research program from mid-1975 to early 1978 to measure alpha radiation levels in natural caves which it administers. Subsequently, a long-term management program was developed which has conducted routine monitoring of radiation levels and has computed employee exposure accumulations in certain NPS caves. The overall program: research and management; was undertaken to evaluate the possible health hazard to cave visitors, interpreters, researchers, maintenance personnel, concessions employees and other workers and to protect their health. The results of this work have been reported extensively elsewhere (see References 1 through 3, 5, 6, 9 through 13, and 14 through 26). This paper deals with the relation of radon gas and daughter produced radiation levels to the cave air flows which mobilize them. These flows are a function of interior cave and exterior ambient air temperatures and pressures and of the cave's geophysical configuration. The low-level, ionizing radiation is produced by minute concentrations of radon and thoron gases which emanate from within caves. Because of confinement, the radiation levels are often appreciably higher than in surface atmospheres. Subsequent radioactive disintegration of the gases into their ionized "daughter" products, which are particulates, permits distribution of the alpha radiation throughout a cave system. The extent and character of this distribution depends upon the particular cave and the air flows which it produces. Thus, the alpha radiation serves as a "tracer" to describe the flows. The flow analysis is divided into two parts: 1) A qualitative description with respect to the two basic geophysical cave types over both long-term (annual) and short-term (diurnal to weekly) periods. 2) A quantitative description of the unsteady, uniform and non-uniform, one-dimensional, incompressible motions for both influent and effluent air flow situations in both basic geophysical cave types. A part of the qualitative description presents "Special Measurement" data: Tsivoglou [vs.] Kusnetz working levels, Tsivoglou individual daughter levels and free ion concentrations, radon gas concentrations, and equilibrium ratios. A great deal of important work has been carried out by Mr. Bobby C. Carson, Cave Radiation Technician at Mammoth Cave National Park, Kentucky. He reports these findings later in this conference (Ref. 6). Some of his results have been used here to establish the cave air flow analysis. Other National Park Service personnel have made measurements at others of the caves for which data are reported here. All of this work and cooperation has been vital to the success of this research program. It is very much appreciated. THEORETICAL FLOW DESCRIPTION Previously reported research (See Ref's. 20, 21, 23 and 25) has established the qualitative relationship between the alpha radiation in caves and their natural air flows. The radiation serves as a representation of these air flows. Changes in radiation with time represent changes in the main forces which produce the air flows. The quantitative data have substantiated that [all caves in which the primary cause of air flow is due to temperature produced gravity (density) gradients and also having minimal man-made disturbances, experience seasonal variations in airborne alpha radiation. The radiation levels increase in summer but decrease in winter], based upon seasonal air movements through each cave system which occur naturally. Two general types of physical cave configurations which control the air flows have been identified as: 1. Those which go up into a hillside or mountainside: Type I ("Upside-down" = USD). 2. Those which go down into the earth; Type II ("Right-side-up" = RSU). These act to control the air flows seasonally. The summer increase in Type I caves is due to increased air flows, whereas in Type II caves it results from stagnation or reduced air flows. This seeming paradox is explained by the physics of the air flow regime in each cave type and has been detailed elsewhere [Ref's. (20), (22) through (25)]. It[ i] true, in general, that air flow decreases airborne radiation in the [immediate vicinity] in which it occurs. Any paradox results from subsequent distribution throughout the case as to [ how] the air moves through a cave [system] with respect to time and space. Exceptions to the cave air flow "rule" are: 1. Caves in which pressure gradients and pressure fluctuations [predominate] in producing the air flows. 2. Caves in which man-made effects and management practices are superimposed on the natural air flow regime. Man-made disturbances which can alter the natural cave air flows are tunnels, elevator shafts, bore holes, sealed and closed portals, etc. If these are not properly sealed, the natural air flows which they change will totally alter the distribution and seasonal variations of the alpha radiation levels. These exceptions may act separately or in combination.

Jan 1, 1981

By T. E. Wayland

Bentonites are clay materials composed principally of minerals in the montmorillonite group. Distinctive physical properties of the montmorillonite minerals are responsible for selected bentonite deposits having become the raw materials source of industrial clay products which are virtually essential to the maintenance of high production standards in the petroleum, foundry, taconite and other basic industries. These versatile materials have no suitable substitutes in either their major applications or in hundreds of speciality products, The economics of the bentonite mining industry follows closely the established pattern of other non-metallic raw materials. Aggressive competition, advanced technologies, progressive marketing techniques, substantial reserves, and vast unmeasured resources insure the continued supply of high quality bentonite to industry at bargain prices. The purpose of this paper is to discuss the geology and economics of bentonite deposits, summarize both major domestic mining districts and foreign deposits, and report significant results of research and development.

Jan 1, 1970

By S. K. Bhatt

This paper reviews major developments in continuous haulage technology for underground coal mines. Haulage systems in use and development are investigated through a comprehensive literature search and visits to mines and manufacturers. The systems include flexible conveyor train, mobile conveyor, multiple- unit continuous haulage, extensible and belt turning systems. Strengths and weaknesses of the systems are assessed in light of their operating under remote control and their application to the computer-assisted continuous mining machine being developed by the US Bureau of Mines. Through mining scenarios, candidate haulage systems are conceptualized to be consistent with the capabilities of the mining machine.

Jan 1, 1991

By Nathaniel White, Todd Kilduff, Justin Laviolette, Dan Laviolette, Randy Zeigler, Sean Sundermann

The Mitchell Point tunnel is a part of several ongoing efforts to connect the 12-mile-long Historic Columbia River trail between Mitchell Point Outlook to Mitchell Point Drive. The tunnel lies inside the Mitchell Spur entablature basalt geologic feature, extending 647 linear feet utilizing a typical horseshoe section with a height of 14.5 feet. The Oregon Department of Transportation (ODOT) required proper vibration control to minimize potential impacts to Interstate 84 and Union Pacific rail immediately below the tunnel excavations and sensitive, rare plants. The method of designing the vibration monitoring program and the results of its implementation show the iterative process of using monitoring to improve blast design as excavation proceeds, such as reducing air overpressure and COVID-related supply chain-constraints.

Dec 1, 2022

By A. Bruynesteyn

The results of leaching experiments in columns simulating 80 and 200 ft deep cores through a leach dump are discussed, By equipping the columns with can precipitation plants, actual plant conditions could be duplicated. The results produced a better understanding of the physical and chemical limitations of the leaching process.

Jan 1, 1975

By S. G. Britton

Thin seam mining presents unique challenges when management or economic conditions require significant productivity increases. These challenges are increased depending upon the presence of various external factors such as labor unions, Federal and state regulations, and market characteristics. This paper explores the turn-around situation occurring at Tanoma Mining Company (TMC), a medium-sized underground coal mining company in central Pennsylvania, USA. Using a systematic approach of improving management controls and direction, labor relations, and communications, coupled with an intensive upgrade/rebuild/replacement program for equipment and systems used at the mine, TMC has begun reversing its' cashflow position from negative to positive within two years.

Jan 1, 1991