Search Documents

By Armando Alatorre

The Republic of México is the world's largest producer of celestite/strontium carbonate and natural sodium sulfate. It is also a significant producer of flourspar, barite, graphite, sulfur, feldspar, salt and gypsum. New production may be brought on stream for borates, wollastonite, garnet, calcium carbonate and others. The country covers a geographic area of approximately 2 million square kilometers (760,000 square miles), and is divided into seven geological/geomorphological provinces. Less than 20 percent has been explored in detail for either nonmetallic or metallic minerals. This leaves large areas available for the discovery of world-class industrial mineral deposits. In addition to new deposits of those minerals currently being produced, there is exploration and development potential for borates, magnesite, rare earths, nepheline syenite, heavy mineral sands and numerous others.

Jan 1, 1995

By Bernard Amadei, Michael J. Robison

The purpose of this paper is to present the results of 102 mu1tiaxial tests conducted on cubical specimens of Indiana limestone using the mu1tiaxial apparatus available at the University of Colorado at Boulder. These tests include (1) uni-axia1 compression and tension, (2) bi-axial and tri-axial compression, (3) biaxial compression- tension and (4) tri-axial compression-compression- tension. The applicabi1ity of existing failure criteria to predict the strength of the tested materia1 is discussed.

Jan 1, 1986

By Joel Nonnweiler, David Young, John Hawley

The Sacramento Regional County Sanitation District has implemented a billion-dollar interceptor system master plan, including the 31 km (19 mile) long Lower Northwest Interceptor (LNWI). For the two LNWI Sacramento River crossings, pipe-jack/micro tunnel drives in excess of 300 meters (1,000 ft) from 30 meter (100 ft) deep shafts in mixed soil conditions below the water table were considered, as were600 meter (2,000 ft) tunnel drives utilizing pressurized-face tunnel boring machines. Operation and maintenance concerns, predicted flood scour, and levee concerns are discussed. A risk assessment process was used to select both profile and construction method. Construction will begin in mid 2004.

Jan 1, 2003

By Robert C. Freas, Donald D. Carr, Lawrence F. Rooney

Perhaps no other mineral commodities in this volume have as many uses as limestone and dolomite. These carbonate rocks are the basic building blocks of the construction industry, the material from which aggregate, cement, lime, and building stone are made. Carbonate rocks, and their derived products, are used as aggregates, fluxes, glass raw material, refractories, fillers, reactive agents in sulfur-oxide removal, abrasives, soil conditioners, ingredients in a host of chemical processes, and much more. Although the use of limestone and dolomite goes back before recorded history, new uses and products are continually being found. Carbonate rocks form about 15% of the earth's sedimentary crust and are widely available for exploitation. Found extensively on all continents, they are quarried and mined from formations that range in age from Precambrian to Holocene. Reserves of carbonate rock are large and will last indefinitely, although high-purity deposits may be absent or have limited availability in certain areas. Limestone and dolomite are so useful and so abundant that in 1989 about 798 Mt were produced in the United States. In fact, about 75% of all stone quarried or mined in the United States was carbonate rock. Sand and gravel was the only mineral commodity produced in greater quantity. In this chapter we have sought to provide the general reader an overview of carbonate rocks, their composition, distribution, production, and uses. The literature on the limestone and dolomite resources of the United States and Canada is so vast and diverse that one can easily become mired in print. We tried to list those references that are easily accessible and that provide the economic geologist with a starting point for more intensive study. The table listing selected references on limestone and dolomite resources in Canada and the United States reflects our attempt to be selective rather than exhaustive and to direct the reader to the best sources of detailed information.

Jan 1, 1994

By V. Galla

In the present paper, two large diameter columns 2 m tall and 1.3 m diameter filled with crushed (finer) and run off mine (coarser) heap leach materials respectively were used to perform unsaturated flow studies. Instruments measuring moisture content and matric suction were placed in the columns at different depths as water was applied at calibrated flow rates from the top of the columns. The outflows from the columns were recorded using tipping bucket rain gauge placed at the bottom of the columns. Unsaturated hydraulic parameters were also obtained for the heap leach materials, scalped (passing 4.75 mm sieve size) and whole (passing 37.5 mm sieve size) sample. The measurements obtained from the columns were later compared with unsaturated flow modeling results. The comparison indicated sensitivity towards the sample size selection for unsaturated hydraulic parameters, and initial conditions considered in the model.

Jan 1, 2009

By Phillip R. Moyle

Voluminous deposits of commercial-grade phosphate occur in sedimentary strata in a 350,000 km2 (135,000 mi2) area of the middle Rocky Mountains of North America known as the Western Phosphate Field. The Permian marine strata that host the phosphate were deposited on the western margin of the North American craton and subsequently deformed, first by folding and thrust faulting of the Laramide orogeny, and then by Cenozoic Basin and Range block faulting. Carbonate fluorapatite is the primary phosphorus-bearing mineral. Organic matter is abundant in some strata, and both biogenic and non-biogenic pyrite are also present. Certain strata are enriched in several trace elements, especially in arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), molybdenum (Mo), selenium (Se), vanadium (V), uranium (U), and zinc (Zn). Phosphate has been mined from the Western Phosphate Field for nearly 100 years. Phosphate mining and processing constitutes the largest mineral industry of Idaho, producing more than $600 million in processed mineral value in 1997. Resource management agencies, phosphate producers, and others are concerned about the release of Se from phosphate mine wastes, especially at Maybe Canyon, and the potential effects that Se and other trace elements may have on the environment and on human health. U.S. Geological Survey (USGS) Mineral Resources Team scientists initiated a multidisciplinary study of the Permian Phosphoria Formation and related rocks in the south- eastern Idaho sector of the Western Phosphate Field in response to a request by the U.S. Bureau of Land Management (BLM). Studies to date reveal that Se is present in several phases, including native Se, and in an as yet unidentified form, possibly an organo-Se compound. Selenium is also present in pyrite and sphalerite. Selenium concentrations range from 1.2 to greater than 1,000 parts per million (ppm) in samples collected from exposures of the Meade Peak Phosphatic Shale Member of the Phosphoria Formation (Meade Peake) at Enoch Valley. The results suggest that Se concentrations vary spatially across strata and with depth, perhaps comparable to spatial variations of phosphate and organic carbon concentrations throughout the Western Phosphate Field demonstrated in previous studies. Some Se-enriched strata may be of adequate dimension to allow selective extraction during mining. Such units could be handled separately from the main ore process or waste streams and isolated in order to reduce the potential for release of Se to the environment

Jan 1, 2001

By Edward I. Erlich

1984 saw the 30th anniversary of a momentous event in Soviet geology-the discovery of kimberlites in Siberia, an event that vaulted the Soviet Union to second rank among the world's producers of both gem and industrial diamonds. There are many legends associated with this story, legends about those who predicted the discovery and those who achieved it in the field. The story told here unfolded during the field campaigns of the 1940s through 1960s, as witnessed by the authors and their companies of an earlier generation. This story illustrates science, chance, and human emotions at work, resulting in a blend of conviction, courage, bureaucratic sniping, and competition for glory. At the same time, it is an illustration of the workings of the Soviet exploration system. In a broader sense, it is the realization of the Russian image-boundless natural wealth, indomitable ingenuity, and the rigid political economic system that permeates the Russian landscape as well as the people. Most accounts of the Siberian diamond saga begin with statements such as, "This discovery confirmed the predictions of...", or "It was a result of predictions of one of the greatest Soviet geologists, Academician V.S. Sobelov...". These are only part of the truth. It had become apparent even in the 1930s that the Siberian Platform contained one of the Earth's greatest Basaltic provinces, described in a monograph by Sobolev...; and at the end of the thirties, G.G. Moor of the Institute of Arctic Geology found alnoites, similar in many ways to kimberlites. At the same time, the famous polar geologist, N.N. Urvantsev found other kimberlite like rocks in the southern Taymir Peninsula, adjacent to the Siberian Platform. In publications describing these rocks, Moor and Urvantsev mentioned for the first time the possibility of finding diamondiferous kimberlites similar to those in South Africa. Unfortunately, Urvantsev spent little time in the field between terms in concentration camps. Moor was considered by his superiors to be no more than a good descriptive petrographer; they suggested to him that his conclusions should be backed up by more highly regarded specialists. Thereupon, Moor asked Sobolev to coauthor a paper with him and this became the widely quoted prediction about diamonds in Siberia. Another early paper should also be mentioned, an unpublished paper found by M.I. Rabkin in the geological archives of the Norilsk Metallurgical Plant, written by Yu. M. Sheinmann when he worked in the concentration camp there in the late forties. This report placed the probable location of yet-to-be-discovered kimberlites within less than 100 km of their correct location.

Jan 1, 1990

By G. Chi, M. C. Fuerstenau, R. C. Bradt, A. Ghosh

Technical Papers, Mining Engineering Vol. 49, No. 12, pp. 70-75, Discussion by McIvor, R. and Fink, R. P. We must challenge what we consider to be dubious statements in the above-mentioned article. Much of what is reported was published elsewhere over a year ago (i.e., in their reference: Chi, G., Fuerstenau, M.C., Brandt, R.C. and Ghosh, A., 1996, "Improved comminution efficiency through controlled blasting during mining," International Journal of Min¬eral Processing, Vol. 47, p. 93). There is nothing unusual or significant about a 10% or more difference in grindability between two materials of apparently similar origin and other attributes (such as chemical assays, hardness and specific gravity). Consider also that: • the materials came from different locations in the pit; • only two sets of four blastholes were considered per blast: • spatial orientation with respect to the face and other blastholes was also altered; • only two pairs of data were collected; • the impact of sampling error and bias, • both of which could be significant in this case; and • normal experimental error in parameter measurement and calculation. It is clearly inappropriate to draw any conclusions with regard to cause-and-effect relationships without first presenting a thorough error analysis. A substantial number of randomly selected test and control areas might provide meaningful statistical evidence of the claimed effect of the variables being studied. Even that appears doubtful, however, because Figures 3 and 4 show about as much variation in crushing energy for the two "regular" conditions vs. regular and altered conditions. On a separate, but also important issue, broad experience with autogenous/semiautogenous milling has shown that smaller or weaker feed material results in reduced tonnage. ? Reply Thank you for the opportunity to respond to the comments of Messrs. Mclvor ant Fink. The points raised are addressed in the order of presentation. As the commenters noted, there are parallels between this article and a previous manuscript. The reason for these complementary articles is that the audiences for the two publications are different, although there is obviously some overlap. We believe that the different audiences each profit from the technical aspects of the two manuscripts. We are not in agreement that a grindability difference of 10% is insignificant. The laboratory work is corroborated by data obtained at plant scale, which confirms that an increase in throughput of the same magnitude (between 5% and 10%) is achieved when the blasting pattern is modified, i.e., reduced from 9 to 8 m (29.5 to 26.2 ft). This increase in throughput translates into substantial power savings for ore grinding. No differences in appearance in the rock were noted between the two adjacent areas. Rock in both areas belonged to the same rock mass/block, which was quite homogeneous and without geological features in between that could create drastic differences in comminution characteristics. Given the resources, we would have sampled from all of the holes. Additional data would certainly have been desirable, as would have been additional funding to expand the study. Their comment, "spatial orientation with respect to the face and other blastholes was also altered," is not clear. Figure 1 does not show the initiation sequence. Without the initiation sequence, we do not understand how the commenters concluded that spatial orientation with respect to the face and other blastholes was altered. The commenters may be trying to make the point that the four-hole configurations with respect to the original bench face are not exactly the same. In fragmenting the

Jan 1, 1999

My "outside exploration" began in November 1908, only 16 months after I had come to Bisbee as a raw engineer. The well publicized reputations of eminent engineers up to that time, including John Hayes Hammond, Herbert Hoover, James Douglas, D.C. Jack- ling, J. Park Channing, and a few others had been due to new mines they had found or brought to successful operation. And here was I, a mere youngster, given a chance to join the group. I knew there would be disappointments but I had no idea how many of them. In spite of the many prospects that turned out to be worthless I never looked at a new one without the feeling that this one might turn out to be the big success. This confidence, blind as it was, gave every arduous examination a zest and it made me climb every mountain on which the owner said there was something worth seeing, or on which T could see a distant staining that might mean ore. If I looked at every showing the owner suggested he at least would think I was honest and would bring other properties to our attention. This reputation of never refusing to go to see an outcrop, no matter how hot the desert sun or how rough the terrain, was probably one of my best assets. High as my hopes were at the start, they proved not to be exaggerated and if I were given a chance to do it again I would not hesitate, in spite of the jaundice, rheumatic fever, and other maladies that beset some of the expeditions. On the whole the results have equaled all my hopes. Toward the end of my years of active exploration I totaled up the score. Out of the prospects submitted to us about two out of three were eliminated after questioning the owner or prospector, without an examination. This left about a 1000 mines or prospects that seemed worth at least a preliminary look. One out of seven of these was worth a little development and a seventh of this seventh turned out to be a modest success or better. And nine or ten in all, or one out of 1000

Jan 1, 1976

By Jason Saldanha, Andrew Evans, Jonathan Baber

"INTRODUCTION The need for a new road crossing at Silvertown is the result of three key drivers:- •,Severe congestion and delay at the Blackwall Tunnel and surrounding road network; •,A lack of network resilience and reliability resulting from a lack of alternative road crossings in east London and the impacts of unplanned closures; and •,The need to support substantial economic development in east and south-east London (jobs and homes) These drivers directly informed the main objectives for a road-based river-crossing solution. The traffic-related problems at Blackwall Tunnel are long-standing and before Transport for London (TfL) assumed control for the strategic road network in London in 2000 the Department for Transport (formerly Dept of Transport) had investigated various relief options including a third tunnel bore and new bridge. This resulted in a new crossing alignment being safeguarded (by direction of the Secretary of State for Transport) and this was refreshed in 2001 in favor of TfL. In recent years (since 2009) TfL as part of the East London River Crossings Programme has undertaken detailed optioneering and feasibility work to address the above ‘need’. This led to the conclusion that a new road tunnel would offer the best solution in preference to bridge, ferry or demand management options. In 2012, in response to a formal request by the Mayor of London, the Secretary of State for Transport confirmed a new road crossing at Silvertown as a Nationally Significant Infrastructure Project (NSIP) by Section 35 direction under the Planning Act 2008. This NSIP designation meant that TfL as scheme promoter must comply with the National Rail and Road Networks National Policy Statement (NNNPS) and must seek the necessary powers to build and operate the crossing by means of a Development Consent Order (DCO) under the Planning Act 2008."

Jan 1, 2016

By A. T. Iannacchione

Recent fatal injuries occurring during pillar retreat coal mining call for better identification of the hazards and recognition of risks. Ground control hazards associated with room-and-pillar retreat mining tend to intensify with depth, requiring extra precautions in the form of additional controls. In many locations these activities are further complicated by local complexities often associated with unique or novel circumstances, such as over-mining or under-mining. One technique recently studied by NIOSH, Major Hazard Risk Assessment (MHRA), may help mine operators to mitigate the risks associated with pillar recovery operations. The approach was trialed at two underground coal mines in southern West Virginia that are currently practicing pillar recovery. The first step in the MHRA process involved reviewing the segments or parts of the pillar extraction mining system and identifying associated hazards and threats to the operation. Some of the high risk hazards at these two sites included: ? Rock fall during pillar extraction covers equipment and injury occurs during recovery operations, ? Rock fall above the roof bolt horizon, potentially injuring ? workers and/or requiring recovery action, ? Rib fall under deep cover, potentially injuring workers, and; ? Strata instabilities associated with subsidence of the interburden due to simultaneously mining two seams in close vertical proximity to one another. The mines? risk assessment teams then considered each threat individually in order to systematically identify potential unwanted events. The top unwanted events were examined individually using structured risk analysis tools. The output from the process includes a list of priority existing controls for monitoring and auditing, and a second list of potential new controls. These controls consisted of: Examples of best practices, ? Enhanced communication, ? Implementing standard operating procedures (SOP), ? Protocols for emergency response actions, ? Effective layouts, ? Efficient monitoring, and; ? Successful audits. This paper documents the process as it unfolded at the two mines, and analyzes the strengths and weaknesses of the MHRA technique as it applies to pillar recovery operations. This work was part of a larger NIOSH research project. NIOSH was responsible for: 1) facilitating the risk assessment process known as Major Hazard Risk Assessment (MHRA), 2) documenting the risk assessment process, and 3) providing mine management with a written draft summary of the risk assessment process. The results of the risk assessment represent the thoughts and opinions of the individual risk assessment teams and should in no way be construed as an endorsement of the risk assessment output by NIOSH or the University of Pittsburgh.

Jan 1, 2009

By E. F. Schnitzer, C. Lidstone, D. Cramer, P. J. Wampler

The River Island mining site is located at approximately river mile (RM) 15 on the Clackamas River, a large gravel-bed river in northwest Oregon. During major flooding in February 1996, rapid channel change occurred. The natural process of meander cutoff, slowed for several years by dike construction, was accelerated by erosion into gravel extraction ponds on the inside of a meander bend during the flood. In a matter of hours, the river cut off a meander and began flowing through a series of gravel pits located on the inside of the meander bend. The cutoff resulted in a reduction in reach length of approximately 1,100 m. Erosion by bed lowering, knick point retreat and lateral erosion of upstream river banks occurred quickly. Within two days of the peak flow, 3.5 hectares of land and 105,500 m3 of gravel were eroded from the river bank just above the cutoff location. Much of this gravel moved a short distance downstream into the excavation. Reach slope increased from 0.0022 to approximately 0.0035 in the cutoff reach. Between 1996 and 2003, the knick point from the meander cutoff has migrated 2,290 m upstream, resulting in increased bed load transport, incision, and local lowering of the water table. In 1993, prior to the meander cutoff, transects were surveyed in the River Island reach upstream of the cutoff location. Resurvey of these transects and aerial photo analysis indicates that 96% of the knick point migration occurred during the first winter following meander cutoff. Connection of the flowing river to the off-channel ponds has had minimal effect on water temperatures in the mainstem Clackamas River. It is likely that this minimal change in temperature will decrease as ponds are isolated from active river flow by gravel bar deposition. Fish net-ting in spring 2002, suggests that salmonid use of the pond in the spring is minimal. The most abundant native species netted were large-scale sucker and northern pikeminnow. The most abundant non-native species netted was brown bullhead. Early regulation by state and federal agencies did not adequately evaluate potential impacts to the river and the floodplain; nor did it evaluate future impacts related to geomorphic processes and sediment transport. New permit evaluation methods, currently implemented by both Oregon and Washington, incorporate 1) river dynamism through historic river migration analysis; 2) stability of human structures in light of river dynamics; and 3) sediment transport and its impact on channel stability and dynamics. The gravel pit capture at River Island highlights the potential risks of mining in an active secondary channel of a large gravel-bed river. Mining deeper than the depth of the adjacent channel, within the active migration zone, may increase off-site impacts. In locations where multiple gravel excavations are present within the meander zone, a comprehensive reclamation and restoration plan should be developed which provides long-term channel stability within the natural variability of the entire river reach.

Jan 1, 2006

By Hubert E. Sherer

The mining industry is presently one of the most heavily capitalized industries in the U.S. (U.S. - Statistical Abstracts, 1979). U.S. sales of new mining equipment (not including environmental, preparation, or long distance transportation equipment) are projected to reach approximately $5 billion/year in 1980 (Frost and Sullivan, 1979). Of these new equipment sales approximately 30 to 40 percent of this equipment will be used to replace old equipment. Therefore, an increase of efficiency in the use of equipment replacement capital could have substantially positive effects for the U.S. mining industry. This is very critical in these times of restricted capital availability, double digit inflation, burdensome governmental regulation, and rising foreign competition in the mining industry. This paper examines the numerous factors that constitute the typical mine equipment replacement problem. A computerized, mathematical model is formulated to utilize historic cost and production information to predict equipment cost versus age for the existing and potential replacement machines. Another part of this computerized model determines the best equipment replacement strategy that accomplishes estimated production goals at a minimum discounted cost. This computerized model is an easily used, consistent method of determining the optimum replacement age for any equipment unit or fleet of equipment at a mining operation.

Jan 1, 1982

By D. Bleazard

Barrick Goldstrike Mines, Inc. is actively involved in improving the reliability of mining and processing equipment through the use of failure analysis and condition monitoring activities. Program results include an increase in equipment capacity and an overall reduction in operating costs. The identification of equipment failure modes and the development of associated capital asset management practices can minimize failure consequences. Successful programs have included; alterations to management practices, equipment modifications, and/or the implementation of condition monitoring programs. By controlling or minimizing the effects of incipient equipment failures, corrective actions can be taken earlier in the failure cycle, resulting in an associated reduction to repair costs and equipment down time.

Jan 1, 1997

By L. Kulik

Sustainability of lignite mining in the Rhenish lignite mining area is ensured by a preceding study of the overall project, with the involvement of all those affected. The supporting holistic consideration of the various sustainability elements is essential for a later balancing of the several ecological, economic and social concerns. In what follows, a brief overview of the Rhenish lignite mining area is given as introduction to the focus of this report, which is on sustainability, starting with the approval procedure under regional planning law incl. opencast mine planning, and extending to concrete on-the-spot implementation, taking the Garzweiler II follow-up mine as example. To illustrate the issues involved, an account is given of some selected sustainability elements.

Jan 1, 2005

By William A. Turcotte

Introduction The need for water is fundamental to every minerals processing operation. Though this may sound rather elementary, it is one area that cannot be over- looked. Frank C. Quinn in his paper entitled "Water Is Water Is Water" (1967) said, "but it isn't as simple as that. Very often research is slowed down and production is hampered because of a lack of appreciation for the behavior of water." The quantity of water needed for any operation is determined from bench and pilot plant testing. The quality required by the process for both fresh and reuse water is also established during these two testing phases. Quinn's statements are true whether the process involves the paper industry, the minerals industry, or any other industry. It is not the author's intent to cover water quality, quantity, or re- cycle in specific terms, but to provide the reader with a general outline of the topic with reference to several valuable sources of information. The first part of the chapter will cover several of the areas that have been de- tailed by others and also provide a list of reference sources. The references at the end of the chapter are not all inclusive but will provide a good starting point. In the second part of the chapter, a detailed description, with flowsheet illustrations, is pro- vided on the evolution of the reclaim (reuse) water system at the Tilden concentrator. Mineral Industry Water Needs Beresford and Edler (1978) surmnarized the minerals industry's need for water this way: "minerals are necessary to a modern complex technological society. The minerals industry, while its water needs are relatively minor compared to large users such as agriculture, nevertheless requires a large quantity of water to carry out daily operations from mining to final product refining." In 1973 total water use in the United States was estimated at 15.14 billion cubic meters (4 trillion gallons) for the minerals industry. Of this, about 69% was recirculated within the system. In 1982 Watt and Horton stated that the percent of recycled water in the minerals industry had improved to 73%, showing the minerals industry is an efficient user of water and that steady improvement in water recycling is something the minerals industry can look to with pride. The percent of water needed by the United States' minerals industry was estimated in 1962 to be about 2% of the total water required by industry

Jan 1, 1986

By Darrell V. B. . McClarty

In 1996, Rio Algom, Denison Mines and the Elliot Lake Research Field Station (ELRFS) formed a consortium to implement a regional environmental information management system (REIMS) for the Elliot Lake area in Ontario, Canada. ELRFS is an affiliate of Laurentian University in Sudbury, Ontario, The discovery of uranium in the Elliot Lake region in post-World War II led to the development of 12 mines and 11 associated mills between 1955 and 1958. During the late 1980s, declining world demand for uranium, combined with the discovery of high-grade uranium ore in other areas of the world, made the Elliot Lake mines uneconomical. As a result, all area mines ceased opera¬tions by the end of 1996. The eight facilities and three tailings management areas operated by Denison Mines and Rio Algom's five mining waste management areas contain 150 Mt (165 million st) of potentially acid-generating tailings. The areas cover 13.2 km2 (3,265 acres) and receive drainage from an additional 13 km2 (3,212 acres). The primary objective of the joint initiative was to implement a personal-computer-based, regional, environmental-information management system for managing historical data and ongoing environmental programs in the Elliot Lake region. The Elliot Lake consortium decided it needed an information system with an integrated, process-oriented and requirements-driven approach to collect and manage the environmental information. Following a study of environmental information management systems currently used by the mining industry, the consortium decided to base REIMS on the "Envista" product. This is a commercially available, environmental information management system marketed by Envista Technologies of Saskatoon, Canada.

Jan 1, 1999

By L. H. E. Weyher

The Bethlehem Mines Corp. is a captive mining subsidiary of Bethlehem Steel Corp. Its coal production is tied to the demands for and production of steel, a situation that has to balance between the following two extreme strategies: (1) either the mines are designed and operated for some optimum production level and the demand fluctuations within the steel corporation are met by supplementary corporate coal sales and purchases, or (2) the mines absorb all the demand fluctuations, regardless of the effects on mine costs. A rational definition of the best strategy between these extremes is, of course, needed but is very difficult to formulate in view of the complexity of the many factors that would have to be included in the analysis. Consequently, rather than setting profit targets for each given mining division and/or individual mine, the practice evolved to set production targets for producing specified tonnages of coking coal for shipments to the ovens located at the corporation's iron and steelmaking plants. This in turn leaves the mines with the dilemma of having to explain demand-related cost-per-ton fluctuations while essentially depriving them of the ability to control profit through tonnage optimization. In the early 1970's, the coal prices rose significantly, while other factors led to sagging productivity in underground coal mining. Thus, the role of Bethlehem's coal operations in the corporate profit picture gained in relative importance. This, in turn, sparked a closer attention to the coal mining cost structure and factors controlling productivity. At the same time, the drastic increase in the capital needed to open a new mine also increased the amount of planning required to minimize risks. All of this called for more well-defined, quantitative operating data. Bethlehem therefore launched, in the early 1970's, a number of innovative steps that, as the future may show, represented pioneering contributions to the growing sophistication of North American underground coal mine planning and management control practices. This case study describes the changes that led to the current implementation of a novel production reporting system at Bethlehem's coal mines. These changes took place in two distinctly different phases. The current system that resulted from the Phase II developments utilizes, of course, experience gained earlier and is expected to be amplified to incorporate more advanced concepts and technology as future experience dictates.

Jan 1, 1979

By Howard M. Wells

The future is uncertain. In these circum- stances how can we rationally decide whether to commit funds to an investment that may or may not turn out to be successful? To date no certain answer to this problem has been found, nor is one likely to be found in the future. At best we can attempt to assess the possible outcome in terms of probability, taking into account all sources of information that may be available at the time the decision must be made. This subject is addressed with some trepidation and much humility. Any attempt to fore- tell the future is by its very nature controversial. The purpose of ' this .chapter is to present a proposed rationale for decision making under uncertainty which relates the probabilistic risk of the investment to the capacity of the firm to absorb possible unfavorable consequences if they should occur. It is not the intention to propose a cut-and-dried methodology but rather to examine the conceptual philosophy on which a methodology may be based.

Jan 1, 1979

By Frank Palkovits

All technologies move through a cycle from infancy to maturity. Thickened tailings have moved into the young adulthood phase of its development. Many mining companies like the idea of reducing their water-taking and water disposal issues. This limits the risks associated with traditional surface water-covered tailings facilities and the reduced dilution possible through underground disposal of thickened or paste tailings. Just as home theater systems advertised as ?plug and play? are rarely quite that straightforward, implementing and improving a thickened-tailings system has its challenges. However, the technology has also developed in recent years so it is more accessible. Some success factors have emerged because of the new technologies. Is thickened tailings the right solution? The first step in success with thickened tailings should be whether it is, in fact, the right solution for a particular mine. And, if so, what type of thickening is best. The answer depends on several factors, including: ? Grain size: The grain size that is optimal for maximizing mill recovery is some-times not suitable for thickening. Other mineralogical factors, such as mica content, may also influence whether the tailings are suitable. ? Water issues: Available water does not always have the purity necessary for the process. Another issue to consider is that if water is in short supply, as is increasingly often the case, thickening may be a way to reduce the need to both take and dispose of water.

Jan 1, 2008