Search Documents

By Jeffrey D. Thatcher, Debra W. Struhsacker

With the burgeoning development of precious metals heap leach mining projects throughout the country regulatory agencies are beginning to take a closer look at the short-and long-term environmental consequences of heap leach mining. This increase in regulatory review is occurring on federal, state and local levels, and is affecting both large- and small-scale mining developments. Small-scale mining developments are receiving especially critical regulatory scrutiny because in the eyes of some regulatory agencies, small developers lack the credibility automatically accorded to major mining companies. This is due in part to a bad image of small miners based upon past environmental problems and permit violations caused by a few, small operators. The proponent of a small mining development thus faces special problems during the project permitting process, and must convince the regulatory authorities of his company's ability and commitment to plan, develop, and decommission a mining operation in compliance with environmental regulations. Not only must the small developer have a thorough understanding of the regulatory requirements affecting his project, he must also devote considerable effort to careful internal planning in order to produce a well organized approach to project permitting. The importance of proper planning cannot be overstated. Project planning is key to convincing the regulatory agencies that the small miner is capable of developing a viable project. More- over, the economics of a small mining project demand permit acquisition at modest cost and in a timely fashion. A well planned permitting effort will thus ensure that permits are received within budget and on schedule. This paper will review the federal, state, and local permitting requirements for heap leach projects, and the variability of these requirements from state to state. The environmental assessment process for projects developed on public lands, and the acquisition of zero- discharge water quality permits, air quality permits, and local special use permits as they apply to small mining developments will be discussed. The paper will conclude with a review of project decommissioning and cyanide neutralization requirements and their implications for small-scale heap leach projects.

Jan 1, 1987

By V. McLemore, N. Dunbar, K. Donahue

There are three principle lines of evidence that indicate the clay minerals found in the Goathill North (GHN) rock pile at the Molycorp mine are predominantly a product of hydrothermal alteration, not weathering. The unweathered drill core and samples from GHN have similar types and abundances of clay-mineral groups based on XRD analysis. Chemical analyses from the electron microprobe reveal similar chemical compositions for the hydrothermal alteration clays in drill-core samples and clays found in the rock pile. Textural evidence gathered from petrographic and microprobe examination also suggests a hydrothermal origin for clay minerals.

Jan 1, 2007

By J. W. Langford

A more effective method of fracturing and chipping the formation is necessary to significantly increase the productivity of blasthole drilling with a roller cone bit. The conventional rotary blasthole bit engages the formation and initiates spalls, chipping and fractures in the formation at a rate dependent on the amount of pull down force applied by the drill. The rotary speed of the drill increases the number of fractures and creates drilled chips that are removed from the hole by the air circulation. An engineering project was motivated to develop a low pressure, low impact downhole percussion hammer to provide an overstrike force to a blasthole bit, in addition to the conventional pull down force and rotary speed. The objective of the project was to utilize existing rig air packages in the range of 50-110 psig and provide an overstrike force to the bit in the range of 1100-1500 impacts per minute. Laboratory testing performed on Barre granite achieved, on average, a 40% improvement in rate of penetration. This performance has been confirmed in actual blasthole drilling in copper and iron ores mines. During the testing phase, additional unexpected benefits have also been realized.

Jan 1, 2011

By V. Gall, J. Rudolf

The Virginia Department of Rail and Public Transportation and the Metropolitan Washington Airports Authority are undertaking the extension of Washington Metropolitan Area Transit Authority’s Metrorail service to Washington Dulles International Airport and beyond to Route 772 in Loudoun County, Virginia. The roughly 37 kilometers long, double track alignment involves two 700 meters long single track, soft ground NATM tunnels at Tysons Corner, two 3.3 kilometers long single track rock TBM tunnels at Dulles Airport and one 25-meter deep station at the airport to be constructed by NATM in sedimentary rock. The design-build project is being implemented in a Public-Private-Partnership. A joint venture of Bechtel and Washington Group International has concluded the preliminary engineering and construction is scheduled to start in late 2007.

Jan 1, 2007

By K. A. Lewandowski

The efficiency of heap leaching is reduced by poor solution flow characteristics (i.e., channeling and ponding) that result from fines migration. Agglomeration of the ore can immobilize fines, but for agglomeration to be successful in copper leaching, an acid-resistant binder is needed to stabilize the agglomerates. Until now, there has not been a satisfactory method to evaluate whether a binder was effective, other than squeezing a handful to see if it ?feels right.? This paper reports on several procedures that have been developed to quantitatively determine whether a binder gives good performance in an acidic solution. These procedures have been used to identify binders that would be suitable for copper heap leaching.

Jan 1, 2008

The safety of personnel is the most important matter during a mine fire. However, there is not enough research on a case when a fire occurs near a shaft and the behavior of the fire gas is not well understood. Therefore, a series of experimental study using a scaled ventilation circuit model was carried out. The behavior of ventilation air during a mine fire near a shaft was investigated. The model consists of two vertical shafts, three horizontal ducts connecting the shafts and an exhaust fan from the shaft bottom. The cross section of the shaft and duct is a square of 200×200mm. The height of the shafts is 3400mm. The length of the ducts is 1540mm. The lower duct is set at the same level as the shaft bottom. The middle and upper duct are set at 750mm and 1760mm above the shaft bottom respectively. The airflow rates through the ducts can be adjusted by regulators installed in each duct. The behavior of the fire gas was measured by anemometer, thermometer, and visualized using laser light .The air was ventilated downward in both shafts before the initiation of the fire. Some amount of fire gas of high temperature rose upward gradually along the shaft wall regardless of the downward ventilation after the initiation of the fire. Then the direction of main ventilation air suddenly reversed upward in the shaft. The direction of ventilation reversed in many places in the model and the fire gas reached even the part not anticipated.

Jan 1, 2009

By Kerry Spickelmier

The only nickel smelter and the only active nickel mine in the United States is Glenbrook Nickel Co., a joint venture (50% each) of Cominco Resources International Ltd. and Cominco Ltd. In 1989, with the nickel price riding high between $2.30 and $2.70/kg ($5 and $6/lb), Glenbrook seized the opportunity to purchase and recommission a southwestern Oregon ferronickel smelter and the adjacent nickel-ore mine. This Douglas County site is only about 97 km (60 miles) due east of the Pacific Ocean, and California's border lies a similar distance to the south. Hanna Mining Co. had closed the operation in 1987. And the following year, the equipment had been largely stripped for salvage value. From November 1990 through August 1992, the mine supplied an average 5 kt/d (5500 wet stpd) of ore. Currently, with import ore supplying 40% of the smelter feed, the mine's daily tonnage averages 4.2 kt (4600 wet st). From November 1990 through August 1993, the mine has delivered 2.1 Mt (2.3 million st) of ore grading 1.22% nickel with an average moisture content of 26%. Buffaloed nickel? A nickel is not worth what it was in 1989 and neither is ferronickel, with recent prices hovering around $1.13/kg ($2.50/lb). To survive, Glenbrook has focused on increasing smelter production to lower its operating costs. And this strategy has triggered several bold moves: • a new, $30 million, port facility and • a 10-year importation contract for ore from New Caledonia, an island approximately 1000 km (625 miles) east of Australia. For a Glenbrook update, a May 25, 1993 visit was made to the company's Oregon operations - the mine and smelter near Riddle plus its new Coos Bay port facility. Unfortunately, as the rain came down that day, so did news of another temporary shutdown. The previous suspension had lasted from Dec. 20, 1992 until Feb. 22, 1993. Barely three months back to work on a wet May afternoon, more than 250 of Glenbrook's approximately 300 employees contemplated yet another shutdown, effective July 31, 1993.

Jan 1, 1993

By John Trefny

Although mining is currently one of the smallest academic units on the Colorado School of Mines(CSM) campus, it is alive and well, with nearly 100 undergraduate and graduate students. For many years, Mines has had undergraduate and graduate programs in hard-rock mining. The school has recently transferred its physical mineral processing activities to the Mining Department. The program has also expanded to include tunneling, underground construction and industrial minerals. There are current discussions about increased research activities on cement and other construction materials. The Mining Department also teaches its share of what is called the “distributed core” courses with curricular requirements common to related programs, as well as mining safety and health, in conjunction with our continuing education department.

Jan 1, 2002

By Pat C. Hautala, J. R. Hoskins

This is a new era for the minerals industry. Never before has there been more need for effective communication. So said Robert Anderson, chairman and chief executive officer of Hanna Mining Co. He was speaking to the American Mining Congress's Communication Workshop. The question is whether there is enough industry concern to meet the challenge. Anderson observed that increased workshop attendance, in continuing tough times, reflects the industry's concern for communication. But, why were students, faculty, engineers, supervisors, and managers not at the conference? Communication applies to every manager, Anderson said. But he was the only operating manager present. And only one company sent operating supervisors. The remaining conference participants were public relations personnel, generally with nonmining backgrounds. And the program dealt mostly with public relations issues. Role of Communication in the Minerals Industry. It is well known that the minerals industry faces economic, political, and social problems. Economic shifts and foreign competition have created an international minerals industry and an international marketplace. This, in turn, calls for worldwide communication. Other factors effecting communication are: • Governmental protectionism as well as regulatory reforms call for increased interaction with governing officials. • Changing social values have created environmental issues and anti-industry attitudes. This intensifies the need for improved public relations. • Traditional work values are shifting towards self-actualization and humanistic movements. The work force is better educated and more informed. Employees demand more satisfaction, equality, and job autonomy. • The mining industry's task of managing its human resources is complicated by layoffs, job uncertainties, and bleak outlooks concerning employee morale and motivation. Technology and Information for a New Era As noted, this is a new communications era, one propelled by technology and information. Technology has led to reduced demand for raw materials by developing substitutes. Copper demand, for example, will never fully recover. Copper cables are replaced by fiberoptics; copper transmission lines, with aluminum. Technology has shifted the US from traditional to high tech and service industries. The speed, frequency, and scope of information transmission have greatly increased. But the most significant characteristic of this information is not the pace of advancing technology. It is the dramatic increase in the importance and frequency of our personal transactions. Knowledge has replaced raw materials and capital as the strategic resource. Information has replaced energy as the transforming resource. And the game against nature has become an interpersonal game (D. Bell, Post-industrial society, Physics Today, '76). In Megatrends, John Naisbitt says that information will soon double every 20 months. So, professionals will become "information workers." And communication will be the life channel of the information age. Thomas Wolfe said you can't go home again. Hanna Anderson said we are, indeed, facing a new day. It will never again be "business as usual." We must move into the information age with the rest of society. We cannot trust that the world will continue to rely on our products. Nor can we place the responsibility and control for problems and solutions outside the minerals industry. Improved communication is not a panacea. But, Anderson said, it is critical to the minerals industry. What is Communication? The word communication is overused. It is applied to every aspect of our lives. Satirist Tom Lehrer got sick of hearing about the need to communicate. He said, "It seems to me that if someone is having all that trouble communicating, the very least he can do is shut up!" Obviously, we cannot follow that advice (though we might wish that some others would do so). Communication is always going on. It is inevitable. Yet we have many misconceptions about com-

Jan 1, 1985

M.S. Azun I have many objections to the content of the author's paper. Before discussing it, however, I would like to repeat the property of semivariogram function. Second order stationary properties of regionalized variables (ReV's) such as semivariogram function y(h) are perfectly known in geostatistics. Also, the kriging equations in the language of mathematical statistics using second order stationary properties are well understood. However, the way to use the sample (estimated) semivariogram function in any one of the kriging procedures is vague. The sample semivariogram function is given as follows: [ ] where N is the total number of samples, Xi is the sample value at the i - th location, Xi+h is the sample value at the i + h - th location, and h is the distance among the samples. An estimation variance of sample semivariogram function of first lag is smaller than that of higher order lag. The theoretical semivariogram function reaches the variance of samples asymptotically. But this is not easily observable because of the larger variation involved in the estimate of semivariogram function. In general, an estimation procedure is done for h = 0, 1, 2, up to the greatest integer less than N/2, even though sample semivariogram function can be computable through N-1. After estimating semivariogram function, the critical question of how to model sample semivariogram function arises. As seen in the above equation, sample semivariogram function is discrete and can be smoothed by the model being selected. Therefore, modeling of sample semivariogram function is the most important step in geostatistics. It not only smoothes a discrete function but also affects the results of the kriging procedure. When the only aim is to model the semivariogram function, which is the basic point of the author's paper, one can employ any fitting techniques, such as curve fitting, or any arbitrary functions, which are called submodels in the paper. The term "arbitrary function" is used rather than "submodel" because there is no basic understanding of developing them. The author suggests that the sum of those submodels can also be used for the modeling of sample semivariogram function. The combination of any arbitrary functions brings many problems instead of giving an insight of the domain structure considered. The author used two arbitrary functions and the nugget effect in response to sample semivariogram function (Fig. 10). For the same example, he stated that the parameters involved in the mixed arbitrary function model can be accepted when the discrepancy between sample semivariogram function and the model is small visually. For verifying the fitting behavior of any selected model, one should not be contented with the visual satisfactory. Some statistical measure such as goodness of fit has to be used. The author's practice is no more than an exercise in curve fitting without any fundamental understanding or conceptualization of the underlying physical mechanism. Furthermore, the selection of any model is not an easy task if the purpose is the search for the "best" response to the observed second order properties of ReV's. I suggest that the Markovian model (Azun, 1983), on the basis of a theoretical understanding of underlying mechanism, which gives more information about the occurrence of regionalized variables, is used to respond all properties of ReV's. There are a lot of problems for modeling of one-dimensional sample semivariogram function. Thus, it is not appropriate to go to higher order dimensional sample semivariogram function modeling. In the meantime, I would recommend that one can connect the values of standardized sample semivariogram function rather than simple values of semivariogram function in the two-dimensional estimation. The standardized values can be computed in dividing the semivariogram function value by the number of sample pairs involved in each lag regardless of the directions. In conclusion, geostatistics is an interdisciplinary area in mining that uses the principles of mathematical statistics. Thus, it should not violate any probabilistic and statistical rules. When Matheron was developing the theory of geostatistical study in the early years of geostatistics, many mining people had a reservation accepting the geostatistical tools. However, this does not mean that we, the geostatisticians, might try to convince those people using some "strange" tools or rules as some authors implied (Baafi and Kim, 1984). Instead, we have to develop and explain the geostatistical tools staying only in the framework of statistical concepts and properties. References Azun, M.S., 1983, "Stochastic Process Modeling of Spatially Distributed Geostatistical Data," Columbia University, Ph.D. Thesis. Baafi, E.Y., and Kim, Y.C., 1984, "Discussion - Comparison of Different Ore Reserve Estimation Methods Using Conditional Simulation," Mining Engineering, Vol. 36, No. 3, p. 280. Reply by J.M. Rendu The interactive method proposed by Rendu allows practitioners to develop semivariogram models that take into account not only the numerical information obtained by sampling, but also highly significant additional information that often cannot be quantified. The geology of the deposit - including hypotheses concerning its genesis, sampling methods, assaying methods, and mathematical methods used to calculate the semivariograms - all have an influence on the numerical results obtained and on how these results should be interpreted. If all the information concerning the spatial distribution of values in a mineral deposit was contained in the sample values, it could be argued that statistical techniques alone would produce optimum models. However, this is rarely, if ever, the case. Methods that allow the user to take into account his experience and his geologic understanding of the deposit should not be rejected for the sake of theoretical statistical purity.

Jan 11, 1985

By S. Noll

Ventilation is an essential part of any underground mining operation. It provides fresh air for workers and machinery, keeps up an adequate mine climate and dilutes and dissipates noxious gases. Possible changes in the economic environment for mining in the future, e.g. increasing energy costs, will necessitate optimization of distribution of airflow within most mines. This paper discusses the scientific set-up for measurements as well as the behavior and influence of parameters of ventilation according to airflow distribution under consideration of technically possible set-ups of mine fans. This study was done in an underground mine with a flat seam room and pillar mining method.

Feb 27, 2013

By E. R. Bauer

In response to the mandates in the MINER Act of 2006, NIOSH conducted refuge alternatives research that included characterizing the utility, practicality and survivability of refuge chambers and outby safe havens. NIOSH also prepared and delivered a report to Congress in late December 2007 that summarized the findings of the research, included recommendations concerning the design and performance specifications for refuge alternatives, and focused on specific information that could inform the regulatory process on refuge alternatives. This document highlights NIOSH's research and recommendations concerning refuge alternatives, survivability evaluations of refuge chambers, and presents a brief review of the current deployment of refuge chambers in underground coal mines in the U.S. The research has lead to the conclusion that refuge alternatives have the potential for saving the lives of mine workers if they are part of a comprehensive escape and rescue plan, and if appropriate training is provided. DISCLAIMER: ?The findings and conclusions in this report have not been formally disseminated by the National Institute for Occupational Safety and Health and should not be construed to represent any agency determination or policy.?

Jan 1, 2009

By V. McLemore, A. Fakhimi, K. Donahue, D. Sweeney, V. Viterbo

In order to evaluate the relationships between weathering and durability and strength of rock samples from the Goathill North rock pile at the Molycorp Questa mine, NM, we conducted slake durability and point load tests. Slake durability index (ID2) values ranged from 84 to 98%. Point load strength index (Is50) averaged for all rock units ranged from 1.1 to 5.7 MPa. Results show a slight positive trend between ID2 and paste pH. Two populations of data are distinguishable when ID2 is plotted versus the percentages of chlorite, illite and internal friction angle. In general, Is50 values increase toward the interior of the rock pile. Preliminary conclusions indicate that the durability and strength of the rock pile material generally increase toward the interior of the rock pile. Pre-rock pile alteration and post-rock pile weathering history have affected the durability of the GHN rock pile samples.

Jan 1, 2007

By Raja V. Ramani

As the new millennium approaches, it is appropriate to assess the progress that has been made in mine health and safety, a matter of concern to management, labor and government. One can hardly look at the major events of the last century — from the birth of the US Bureau of Mines through the enactment of the modern health and safety laws — without realizing that the march has been relentless toward eradication of health and safety threats in mining. The progress is spectacular in mine safety and significant in mine health. In looking at the future, it is safe to assume that societal demands will increase for improved health and safety conditions in the workplace. So will the demands for greater technological leaps. The standards will for measuring success and the expectations of progress in creating a safer and healthier mine environment will grow. The possibilities are enormous of meeting these exacting requirements in the 21st century.

Jan 1, 1999

The SFR system utilizes a skimmer or extractor placed at or near the slurry-froth interface where there is a higher concentration of valuable mineral particles. With assistance of hydrocyclones, it is possible to classify the extracted particles into coarse and fine particle streams, that can be handled separately. It also allows the coarser solids to be separated from entrained low-value fines. The first test results with the SFR system significantly improved both coarse and fine particle recovery in a flotation cell. The SFR system was tested in the flotation circuit at a copper-moly concentrator, and the results show that the use of the skimmer has huge potential to increase the froth recovery (Rf) of both molybdenum and copper.

Jan 1, 2012

By Louis M. Schlesinger, Michael J. Garska, Joel F. Hutwelker, James T. Jr. Tanner

A pilot plant was constructed and operated to investigate the column flotation of 20 x 200 mesh North Carolina phosphate ore, using high throughput, high solids operating conditions developed at the NCSU Minerals Research Laboratory. Flotation was performed at 45% solids in a 9.5 cm (3.75 in.) diameter by 2.26 m (7.4 ft.) tall column at throughputs of 19.1 t/hr/m2 (2.0 stph/ft2) and 31.7 t/hr/m2 (3.3 stph/ft2). Recoveries in excess of 98% of the phosphate value were obtained at the lower throughput -- while obtaining concentrate grades containing over 28% P205 (61.2% BPL) at that recovery. Recoveries of about 95% of the phosphate value were obtained at the higher throughput, while making a concentrate averaging 27.6% P205 (60.3% BPL). In addition, a better understanding of the variables governing the column flotation of coarse nonmetallic minerals was gained. Variables examined included superficial air velocity, throughput (superficial feed velocity), frother type, frother dosage, and bias rate.

Jan 1, 1993

By H. -J. Langhoff

"The paper describes not a result, but a starting point to implement sustainable development to a region characterized by a typical down river landscape, agriculture, and extractive industry. The NaturFreizeitNiederrhein GmbH (NFN) is a private company with associates from administrative bodies, the local mining companies and multiple representatives of environmental protection groups (local and national), tourism organizations, cultural societies and also aquatic sport and fishing clubs. Center of the concept is the "NFN Lake District." The development concept aims to provide the agricultural industry with alternative means of income, while protecting wildlife and the ecological balance as well as preserving the social und cultural system and enhance the safety against flooding from the river Rhine. The mining industry contributes their coordination of obligation concerning reclamation and recultivation of the already existing individual projects. While designing the landscape components and establishing the infrastructure for the different tasks, the production of gravel and sand is yield as a by product. The result is a long term perspective for region and industry."

Jan 1, 2005

By Tom Szaraz, Steve Skelhorn

Part of a major sewer expansion for the City of Columbus, Ohio. The Big Walnut Outfall Augmentation Sewer (BWOAS) consists of 4,000m (13,200 ft) of 3.66m (12 ft)diameter tunnel passing mainly through glacial deposits with a water head of up to 2 bar. The project involves many new innovations, including: Slurry wall work shaft with excavation below the water table; Hybrid universal rings combining traditional steel reinforcement with fibers; New, full EPB Lovat TBM; Two component grout system pumped to the TBM from the surface; and, Linabond corrosion protection liner. The paper looks at the planning approach adopted to meet the various challenges presented, combined with an overview of progress to date.

Jan 1, 2007

By Dermot Winters

The Surface Mining Control and Reclamation Act (SMCRA, or the Act) was enacted on August 3, 1977. The Act was written, in part, to put an end to uneven environmental standards and to establish minimum national standards. Certainly, one of the motivating factors for passage of the Act was the success of the Federal Coal Mining Health and Safety Act of 1969 in reducing deaths and injuries in the coal industry nationwide. Section 516 (b) (1) of the Act requires *that subsidence be prevented from causing material damage to the extent technologically and economically feasible except in those instances where the mining technology requires planned subsidence in a predictable and controlled manner. Section 516 (c) of the Act authorizes the regulatory authority to suspend underground mining if there is imminent danger to inhabitants of urbanized areas, cities, towns, and communities. On December 13, 1977, the interim program, which applies a portion of the performance standards of the Act, was promulgated. Then on September 18, 1978, the proposed permanent program was published for public comment. Finally, on March 13, 1979, the final permanent program was promulgated and the States were given a period of time to submit their programs for approval.

Jan 1, 1986

By Daryl E. Radcliffe, Raymond M. Stateham

The Bureau of Mines, under a Cooperative Agreement with the Bear Coal Company, Somerset, Colorado, conducted a large scale evaluation of the effect of time lapse on roof stability. Time lapse in this study is the interval between exposure and permanent support of the mine roof. The study indicates that time lapse is not a critical factor in roof stability provided permanent support is installed before catastrophic failure begins. Concurrently with the time lapse study, investigations were made of stress distribution around resin-grouted bolts, the regional stress field, and anomalous geologic conditions. The behavior of the resin-grouted bolts, at least in the Bear mine, appears to fit the Coulomb-Navier Theory. Geologic conditions are primary factors in trends of roof stability that extend across the mine.

Jan 1, 1982