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By Jean E. Kiel, Rob Dorey, Dirk J. A. van Zyl

1.1 INTRODUCTION This chapter seeks to provide an overview of important factors involved in the implementation of heap leach technology as a vehicle for gold extraction from its ores. Toward this end, brief discussions of the various elements important to this process are presented here. Topics covered in this chapter include a brief history of the process; basic chemical reactions responsible for the process ; characteristics of ores amenable to heap leaching; location of the greatest concentration of heap leach projects in the U.S.; heap leach components, methods, regulatory/permitting considerations; and economic considerations. Most of these subjects are treated at much greater length in subsequent chapters. Thus, this chapter serves as a summary for those which follow, in addition to providing the reader with a feeling for those topics which may be of most immediate interest. 1.1.1 History of the Process Modern Day Precious metal heap leaching technology has developed over the past decade, although the principles of heap leaching per se, as well as those of gold extraction through cyanidation have a long history (see discussion below). However, it is in the past 10 years that heap leaching has developed into an efficient method of treating oxidized gold and silver ores. It has proven to be both an efficient way to extract precious metals from small, shallow deposits, as well as an attractive way to treat large, low- grade, disseminated deposits. Heap leaching has several advantages compared to conventional milling (i .e., crushing, grinding, and agitation leaching). In general, these advantages include simplicity, lower capital and operating costs, shorter start-up times, and less intensive environmental regulatory concerns. A possible disadvantage of currently existing heap leach technology is a potentially lower percentage of metal extraction being obtained from the ore than would be the case with conventional milling (Potter, 1981; Hiskey, 1985; and Thorstad, 1987) The actual principle of heap leaching has a long history as inferred previously. For example, mines in Hungary recycled copper-bearing solutions through waste heaps in the mid-sixteenth century (Hiskey, 1985), and Spanish miners percolated acid solutions through large heaps of oxide copper ore on the banks of the Rio Tinto around 1752. By 1900, leaching operations were employing such techniques as leach/rest cycles to maximize copper recovery (Taylor and Whelan, 1942; Thorstad, 1987). Copper dump leaching is currently

Jan 1, 1988

By J. J. Crowhurst

The modem open pit-heap leach operation by Pegasus Gold Ltd. at Zortman and Landusky in Phillips County, Montana, is a new chapter in the mining of gold in these districts. The discovery of bulk tonnage ore bodies and their development and ultimate production was based on a long history of mining and exploration in that part of Montana. Gold was originally discovered in the Little Rocky Mountains as placer deposits by Pike Landusky and Lou Myers. This discovery in the 1880s was not significant, but Pike Landusky continued prospecting for lode deposits, and he eventually located the Gold Bug and Little Ben, two of the larger Au-Ag producers in the district. Eventually two camps, Landusky and Zortman, grew in the LittleRocky Mountains. By the time Landusky was killed in 1894 by Kid Curry, the district was still a discontinuous small producer. Steady production commenced in 1907 with the organization of the August Gold Mining Co. Eventually high grade ores on specific veins were exhausted by selective underground mining and the district was idle by May 1942. After World War II in the early 1950s. E.A. Scholz tried to continue selective underground mining, but he realized the stockworks surrounding the larger veins constituted bulk tonnage targets. Ultimately in the 1976- 1979 period he organized two exploration efforts, one each for the Landusky and Zortman areas, and brought these into production as the Argo and Pegasus gold mines. By the time of his death, Apr. 8, 1980, both operations were producing gold. Later the two companies were merged as Pegasus Gold Ltd. Upon the death of Scholz, V.F. Hollister continued as the geological consultant, Ed Roper was engaged as general manager, and J. J. Crowhurst was given the responsibility of executive vice president. The discovery of open pittable ores and the application of heap leach technology was important in the development of mining. Both contributed to the low cost operation that continues to this day. The attached article by L.M. Rogers, then chief geologist, and M.S. Enders, his assistant, describes the geology of the deposit. It was presented at the Northwest Mining Association meeting in 1982.

Jan 1, 1990

By John M. Ackerman

INTRODUCTION In the spring of 1988 the Joint Venture of Freeport-McMoran Resource Partners, Limited Partnership, IMC Fertilizer Inc, and Homestake Mining Co. was awarded the sulphur lease for Main Pass Block 299, lease number OCS-G 9372. This was one of eleven leases awarded to the Joint Venturers. Following the initial discovery wells in December 1988, a program of delineation drilling confirmed proven sulphur reserves of 67 million long tons. Proven, recoverable oil and gas reserves are 39.4 million barrels and 7.2 billion cubic feet, respectively. Development of the sulphur mine was given approval as a fast-track project by the Joint Venturers in 1989. The oil and gas reserves were acquired from the original hydrocarbon lessee in 1990 and given fast- track status immediately. Fast-track for these projects meant design and engineering would not be complete before construction began JOINT VENTURE The Main Pass Joint Venture is one of thirteen joint ventures formed between Freeport and three other companies - IMC Fertilizer, Inc., Felmont Oil Corporation, a wholly owned subsidiary of Homestake Mining Co., and Texasgulf Minerals and Metals Co. Felmont has subsequently changed its name to Homestake Sulphur Co. and Texasgulf assigned their interests in the three leases they participated in to their parent company. Texasgulf did not participate in the Main Pass 299 joint venture. Joint venture negotiations, anticipating a lease sale in mid-1988, began in December of 1987. This Joint Venture was the first of its kind; created to acquire offshore leases, explore, develop and mine sulphur. The Minerals Management Service announced a lease sale date of February 24, 1988 on the first business day of 1988. This greatly accelerated the joint venture negotiations. Of the thirteen leases the Joint Ventures bid on, eleven were awarded. Freeport holds its interest in all the leases through its ownership interest in Freeport-McMoRan Resource Partners, Limited Partnership, and Resource Partners is the operator on all of the leases. The Main Pass joint venture percentage ownership is: 58.33 Freeport-McMoRan Resource Partners 25.00 IMC Fertilizer, Inc. 16.67 Homestake Sulphur Co. 100.00 The Main Pass Joint Venture paid $3,401,757 for the Main Pass lease and will pay a royalty of 12.5 percent of production value to the MMS . LOCATION The Main Pass mine complex is located in the Gulf of Mexico, in U. S. federal waters, about 27 kilometers (17 miles) east of Venice, Louisiana or 140 kilometers south east of New Orleans, Louisiana. It is situated in about 63 meters (210 feet) of water. HISTORY The Minerals Management Service (MMS) of the United States Department of the Interior administers the mineral properties of the United States located in federal waters. Periodically the MMS holds lease sales of blocks under its jurisdiction. Prior to the offshore discoveries of sulphur associated with salt domes leased for hydrocarbons, the MMS leased blocks with all minerals including hydrocarbons awarded to the successful bidder for the block. In 1963 MMS held the first lease sale of blocks specifically for sulphur. This sale was followed by a similar sale in

Jan 1, 1992

By Robert A. Jankowski, George E. Niewiadomski

INTRODUCTION The utilization of longwall mining technology in the United States has steadily increased since the first longwall plow system was installed in 1952. At the errs of FY 1992, some 76 coal mines were employing longwall mining systems for coal extraction, and approximately 78 shearer and 3 plow faces are operating nationwide at any given time. Although the number of operating longwalls has remained relatively constant over the last five years, longwall production levels have increased significantly during this period. During the same timeframe, the number of continuous miner sections has decreased by 13 pct., from approximately 1438 in FY 1988 to less than 1250 in FY 1992. According to Mine Safety and Health Administration (MSHA) data, the average production of longwall sections increased from approximately 2400 tons per shift (tps) in FY 1988 to more than 3100 tps FY 1992. In fact, the average production has more than tripled since 1978, when it was only 850 tps. Approximately 25 pct. of operating longwalls are capable of producing in excess of 4000 tps. Longwall production currently accounts for nearly 36 percent of U.S. underground coal production, compared to 4 pct. in 1978. These improvements are attributed to improved longwall equipment and increased availability, larger longwall panels and automation. While longwalls are highly productive and offer other advantages, operations employing this method of mining continue to experience dust compliance problems more frequently than other mining system. Although dust levels have remained relatively unchanged over the past five years, averaging 1.6 mg/m3 and 1.9 mg/m3 based on results of operator and inspector sampling, respectively, during FY 1992, approximately 25 pct. of the operating longwalls were in noncompliance during any given bimonthly sampling cycle. Although modest gains in longwall dust control technology have been made, these have been overshadowed by significant increases in production rates. As more coal is mined, more dust is generated (Figure 1). Therefore, the increase in longwall productivity has meant that far more dust is being produced which must be controlled. [ ] In view of the current compliance record, any efforts to further increase longwall output, as has been forecasted, must be accompanied by: (1) the reduction of dust levels at existing operations through the proper installation and maintenance of suitable engineering dust controls; and (2) the advancement of dust control technology for today's and future longwalls that will enable all face personnel o work in an environment that is free of excessive levels of respirable coal mine dust. MSHA'S RESPIRABLE DUST CONTROL PROGRAM Since 1972, federal regulations have required each coal mine operator to continuously maintain the average concentration of respirable dust in the mine atmosphere during each shift in the active workings at or below 2.0 mg/m3 through the application of environmental dust control methods. The regulations provide for further reduction in the dust standard whenever the

Jan 1, 1993

By D. J. Hutchinson, S. Nickson

Cable bolts are used as a means of rock support around underground excavations in many mines across Canada and around the world. A substantial body of research on cable bolting was conducted at a number of Canadian universities and mines from the mid-1980s through the 1990s. Since then, research into selected areas of cable bolting practice has continued in Canada. The research has focussed on cable bolt instrumentation and on the inclusion of cable bolts in empirical stope design techniques. A review of cable bolting practice is now warranted at many mines. It has been five years since the completion of the previous substantial body of Canadian academic research and the associated advancement in understanding of cable bolt design, implementation and verification practice. Attempts were made at that time to transfer the new design procedures and performance assessment technologies to mine-site personnel. In some cases, this was effective, and ground control personnel continue to improve on their cable bolting practice at each specific mine site. However, at other sites, experienced people have moved on, and the new, less experienced personnel do not have access to the training or technical resources required to improve their understanding of the subject. In other cases, the technology was not transferred effectively to practitioners, with the result that substantial improvements can be made to the cable bolting practice at those mines. Guidelines for auditing cable bolting practice are provided in this paper. The guidelines include a discussion of the objectives of the audit, suggestions for audit procedure and a summary of the possible outcomes of a cable bolt audit. The objectives of an audit might include assessing the reasons for unexpected cable bolt failures, evaluating the quality of the installation procedures, quantifying the efficiency of the cable bolt system and assessing training requirements and procedures. A cable bolt audit should include consideration of all aspects of the cable bolting cycle, including the design, implementation and verification phases of the operation. At the end of the audit, a ranking should be assigned to the components of the cycle. The ranking system can then be used to identify items that require immediate attention, others that could be improved and others that are adequate. Following completion of a cable bolt audit, increased confidence in the support system and its application is generally, found, along with the potential for cost savings in many cases.

Jan 1, 2002

By W. M. Jr. Aubrey, R. L. Stone

INTRODUCTION Most metallic minerals and some industrial minerals have a relatively high specific gravity and most have at one time or another been concentrated by gravity methods. The principles of gravity concentration are straightforward, well documented and easy to understand, but in practice there are many pitfalls that await the engineer in the development of an integrated flowsheet. Gravity concentration equipment has a long history of use and there is a great diversity available. The equipment is capable of treating material over a broad size range, only falling off in efficiency in the very fine sizes. Gravity concentration is also inexpensive, generally free of environmental problems, and commercial equipment can process large tonnages of ore with a minimum of capital cost. As might be expected of an efficient and low cost process, the bulk of the tonnage quickly and inexpensively. Another obvious application is treating mineral deposits such as hematite and manganese ores that are sufficiently liberated after a minimum of crushing to allow production of a coarse concentrate that will meet market specifications. Except for hand picking and mechanical sorting, there is no competing process on coarse size material. Conversely, it is sometimes obvious that gravity concentration does not warrant consideration. Examples are ores that require very fine grinding to attain liberation, for ores where the minerals of interest have a gravity similar to the gangue, and ores that are strongly magnetic. Actually a mineral processing engineer may not know if gravity is the best way to concentrate an ore, but he should have little difficulty recognizing when gravity concentration deserves consideration based upon specific gravity differences and liberation gravity concentration has wide use. size. His challenge then is to At times its selection as the identify and test the applicable primary concentration process is processes, to develop a obvious. Low grade placer deposits metallurgical balance and flowsheet of tin, gold and beach sands usually for the best process, to estimate are only profitable because gravity production rate over the life of concentration is able to throw away the deposit and to make equipment

Jan 1, 1986

By A. C. T. Bigg

Heavy media separation is one of a number of ore-concentration techniques for coarse? feed which, when the ore is amenable, offers economic advantages in the mining stage and/or the processing stage. In mining, simpler and cheaper methods may be used if a greater proportion of waste material can be included in the mining blocks that can later be re-moved efficiently at a coarse size. In the mill, pre-concentration can mean considerable savings in capital and operating costs by down-scaling of equipment sizes particularly in the grinding section. Conversely, throughput may be increased using the equipment already in-stalled in the concentrator.

Jan 1, 1988

By Silver Miller, William A. Vogely, J. C. Emerick

After location and verification of exploitable mineral resources, mineral development re- quires capital goods, labor, and energy to extract the deposit. In addition, a growing social awareness of the need for a healthy environment re- quires inclusion of environmental burdens to the total costs incurred. This is because mineral development is detrimental to the environment in a number of ways. All mining .operations involve the separation of valuable minerals from the surrounding waste rock, which in turn re- quires permanent disposal of unwanted or un- used materials. Mine overburden, wastes, and tailings are often transferred to peripheral areas where they remain as unsightly features in the natural landscape. Some mine spoils contain harmful or contaminating substances as heavy metal salts or acid forming materials which subsequently are released to the environment. Many types of mining operations handle significant quantities of water during extraction or beneficiation processes. When discharged, the quality of such water often is unsuitable for residential, agricultural, or recreational use. Since mining activity disturbs the natural vegetation in the project area, water may be allowed to transport soil materials into streams, causing erosion and siltation. In particular, surface mining operations disturb the top layers of soils, resulting in losses of productivity for long periods of time. Excavation, transportation, and further processing of large volumes of both ores and waste materials generate substantial quantities of particulate and gaseous emissions, some of which contain metal dusts or compounds of sulfur. Such fugitive and point source emissions can be transported beyond the confines of mineral operations to cause annoyance and damage at more distant locations. Environmental degredation or pollution can be viewed as the alteration of the environment by man through the introduction of materials which represent potential or real hazards to hu- man health, disruption to living resources and ecological systems, impairment to structures or amenity, or interference with socially desired uses of the environment. The significance of environmental degradation is reflected in its effects on a range of receptors, including humans as well as the resources and ecological systems upon which we depend. Pollution also is judged in the social context of damage to environmental structures and amenities. The demand for restoration and maintenance of environmental quality presents the mineral industry with a challenge to successfully man- age discharges and returns to the environment in order to avoid undesirable and harmful consequences. AIR QUALITY Impacts of Mining and Beneficiation Operations Air quality generally is degraded by mining operations through the addition of dust or total suspended particulates (TSP), carbon monoxide (CO), sulfur dioxide (SO2), nitrogen oxides (NOx), and hydrocarbons (HC) to the atmos-

Jan 1, 1985

By C. E. Brechtel

Bench cut-and-fill stopes with heights between 85 and 105 ft are being excavated in the lower levels of the B-NEATH Zone. Estimates of pillar strength and pillar loading indicated a high probability of pillar failure. Some changes in mining practice were made to minimize impacts of pillar failure and a rock mechanics instrumentation program was employed to monitor stability during mining of the first stopes. Limited pillar failure, in the form of destressing, was observed in the initial stopes; however, global stability during mining was good. Instrumentation data indicated that predictions of pillar strength and stress were quite close to field results.

Jan 1, 1989

By David J. Starbuck

For small precious metals mining to show a comeback a different perspective must be taken than that of larger mining companies. This perspective must be much the same as that of past successful smaller mining enterprises such as when the US had a need for Uranium. Abandoned mines and environmental concerns in older mining districts have discouraged many from entering with the attitudes of why try there if so many unsuccessful mines exist. A small mining venture can be successful there but must have a "think smart'' attitude. There must be a thorough understanding of deposits, utilization of advanced technology and a properly managed mining operation. "THINK SMART" MINING The small mine operator is usually looking for small high grade deposits, consequently, long term success depends on a series of small successful mining operations. The small miner must succeed right-off or credibility and future project funding will suffer. No veteran of even a few years in the mining industry needs to be told that a dollar spent on production today fails to yield as much as it once did. More efficient equipment and techniques have helped soften the problem, but there is little likelihood that a mining company can do much to control inflation, wages, regulations, or grade. That leaves the small miner to "think smart" as one area where operating dollars can still be stretched to produce more than they presently do (Gardner. 1981). In the planning stage of a mining venture, when most options are still open, the main controllable elements are market timing, deposit selection, cutoff grade, mining method, mine design, mining sequence, rate of production build up, process design, project financing structure, project management, and project ownership structure. During planning, optimum criteria can be established for each of these. Once a mine is in production, these options are foreclosed or at least severely constrained. The more thought given to a mining program using all information available the less the risk of encountering disabling surprises. Thus the intent of this paper is to suggest the "think smart" attitude most small mine operations use for long term success. If one looks at a number of successful mining ventures, whether large or small, there is a general logic most have followed to be successful. They have used proven exploration, mining and processing techniques along with economic evaluation and experienced personnel to improve their odds. LOGIC IN DEVELOPING A FEASIBLE VENTURE Most successful small mine ventures achieve positive cash flow as quickly as possible by seeking out those deposits which require the least time and expense on activities leading up to production. To do this they look for deposits that are the most accessible, easily investigated, mined and processed with the cheapest fundamental methods. The general sequence of events starting with district selection are deposit selection, preliminary feasibility, exploration, detailed economic feasibility, mine planning, development and production. Each successive step becomes more costly requiring intermediate decisions along the way. District Selection Small operations should look for known deposits which favor the occurrence of the type deposit sought rather than efforts in unproductive areas. Known deposits in developed areas have some advantages over remote areas: 1. More alternative methods of transportation are available. 2. A larger stable work force is available. 3. The area is usually more pro-mining. 4. Power, water, housing, technical services, skilled services, schools, recreation and shopping are available.

Jan 1, 1987

By P. B. Queneau, J. E. Litz, T. P. McNulty

I. INTRODUCTION Modern hydrometallurgy has its roots in such notable successes as heap leaching for recovery of copper, cyanidation of gold ores, the Bayer process, the Oxland process for tungsten, electrorefining of copper, roast/ leach/electrowin process for zinc, and production of yellowcake from lowgrade uranium ores. Metallurgical testing techniques, sampling and analytical procedures, operating and maintenance practices, and improved methods and materials of construction which were pioneered in these processes have promoted the extension of hydrometallurgy into other applications. Periodically, new tools such as solvent extraction, resin ion exchange, and flocculants have opened new avenues to hydrometallurgists. Conversely, pursuit of more complex mineralization, the rising costs of energy and environmental quality preservation, and declining ore grades continue to create new challenges. For much of this century, it can be fairly said that practically any hydrometallurgical development moved the frontier of technology. The 1970's and 1980fs, however, have seen a significant maturing of hydrometallurgy's role in process metallurgy. Simplistically, this maturing seems to derive from a growing awareness of the strengths and weaknesses of hydrometallurgy and a determined effort to capitalize on the strengths. For example, many of us were among those revolutionaries of the 1960's and 1970's who taught that "chemical smelting" was the answer to the treatment of all sulfides. We now recognize, however, that only in very special cases can hydrometallurgy offer economic advantage over the generally less energy-intensive pyrometallurgical systems. The maturing of hydrometallurgy does not, however, signal stagnation. Important innovations are being studied and developed in most extractive areas, and a number are approaching or have achieved commercialization. From our company's perspective, that of an organization dealing with the development of the most economic solutions to metallurgical problems, innovation must be defined as the commercially successful reduction of an idea to practice. There appears to be no shortage of ideas, nor has there ever been a shortage. Many ideas now being implemented were conceived decades ago, but reduction to practice was foiled by the lack of such technology as responsive process control and economical materials of construction capable of withstanding highly corrosive or erosive environments. Commercialization of a new process is a particularly challenging undertaking. Even if technical risks are reduced to a minimum through careful and thoughtful process development, there are inevitable uncertainties in feed characteristics, variable costs, and product prices. Commercialization takes courage, both on the part of innovators who may be staking their careers or reputations and of investors who may face financial disaster in the event of project failure. This paper discusses innovative programs and recently commercialized processes which either have been discussed in the literature or disclosed to Hazen Research staff in private nonconfidential conversations with contacts in industry. Regarding this latter category of information, relative ease of communication has resulted in many of our observations being of North American origin.

Jan 1, 1985

By Keith G. Papke

Industrial-mineral mining started early in the history of the State when salt was extensively mined for use in processing gold and silver ores, and borates were produced to meet most of the world's needs. After this start, industrial-mineral production grew slowly until World War II, mostly because of the remoteness of the State and the small population. Nevada now has a large and varied industrial-mineral industry. In 1983, 14 principal commodities were produced from 48 deposits; the total value of these materials was 168 million dollars. Nevada ranks first in domestic production of barite and magnesite; second in diatomite, gem stones, and lithium; third in fluorspar; and sixth in gypsum. Other materials produced are carbonate rocks, cement, clays, decorative and crushed stone, light- weight aggregate, perlite, pyritic soil additive, salt, sand and gravel, and silica. From 1978 through 1982 barite was the most important commodity; in 1983 diatomite surpassed barite in value of production. Most of the Nevada production consists of high-value commodities that are consumed out of the State. Approximately 430 significant deposits with 20 principal commodities are present in Nevada. This abundance can be attributed to the numerous and diverse geologic processes that have been operative. Seven major modes of origin have been identified: hydrothermal activity, sedimentation, combined hydrothermal activity-sedimentation, evaporative precipitation, brine formation, extrusion of igneous rocks, and alteration by ground water. The hydrothermal type accounted for 39 percent of the deposits, the combined hydrothermal-sedimentary type for 28 percent, and the sedimentary type for 13 percent. Nevada diatomite production is about 200,000 short tons/year valued at 30 million dollars. In 1984 three companies operated in Nevada producing diatomite from six open pits and processing it at four plants - one plant producing filter-grade materials and the others adsorbents and fillers. The diatomite occurs in about 60 areas, almost all in the western one-third of the State. The diatomites were deposited in long-lasting, fresh-water lakes in topographically closed valleys formed by basin-and-range faulting. About 85 percent of the barite mined in the United States is produced in Nevada. In 1981 the high point of production,-2.5 million short tons of bedded barite was produced from about 30 open-pit mines. About 120 significant bedded-barite deposits are known in Nevada; 38 of these have had past production of more than 25,000 short tons. The deposits are associated with marine siliceous rocks of Cambrian through Devonian age and occur in a zone about 300 miles long and 60 miles wide. Abundant evidence supports the theory that the bedded barite is of exhalative sedimentary origin.

Jan 1, 1987

By Howard M. Wells

Investment in minerals development usually entails big financial outlays. which will remain at risk for a long time before the venture can begin to generate a return cash flow. Before 'committing himself to such a venture the investor would be wise to carefully examine the possible consequences of his exposure to risk. In this context risk is defined in multiple terms, which relate the magnitude of possible loss with the probability that such loss may occur--normally the probability will decrease as the amount of possible loss increases. The analysis of risk is an essential component of the decision making process, especially so in the case of low grade high tonnage mining ventures where a very real possibility exists that future unfavorable circumstances may lead to losses that could cripple or ruin even the richest corporation. Wells (1979) postulates a rationale for making the investment decision under uncertainty based on the comparison of two independent risk criteria: 1) the risk inherent in the venture represented by the negative portion of the cumulative distribution of the net present value (NPV), as derived by a stochastic evaluation procedure, 2) the limits of risk the decision maker is willing to accept, taking account of the financial capacity-of the 'firm to absorb various levels of future cash shortfall should the venture prove disappointing. The chance the investor would be prepared to accept can be expected to decrease as the amount of the possible shortfall increases. The limits of acceptable risk are-defined by a curve called the "LL-curve" which can be directly compared with the cumu¬lative NPV curve. A positive investment decision is implied if the limits of acceptable risk are not exceeded.

Jan 1, 1982

By Earle J. Klohn

INTRODUCTION The paper presents a broad overview of the geotechnical site studies required for siting uranium tailings dams. These studies, which are interdisciplinary in nature, touch upon such related fields as: hydrogeology, hydrology, and seismicity. Tailings dams are commonly used to develop tailings ponds for the storage of the waste products generated by mine milling operations. In the past, most tailings ponds have been developed either above ground on dry land, or in existing lakes. In the United States a majority of the uranium mines are located in arid or semi-arid regions and past practice has been to store the wastes above ground on dry land (1,2). Currently, the United States Nuclear Regulatory Commission (N.R.C.) recommends below ground disposal of uranium waste products, although they indicate that they will consider above ground alternatives (3). In Canada many of the existing uranium mines are located in a wet environment and past practice has been to use small lakes and depressions as tailings ponds (1,4). However, current practice in Canada leans towards above ground, dry-land storage (5,6,7), and the Atomic Energy Control Board (AECB) guidelines (5) indicate this to be the preferable method. In B.C., where a moratorium on uranium mining has been declared by the Provincial Government, there are no existing uranium tailings ponds. However, both the formerly proposed Birch Island and Blizzard uranium developments would have used dry land storage. Most of the existing non-uranium mill wastes in B.C. are stored behind tailings dams on dry land. The waste products delivered to the tailings pond comprise, the ground-up rock that remains after most of the uranium values have been removed and the excess chemicals used in the milling process. These waste products, which are called "tailings", are normally mixed with water to produce a slurry and then pumped to the tailings pond. Since the uranium recovered constitutes only a small percentage of the ore (usually less than 1%) (8), large quantities of waste rock and associated transportation water are discharged into the tailings impoundment area. Consequently, relatively large tailings pond areas are required for the uranium tailings. In recent years, major advances have been made in the design, construction, and operation of non-uranium tailings storage facilities (9,10,11,12,13,14, 15). These improvements have been based on combining the latest advances

Jan 1, 1980

By J. L. Chakravatti

INTRODUCTION Mining of uranium does not differ, in many respects, from the mining of other metals; the ore must be drilled, blasted and transported in an underground or surface mine. Underground mining proceeds by the continuous development and advancement of a network of passages and rooms or stopes from which ore is excavated. As in most mines, rock conditions and ore grades in uranium deposits vary from area to area and between different mines. For mineral benefications of this ore in the mills, use is made of various chemicals, often with toxic or hazardous properties.1 As well as the need to control the more conventional hazards associated with any mining and milling operation, special care needs to be exercised in the mining and milling of uranium because of the radioactive nature of the ore. This requires that we examine closely the radiation hazard areas encountered in the mining and milling of uranium, with the broad overview of some of the basic facts in the radiation hazard control programme. To place the hazard in its proper perspective, we require recognition, evaluation and control of those factors arising in and from the workplace which may cause sickness, impaired health and affect the well being among workers or citizens of the community. The radiation environment in uranium mine is complex and variable. Although uranium ore is only mildly radioactive, it naturally contains a complex mixture of radioactive isotopes. Workers are exposed to external gamma radiation, to some beta radiation and to airborne radon, radon daughters and ore dust. All of these types of exposures warrant considerations in formulating control procedures but, in general, radon daughters are known to present the dominant risk. The basis of dose limitation in radiological protection is risk limitation. Long-term epidemiologic studies of United States uranium miners and that of miners in Czechoslovakia indicate that the incidence of lung cancer can be accounted for by a linear relationship with exposure to radon decay products.2 On the basis of this proportional exposure-risk relationship, a risk coefficient for lung cancer in the range of 1-5.10-4 WLM-1 during the total lifetime, has been estimated by UNSCEAR3 and other researchers. It should be noted that this risk coefficient includes the excess lung cancer risk from external gamma radiation in mines and from other carcinogenic chemical effects, if any, to which the miners are normally exposed during their underground work. It also takes into regard the possible synergistic influences. This paper reviews the occurrence of radiation and its control factors and the development of engineering design features for the environmental control at Denison Mine. NATURAL URANIUM SERIES Uranium is the most common element in the Earth's crust. It is widely distributed in nature in all rocks and is readily measurable in the sea. Hence, radon gas is universally produced in every part of the globe. Mining is patently confined to ores containing more than half a kilogram, or so, per tonne of uranium unless it is combined with other marketable metals. Uranium-238 is the first element in the uranium series. In all, there are 13 radioactive decay products of 238U (Fig. 1), ending up as a stable isotope of Lead-206. The whole basis of the radiological hazards associated with the mining and milling of uranium is dependent on the behaviour of these isotopes during each phase of the process.

Jan 1, 1981

By J. A. Herbst, L. B. Hales, R. Zaragoza

INTRODUCTION The Control Problem The need for automatic control in flotation plants stems from frequent and randomly occurring disturbances to the feed slurry. Typical disturbances occur in the solids feedrate, the slurry percent sol ids, and the mineralogy and flotability of the gangue and valuable minerals. In plants where semi -autogenous grinding mills (SAG) are used, feedrate changes are very large and changes in feed percent solids of 1m or more are common. Mineralogy changes between valuable minerals are common, as are changes in the host gangue rock. As these changes occur, the operator can attempt to compensate for them by making adjustments to the flotation cell levels, the dosage rates of the collectors and frothers, the pH, and in some cases the aeration rate of the cells. This problem is sometimes complicated by the fact that different sections of the flotation plant will be processing different ore types at the same time. Potential Savings with Control Flotation control brings about savings or plant improvements in two areas; the first is in improved metallurgy and the second is in reagent savings. Improved metallurgy includes increases in the average plant recovery and achieves target concentrate grade level s more consistently. Average recovery increases between 1.0 and 5.0 percentage points have been widely reported (Paakkinen, 1979; Sutherland, 1984). Reagent savings of up to 40 percent have also been reported (Hales, 1985). VARIABLES OF IMPORTANCE Control led, Manipulated, and Disturbance Variables The initial step in the analysis of the flotation control problem is identification of important variables which can affect the efficiency of separation. The efficiency of separation is represented by a group of controlled variables which can quantify the performance of a flotation circuit. This group includes variables such as grade, recovery, tonnage through- put, and circulating loads. The efficiency of separation of a flotation circuit may generally be defined by a grade recovery map, where each point on this map re- presents a set of operating conditions (see Figure 1). However, the combination of operating conditions must be set to operate close to the economic optimum. The group of operating variables which are changed in order to achieve desired circuit performance are called manipulated variables and can be classified into two

Jan 1, 1986

By J. Drelick

Among the wide variety of modern surface chemistry analytical techniques, contact angle measurements still remain attractive for wetting characterization of solid surfaces. The captive-bubble and sessile-drop techniques are the most popular methods for the examination of flotation systems. Systematic measurements of advancing and receding contact angles for several three-phase systems using the captive-bubble and sessile-drop techniques show that the contact angle measurements depend on the technique used and may differ significantly for some heterogeneous and rough solid surfaces. Importantly, it was found that these discrepancies in contact angle measurements depend on the bubble (drop) size. Contact angles as measured with the static captive-bubble technique are compared with those measured with the dynamic captive-bubble technique, in which the capture of a bubble at the solid surface results after buoyant transport and attachment The dynamic captive-bubble technique allows for the formation of much smaller bubbles than is possible with the static placement technique in which a bubble is placed at the solid surface with a microsyringe. Although this dynamic technique cannot be recommended for the systematic wetting characterization of solid surfaces, its significant advantage is the ability to examine the contact angle/bubble size relationship over a wide range of bubble sizes, from several micrometers to several millimeters in diameter.

Jan 1, 1995

By Joseph T. Duncan, Syd Peng, Larry G. Stolarczyk

The mining business has numerous risks: equipment availability, labor disruptions, foreign exchange rate, etc., but one of the more important risks is assessing the geology. Improving the “intelligence” of geology can and will have significant positive effect on reducing mining risk and thus enhancing operational and financial performance. The use of the advanced Radio Imaging Method (RIM-IV) on coal seams and ore bodies can create useful two-dimensional (2-D) and three-dimensional (3-D) high-resolution images that provide mining engineers with additional intelligence to better plan and improve operations. Improved operational performance will reduce costs and enable mining companies to meet market and financial commitments. For the past decade the underground coal mining industry has been moving toward “super panels” in long-wall mining, and “super sections” for room-and-pillar mining. These mining conventions employ wider faces, longer gate roads, greater room-and-pillar density, and an increased scale in the amount and complexity of mining equipment. An obvious economy of scale exists: amortization of setup investments over greater volume of coal enables mine management to reduce fixed cost per ton. Restricted by equipment considerations, face widths have currently reached about 1,100 ft. Wider longwall panels are planned, with 1,400-ft widths, but this requires an incremental step in hardware that the original equipment manufacturers will soon bring to market. However, longwall panel length has not yet reached its limits, with some panels planned up to 25,000 ft. While longwall panel length is generally dictated by reserve size and extent, practical restrictions in mine planning also include seam thickness, ventilation requirements, or restrictions involving methane drainage. Super panels have certainly enabled the industry to keep pushing the limits of productivity improvement. However, important considerations in mine planning, now and especially in the future, will be driven in large part by geological factors. While larger developments improve productivity and capture economies of scale, the fact that super panels can contain at least four times the area or coal volume means that the probability of encountering serious anomalies is at least four times greater than with the “conventional” panels. Given the increased probability of encountering anomalies, improved assessment of geology is important for super panels and super sections. Proper due diligence requires a thorough and competent evaluation of a mining property and its ore reserve. Using improved geostatistical techniques is most important, and improving the base data for the analysis is equally important. The old cliché “garbage in, garbage out” certainly applies. Also, the quality of coal reserves is (or has been) declining, so, in the future, mining will be in deeper and most likely thinner seams—and these seams appear to contain greater anomalies that threaten efficient operations. To counter the impact of reserve deterioration, the industry is moving toward greater use of geophysical tools and services. Fortunately, tools such as the Radio Imaging Method™ (RIM-IV) system have been improved and can provide the industry with enhanced 2-D and 3-D images of coal seams and ore bodies. To identify and profile the best areas of a coal reserve, geologists, engineers, and mine managers need greater intelligence in the form of RIM-IV tomographic maps of longwall panels and room-and-pillar sections. These images have enhanced the understanding of in-seam features, which in turn has improved operational plans and performance.

Jan 1, 2005

By Larry Powell

Rend Lake is an Army Corps of Engineers reservoir located in Franklin and Jefferson Counties in south-central Illinois. The lake consists of 20,000 acres of water and 19,000 acres of public access land. The site attracts over two million visitors a year and is surrounded by campgrounds and other recreational facilities. The lake overlies the largest tonnage of low sulfur coal in the state. Coal is being removed beneath the lake from five mines operated by three coal companies. Currently high extraction mining operations are approaching low-lying, environmentally sensitive, and high-use recreational areas. Advanced planning to maximize coal extraction and minimize potential effects of subsidence requires the development of procedures to assess the impact of high-extraction mining on the land use of the area. The Bureau of Mines, the Corps of Engineers, and the coal companies have initiated research to assess the following proposed planning steps to ensure the maximum recovery of the coal resources while minimizing impacts to surface land use: 1) Establish a dialogue between the surface and mineral owners; 2) develop a geographic information system to aid in assessing existing land use and potential changes; 3) assess the potential effects of subsidence on drainage, wildlife habitats, and changes in land use prior to mining; 4) coordinate the mining displacements with surface activities to minimize disruption; and 5) develop appropriate mitigation plans before mining occurs.

Jan 1, 1986

By John G. Myers, William A. Vogely, Harold J. Barnett

INTRODUCTION, CONCEPTS, AND MEASUREMENT Introduction Periods in the history of man, from his earliest appearance to the present, are often characterized by the principal materials used. In nearly all cases, the material or fuel is of mineral origin-stone, copper, bronze, iron, coal, and so forth-indicating the principal ingredient of the tools or source of power of the period. Each of these periods represented great improvement over the preceding one in terms of human well-being, as measured by population growth and other indicators (Cipolla, 1978). A major reason for the improvements in production and well-being was the nature of the material or fuel, each successively superior to the preceding, which made it possible to produce more food, fuel, shelter, and clothing with a given amount of labor. If we accept this well-documented description of economic progress as accurate, we may then turn to the consideration of two related questions concerning this development. The first, easily answered,-is why man spent long periods of time (millenia, in many cases) making tools from inferior materials, such as copper, instead of passing directly to superior materials, such as iron and steel. The second, closely related question, concerns the relation between the rate of economic growth and the quantity of mineral reserves available at any time. For the first question, the answer is that the technology required to discover, extract, and process each successive material had to be discovered and developed before the material could be used. Once the technology was available, the new material could be and was exploited widely, raising productivity-output per unit of labor- and consequent consumption per person. This familiar idea underlies a fundamental principle of the economics of resources, namely, at any time, available resources depend upon available technology. No mineral or other raw material is a resource unless the technology has been developed to utilize it. But once the technology is at hand, the new resources associated with it provide the means for economic growth and rising levels of living. This principle is subject to certain conditions. For example, governments or other institutions may prevent a mineral from being used, even though the technology is available. And, if a mineral is located in a remote place, transportation charges may make it uneconomic to exploit. Such minor qualifications do not, however, change the thrust of the argument that technology is the overriding determinant. With respect to the second question, it might seem apparent that the greater the quantity of reserves available, up to some point, the more economic growth will be facilitated. This line of reasoning leads to the conclusion that as re- serves are consumed the quantity available will be reduced and economic growth will eventually be restrained. Reasoning of this sort underlies much popular (and scholarly) thought, in which depletion of mineral and other resources is assumed to lead to constraints on economic growth, through higher materials costs and absolute limitations on materials use. Two important qualifications must be made to this explanation, however, which together

Jan 1, 1985