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By William A. Vogely, Lawrence J. MacDonnell

This section begins with an introduction to several key environmental laws. This is followed by a discussion of some of the issues raised by such environmental regulation. Finally the subject of regulatory reform is addressed. Overview of Selected Major Environmental Laws The number, type and complexity of environmental laws and regulations affecting mineral resources development have grown at an astonishing rate since the 1960s. The most significant laws and regulations are those addressing the use of the public lands; those concerned with air quality, water quality, and surface reclamation; and those defining government responsibility for its actions having important environmental consequences. The laws and regulations governing activities on the public lands will be taken up in the section 5.15C, "Minerals and Land Management." In this section we will concentrate on five primary laws: the Clean Air Act, the Clean Water Act, the Surface Mining Control and Reclamation Act, the Endangered Species Act, and the National Environmental Policy Act. The Clean Air Act: The legislative and regulatory framework for controlling air pollution has developed in a series of steps. Most important for present purposes are the Clean Air Act of 1970 (P.L. 9 1-604) and the 1977 Amendments (P.L. 95-95). The rather complex air quality control scheme includes four key elements-national ambient air quality standards, state implementation plans, the prevention of significant deterioration program, and the non- attainment program. National Air Quality Standards. The 1970 Clean Air Act is a landmark law because it contains the first explicit recognition that pollution is a nationwide problem requiring a national control program. The federal government through the Environmental Protection Agency (EPA) was to establish national air quality standards for at least the six pollutants named in the Act (sulfur dioxide, carbon monoxide, total suspended particulates, photochemical oxidants, hydrocarbons, and nitrogen dioxide). These standards were to be established so as to protect public health, "allowing an adequate margin of safety." The cost of achieving these standards is not to be considered. The 1970 Act unrealistically required that these standards be achieved in all areas of the country by 1975. As the program has developed, the air quality control regions are now to be designated as "attainment" or "nonattainment" with respect to each of the national standards. State Implementation Plans. Under the Act the states are given the primary role in achieving the ambient standards. States are to develop and implement control plans governing emissions from all existing and new sources. These plans can include emission limitations for existing stationary sources, transportation control plans to reduce emissions from mobile sources, and pre- construction review of new stationary sources to assure compliance with new source performance standards. The EPA must approve all state implementation plans. Sanctions are given to the EPA to be applied if states fail to submit acceptable

Jan 1, 1985

By A. J. Lynch, M. J. Lees

Introduction The design of wet grinding circuits may vary considerably according to the duty which is to be performed. Grinding machines which are commonly used in these circuits are rod mills, ball mills, autoge¬nous mills, and pebble mills while size separation machines commonly used are vibrating and wedge-wire screens, hydrocyclones, and rake classifiers. In some circuits, such as those producing feed to cement kilns, all the ore entering the circuit is discharged in a single product stream. In others, such as those operating on magnetite-taconite ores, the feed entering the circuit leaves in two or more streams. Grinding circuits in flotation plants normally include sections in which either the concentrate or the tailings from the primary flotation circuit is reground and these additional sections should be regarded as an inte¬gral part of the grinding circuit. A typical circuit is shown in Fig. 18. Problems in achieving maximum efficiency may occur at three stages: 1) At the design stage when the optimum size reduction flow¬sheet must be selected with respect to the types, numbers, and sizes of processing units. 2) At the operating stage when the correct selection of values must be made for those variables which may be altered while the circuit is off-line but which are constant while the circuit is on-line, for instance the vortex finder diameter of the cyclones. 3) Under conditions of continuous operation when changes in the circuit feed or in the mechanical operation of the circuit may cause undesirable changes in the circuit product. The first two prob¬lems are concerned with optimization, that is, with making the best choice from many possibilities, and the last with control. Optimization Problems. The main purpose of a wet grinding circuit is to produce particles with a sizing distribution which will ensure optimum performance of the later chemical reaction or physical concentration circuits, because it is on the efficiency of these later circuits that the economics of the total mineral treatment process depend. The size distribution of the product from a grinding circuit may be affected by many variables, some concerned with the arrange¬ment and operation of the machines and some concerned with the ore characteristics, and it is important that these should be recognized in the design and operation of the circuit. For instance, in a simple ball mill-cyclone circuit the variables which affect the product size even for constant feed characteristics are shown in Fig. 19. In addition, the rate, size, hardness, and mineralogical composition of the feed will affect the performance of the circuit and the product size. When the circuit contains more than one mill, both the number of choices available and the complexity of the problem are increased consider¬ably. Consequently, one type of problem which is to be solved if an optimum product is to be obtained from an existing grinding circuit is that of circuit design, and this includes arrangement of processing units and selection of those operating conditions which cannot be altered when the circuit is operating, such as mill speed and cyclone inlet and outlet dimensions. The other major problem in optimization is encountered at the design stage when a choice must be made about the type, number, and size of processing units. For instance, for a typical high-capacity size reduction operation, should two circuits each containing one rod mill and two ball mills or three circuits each containing one rod mill and one ball mill be used? Alternatively, should ball mills only be used and if so, how many, what size, and what arrangement?

Jan 1, 1985

This paper presents a method for evaluating the economic feasibility of solution mining a hypothetical uranium roll-front deposit. It is assumed the wellfield will be operated in a prudent manner and that leaching tests were performed in depth in both lab and field (push-pull) prior to startup. Leach test results are reduced to two important parameters and used as the basis for solution mining a wellfield. This case study assumes a 10 mil- lion-lb uranium deposit with 40 possible small wellfields; four are kept in operation simultaneously until the deposit is depleted. The wellfields have different ore reserves and grades, lixiviant circulation rates, leach rates, and peak concentrations, and thus the daily uranium production will vary. Daily production is used to assess the profitability of a particular lixiviant and the mode of well- field operation in light of realistic market price estimates. The mathematical procedure is simple and straightforward, based on reasonable in-situ leaching relationships as well as accepted accounting practices.

Jan 1, 1985

By L. B. Phelps

Many coal mining companies have potential surface mine reserves which either are known or suspected to have had prior drift mining activity on them. In many cases, there is no documentation on these mines or at best, very fragmented records. These undocumented abandoned underground mines are creating engineering, financial, and environmental difficulties and concerns for both surface coal mine operators and regulatory personnel. This paper examines the use of resistivity techniques in detecting entries of abandoned drift coal mines. The detection of such a drift mine entry would confirm the presence and orientation of an abandoned underground coal mine.

Jan 1, 1985

By William C. Beebe, Russell E. Martin

An account of driving and concreting two 900 m railroad tunnels for the Denver and Rio Grande Western Railroad under emergency conditions. Details the importance of on-site decision making by the Owner in completing the project successfully in record time. A general description of the geology and construction methods. The Thistle Drainage Tunnel drained water impounded behind the Thistle slide and serves as permanent diversion of the Spanish Fork River and Thistle Creek around the slide area. The project involved 684 meters of 5 m horseshoe tunnel, a 5 m diameter raised shaft and 23,000 cm of cut excavation.

Jan 1, 1985

By Jerome C. Neyer

Within most of Canada and the northern third of the United States, the soils overlying bedrock are of glacial origin. Tunnelling in glacial soils presents numerous challenges to the contractor, including abrupt changes in soil type, boulders and glacial erratics, water bearing fine sands and silts, toxic or explosive gases, and glacial till. This paper examines the available techniques for geotechnical exploration in glacial soils; the relationship between subsurface conditions predicted by various techniques and conditions actually encountered during tunnel construction; and potential improvements in the planning and implementation of geotechnical explorations. Case histories of geotechnical exploration and tunnel construction in glacial soils are also reviewed.

Jan 1, 1985

By C. D. Harrison

This paper presents the results of 18 high-G centrifuge tests performed at the Electric Power Research Institute's Coal Cleaning Test Facility in January 1985. These tests, using -28 mesh (0.6mm) froth flotation product, show that the high-G, solid-bowl centrifuge can produce clean-coal moistures of less than 12 percent at solids recovery rates exceeding 98 percent. The high-G centrifuge achieved these low moistures by applying centrifugal forces up to 2,000 times gravity. Because these forces are two to three times the forces used in a screen-bowl centrifuge, the high-G centrifuge can use a solid bowl and still produce a low-moisture product. The solid bowl captures ultrafines that would pass through a screen bowl, and thus obtains higher recovery rates than a screen-bowl centrifuge.

Jan 1, 1985

By John Cline

The economic value of calcium carbonate when used as an extender or filler basically falls into two categories: 1. Lessening the cost of the final product to which it is added. 2. Contributing desirable physicals to the final product. In most instances, a combination of these two may be achieved. The mineral limestone which is found in abundant quantities in many areas of the world is the source of 99% (+) of the calcium carbonate used as fillers and extenders. Precipitated, or chemically formed, calcium carbonate is also available, but by comparison, in very limited quantities.

Jan 1, 1985

By W. C. Dailey

The National Steel Pellet Company is owned by National Steel Corporation, managed by the M. A. Hanna Company and located near the town of Keewatin in northern Minnesota. Annually, the concentrator processes 15.24-Mt (15.0 million It) crude taconite with eight 8.2-m diameter by 5.5-m long (27 ft x 18 ft) wet semi-autogenous (SAG) mills to produce 4.57-Mt (4.50 million It) of iron ore pellets. To improve operating costs and primary mill grinding circuit efficiencies, a task force on liners was formed with the operation, maintenance and engineering staff at N.S.P.C. along with the local supplier of mill liners. Results of the task force recommendations since 1980 along with improvements made in the primary circuit operations, are presented. Mill Liner Design and Metallurgy Changes The primary mill liner task force was formed in 1977. Its function was to improve the operating costs and milling efficiencies of the ten 8.2-m x 5.5-m (27 ft x 18 ft) wet SAG mills that were operating at the time. The SAG mills are driven by two 3500 HP motors drawing a total of 5450 kW at 76% of critical speed.

Jan 1, 1985

By C. E. Jordan

The fundamental properties of the Bureau of Mines patented dielectric separator were studied to provide insight regarding its design and operating characteristics. Force equations for mineral particles were derived and evaluated experimentally. High dielectric mineral recovery was proportional to the calculated effective dielectric force volume that surrounded each drum electrode wire. Electrode spacing was the most sensitive design parameter, requiring less than 0.4-cm electrode spacing for a good separation. Operating characteristics and ore characteristics were investigated. With a dielectric constant difference as small as 2, good separations were made on a laboratory scale at energy consumption below 12 kw?h/mt.

Jan 1, 1985

By J. C. Agarwal

Major scientific discoveries cannot be programmed. New or frontier technology, however, can and should be planned. It is the vital force underlying the business strategy of a vigorous and profitable mining and metals company. Generally, a radical departure from existing technology is required to 1) Enhance the competitive value of ore reserves, i.e., to turn low grade or marginal reserves into competitive reserves. 2) To increase yield and decrease costs. 3) To decrease investment. 4) To increase mine life. 5) To improve product quality to meet market demands. The very definition of frontier technology implies that it is so different that the old plant, if already in use, will not be directly suitable to use the new technology. Therefore, a priori, we know that the commercialization of frontier technology would very likely involve new investment. The recommended technique of economic and technical analyses, I propose to call "Success Analysis.'' Simply stated, it forces us, by step- by-step procedure, to ask "what is needed to succeed in this particular project." Therefore, the first step is to identify what is meant by "success." The definition of "success" requires an agreement with top management or sponsors of the project as to what constitutes "success" in their minds as contrast to the technical people perception of "success." In general, top management would define success as meeting: 1) The technical objectives, i.e., technology being developed would produce the desired product at the acceptable quality. 2) Financial objectives, i.e., when commercialized, the project's capital cost, operating costs and return on investment are better than the projects they would normally fund. The return has to be better because new technology is inherently riskier. 3) Marketing objectives in that the project will produce product of acceptable quality in timely manner, i.e., scale-up to commercial plant would not cause undue delays in start-up and that large fix-up expenditure would not be required to protect the projected return on the investment. Many projects are started in the laboratory to develop "Frontier Technology" in mineral processing. Most of these efforts are never commercialized. There are many causes of these failures. The major causes are listed below: 1) Inadequate communication with the sponsors of the project so that project objectives are defined and agreed to by all. 2) Ill-defined technical problems. 3) Incomplete development of technology. This has two major components: a. Incorrect scale-up and engineering. b. Inadequate start-up and maintenance planning. 4) Incomplete and over-optimistic process economics. 5) Lack of understanding of the future behavior of the marketplace. 6) Failure to complete R&D effort by the time it is needed. 7) Incorrect projections of human resources required; that is, technical, managerial and operating. 8) Lack of realistic forecast of the expenditures required for commercialization of the R&D effort. These pitfalls can be avoided by comprehensive planning and the use of success analysis technique. The major elements in "Success Analysis" are: 1) Identification of the "need" for new technology. 2) Unbiased and complete scale-up engineering. 3) Acceptable economic feasibility with enough margin of error in the sale prices and operating costs to justify the inherent risks in frontier technology. 4) Timing for availability of investment capital and markets. Many failures in the development of frontier technology are preordained because the initial selection of the research project has been without adequate attention to the needs of the industry. Many very innovative hydrometallurgical processes for recovery of copper from concentrates were developed in the past twenty years. They have not adapted except to a very minor extent because they did not satisfy the success analysis criteria. The copper industry in North America needed a process to compete against high grade ores and to avoid

Jan 1, 1985

By K. H. E. Kroemer

Selecting persons who are unlikely to suffer an overexertion injury is one of three methods to reduce the risk of musculo-skeletal disorders in manual material handling. This paper describes the underlying models, methods, and techniques for such personnel selection. In particular, it describes the isoinertial LIFTEST in which persons actually lift weights to assess their capability for doing so on the job.

Jan 1, 1985

By Corale L. Brierley

The depressed economic condition resulting from normal cyclic behavior, a more fundamental structural alteration, or both, is a mandate for change within the mining industry. Although several strategies for change have been proposed, the option of applying high technology processes to this smokestack industry offers the greatest opportunity for regaining global competitiveness and a new vitality. Research and development to secure new technologies require a corporate commitment for substantive change, a tech¬nologically enlightened management, a well¬funded and stable science and engineering effort, and a dedicated and motivated technical team--features in short supply in the mining industry today. However, an alternative to in-house development of frontier technologies is available to this beleagured industry through entrepreneurial, high-tech companies. These entities, with their dedicated focus toward product development, motivated and streamlined teams, high productivity and efficiency, and low costs offer a unique opportunity for large corporations to obtain high-tech products and services. These commodities are available through traditional commercial channels and an array of creative business arrangements. The latter offers notable benefits to large companies including windows on frontier technologies and mitigation of risk. Likewise, entrepreneurial companies profit through manufacturing and marketing relationships and an expanded financial base.

Jan 1, 1985

By J. Korak

Belt conveyor systems, long the standard transportation technique in soft-rock open-pit applications, are encountering growing interest in the hard-rock open-pit sector as economic factors force companies to seek an alternative to costly truck haulage. A general review of mine conveyor systems is followed by detailed analysis of the mobile and semi-mobile in-pit crushing plant essential to successful use of mine conveyors. A final section presents case studies of three crusher-conveyor systems handling overburden, copper ore and granite.

Jan 1, 1985

By M. E. Gershon

Conventional methods of drill hole site selection are reviewed briefly. Two approaches using geostatistics are then discussed, both of which have been shown to yield improved results. Finally, a branch and bound algorithm is described which will select the best locations for drilling from a user specified number of possible drill sites. Two options are discussed. First, the user can specify a maximum drilling investment or a maximum number of drill holes and the program will select the locations yielding the minimum estimation variance. This amounts to getting the most for a given investment. Alternatively, a maximum tolerable estimation variance can be specified and the program will select the number and location of the drill holes to obtain the desired information at a minimum cost. Another benefit of the approach is the quantification of the tradeoffs between investment and information obtained.

Jan 1, 1985

By G. W. Riley, D. E. Pickett

HINDERED SETTLING CONCENTRATION In the free settling of mineral particles in a liquid, the falling particles are at a distance from each other so that no particle is affected by its neighbor. In hindered settling, the concentration of particles is sufficiently high so that each particle is affected by its proximity to other particles in the suspension. Richards and Locke86 have described the hindered settling phenomenon as the condition “.. where particles of mixed sizes, shapes and densities in a crowded mass, yet free to move along themselves, are sorted in a rising current of water, the velocity of which is much less than the free-falling velocity of the particles but yet fast enough so the particles are in motion." This is the condition normally encountered in mineral con¬centration processes. The well known Newton equation for free settling of coarse (ap proximately +10-mesh, 1/16-in. or -- 2000-µm) spherical particles is:87 where v," is free settling velocity, cm/sec; p' is density of the fluid; p is density of the particle, g/cm3; d is particle diameter, cm; g is acceleration due to gravity, cm/sec2; and Q is coefficient of resistance, dimensionless, ~0.4. For the settling of fine spheres in water (approximately 150 mesh or 100 µm) the equation of Stokes pertains:87 where µ is viscosity of the fluid in poises and the other symbols have the same meaning as those in Eq. 1. For particles whose size lies between about 10 mesh (--2000 µm) and 150 mesh (100 µm), their settling velocity can be determined from experimental data. These data are available in convenient form in the text by Taggart88 based on the original work of Richards. Alternatively, a Reynolds number-coefficient of resistance plot may be used to determine the settling rate of such particles.87 The settling rate of spherical particles under hindered settling conditions can also be calculated from Eqs. I and 2 by replacing p', the density of the fluid, by p" the apparent density of the suspen¬sion. The concentration of particles in the fluid thus imparts an appar¬ent density to the composite fluid or suspension greater than that of the liquid alone, resulting in a buoyant effect on the larger particles. Particle shape affects the settling rate of both coarse and fine particles. The general effect is to reduce their settling velocities and the effect is greater for coarse particles and for those settling under hindered settling conditions than for fine particles or free settling ones. For two particles of differing densities but settling at the same velocity under Newtonian conditions, the ratio of their diameters from Eq. 1, called the free settling ratio is: where L signifies the lighter particle and H, the heavier particle. Under Stokesian conditions the exponent would be 0.5. For hindered settling conditions the fluid density p' is replaced by the apparent density of the suspension, p", to obtain a generalized equation for the hindered settling ratio: assuming both particles settle in approximately the same regime. The free settling ratio as given by Eq. 3 has been called by Taggart88 the "concentration criterion" and is used to predict the effectiveness of any gravity concentration process (see Introduction to this section). Based on Eqs. 3 and 4, if two particles of densities pH and p,, settle at the same velocity, the diameter of the lighter particle will be larger than that of the heavier particle. For example, in the case of galena (pH = 7.5) and quartz (pL = 2.65) settling in water (p =1.0) under free settling, Newtonian conditions 3.9. Thus, a quartz particle nearly four times as large as a galena particle will settle at the same velocity. Any quartz particle just slightly less than four times the diameter of the largest galena particle may be separated from it. Under hindered settling, Newtonian condi¬tions in a suspension where p" = 1.65, dL/dH = 5.85 or any quartz particle just slightly less than about six times the largest galena particle may be separated from it. Reference to Eq. 4 indicates that a superior separation between two minerals of differing densities is favored by: (1) coarse particles settling under Newtonian conditions, (2) a large difference in (pa - PL), and (3) separation under hindered settling conditions where p" is high. Of course, there are practical limits to increasing p" excessively because at very high percent solids suspen¬sion fluidity would be lost and the hindered settling separation process defeated. Examples of hindered settling separators are the Dorrco-Fahren¬wald sizer,89 the Rheolaveur box 90 the Spitzkasten,89 and the Willoughby washer.91 These devices make a mineral separation on the basis of both specific gravity and size and all of them are essentially obsolete except for the Dorrco-Fahrenwald sizer and similar devices which still find application for the removal of coarse particles from a much finer particle assemblage and for preconcentration ahead of shaking tables. However, nearly all gravity concentration processes (jigs, tables, flowing film concentrators, heavy media separators) and many sizing devices (sizing classifiers, clarifiers, thickeners, hydrosepa¬rators) make use of the hindered settling phenomenon during the separation of particles. JIGGING Introduction In jigging, a mixture of ore particles, supported on a perforated plate or screen in a layer or "bed" with a depth many times the thickness of the largest particle, is subjected to an alternating rising and falling (pulsating) flow of fluid with the objective of causing all

Jan 1, 1985

By J. Patrick Powers, Arthur B. Corwin

Modern improvements in hydrogeology make it possible to predict with good reliability the performance and cost of ground water pumping systems in many tunneling situations. The testing and analysis techniques are presented. Data from the Buffalo NY LRRTS (1978-1980) illustrate the successful application of the technique for tunneling in rock. Data from the Red Hook Interceptor Tunnel in Brooklyn NY (1978) illustrate the application in soft ground. The Red Hook project also illustrates concerns for the side effects from dewatering, such as ground settlement and damage to timber structures. At Red Hook protective measures included compressed air, artificial recharge and controlled dewatering. Given the uncertainties of the underground, the possibility of unexpected situations must be considered. A hard rock sewer tunnel in Atlanta, Georgia (1982) illustrates an unexpected problem, and the emergency measures used to solve it.

Jan 1, 1985

By C. B. Rash, W. W. Fowler, Gill Montgomery

INTRODUCTION Fluorspar is the common term used for the mineral fluorite, which is naturally occurring calcium fluoride (CaF2). It is the principal source of fluorine, the most reactive of the chemical elements, from which a great variety of unique and strategically important chemicals are produced. Commercial deposits of fluorspar are widespread throughout the world, and its availability is essential to the industrial progress of all nations. GEOLOGY AND MINERALOGY In its pure form fluorspar, CaF2, contains 51.1% calcium and 48.9% fluorine, and has a sp gr of 3.18 and a hardness of 4. It is commonly a glassy mineral. colorless, white, or grayish. but may also be various shades of purple, pink, blue, green, yellow, or tan. It belongs to the cubic system mineralogically, and commonly crystallizes into cubic shapes in vugs and cavities, although most of it is massive, with interlocking crystals. Minable fluorspar deposits, in descending order of importance, occur as bedded limestone replacement deposits along fault zones; fissure-filling vein deposits; breccia filling in limestones, dolomites,

Jan 1, 1985

By A. J. Hendron, J. E. Monsees

INTRODUCTION This paper is the outgrowth of work done by the authors to prepare the seismic design criteria for underground structures on the Southern California Rapid Transit District (SCRTD) Metro Rail Project. It is a follow-on to a similar paper presented at the October, 1984, ASCE National Convention (17). For design, the earthquake-induced distortions recommended herein are to be added to the normal static loading conditions for the underground structure. This design approach has been used by 18 section designers on the SCRTD Project. Preliminary results from two- and three-dimensional finite element solutions have partially verified the approach. Areas where additional research is needed for special cases are identified. EFFECTS OF EARTHQUAKE The effects of earthquakes on underground structures may be broadly grouped into two general classes -shaking and faulting. In response to earthquake motion of bedrock (shaking) , the soil transmits energy by waves. Seismologists identify various types of earthquake waves, but underground engineers are generally interested in the effects of transverse shear waves which produce a displacement of the ground transverse to the axis of wave propagation. The orientation of propagation is generally random with respect to any specific structure. Waves

Jan 1, 1985

By R. P. Schneider

The Chino mine, concentrator, and smelter are located in Grant County in Southwestern New Mexico. Chino Mines Company is a partnership two-thirds owned and operated by Kennecott Santa Fe Corp., and one-third owned by MC Minerals Corp. (Mitsubishi) of Japan. The Chino Ore Body The Chino ore body is a widely varied deposit of rock types and contains intrusive stocks and sediments. The stocks contain chalcocite in a matrix of quartz, mica, and feldspar. Much of the feldspar is altered to clay. Some of these stocks are enriched with native copper. The sediments contain chalcopyrite associated with gangue minerals including magnetite, pyrite, garnet chlorite, and epidote. The contact of the stock and sediment is heavily altered to chlorite and clay. The stock ores contain economic quantities of molybdenite. The operating work index of Chino ore varies from 5 to 20 kwh/ton and averages 8.5 kwh/ton. The ore head to the concentrator averaged 0.81% copper and 0.010% molybdenum. Fifteen percent of the total copper head exists as nonsulfide mineralization.

Jan 1, 1985