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By R. E. Cook

"Mineral deposits require substantial amounts of energy to transport and be processed into usable form and, as such, present a real processing challenge in that the deposits are never homogeneous and orebody compositional characteristics are all over the map. Extracting the desired mineral(s) from the deposit at sufficient profit margin, despite severe fluctuations in market price, requires process automation architecture capable of supporting an integrated enterprise solution. Such an architecture will encompasses the activities of individuals, process units, process areas, plant level activities, mine management and business planning, and accounting systems. Key to the automation process is the aspect of value generation. This article brings together the various requirements for the automation of a mining enterprise and presents the different aspects of how to obtain value across the entire mining operation.Minerals’ processing sites are historically long lived, with 20-year life-of-mine not uncommon and 75 years not unheard of. Considering that hardware technology advancements are introduced every six months, or less, it is prudent to select process automation systems that adhere to “open” industrial standards versus proprietary based systems. In the minerals processing industry, the key to survival is driving the cost of production per unit volume to the lowest possible level and provide enough profit to sustain operations. Control system architecture and business information technology are rapidly becoming important tools in the quest for productivity. Getting key dynamic business performance information at the right time to the right person or process unit is crucial to successfully achieving corporate goals. The process automation architecture selected must, therefore, be able to integrate to the various networking enterprises and business systems.The mining industry is generally known as an extractive industry that is physically oriented with respect to operations and the activities in which workers engage. Large numbers of people performing manual tasks in difficult surroundings, produce variable outputs. But times are changing – and so are industry best practices. While the nature of work still consists of activities such as ore extraction, ore movement, ore concentration, refinement and logistics, automation innovations are starting to change the nature of many of the production steps. The industry has transitioned from requiring more physical activities by workers to more information management, automated control and collaboration within the operation. Humans are good at situational intervention and nonlinear reasoning and do best when empowered with an overall production perspective. Machines and automation are good at repetitive functions, steady state operation, and managing transitions. Thus, a combination of advanced technology solutions, reliable and useful information and full human contributions are necessary to mining operations for value generation."

Jan 1, 2015

By James R. Evans

Forecasting demand is an art as well as a science, and much personal judgment is required. National forecasts made for sand and gravel, crushed stone, and/or aggregate may be misleading or unhelpful locally. This is because of significant variation in demand within different geographic and/or political areas in the United States, and/or the use of an inadequate data base and forecasting methodology. The best forecasts may be made for local or regional market areas, irrespective of geographic or political boundaries, provided a proper data base is available. The Bureau of Mines compiles detailed statistics on commodities sold or used in the construction industries and, therefore, is in an advantageous position to make national aggregate demand forecasts.

Jan 1, 1978

By Kadri Dagdelen, Lee J. Zamalloa

Modern surface mining operations are always seeking for minimizing costs while increasing production rates, among the optimization of other specific tasks that have an impact on the economics of the mine. Specifically, the cost related to the production fleet operation (shovels and trucks), the maximization of the overall performance of the equipment, and the uncertainty to meet the goals at the end of the operational time horizon are always topics of discussion with no apparent simple answer. On the other hand, truck-shovel dispatch systems based on Linear/Non-Linear Programming Algorithms have been in operation since mid-1990’s with different levels of success depending on the correct arrangement of operational resources and the complexity of the mine, but having in most cases some important shortcomings related to the way these systems deal with the decision making of the operational objectives, being necessary to have a human agent (dispatcher) to guide the system when the operational parameters change, creating the possibility of suboptimal decisions due to the human factor. This paper discusses the implementation of a novel methodology based on AI techniques to assist in the decision making of the best goal selection when operating a Fleet Management System, taking into consideration time periods as variables and integrating them as part of the analysis, providing a better overview of the forecast plan completion with respect to previous production numbers and evaluating best alternative to handle future events to minimize losses or maximize profits, resulting in better truck assignments, minimum shovel idle times and overall productivity improvements of the operation at the end of the time horizon.

Jun 25, 2023

By U. Thorley

This paper presents an overview of surface mining activity in the Canadian oil sands and how the mine operators interact with the province of Alberta's Mine Financial Security Program (MFSP), which took effect April 1, 2011. The MFSP approach to reclamation assurance results in the government of Alberta sharing a portion of reclamation liability through the majority of an oil sand mine's life. In order to determine the potential fiscal magnitude of this shared liability, an examination of the expected costs of oil sands reclamation activities through a study of corporate asset retirement obligation (ARO) liabilities and other corporate disclosures is presented. The province of Alberta's Environmental Protection Security Fund (EPSF), which formerly secured oil sands mine reclamation activities is discussed. Reclamation costs in the oil sands are poorly understood. The MFSP provides what it characterizes as a conservative estimate of C$75,000/ha, while corporate disclosures by Canadian Oil Sands Ltd. place expected costs at C$180,000/ha. There is significant risk associated with the apparent uncertainty surrounding reclamation costs.

Jan 1, 2012

By Douglas J. Lootens

Geologic mapping was undertaken in the Sierrita Mountains as part of a Doctoral program at the University of Arizona, Tucson. During the study, approximately 35 square miles was mapped in detail, with particular attention given to specific areas of great or significant structural complexity and their relation to mineralization in the vicinity. A combination, of field studies and photogeologic interpretation was used in order to define regional and local structural controls for disseminated copper-molybdenum mineralization in and adjacent to the study area. Gratitude is expressed to the faculty of the University of Arizona, Department of Geology for their assistance in this work and to Bear Creek Mining Company for making numerous reports and drill cores available for study.

Jan 1, 1965

By D. M. Abbott

The problem with best practices occurs when they do not work. This happens when the seldom-stated assumptions underlying the practice are not met. This paper provides some examples for the mining industry: (1) when core splitting is inappropriate, (2) when the use of fire assays for placer samples is inappropriate, and (3) when high-grading may be acceptable. Geologic conclusions are, in the final analysis, expressions of judgment predicated upon knowledge and experience. A geologic conclusion, however, purports to be more than an arbitrary determination—it is reached as a consequence of method. No specific method is required, but the method used must be an orthodox method, in accordance with orthodox definition of terms, and the one best adapted to the dealing with the questions asked about the property in question. Whether the so-called “best practice” is really applicable to the job at hand must be decided on the basis of professional scientific judgment. When one decides to deviate from a published “best practice” for sound scientific reasons, describe in detail in the report what the so-called “best practice” is, why it was inappropriate for the project, and why the method used was better. If one becomes aware that a “best practice” is being proposed, actively urge those proposing it to include in its description the underlying assumptions that must be met in order for the “best practice” to be valid.

Jan 1, 2014

By M. E. Volin

Reagent control for optimum concentrate yield was studied by laboratory batch flotation tests simulating the Groveland plant flotation circuit in which a rougher concentrate is cleaned twice. The reagents were a fatty acid collector, a sulphonate collector and sulphuric acid. The study included two types of flotation feed representative of the reground and deslimed tailing from the spiral concentration circuit, one when the ore mineral is predominantly specularite and the other when it is magnetite. The factorial design included three levels of fatty acid, five levels of sulphonate and five levels of H2S04, with the two types of ore in nested blocks, making up a total of 75 tests. Similarity of results and reproducibility were established in preliminary tests. The final tests were performed in random order under closely controlled conditions following the established procedure.

Jan 1, 1965

By John S. Summer

The induced polarization (IP) method of geophysical exploration is capable of detecting even small amounts of metallic luster minerals in a rock mass. Consequently, in the years since discovery, IP surveying has become the most popular ground geophysical survey method. It is not too difficult to understand many applications of IP surveying as used in the search for mineral deposits. However, the basic theory of the IP phenomenon is not well developed or understood, and there has been some disagreement on fundamental concepts. In order to most effectively apply the IP method in the field it is necessary to know the physical characteristics of the sought-for deposit including its size, shape, depth, and electrical properties. With this information an optimum IP search arrangement can be devised and one could use the best possible electrode interval, type of array, and line spacing. With uncertain target characteristics as encountered in the real world, geological guidance must be used to help direct an optimized IP survey.

Jan 1, 1972

By V. R. Degner

The minerals industry trend toward very flotation machines, exceeding 10 m3, began in the late 1960's and responds to the continuing desire to achieve better plant economics through improved plant floor-space utilization, power requirements, and operational /maintenance manpower heeds. In general, as process design tonnage increases, the benefits of the larger flotation machine becomes more evident. The development of the larger flotation machine can be distingushed from earlier, smaller, machines in demanding a rational "scale-up" procedure to guide the basic design, thereby producing a machine prototype capable of satisfactory-operational evaluation at minimum cost. Proven flotation machine "hydrodynamic" scale-up consideration, successfully applied in the development of both the WEMCO No. 164 (28.3 m3) and No. 190 (42.5 m3) machine will be reviewed, and the resulting economic benefits of large flotation machines in high tonnage applications will be summarized.

Jan 1, 1985

By J. J. Renton

The iron disulphide minerals, pyrite and to a lesser extent marcasite, are ubiquitous to coal and coal associated rocks and are the source of nearly all the environmental problems associated with the mining, processing and utilization of coal. The iron disulphides as well as the other minerals in coal exhibit systematic spatial pat- terns of distribution on both regional and local scales and show predictable associations, most of which are determined by the geochemical-sedimentological controls under which they form. It is the purpose of this paper to discuss the geochemical-sedimentological conditions responsible for the formation of coal minerals with special emphasis on the formation of iron disulphides, to illustrate the regional and local patterns of mineral occurrence within coal, to present the microscopic associations of the iron disulphides and finally, to discuss the most important single environmental aspect of the iron disulphide content of coal and coal associated rocks; the production of acid mine drainage.

Jan 1, 1986

By Andrew Cho, Changsoo (Kevin) Moon, Richard Flanagan, Brian Larsen

"INTRODUCTION Project Background The U.S. Army Corps of Engineers (USACE)/Port Authority of New York & New Jersey (PANYNJ), as part of their New York and New Jersey Harbor Deepening Project, will dredge this shipping channel to a depth of 16.5 m below mean low water (MLW). By deepening the channel, the new generation of larger, “post-panamax” container ships coming to U.S. waters as a result of the expansion of Panama Canal can be accommodated in local marine terminals, helping to retain the nearly 300,000 jobs and $12 billion in annual wages the PANYNJ provides to the region. The existing siphons are situated at a depth that could be compromised by the planned dredging of the channel (nycedc.com). The purpose of this project is to build a new 1.83 m diameter water main inside a 3.66m diameter tunnel replacing the two existing siphons in order to provide the necessary backup water supply to Staten Island across the Anchorage Channel within the Upper New York Bay from Brooklyn. The proposed tunnel is approximately 2.9 km long and at a depth of at least 26 m below MLW. The project is funded jointly by New York City’s Department of Environmental Protection (NYCDEP) and PANYNJ and is managed by New York City Economic Development Corporation (NYCEDC). The contractor of the project is Tully/OHL JV, the designer is CDM/HMM JV, and the CM is LiRo/PB JV. History of New York City’s Soft Ground Tunneling The New York City area has a relatively long history of soft ground tunneling, commencing in the late 19th century. Construction of the first Hudson River tunnel crossings was begun (but not completed) in 1874 for the Hudson & Manhattan Railroad using compressed air supplying a shield. The work continued intermittently until the project finally opened for service in 1907. These 1.72km long tunnels (maximum depths of 29 m) are still in operation and now operated as the PATH Tunnels. They are approximately 5.5m diameter utilizing cast iron segments. The river bed consisted of primarily silt with shallow rock near the New York side. Air “leaks” occurred during the compressed air excavations resulting in some serious “blows” with water and soil entering the tunnel, including one incident with 20 deaths."

Jan 1, 2016

By Fatima-Zahra Houmymid, Elena Chiriotti, Mahdi, Samy

"The Greater Paris projects involves the creation of a 200km extension of the actual public transport network on the close outskirt of Paris. In 2011, SYSTRA has been awarded the Engineering studies of a 20km underground section in the densely urbanized southeast quarter of the Parisian suburb. In order to both guide the TBM technology choice and identify and mitigate the risk due to soil settlement during tunnel boring, several analysis have been carried out and integrated into a Geographical Information System to share and manage this risk during the successive design phases of the project. The geological context‘s complexity and the Owner‘ requirements have led to the necessity of using an innovative analysis approach, leveraging both the numerical modelling analysis’s accuracy and the analytical method‘s ease of programming and implementation in a GIS, by the mean of the calibration of the analytical approach’ parameters on the FEM results.INTRODUCTIONThe Greater Paris Transport Project foresees the extension of the actual public transport network to the close outskirt of Paris through the extension lines 11 and 14, the creation of a circular new line around Paris - line 15 completed by lines 16 and 18 linking developing territories - and line 17 to Roissy-Charlesde- Gaulle airport.The SOCIETE DU GRAND PARIS (SGP) is the public institution that promotes this project and awards SYSTRA as Engineering for the 15th Line southeast section.Line 15th – South-East sectionIn 2011, the Owner SGP (SOCIÉTÉ DU GRAND PARIS) awarded to SYSTRA the preliminary and detailed design of a 20km-long underground section of Line 15, between the stations of Villejuif-Louis-Aragon and Noisy-Champs. The double-track, single-tube tunnel has an inner diameter of 8.5m (about 9.8m excavated diameter, 75m2 excavated cross-section). The tunnel is inserted in a densely urbanized context."

Jan 1, 2016

By Mark E. Gershon

A mixed-integer formulation of the mine scheduling problem is discussed and applied for the purpose of optimizing both the mine production sequencing and the mill blending and processing problems simultaneously. Previous attempts at solving these problems separately, although successful, fail to take into account the interrelationships between these problems. Project structure serves as the outline of this paper, which is directed towards a mining engineering audience. Generalized in its organization, this concept is useful for long, intermediate and short range scheduling. Actual applications are mentioned which show that the concept is also applicable to mining a variety of ores.

Jan 1, 1982

By Hans-Werner Tonscheidt

Introduction The endeavours to mechanise the shaft sinking operations have led to the development of shaft boring using a V-Mole. The method implies competent ground and a pilot hole of sufficient verticality. This connects the top and the bottom of the shaft and serves for air ventilation and the transport of mullock. The shaft boring machine - nick name V-Mole - with a general pattern similar to a tunnel-borer reames the pilot hole to the designed diameter of the shaft. (Figure 1) The excavating of the rock, the removal of the mullock from the face and the lining of the shaft wall are done simultaneously. If they can be done also continuously this than creates a high potential of productivity. The verticality of the shaft can be garanteed due to the laser beam guided steering system. The diameter of the shaft is variable in steps of 0.5 m between 6.0 and 10 m in accordance with the need. It decides the capacity of the V-Mole to be applied. The depth of the shaft does not depend on the machine. It is practically unlimited as long as a suitable pilot hole is available. Up to 1988 almost 12.656 m of shaft have been drilled on 40 individual projects in Germany and the U.S.A. using a V-Mole. The rocks penetrated were Carboniferous sediments consisting of Sandstones, Shales, Conglomerates and Coal seams. The average uniaxial compressive strength was in the range of 300 - 700 Mpa with a maximum of 1700 Mpa in some singular sandstones.

Jan 1, 1991

By Mustafa Akser

Dwindling economic deposits of rutile (TiO2) prompted research on recovering it from secondary sources. One such resource is in Southwestern Turkey feldspar mining rejects that contain 5%-6% TiO2 mostly rutile. Previous studies could only upgrade the TiO2 to 36% TiO2 grade, claiming that the leftover flotation reagents on the surfaces of rutile and host minerals detrimentally affected upgrading of the rutile. As a potential remedy to this concern, a laboratory sample (from an operating feldspar mine in Milas, Turkey) was first caustic scrubbed, then air calcined at 400°C to evaporate the oily reagents. Subsequent physical separation of rutile included wet screening, gravity, magnetic, and electrostatic separation technologies. Such processes indeed improved the grade of the rutile concentrate up to 83 % TiO2 Low recovery of the TiO2 (<20%), was attributed to lack of full liberation of rutile, even at 125x44 micron range; interference with impurity minerals such as sphene and zircon; and simply the process inefficiency in upgrading the fine grains through conventional separation technologies for heavy minerals.

Jan 1, 1999

Two years ago, about the only US mining ventures that could turn even marginal profits were precious metals. In 1986, the price of gold dramatically increased, as did earnings from precious metals, mostly gold mines. First quarter results for 1987 show that gold will again be the most profitable type of mining in the US. All this money being made in gold resulted in many new mines being opened and hundreds of old workings being re-evaluated. The Society of Mining Engineers has put together a technical program to aid in developing precious metals mines. Small Mines Development in Precious Metals will take place Aug. 30-Sept. 2, 1987 at Bally&apos;s Hotel, Reno, NV. For registration and hotel information see page 426 or contact Meetings Department, SME, P.O. Box 625002, Littleton, CO 80162-5002, 303-973-9550. Topics at this meeting will include Problems Facing Small Miners; Understanding Geology and Ore Reserves; Mining-Production Options to Maintain Competitiveness; Processing for Precious Metals; Financing and Economics that Work for Small Miners; and Understanding the Environmental and Permit Maze. Problems facing the small miner The small miner has found and started most of the productive mines in the world, says Alfred G. Hoyl, of Coal Fuels Corp., Rollinsville, CO. Hoyl will state his case for small mines development in the opening session of the program. He will make the point that government regulations must never restrict the small mine or miner. And the mining industry must be careful not to crowd out the independent miner. "To restrict small mining is to say to our young men and women entering the mineral industry `There is no place for you as an independent.&apos; Small is a relative term and we must never feel that starting small will restrict our possibilities of becoming big." In the same session, David J. Starbuck, Starbuck Minerals Management, Mayer, AZ will take a look at why smaller precious metals mines are profitable. Mining companies have changed their perspective on reworking previously mined properties. They are looking at abandoned properties in older mining districts. The attitude is that smaller operations in these districts can be profitable with the present economic climate, more advanced technology, and better management. Small, independent mining companies may not have the same resources to draw from as the majors. But there are affordable technologies available that fit into the independents&apos; budget. Betty Gibbs, of Gibbs Associates, Boulder, Co will explain how a personal computer can help a small operation to analyze data more effectively and respond quickly to changing conditions. Scenarios will be developed that will describe how PCs can be incorporated into all phases of an operation. Financial institutions are becoming more willing to consider venture capital for small precious metals mines, according to Stanley Dempsey, Denver Mining Finance Co., Denver, CO. This may be in the form of equity or debt, he says, but they want to receive assurances of the quality of the resource. And they will ask about the ore reserves. Next, the potential lender will want to know about the mining method and en¬vironmental regulations. Dempsey will discuss these requirements. Once a high grade gold mineralization is located and reserves proven, it must be evaluated to determine which recovery process is best suited for this deposit. Robert Martinez, Amselco Minerals, Ely, NV will evaluate processes for such a deposit located in Mexico. Heap leaching, vat leaching, and a carbon-in-pulp circuit are all viable options, he says. He will explain which recovery process proved to be the most economic. Other papers in the introductory session include How to Best Use Consulting Firms to Accelerate the Development Process, by H. Schreiber and R.P. Fronk, both of Behre Dolbear-Riverside, New York, NY. And W. Mayrsohn of Asamera Minerals, Denver, CO will present Marketing Fundamentals that Work for Small Mines. Understanding geology and ore reserves In the current scheme of fast-track exploration and mine development, insufficient time and thought is given to understanding the geology of a deposit as it relates to controls of mineralization and subsequent mine development, say D.S. Bolin and J.W. Rozelle, of Pincock, Allen & Holt,

Jan 6, 1987

By JÖRG DEHNERT, PETER WINDISCH, Bernd Schönherrt, JENS STOPP

The Quick-Erect Stopping System (QESS) offers a new way of reducing the radon exposures of miners in Germany, especially during remediation work in old mines. The QESS is a light-weight, modular, and reusable construction kit of interlocking telescopic aluminum tubes, radon-proof foil, and expanding foam. It is designed to seal off radon-rich parts of galleries within only a few minutes. Originally, the QESS was developed to protect miners against radon exposures. Then, the QESS found the attention of several mine rescue teams at a German mining conference. The Student Mine Rescue of the Technical University Bergakademie Freiberg and the Wismut Mine Rescue carried out firstmine rescue drills in Freiberg and Schlema. Additionally, a mine rescue drill was carried out by the Front Range Mine Rescue in the Edgar Experimental Mine of the Colorado School of Mines. These drills helped to improve the systemand highlighted its potential for mine rescue operations. Now, the QESS is wellsuited for small-scale mining. The QESS can be used to seal off galleries in only a few minutes to both protect miners fromradon exposures and to support mine rescue operations. Moreover, the QESS was also successfully used in ventilation experiments.

Jul 23, 2020

By Jerome F. Sheldon

The earliest recorded history in the use of belt conveyors in the United States is in O. Evans&apos; "Miller&apos;s Guide" published in Philadelphia in 1795. Evans defines a conveyor as a "broad endless strap of thin pliant leather or canvas revolving over two pulleys in a case or trough." (Ref. 1) In this definition, pulleys are being used in a bulk material belt conveyor application. Pulleys used in belt drives can trace their origin back to 1200 A.D. In fact, Engineers had considerable experience designing them into drives transmitting greater horsepower than those used in the early belt conveyors. In belt conveyor application, a pulley&apos;s purpose is primarily three-fold, 1) support the belt in directional changes, as designed in the conveyor, 2) transmit driving power to the belt, and 3) guide or train the belt. There are various types of pulleys used in belt conveyor systems and these are thoroughly covered in "Belt Conveyors For Bulk Materials" prepared by CEMA, 1966. For our discussion, however, the most common used in belt conveyors are drive pulleys, snub pulleys, head pulleys, tail pulleys, takeup pulleys and bend pulleys. The drive pulley imparts the driving force to the belt and may be located at the head or discharge end of the conveyor, in return strand, or at the tailor loading end of the conveyor. A snub pulley is located near the drive pulley to provide more arc of contact between the belt and pulley for maximum

Jan 1, 1971

By M. M. Hajdasinki

A project&apos;s rates of return (RORs)1, be it the internal rates return (IRRs) or one of the many IRR surrogates, frequently needs to be approximated. The success and efficiency an ROR- approximation procedure depend on the quality the approximation-initiating parameters, such as bounds or seed values (guesses). The existing approximation procedures commonly use bounds and guesses suggested by intuition rather than supported by mathematical considerations. This paper presents three mathematically founded ROR-bounding and eleven ROR-guessing approaches and examines their suitability by using examples of typical project cash-flowpatterns (CFPs). The calculated bounds and guesses not only improve the approximation efficiency, but also allow the process of the ROR discovery to be automated, thereby making it more convenient and reliable.

Jan 1, 1999

By E. K. C. Chanda

The best use of available reserves to give good metal recoveries relies on short term mine production scheduling.-The aim is usually to produce a plan to guide mining in specific areas that will enable mine operations to deliver the budgeted tonnes and grade to the mill and keep within the long range mine plan. Thus, short term production scheduling is an important aspect of the open pit mine planning function. Since the 60&apos;s increased attention has been paid to effective production scheduling as a means of improving the economic viability of existing mines. Hence, mine scheduling scheduling systems have been evolving rapidly during the last two decades. These systems include manual techniques, computer based simulation, mathematical programming and more recently Computer Aided Design (CAD). Some general drawbacks of the current scheduling systems are that firstly, the costs of acquiring and using them are not at all insignificant especially for small to medium sized pits. Secondly, there is an inherent trial-and-error aspect in these systems. Thirdly, they tend to be suited for specific orebody geometries, hence lacking the necessary generality. For instance, the use of computer programs for planning open pits to mine stratiform orebodies raises problems which are not usually met when massive orebodies are considered. There for, a need exists to develop simpler but effective short term pit scheduling procedures suitable for stratiform type orebodies, considering their geometry and geology. This paper describes a PC- based model designed to assist the planning engineer in optimizing the short term production schedule in open pit mines with stratiform orebodies. The model is based on a combination of linear goal programming and deterministic mining simulation. The orebody model is made up of ore and waste mining regions where winning and and/or stripping are taking place. These shovel regions form the basic planning elements in the model. This approach does not require the laborious preparation and use of a regular block model. The computer program consists of main modules: (i) Data capture - processes the raw data into the required format for mine planning. (ii) Precedence mining constraints - checks the status of each shovel .region at the beginning of a given scheduling period with regard to geometrical mining constraints such as undercutting. (ii) LP- Optimization - provides an optimal selection of ore shovel regions which do not violet geometrical constraints for mining in the period, the objective, being to maximize the contained metal equivalent in the blended R-O-M ore and at the same time to minimize deviations in grade and tonnage from the call values. (iv) Post LP-Simulation - enables the user to smooth out the LP solution in order to adjust it to a practically executable plan and simulates mining of ore and waste for the period. Shovel allocation to selected ore and waste shovel regions, unit operations and depletion of reserves are executed in this module. Preliminary testing of the model for monthly production scheduling using data from Nchanga OPen Pit on the Zambian Copperbelt indicates that it can be a useful planning tool and gives acceptable results.

Jan 1, 1992