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By J. Lizak

Calcium carbonate is one of the highest volume industrial mineral products in North America. It is used in filler and extender applications, roofing products, floor tile, glass manufacture, etc. Calcium carbonate has over a dozen major filler and extender applications plus a host of minor uses. North American consumption of calcium carbonate fillers and extenders in 1991 is estimated at over 5,000,000 tons valued in excess of $400,000,000. There were five major suppliers of calcium carbonate fillers in the Middle Atlantic region in 1988 :?Bestone, Genstar, National Gypsum, Thomasville Stone and Lime, and White Pigment. With the exception of Genstar's Maryland operation, all of these operations are within a few miles of York, Pennsylvania. The Millington Group (TMG) purchased the assets of Bestone Corporation in February of 1989. TMG then seized the opportunity to strengthen its business position by acquiring National Gypsum's and White Pigment's Pennsylvania filler businesses in December, 1989 and July, 1990, respectively. By July of 1990 TMG's filler business acquisitions included six quarries and one underground mine, totaling over 1,200 acres and three processing facilities. The assets were restructured into two new companies - Delta Carbonate, Inc. and Penroc, Inc. (hereafter collectively referred to as Delta). Delta identified the assets of the three predecessor companies as undervalued from the outset. The initial phase of Delta's turnaround strategy was to reassess the combined mineral. mining, processing, transportation and marketing assets. The second phase was to effectively integrate these resources in order to exploit their inherent synergy.

Jan 1, 1992

By J. W. Devon

The coal mining industry is divided into two distinct economic segments based on Coal Supply Agreements. Coal supply agreements generally fall into two categories, spot or long-term, with the selected contract term being driven by the buyer's market expectations, security of supply considerations, fuel tonnage and quality requirements, and economics. Short-term or spot coal purchases are generally market driven and are highly competitive in today's marketplace. Long-term contracts, particularly those involving captive mines and mine-mouth power plants, are commonly driven by considerations other than economics. These other considerations, such as Reserve Conservation and Resource Recovery, Security of Supply, and Maintenance of Levelized Costs may increase the cost of coal, often needlessly and without benefit to the buyer or seller. The basic economic principles which guide the market driven metals industry and generally guide the spot coal sector of the coal industry should apply equally well to the long-term coal supply contract. The artificial constraints imposed as a result of regulated rates of return should be re-examined and in most cases, abandoned. There are many methods of surface and underground coal mining being used today such as, open-pit, contour, mountaintop, and area mining for surface mineable reserves; conventional, standard continuous and super-section continuous miners, and longwalls for deep reserves; and highwall miners, thin seam miners and augers in between. This discussion is primarily directed to surface mining, however the same principles of least cost mining on a Net Present Value basis must be considered in all cases.

Jan 1, 1994

By S. K. Jena, S. Singh, B. Das, N. Dhawan, P. K. Misra, D. S. Rao

"Iron as an impurity in pyrophyllite ore affects pottery, ceramics and tile quality. We carried out the characterization of a pyrophyllite ore sample using optical microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and wet chemical analysis. The study revealed the presence of 2.15% iron oxide (Fe2O3 ) along with silica and alumina as the major components, which constituted around 90% of the total sample. We carried out the removal of iron from the pyrophyllite using magnetic separation and acid leaching and found that wet high-intensity magnetic separation (WHIMS) could remove 28% of iron values while oxalic acid leaching could remove up to 99.3%. The leaching kinetics of iron removal and the effects of pulp density, acid concentration, leaching time and temperature were also investigated. The optimum conditions for leaching were found to be leaching time of 60 minutes, temperature of 90°C, pulp density of 5%, oxalic acid concentration of 0.3 M, and particle size below 100 microns. Iron dissolution from the pyrophyllite sample can be best described by the diffusion of ions through the product layer of constant-size spherical particles. The breakdown of the pyrophyllite structure was evident from the FTIR and TGA studies. The activation energy of the leaching process over the temperature range was calculated to be 43.47 kJ/mol. IntroductionPyrophyllite is a naturally occurring phyllosilicate mineral composed of aluminum silicate hydroxide [Al2Si4O10(OH)2] as the major component and often associated with other minerals such as kaolinite, mica, quartz, rutile and epidote. It occurs in fine-grained sericite schist that is quarried as pyrophyllite (Pandit et al., 2008). In India, pyrophyllite occurs mainly in Madhya Pradesh state, Uttar Pradesh state and the Keonjhar district of Odisha state (Harpavat, 1995). Pure pyrophyllite is a highly desirable material for various applications due to its unique properties. It exhibits high refractive behavior, low thermalelectrical conductivity, low expansion coefficient, low hot-load deformation, low bulk density and high corrosion resistance to molten metal and basic slag (Rieger, 1997). It is used in the ceramics, refractory, foundry, electrical-insulation, sanitary-ware, glassmaking, pesticide and rubber fields. Compared with clay, it has lower thermal conductivity and coefficient of expansion, making it more suitable for refractory applications (Harben, 2002; The Minerals Yearbook, 2011)."

Jan 1, 2015

By Bruce W. Cavender

In an effort to lower production costs and improve profitability, mining companies have adopted a variety of management practices emphasizing productivity and cost containment. One set of practices that has been used successfully in the manufacturing and electronics industries is "world-class manufacturing" (WCM). It is applicable to mining as well. World-class manufacturing is based on the twin concepts of "just-in-time" inventory practices and total quality control. A few mining companies have implemented quality control programs that are similar to WCM in some ways and substantially different in others. This article considers the use of WCM in the processing environment, although the techniques are applicable throughout a mining operation. The article is also mindful of the variety of customers to whom mineral products are sold. Industrial minerals producers may sell brand-name products to specific customers with exacting requirements, while metals producers often sell their fungible output on a faceless commodity market. Customer requirements are emphasized in WCM, and so the range of these requirements must be recognized. World-class manufacturing In any milling process, specific goals are set for product and process characteristics - concentrate grades, minimum daily throughput, moisture content, etc. WCM has two overriding objectives: the reduction of deviation from these standards, and the reduction of variability in all aspects of the process and product. By definition, reduction of deviation also includes minimizing plant downtime for repairs or process changes. WCM plants use just-in-time inventory practices and total quality control. WCM plants use these techniques to simultaneously improve productivity and reduce costs.

Jan 1, 1993

By D. Hulse

"The science of “optimal economic pit design” has been highly refined in the last decades. Even with the proliferation of optimizing and heuristic algorithms exploiting ever faster computers, the most common input is a single block model and a single set of cost assumptions, each of which is an estimate and prone to errors. An analysis of price assumptions produces a suite of nested economic shells, each with its own quantities of ore, waste, grade, and profit, but due to irregularities in the mineralized body, the growth of these shells can be erratic. To control the impact of the errors of the model and cost assumptions when choosing the pit shell for design, graphs of pit shells characteristics, such as stripping ratio, cost per unit of product and profit/ton, can be analyzed to consider points with higher stability, or robust pits. Selection of robust shells for a pit limit and for push backs can help to understand the impact to profit and risk. The robust shells also guide the preferred solution sets for final pit and cutoff optimization. INTRODUCTION “An open pit mining operation can be viewed as a process by which the open surface of a mine is continuously deformed. The planning of a mining program involves the design of the final shape of this open surface.” Optimum Design of Open-Pit Mines, Lerchs, H. and Grossmann, I. Transactions C.I.M. Volume LXVIII 1965. Traditionally an analysis of economic pit shells and sensitivity was performed by varying the input metal price. This was done with both floating cone algorithms as well as early versions of the Lerchs-Grossmann (L-G) algorithm. This gave an indication of the pit sensitivity to price but since other variables also change, some with metal price (perhaps steel and equipment), and some independently (fuel and tires) the understanding of these different pits was restricted. In addition, a run of the program could take hours, making a detailed analysis of small changes unwieldy. The L-G algorithm was programmed by a variety of people and sold as part of commercial mining packages, however it was first and most successfully commercialized by Jeff Whittle in 1984. When Whittle’s 3-D™ was expanded to 4-D the parameterization of the economic inputs was considered and the ability to run a suite of “pit shells” became automatic. The competing NPV Scheduler™ program sold by DataMine™ offers similar pit shell analysis capabilities."

Jan 1, 2018

By C. S. Vender

Knife River Coal Mining Company's Beulah Mine is a multiple seam lignite operation located in western North Dakota. The mine began production in 1963 with annual production at 450,000 metric ton and now produces 2.2 mm ton. As development progresses, operations have advanced into more complex geologic areas. Various techniques have been analyzed to maximize coal recovery in a cost effective manner. Additional studies are on-going to determine what changes will be implemented as we encounter deep wet sands in the reserve area.

Jan 1, 1991

By R. W. Smith, D. L. Taylor, K. A. Altman

The importance of metallurgical information in reaching appropriate decisions during the development of mining projects is demonstrated. A financial analysis is calculated using a simulation that includes random number generators. The results are compared to the results of a traditional sensitivity analysis. The traditional analysis is shown to have the potential to overestimate the value of mining projects. The type of statistical distribution selected for the random number generator affects the results significantly. The statistical method of analysis provides insight into the amount of metallurgical testing to be completed and verification of how representative the samples are.

Jan 1, 2000

By C. Cho

One problem with the application of neural networks to the multivariable control of mineral and extractive processing is deciding whether and how best to use them. The objective was to compare neural network control to more conventional strategies and find any advantages in terms of set point tracking, rise time, settling time, disturbance rejection, and other criteria. The procedure was to develop neural network controllers using both historic plant data and simulation models. We tried various neural network control patterns including both inverse and direct neural network plant models. These were compared to state space controllers that were, by nature, linear. For grinding and leaching circuits, a nonlinear neural network-based model predictive control strategy was superior to a state space-based linear quadratic Gaussian controller. We also learned the importance of incorporating state space into neural networks by making them recurrent--feeding certain output state variables into input nodes in the neural network. We concluded that neural network controllers can have better disturbance rejection, set point tracking, rise time, settling time, lower set point overshoot, and can be more foolproof and easy to implement in complex, multivariable plants.

Jan 1, 1996

By Roger S. Dewey

1.1. INTRODUCTION Despite indications of a general economic recovery in the U.S. during the mid-19801s, mine operators have not generally shared in the benefits of these reported better times. Budgets have not rebounded, borrowing is tougher, parent companies' pockets are not as deep as in previous years, and margins are not any better -- if there is any left over at all. Managing capital equipment budgets is always a challenge, and the last five years of stretched equipment lives make these decisions more tenuous. Delays and avoidance of replacements due to tough times inevitably makes those decisions increasingly difficult and usually more expensive The purposes of this paper are to present. a brief refresher outline of the fundamentals of equipment replacement analysis, to suggest a number of papers where analysis methods are explained in greater detail. and to recommend the use of a widespread microcomputer software capability (1-2-3) as the easiest path to a much-needed solution for a very difficult, and usually under-supported management decision problem 2. REPLACEMENT DECISION POLICY Investments in equipment replacements must compete for capital with all other investment alternatives. Capital for replacements of ten represents a greater commitment than do the new projects which a company might handle in a given year. But. sadly, formal policies for standardized analysis of replacements rarely exist, even in major companies. Yet this policy can be very significant in determining the competitiveness of a firm. Whereas many replacement decisions are based on cost minimization, economists and financial analysts agree that wealth maximization or return on investment is the superior criterion. Though the difference may seem slight, agreement on a firm's financial objective is vital. Replacement policy should be straight- forward. have a logical basis, and a proper level of sophistication. There are several reasons to develop a policy for replacement decision-making: [I] 1 - equipment's optimal economic life is nearly always shorter than its physical life; 2 - mine life often exceeds equipment life, so management must face these decisions routinly 3 - replacement capital costs, on an undiscounted basis, can run 25 to 75% of original capital 4 - technological changes may result in a newer machine or system which can operate more efficiently, more safely. or less expensively 5 - estimates should be made consistently in the fundamental areas of life expectancy, availability, utilization. price escalation, taxes 6 - long-term and short-term budgeting without decent data and analytical capability is nearly impossible, or at least ineffective Policy development assumptions which must be considered include: the planning horizon, cost patterns, interest rates, availability of capital, replacement vs. expansion, technology advances.

Jan 1, 1987

By K. Sasaki, W. Astuti, N. Okibe, T. Hirajima

"The kinetics of leaching of a saprolitic ore from Indonesia by citric acid solution under atmospheric pressure was investigated. An examination of the effects of leaching temperature, citric acid concentration, pulp density and ore particle size on the dissolution rate of nickel found that they all had significant influence on the rate. The highest nickel recovery (95.6 percent) was achieved under the leaching conditions of ore particle size of 212-355 microns, citric acid concentration of 1 M, leaching time of 15 days, pulp density of 20 weight/volume percent, leaching temperature of 40°C and shaker speed of 200 rpm. The shrinking core model was found to be appropriate for describing the leaching kinetics of this ore in citric acid solutions at atmospheric pressure. The experimental data were well interpreted by this model with rate of reaction controlled by diffusion through the solid product layer. Using the Arrhenius expression, the apparent activation energy for nickel dissolution was evaluated as 12.38 kJ/mol. Finally, on the basis of the shrinking core model, a proposed empirical kinetic model for the leaching of nickel from this Indonesian saprolitic ore was expressed as a mathematical model, which was verified as consistent with the observed experimental results.IntroductionIndonesia has some of the world’s largest nickel laterite reserves and was the largest producer of nickel – in the form of nickel lateritic ores – in the world in 2013 (Merchant Research and Consulting Ltd, 2014). However, only high-grade saprolites are processed in Indonesia using pyrometallurgical methods to produce ferronickel and nickel matte. Lower-grade saprolites and limonites are removed, becoming waste or overburden in mining site areas. Hydrometallurgical methods, involving either chemical leaching or bioleaching, are now seen as the most important technologies for treating nickel laterites in the future because of their advantage of not only extracting nickel and iron but also other valuable elements. In addition, hydrometallurgical methods consume less energy and have lower capital and operational costs. Although they are recognized to be more suited to limonites, some researchers have studied their use in the extraction of nickel and other metals from saprolites (Guo et al., 2009; Lu et al., 2013). Hydrometallurgical processes for the extraction of metals, especially nickel, promise to be meaningful alternatives to pyrometallurgical processes to primarily treat low-grade saprolites for which pyrometallurgical processing is not favorable"

Jan 1, 2015

By William R. Yernberg

The early part of the decade was marked by world-wide problems and economic difficulties. In 1980, President Jimmy Carter ordered the failed military mission to rescue hostages in the U.S. Embassy in Iran, Mt. Saint Helens, WA erupted killing 60 people and the Soviets and Mujaheddin guerrillas clashed in Afghanistan after the Soviet invasion. Later in the year, Ronald Reagan was elected president, defeating Carter. The first launch of a space shuttle (Columbia) occurred in 1981. Also in 1981, the first IBM-PC’s begin to roll off the lines. In 1982, Argentina invaded the Falkland Islands and Mexico’s economy was in collapse. In 1980, the U.S. unemployment rate stood at 7.1 percent, and by 1982 the rate increased to 9.7 percent. 1980 marked SME’s first full year in its new office building in Littleton, CO. The new facility was dedicated in November 1979. Claude L. Crowley was executive director of SME in 1980 and remained in that position throughout the decade. SME’s membership stood at about 26,000 throughout this period (1980-1982).

Jan 1, 2007

By Mario E. Rossi

Often geometallurgical models are prepared at various project stages from very few data and are assumed to be representative of very large tonnages. These may include recovery models; crushing and grinding parameters and models; models of concentrate grades; models of acid consumption; etc. These models commonly do not carry a measure of uncertainty or variability, and are taken at face value at the time of design and planning. This paper proposes a proactive approach to modelling variability, providing uncertainty estimates and thus allowing for risk analysis and mitigation of geometallurgical models. The variability model is built up by understanding the limitations of the pillars of a geometallurgical model: data uncertainty; geologic model uncertainty; domain definition uncertainty; and parameter estimation uncertainty. Of these factors, typically domain definition is the most significant contributor to geometallurgical model variability. First, the fundamental supports for these models are briefly discussed, with domain definition emphasized. Second, two methods for uncertainty modelling are proposed. The first, more applicable to conceptual or early-stage projects, is a simpler and more expedient alternative that provides initial assessments of variability. This is intended to aid management in decision-making related to budgeting, including further sampling and testing. The second, a block-by-block approach that allows a detailed assessment of risk for specific designs and mine plans, thus providing further opportunities for mitigation. In the example provided, emphasis is placed in communicating this variability to both management and technical personnel in the form of “measured-indicated-inferred” indicators and also block-by-block confidence intervals.

Jun 25, 2023

By Ron F. Schritt

Over the many years since the development of the steam powered shovel, various powering and control techniques have been employed for the various shovel functions. While volumes have been published on this subject, this paper will be limited to a very brief discus-sion of one of the latest of these and its application to a unique machine. The evaluation of the subject machine is far beyond the scope of this discussion, which will be limited to the techniques and equipment employed, and the considerations involved in their choice. The basic requirements for any power and associated control system for any power shovel function have remained relatively un-changed over the years. To the extent possible, such an equipment grouping must be: Easy to install during fabrication Easy to maintain and repair by available personnel Life cycle cost competitive Adequately reliable Adequately responsive And as may be expected these factors are arranged in various orders of priority by different manufacturers and users. All the various time honored approaches have to some extent fulfilled these require-ments but were discarded or fell into disuse when more effective approaches were developed. The latest in this long line of develop-ments and perhaps the most promising is that of electro-hydraulic controls and hydraulic drive.

Jan 1, 1977

By R. M. Corn

The Non-Time Critical Forest service CERCLA Action at Mansfield Canyon, Santa Cruz County, Arizona designated previous locators of unpatented mining claims as owners/operators of the Hazardous Waste Facility, retroactively liable for all reclamation costs including reclamation of mines acquired by the Forest Service. The CERCLA Action is based on non-existent tailings, a non-existent permanent resident, inaccurate and unreliable data and did not review or consider prior USGS and USBM data. The consequences of the Forest Service action include(1) reduced exploration, (2) loss of credibility, (3)public disillusionment and distrust.

Jan 1, 2000

By Eduardo Velasco, Paz Navarro, Alfonso Navarro, Claudio Cimiotti, Alejandro Sanz, Nick Karlin

The LA Effluent Outfall tunnel is a 7-mile long, 18' internal diameter, secondary treated effluent discharge tunnel currently under construction by Dragados USA for the Los Angeles County Sanitation District No. 2 (LACSD). The purpose of this tunnel is to add redundancy and increased capacity for discharge of secondary treated effluent from the LACSD’s Joint Water Pollution Control Plant, located in Wilmington, California within Southern Los Angeles County. Current discharge from this facility flows through two existing tunnels of 8' and 12' horseshoe profile, constructed in 1937 and 1958, respectively. When the new tunnel is complete, it will add an additional capacity of 670MGD in peak wet weather flow conditions. Geology of the roughly 7 mile long tunnel was divided into six reaches by the contract documents. Tunnel Reaches (TR) 1 to 3, comprising 19,550' will be excavated in alluvial sands of the San Pedro and Lakewood formations, with cover ranging from 45 to 90 feet. In this reach the tunnel intersects the seismically active Palos Verdes fault Zone. TR 4 is a 1,600' transitional zone between alluvium and the rock formations of the Palos Verdes (PV) Hills, comprised mostly of Malaga Mudstone. TR’s 5 and 6 total 15,591', and are within the rock formations of the PV Hills with overburden ranging from 315' to 475'. The primary constituent of the PV Hills is Altamira

Jun 13, 2021

By Peter G. Chamberlain

Domestic mining will not produce a significant portion of the manganese consumed in the United States unless new mining and processing techniques are implemented that will enable domestic lean ores to economically compete with rich foreign ores. One mining-processing technique that appears promising for certain deposits is in situ and/or heap leaching with aqueous SO2. Since leaching offers economic advantages of low capital costs, low operating costs, and short start-up times as well as environmental and safety improvements over conventional mining-processing, the Bureau of Mines studied the leachability of manganese deposits from several districts. Manganese oxides, hydroxides, and carbonates were leached to 80 to 90 pct recovery in 7 to 40 days of leaching with a solution containing 5 pct SO2 in column leaching tests. Preliminary cost analyses of surface mining-heap leaching, block caving-in situ leaching, and shrinkage stoping-in situ leaching indicate that the products of manganese leaching may be economically produced for the chemical and electrolytic manganese industries. The easiest marketable product to obtain would be a manganese sulfate commonly used as a fertilizer amendment. Manganese carbonates and hydroxides could also be precipitated from the pregnant leach solutions.

Jan 1, 1983

By G. A. Hufford

The cutoff grade applied to a disseminated orebody mined by open pit affects both the waste ratio, hence the cost of producing ore, and the ore grade, hence the quantity of metal recovered. As such it has a significant impact not only on the annual profit or loss, but also on the life of a mining property. Cutoff Grade Strategies Some commonly used objectives in calculating cutoff grades are as follows: Minimize Unit Cost of Product (1) This is found by adding all costs associated with each possible cutoff such as mining, processing, and marketing. This is divided by the quantity of marketable product obtained at each cutoff grade, then finding the minimum. Because the market value of the product does not enter the calculation it has no effect on this strategy: the same cutoff is selected in good times and bad.

Jan 1, 1986

By L. Harris

The Yanacocha project is the first foreign investment in Peruvian mining since Cuajone during 1976. Three years after the project began, it has become the largest producer of gold from heap-leach operations in the world and the top producer in Latin America. The success of Minera Yanacocha SA (MYSA) opens a new chapter in Peruvian mining with the exploitation of its widely spread gold deposits. And it has attracted the interest of foreign investors in Peru’s mineral resources. Construction began on Aug. 1, 1992. The first gold bar was poured on Aug. 7, 1993 from ore from the Carachugo Mine. During 1993, Minera Yanacocha produced 2.5 t (81,000 oz) of gold and 9.4 t (304,000 oz) during1994 (40% above budget). Production was expected to exceed 15.5 t (500,000oz) during 1995 with the start-up the Maqui Maqui Mine.

Jan 1, 1996

By Gary English

"Tunnel safety is evolving as science, engineering and technology make advances. Applicable safety codes and standards simply do not cover all the potentials of design, construction and operation. This paper reviews a series of tunnel projects code gaps in Seattle USA that were uncovered during the design and construction of a new highway tunnel, conversion of bus tunnels to combined road and rail tunnels, new rail tunnels using TBM and NATM, conversion of a road tunnel to light rail, and retrofit of an existing road tunnel to add lanes and improve safety systems. The perspectives of the ‘fire code official’ (Authority Having Jurisdiction) on methods to identify and resolve gaps in safety code and standard regulations, while garnering the consensus of the owner, designer, and contractors are presented. Additionally, the emergency responder command perspective on safe tunnel design, tunnel rescue during construction and operational safety is explained TUNNEL SAFETY EVOLUTION The underground has become nearly the only option to provide essential transportation corridors to continue our economic growth in key global areas. Tunnels are not built on a whim. Often significant portion of a regions wealth are invested to meet current, and hopefully future transportation demands. There are more transportation tunnels being built now than at any time in the planets history. The location of these tunnels is often selected for us based upon regional demand. Most commonly under densely populated urban centers and between populations’ centers to bypass geologic conditions like mountains and water bodies. Tunnels are being built in unforgiving soils, between tectonic plates, in extremes environmental conditions and often, under the very heart of the highest density population centers on the planet. All of these locations can bring with it conditions that challenge our common assumptions about safety. These extraordinary locations and soils create risks for both those constructing the tunnel, and in design engineering to meet the ‘minimum’ requirements at the lowest costs. There is lengthy history of above ground safety. Most countries and major local jurisdictions have adopted, or created safety requirements for the construction of above ground buildings. Through decades of use, these safety requirements have evolved, changed and been expanded to cover a wide gamut of actual and potential safety risks. However, the use of the underground for tunnel transportation corridors has grown exponentially with limited attention to safety requirements."

Jan 1, 2016

By Ki Chun

Optimizing ore processing requires a thorough understanding of not only the process itself but the economic constraints which influence business decisions. No single modeling technique is able to model all the different processes running in today's mines. The solution then is to use a number of different model­ing techniques, each competing with the others to best correlate the data. Among these modeling techniques are: Neural Networks, Genetic Algorithms, Fuzzy Logic, Crisp Logic, Statistics, First Principal Models, and System Identification models. Once a model has captured the behavior of the process, a numerical optimization determines the optimal operating point and set point parameters. A single step is then taken in the direc­tion of the optimal location by changing all the process parame­ters to the setting recommended by the optimization system. As the process begins to re-stabilize, the models are updated, the new optimal determined and another step is taken in the direction of the optimum. Through the use of multiple competing models integrated into a numerical optimization the process can achieve the optimal running condition even if the ambient conditions fluctuate dynamically.

Jan 1, 1998