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By J. D. Megeath

In the October 1988 issue of MINING ENGINEERING, J.G. Wargo's paper discusses the problem of measuring and analyzing permeability, porosity, and fracturing in its relation to in situ leaching of disseminated gold deposits. This paper made me suspect that a good deal of information and analysis may have been done on this in reverse in the petroleum industry. Some years ago, I was involved with the US Geological Survey in a project studying the Devonian shale of the eastern United States. The Devonian shale contains gas deposits that have the characteristic of slowly seeping gas over a very long time period. To understand the rate of seepage, considerable study and analysis was done on the interrelationship of porosity, permeability, and fracturing. The purpose was to find out how and why the gas could escape in the varying rates found in wells throughout the formation. It strikes me that this is the mirror image of the problem faced in attempting to understand how a cyanide solution will travel into a deposit. To possibly invent our own personal wheel a little faster, I would suggest a look at the work done on the Devonian shale. Some of it is contained in "Estimates of Unconventional Natural-Gas Resources of the Devonian Shale," US Geological Survey Open-file Report 82-474, 1982, and "Additional Data for the Estimates of Unconventional Natural-Gas Resources of the Devonian Shale," Open-file Report 83-676, 1983. It is entirely possible that some of this previous work could shorten the time required to make in situ leaching of disseminated gold deposits a profitable technique.

Jan 1, 1990

By Donald R. East

The impacts of the economic storage or disposal of mill tailing wastes are becoming more important to the mining industry as environmental regulations become more demanding. Mill tailings have long been considered the stepchild of the extraction process and have not, until recent years, been treated as a separate entity of the mining and milling process with distinct and complex physical and chemical characteristics. As a waste product, the economic value of mill tailing is usually very small whilst economic and the environmental liabilities can significant. be Disposal of tailing is commonly identified as the single most important source of environmental impact for many mining projects.

Jan 1, 1990

By Simon J. D. Cox, Nicholas J. Archibald, Steve Nichols, Peter B. Ketelaar, Donelle C. Davies, William L. Power

In the mining industry, there is a critical need to communicate complex, three dimensional information about the geology, ore reserves and development plans for mining operations. This information has to be communicated to a diverse audience, the members of which may not be trained in all of the disciplines required to create, utilise, or interpret the information. Software developed to support World Wide Web (WWW) activities has the potential to improve and change the way exploration and mining data and in- formation is organised, presented, and processed. In this paper, we discuss the creation of interactive displays of complex three dimensional data for the mining industry.

Jan 1, 1996

By Leslie E. Apodaca

INTRODTUCTION The use of spiral concentrators for processing fine coal particles is an old idea that has recently gained acceptance in the 11.S. coal industry. It was not onti1 the Australian Minerals Industry developed a spiral concentrator specifically for separating coal from ash in the latter 1970's and early 1980's that spiral concentrators were seriously considered as viable equipment for processing fine coal. The Wright Coal Spiral was introduced in 1980, the Mineral Deposits Limited Mark 10 Coal Spiral was introduced in 1982, and the Vickers Wyong Coal Spiral was introduced in the latter part of 1984. Each spiral design was different and utilized constant profile troughs, constant pitch troughs, compound profile troughs, and various splitter arrangements. Mineral Deposits Limited has combined the best features of the compound profile trough and constant pitch trough with critically-placed splitters to develop the MDL LD4 spiral concentrator which is a truly efficient coal washing spiral. This spiral concentrator was introduced into the U.S. Coal Industry in 1987. Recently, Mineral Engineering Technology of the United Kingdom and Multotec of South Africa have introduced their own coal spiral designs. Spiral concentrators were first installed in fine coal processing circuits in the Australian, South African, and Canadian Coal Industries in the early 1980's and in the U.S. Coal Industry in 1985. SPIRAL CONCENTRATOR SEPARATION PROCESS The separation process that occurs within the spiral concentrator trough is very complex, as it is a combination of three gravity separation processes. When the coal slurry first enters the spiral trough, each coal and ash particle and the water is subjected to centrifugal forces. These forces cause the water, light coal particles, fine heavy ash particles, and medium middlings particles to the outer vertical portion of the spiral trough. The coarse ash particles and the coarse middling particles remain on the inside of the spiral trough. The center or transitional area of the trough contains a mixture of middlings particles and near-gravity material that is present in the slurry, as shown in Figure 1. At the same time the coal and ash particles are suhjected to centrifugal forces, the trough design (both profile and pitch) causes the particles to be subjected to flowing film and stratified bed separations. The combination of these three separations, whose efficiency is dictated by the spiral troogh design, will effect the separation of the lighter coal particles from the heavier ash and middlings particles. As the slurry flows down the spiral, the profile and pitch design of the trough will counteract the centrifugal forces on the fine, heavy ash particles and fine middlings particles and cause them to migrate from the vertical portion of the trough to the center or inner portion of the trough. At the same time, any heavy particles trapped in the transitional area of the trough will be forced to migrate to the inner edge of the trough and any coal particles will be forced to migrate to the outer edge of the trough. SPIRAL SPLI'TTEP ARRANGEMENT The critical placement of splitters along the inner edge of the trough for removal of the heavy ash particles as the slurry flows down the trough further enhances the separation of the coal particles. At the bottom of the spiral trough are product splitters arranged to make a final separation of the slurry stream into clean coal, middlings, and refuse products.

Jan 1, 1988

By Truman Harrington

During the last decade, diesel engine manufacturers focused their research efforts on higher efficiencies and horsepower-to-weight ratios. The result was horsepower increases of between 20% and 30%. At the same time, coolant volume decreased by about the same amount. This has made coolant maintenance more important to ensure a long life for the engine and its cooling system. Due to dilution and additive depletion, supplemental conditioners are usually added to the coolant system during an oil change. Dilution occurs when coolant leaks from the system, and water or non-conditioned antifreeze is added. Depletion is a more complicated process that involves oxidation, neutralization, precipitation and metal surface reactions.

Jan 1, 1991

By J. W. Rinard

This paper is intended to introduce "non engineers" to one of the more misunderstood pump performance parameters, NPSH (Net Positive Suction Head). This basic presentation and resultant review should provide a practical understanding of NPSH and what its importance is to pump operation and reliability.

Jan 1, 1996

By R. Renzoni, S. Belboom, F. Tourneur, A. Léonard

"Construction is a field which is concerned by environment. Tools as environmental product declarations are increasingly often used to compare several products and to take account of the environmental sphere in the choice. Environmental declarations of Belgian bluestone and sandstone products were realized in accordance with the ISO standards and following the standard NF P 01-010. The main goals of these studies were to obtain Belgian environmental product declarations to strengthen existing databases and to provide defences against Asian competition. Indeed, competition with China for bluestone products and with India for sandstone pavement is very important due the fact of the very competitive prices for foreign products. The impacts on climate change, resources and acidification of the sole transport were taken into account for foreign products"

Jan 1, 2011

By Charles S. Phillips

Kaiser Aluminum and Chemical Corp. (KACC) had been discharging spent bauxite-generally referred to as red mud-into the Mississippi River for almost 20 years when, in 1972, it agreed to store the waste solids on land. KACC decided to utilize a DREW system (decantation, drainage, and evaporation of water) where the spent bauxite is deposited in a large drying bed, surrounded by a 9-m-high levee. At the bottom of the bed, corrugated, perforated plastic pipe is encased in filter sand. The company built one DREW bed at Gramercy, LA, in 1973 and a second at Baton Rouge in 1974 using draglines, tractors, and rubber-tired scrapers. When a third bed was needed in 1977, the estimated construction cost using draglines was judged too high and KACC personnel began searching for a better, less expensive method for constructing the levee. A bucket-wheel excavator and conveyor system was selected and has proved to be less costly than more traditional earth-moving systems.

Jan 7, 1980

By Dan Plazak

Discussion by Dan Plazak The authors are to be congratulated for presenting a simple and practical tool for quick estimates of ground water flow rates. At the risk of detracting from the simplicity of the method, I would like to suggest a slight refinement to the equation as presented. As the authors noted, the Jacob-Lohman equation (1952) assumes confined-aquifer conditions. To use confined-aquifer equations in water-table aquifers, Jacob (1963) presented a correction to convert water-table aquifer drawdowns [Ahw] to equivalent confined aquifer drawdowns [Ah,: 2] [Ah Ah = Ah - w(1) Cw 2H where: Ah, = Drawdown in confined aquifer: Ahw = Drawdown in water-table aquifer and H = Original saturated thickness of aquifer] Substituting the above in equation ( I) of Hanna. Azrag and Atkinson [4nT Ah - 2H ) Qj2.25 T t(2) 1 nr2 S W] Since the above expression predicts lower pump rates, it causes the Jacob-Lohman equation to agree more closely with appropriate analytical and numerical models. Figure 1, adapted from Fig. 5 of Hanna. Azrag and Atkinson, illustrates the closer agreement of the modified equation to their numerical model, as reflected in Qm/QJL ratios closer to unity. The agreement improves particularly as drawdown [Ah] becomes large in relation to aquifer thickness H. An additional advantage of the modified equation is that Hanna, Azrag and Atkinson's correction factor C is much more stable as pit depth increases. Assuming, as did Hanna, Azrag and Atkinson, that their numerical model is an accurate predictor, it is clear that the modification incorporated in equation (2) improves the accuracy of preliminary estimates of ground water flow to a pit.[ ] References Jacob, C.E and Lohman. S. W.. 1952, "Nonsteady flow to a well of constant drawdown in an extensive aquifer." Transactions, American Geophysical Union. Vol, 33, No. 4. pp. 559-569. Jacob. C. E.. 1963, `Determining the permeability of water-table aquifers,' USGS Water-Supply Paper 1536-1, pp. 245-271

Jan 1, 1995

By Thomas F. Martin, Daniel J. Sieve

In April 1988, the joint venture of Morrison-Knudsen and Paschen Contractors (M-K/P) was the successful low bidder for the Metropolitan Water Reclamation District of Greater Chicago's (MWRD) Contract Number 73-164-2H. This project is yet another in the MWRD Tunnel and Reservoir Plan (TARP) devised to control and treat overflows from combined sanitary and stormwater flows. M-K/P's project, located along the Des Plaines River, consists of 21,569' of tunnel mined to a 35' diameter and two tunnels totaling 14,529' mined to a 12' diameter. All three tunnels will have 12" thick reinforced concrete lining. The path for combined sewer/storm waters to reach the tunnels begins at a connection structure, continues through an approach sewer, a sluice gate structure and down a vertical shaft which is topped by a backflow structure. The purpose of the backflow structure is to prevent water surging to the surface as the system fills rapidly. Backflow preventors represent a change in design after problems developed on earlier constructed portions of the T.A.R.P.. On this project, 14 drop shafts channel flows to the tunnel system. In addition to the drop shafts, contract specifications require an emergency or escape shaft be located not more than 4000 feet from the tunnel headings. Due to long reaches without drop shafts, four access shafts had to be constructed. Thus, the total shafts constructed under this contract will be eighteen plus one 30' finished diameter construction shaft located within Miller's Meadows. Figure 1 shows the overall Des Plaines River System and the M-K/P contract connection to previous and future MWRD projects.

Jan 1, 1991

By Gregory Owen Lewis, Wendy Bouwer

Various processing strategies have been implemented in an effort to limit the loss of gold, during leaching, to the naturally-occurring carbonaceous 'preg-robbing' constituents present within certain gold bearing ore sources. Certain processing routes include complex and costly pre­treatment steps to reduce the negative effects of the preg­robber prior to dissolution, while others adopt a simpler direct leach/recovery approach. Process selection is largely dependent upon the gold deportment and the nature of the preg-robbing constituents within the particular ore. In the case of carbonaceous ores in which the bulk of the contained gold is available to direct cyanidation, carbon-in­leach (CIL) technology is generally applied with varying degrees of success. The effectiveness of the CIL route is governed by the competitiveness of the preg-robbing constituents in relation to activated carbon for the preferential adsorption of the solubilized gold. Trials have shown that the DOWEX MINIX strong-base gold-selective ion exchange resin has gold loading characteristics superior to those of activated carbon. The faster gold loading kinetics, together with the higher capacity of this resin, favour its use in an in-leach application as a more effective adsorbent for complex ores. This paper introduces the alternative resin-in-leach (RIL) technology, compares the metallurgical responses to RIL processing of different problematic ore sources, and discusses the interaction between various process conditions. Selected results from laboratory and pilot-scale testwork are presented to highlight the discussion.

Jan 1, 2000

By K. R. Weller

In recent years, a variety of new or substantially modified grinding machines have been offered to the mining industry with claims of improved performance relative to standard grinding machines especially rod and ball mills. The incentive for developing such new machines is high, because costs associated with grinding are a very substantial part of the total costs of processing run-of-mine ore, and gold ores are no exception in this regard. The incentive is also high because of the very low conversion of input energy to comminution energy in most tumbling mills. If the most energy-efficient means of mechanical size reduction is slow compression of single particles, then this energy amounts to only about 3% of that used in tumbling mills. It would seem, therefore, that there is a huge potential to do better. This paper examines three types of grinding machine for which claims of higher energy utilisation ( amongst other beneficial claims) have been made, namely the high pressure grinding rolls, the vibrating drum mill and various styles of stirred mill. It presents evidence concerning the claims, examines the range of particle size and particle size reduction over which benefits might reasonably be expected to accrue, discusses the major issues in contention and briefly describes the research the CSIRO Division of Minerals has in progress, both independently and collaboratively, the latter mainly with the Julius Kruttschnitt Mineral Research Centre (JKMRC) via the Cooperative Research Centre for Mining Technology and Equipment (CMTE) and the Australian Mineral Industries Research Association (AMIRA). There are many criteria which may be chosen to assess relative performance of grinding machines. Those used below are:

Jan 1, 1995

By Nathaniel Arbiter, Brij M. Moudgil

Separating oil shale from waste material or into high- and low-grade fractions can have a major economic influence on the surface retorting process. Different shale rock components vary significantly in physical and surface chemical properties, such as specific gravity, color, and water wettability. Various techniques that use the differences in one or more of these properties have been proposed to preconcentrate oil shale before retorting. This article discusses some proposed techniques, such as gravity separation, sorting, and froth flotation. Retorting oil shale is the most common method for recovering oil from the rock. This process is accomplished either underground (in situ) or above ground (ex-situ or surface retorting). Both techniques have serious limitations, such as low recoveries in the underground method and the ability to process rich shales only in the above ground retorting method. Also, environmental problems are associated with both techniques. Some of these limitations could be overcome if feed to the retorts is of consistent grade. This could be achieved by selecting appropriate sites for in situ retorting and selective mining for surface oil shale retorting. Both of these, however, would have a serious economic impact on shale oil recovery. Obviously, little control can be exercised over preparing feed material in the in situ retorting process, but beneficiation of oil shale could definitely be advantageous in surface retorting, and should have positive influence on the overall economics of recovering oil from the shales. For example, preconcentration of mined shale could result not only in reduced costs for materials handling, but also in waste disposal costs, since waste characteristics before and after the retorting process are significantly different. Upgrading the oil shale might also allow substitution of alternate technology for retorting as well as extend the process to recover oil from marginal deposits. Also, the separated material may become a potential source for recovering other values from shale deposits. Overall, the incentives for preconcentration are to reduce costs and improve thermal efficiency of the recovery process. Oil Shale Properties Important to Preconcentration Oil shale is a carbonaceous rock assaying 5-30% organic material (kerogen) and 70-95% ash-forming minerals. Kerogen is soft, nonbrit¬tle or semi-brittle material, and generally forms a matrix between irregularly distributed mineral grains. Inorganic mineral mat¬ter-quartz, feldspar, dolomite, kaolinite, dawsonite, and nahco-

Jan 9, 1982

By J. D. Megeath

In the October 1988 issue of MINING ENGINEERING, J.G. Wargo's paper discusses the problem of measuring and analyzing permeability, porosity, and fracturing in its relation to in situ leaching of disseminated gold deposits. This paper made me suspect that a good deal of information and analysis may have been done on this in reverse in the petroleum industry. Some years ago, I was involved with the US Geological Survey in a project studying the Devonian shale of the eastern United States. The Devonian shale contains gas deposits that have the characteristic of slowly seeping gas over a very long time period. To understand the rate of seepage, considerable study and analysis was done on the interrelationship of poros¬ity, permeability, and fracturing. The purpose was to find out how and why the gas could escape in the varying rates found in wells throughout the formation. It strikes me that this is the mirror image of the problem faced in attempting to understand how a cyanide solution will travel into a deposit. To possibly invent our own personal wheel a little faster, I would suggest a look at the work done on the Devonian shale. Some of it is contained in "Estimates of Unconventional Natural-Gas Resources of the Devonian Shale," US Geologi¬cal Survey Open-file Report 82-474, 1982, and "Additional Data for the Estimates of Unconventional Natural-Gas Re¬sources of the Devonian Shale," Open-file Report 83-676, 1983. It is entirely possible that some of this previous work could shorten the time required to make in situ leaching of dissemi¬nated gold deposits a profitable technique.

Jan 1, 1989

By J. I. Schoenherr, T. A. Baloun

Mixed cable waste, which amounts to more than 200,000 tpy in Germany, is subjected to recycling. In most cases cable recycling means only recovering copper and/or aluminum metals. The remaining cable waste contains nearly 3-8% of the reusable materials, and is disposed of in landfills. Aluminum is recovered within copper products and leads to lower product prices. Preliminary laboratory tests show that the use of shaking hydro-tables as well as electrostatic separators result in less than 1 % of metals in the residual material. The products are high in grade at metal recoveries of more than 85%. Furthermore, applying a modified electrostatic separator may also lead to an efficient Cu-Al separation. The separation efficiency amounts to up to 95%.

Jan 1, 2002

By Robert M. St. Louis, Frank D. Wicks, John E. Huffman, Edward E. Maurer

The treatment of Mercur's refractory ores has been well published; however, the processing of the remaining semi-refractory or oxide ores has not been discussed. Although ore control at Mercur is efficient, refractory vestiges are left with the mill-feed, oxide ores. Also, these ores as mined are not necessarily completely oxidized at Mercur and should be termed semi-refractory ores. This paper will discuss those steps taken at Mercur to enhance the recovery of gold from partially oxidized ores at Mercur. The Mercur mill is a conventional SAG/ball mill grinding circuit feeding a GIL plant. The circuit has been well published and will not be further reviewed.

Jan 1, 1990

By H. Hejny

The objective of the project is to construct and operate a pan-European underground drainage and minewater management research centre, which would be the hub for data gathering and dissemination in real time of new data to users for analysis and interpretation, as well as serving as a model for consistency, for other centres at key water management sites throughout Europe which would feed data in real time through the hub. The data from the centre will be essential for informing River Basin Management Plans arising from the EU Water Framework Directive, which is an important driver for the project. The implementation of this Directive sets out a requirement for all Member States to develop River Basin Management Plans for all water resource systems. The facility would be a major contribution to sustainable water management in Europe.

Jan 1, 2007

By Kenneth G. Knight, Frank L. Lynch

It's 12:30 A.M. The day before had been a long one with problems ranging from proper application of shotcrete during cold weather and the follow-on precautions for curing, meetings with city officials to avert a job shutdown because traffic wasn't being maintained properly and finally a briefing before METRO's General Manager to bring him up to date on projections for meeting the operational date of June 1975. The phone rings and Officer Jones of the Park Police says "Mr. Lynch, this lady in the apartments overlooking the jobsite is complaining of noise and she wants the job shutdown". "Officer Jones, have you called the Project Manager or the Resident Engineer?" "Yes, sir, but there is no answer!" "O.K., Officer, I'll check it out." In calling the job, I can only get the guard, because the inspector is in the tunnel. After some time, the guard calls back and says he doesn't know the way down into the tunnel. I have since had a difficult time believing that one. In the interim I finally reached the Resident Engineer and explained the situation. And finally at 1:30 A.M. the inspector called the Resident to say that the Park Police stopped the job at 1:00 A.M. because we didn't respond promptly. A similar situation had occurred some 2 years previously. With great expectation, noise specifications were developed to correct the earlier situation that had occurred. These newly developed specifications were in force at the time of this most recent shutdown. Common sense would tell you that even though we had developed and implemented, we believe, some of the best and most practical noise specifications in construction practice today, we had not enforced them. What caused the shutdown - a noisy

Jan 1, 1974

By Dale R. Ralston, Roy E. Williams, Gerry V. Winter, George L. Bloomsburg

Aquifer. A formation, group of formations, or part of a formation that contains sufficient satu rated permeable material to yield significant quan tities of water to wells and springs. Artesian. Synonymous with confined; see ground water, confined. Capillary fringe. The zone immediately above the water table in which all or some of the interstices are filled with water that is under less than atmospheric pressure and that is continuous with the water below the water table. Conceptual model. A conceptualization of a field hydrogeologic framework that facilitates the development of analytical field testing procedures. The results of the test(s) may force changes in the initial conceptual model. Conductivity, hydraulic. Replaces the term "field coefficient of permeability." The volume of water at the existing kinematic viscosity that will move in unit time under a unit hydraulic gradient through a unit area measured at right angles to the direction of flow, if the porous medium is isotropic and the fluid homogeneous. Confining bed. A body of "impermeable" material stratigraphically adjacent to one or more aquifers; its hydraulic conductivity may range from nearly zero to some value distinctly lower than that of the aquifer. Flow, steady. Any point where the magnitude and direction of the specific discharge are constant in time. Flow, uniform. At every point the specific discharge has the same magnitude and direction. Flow, unsteady. At any point the magnitude or direction of the specific discharge changes with time. Fluid potential. The mechanical energy per unit mass of a fluid at any given point in space and time with respect to an arbitrary state and datum; the fluid potential is proportional to the head. Ground water, confined. Ground water under pressure significantly greater than atmospheric; its upper limit is the bottom of a bed of distinctly lower hydraulic conductivity than that of the material in which the confined water occurs. Ground water, perched. Unconfined ground water separated from an underlying body of ground water by an unsaturated zone. Ground water, unconfined. Water in an aquifer that has a water table. Head, static. Height above a standard datum of the surface of a column of water (or other liquid) that can be supported by the static pressure at a given point. Homogeneity. Hydrogeologic properties are identical everywhere. Hydraulic gradient. Change in static head per unit of distance in a given direction. Hydrostratigraphic unit. A body of material having considerable lateral extent and comprising a geologic framework for a reasonably distinct hydrogeologic system. Isotropy. Condition in which all significant properties are independent of direction. Porosity. Property of containing interstices or voids; may be expressed quantitatively as the ratio of the volume of its interstices to its total volume. Porosity, effective. Interconnected pore space available for fluid transmission; expressed as a percentage of the total volume occupied by the interconnecting interstices. Potentiometric surface. A surface that represents the static head along a particular specified surface or stratum. Specific retention. Ratio of the volume of water that the rock or soil, after being saturated, will retain against the pull of gravity to the volume of the rock or soil. Specific yield. Ratio of the volume of water that the rock or soil, after being saturated, will yield by gravity to the volume of the rock or soil. Storage, specific. The volume of water released from or taken into storage per unit volume of the porous medium per unit change in head.

Jan 1, 1986

By Eileen Ashworth

Introduction A study was completed that investigated the enrollment in mining engineering programs in 24 universities and colleges. All programs considered in the study award four-year bachelor of science degrees in mining engineering. They also provide all the engineers for the mining industry and a large portion of the geotechnical engineers working on environmental problems, storage of hazardous waste, civic, and Federal government underground projects. The numbers used as the base for the study are those reported by each program to SME-AIME and published yearly (SME, 1986). Data for the study came from the period 1975-1985. Also, since some programs include students in related disciplines and special categories, such as cooperative students, a few inaccuracies were unavoidable. A 23-page document has been prepared that reports on the overall picture of current enrollment, the trends, and discusses the results, perceived effects, and what can, or should, be done. There has been an obvious, and dramatic decrease in total undergraduate enrollment since the late 1970s. In 1978, 3117 students were enrolled. In the 1985 fall semester, enrollment was 1022, less than one-third. There were 485 seniors, 265 juniors, 147 sophomores, and 125 freshmen. The downward trend in total enrollment is likely to continue for at least another two years. Class size The catastrophic drop in enrollment is shared by all programs across the country. It does not discriminate between types of programs, coal or hard rock mining, or location. In general, 1985's enrollment is about 30% of whatever the maximum enrollment was in any program, though this varies from the teens to 50%. The latter percentage occurs only for some programs with special circumstances, particularly new programs not well established in the late 1970s. The beginning of the decline in enrollment has occurred at slightly different times as affected by the demise of each program's local industry. The numbers in each class produced from a specific freshmen year (Fig. 1) are worthy of comment. The dramatic drop in enrollment for all classes after 1982 is clearly demonstrated. The timing coincides with the general downturn in the mining industry, when many employed engineers were laid off and new graduates could not find jobs. Also, significantly fewer students are being attracted to mining programs as freshmen. The number of seniors shown seems inappropriate. Where did so many seniors come from and why are so few graduates produced? There is an increasing trend for students to take four-and-a-half or five years to graduate. Therefore, they are counted twice, once when they are first classed as seniors and again the following year. Some students purposely delay graduation to obtain more summer work experience and take additional courses. They believe that this gives them a better

Jan 8, 1986