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By Lyle A. Hale

The subject area known as upper Dry Valley is located 15 miles due east of Soda Springs in Sections 14 and 23, Township 9 South, Range 44 East, Caribou County, Idaho. The railroad extending from Soda Springs to its terminus at El Paso's Maybe Canyon mine is 8z miles to the north in lower Dry Valley. Initial data derived from trench work in 1962 revealed a variety of econom¬ically significant alterations of the phosphatic beds related to the rather unique geomorphic development in the northern part of phosphate lease 1-012989. It was apparent that such conditions, while valid for near-surface beds in a strike direction, would be misleading if projected to the proposed depth limits of strip mining. Consequently, a subsurface mapping program was initiated in 1963 to determine: (1) the depth and horizontal extent of weathering and related phe¬nomena, (2) the depth, thickness, and quality of ore beds and intervening strata, and (3) structural geology as a guide for mining procedures. Successful use of a scintillometer in 1956 to detect the subcrop position of phosphate beds in the Smokey Canyon area of southeastern Idaho led to the conclusion that gamma radiation surveys of drill holes could be a useful aid in subsurface mapping. The objectives of this paper are: (1) briefly to describe geologic features characteristic of the phosphate lease area and (2) to demonstrate the practical application and theory behind gamma radiation logging as an effective tool in the economic evaluation of a phosphate lease.

Jan 1, 1969

By D. M. Larsen, K. R. Gardner, P. B. Altringer

The Bureau of Mines, U.S. Department of the Interior, is conducting batch and small- scale continuous laboratory studies on the biologically assisted removal of selenium from process waste waters. Mixed cultures of gram- negative bacteria isolated from several brackish water marshes are capable of reducing selenate [Se(VI)I to selenite [Se(IV)I and precipitating an amorphous elemental selenium product. Selenium extractions ranged from 80 to 96% regardless of the initial selenium concentration. The conditions for rapid bacterial growth and reactor design for optimal selenium removal have been investigated. The mechanisms of bacterial reduction and the rate of selenium removal for scaleup to larger systems is discussed.

Jan 1, 1989

By Frank F. Aplan

Introduction Gravity concentration may be defined as that process where particles of mixed sizes, shapes, and specific gravities are separated from each other by the force of gravity or by centrifugal force. The nature of the process is such that size and shape classification are an inherent part of the process in addition to separation on the basis of specific gravity from whence the process got its name. Mother nature has long practiced this form of mineral concentration by concentrating such heavy and relatively indestructible minerals as gold, platinum, cassiterite, ilmenite, zircon, and diamonds in placer or beach sand deposits. Once freed of their host granitic or other rock through natural weathering processes, these minerals are then subjected to stream or wave action producing a natural classification and concentration of the heavy minerals. Gravity concentration dates back to antiquity and was certainly the first ore concentration process used when selective mining and hand sorting would no longer suffice to produce the quality of concentrate desired. Forerunners of the present day sluice box and panning techniques were undoubtedly used by the ancient Egyptians on the upper Nile to separate gold from stream gravel. By the second century BC the extraction of gold from veins in quartz was well detailed by Agatharchides, but there is evidence that gold was brought into Egypt from the south as early as the XI1 Dynasty (~1900 BC).1 Most assuredly gravity concentration devices were used during the later Bronze Age to separate the heavier tin and copper minerals from their lighter gangue minerals. The Athenians used an elementary form of Rowing film concentration at their lead-silver mines at Laurium,2 and elementary jigging using wicker baskets was also probably developed at this time. Agricola's famous treatise De Re Metallica3 demonstrates that by the 16th century gravity concentration technology was well advanced and a large number of devices had been developed. Chinese

Jan 1, 1985

By Yu. A. Polozov, V. A. Lagunov, O. Yu. Lushinkova, Yu. I. Svirskiy, Eh. Ya. Kipko, Roy A. Williams

Hydrodynamic investigations in exploratory boreholes and grouting holes are conducted for the purpose of obtain¬ing information about the hydraulic properties of the hydrostratigraphic section to be intersected by the proposed underground workings. The information obtained from the investigations provides the basis for calculating the hydrau¬lic coefficients of fractured permeable rock, the dimensions of the anticipated grout isolation curtain(s) around the un¬derground workings, the number and location of grouting holes, the injection pressure modes, and also the volume(s) of grout that will be required (Anon., 1976, 1978). The following data on each aquifer are obtained from the investigations conducted in monitoring and grouting bore¬holes and the analysis of the results: 1) the top of each hydrostratigraphic unit, 2) the thickness of each unit, 3) the ground water fluid potential distribution in each unit, 4) the coefficient of permeability, 5) the piezoconductivity, 6) the fracture porosity, 7) the geometry of the fractures in the rock, 8) the elasticity-compressibility coefficient of the fractured rock, 9) the chemical composition of the ground water, 10) the direction of flow of the ground water, and 11) the expected inflow rate of water into the shaft, drift or tunnel. STG uses its DAU-3M type flowmeter to conduct in¬vestigations of directions of flow in vertical, inclined and horizontal drillholes. The DAU-6 instrument is used to de¬termine the direction of flow of ground water in each frac¬ture or fractured aquifer. Various singular and double DAU type packers are used for pumping and for injection studies (tests) and for flowmeter investigations. Normally the instruments enumerated above permit in¬vestigations to be conducted in each separate aquifer with¬out reinforcing the holes with casings. On the basis of these investigative data, both the hydraulic properties of unfractured rock and the hydraulic properties of the fractured rock are estimated. Dual porosity rocks require special attention because they tend to segregate the grout. 3.1 FLOWMETER INVESTIGATIONS IN BOREHOLES The STG flowmetric methodology is based on the mea¬surement of the ground water flow rate through the borehole by hydrostratigraphic interval after the disturbance of the hydrostatic equilibrium in the "hole-aquifer system" (after pumping or injecting). The relationship of the head changes to the discharge into or from a particular hydrostratigraphic unit obtained during the tests serve as the basis for calcu¬lating the hydraulic properties. Flowmetric investigations facilitate the determination of the number of aquifers, their depths, their thickness, the hydraulic properties of the fractured rock and the magnitude and direction of the flow of ground water. 3.1.1 FLOWMETER HARDWARE STG conducts flowmetric investigations in boreholes using its DAU-3M-108, DAU-3M-73, DAU-3M-57 and DAU-3M-44 instruments.' They have respective external diameters of 108, 73, 57 and 44 mm. The type of flowmeter selected for use depends on the borehole geometry and the technological scheme for carrying out the investigations. Boreholes with a drilling diameter of 76-93 mm are inves¬tigated with the DAU-3M-73 flowmeter; boreholes drilled by bits with a diameter of 112 mm and more are investi¬gated using the DAU-3M-108 flowmeter. The DAU-3M¬108 and DAU-3M-57 instruments are used for flowmetric investigations with a packer. 3.1.1.1 The Downhole Sensor The sensor design of the DAU-3M-73 hole flowmeter is shown in Fig. 2. The design of the DAU-3M-108 instru¬ment is similar to the design of the DAU-3M-73 instrument. The frame of the flowmeter sensor shown in Fig. 2 consists of a casing, an upper and lower centering mount and two rings to which the guiding rods are attached. The upper rods are built into the connector bushing; the lower rods are built into the coupling sleeve. The borehole cable is attached using a half-coupling, a packing ring and a constriction nut. Thus, the frame of the flowmeter sensor is made so that the free passage of water to the impeller is facilitated along with the necessary rigidity. The primary moving component of the flowmeter is the double-bladed impeller, which rotates on cobalt-tungsten pivots and agate thrust bearings. Special extended air cham¬bers protect the supports of the impeller from the action of the borehole fluid which may contain fibrous and abrasive particles. The air located in the chambers shields the sup¬ports from direct contact with the borehole fluid when the sensor operates in a borehole. The hollow casing of the impeller serves the function of a lower cap. The upper cap is attached to the casing using a threaded connector; it is affixed also with a lock-nut. An adjusting screw with a

Jan 1, 1993

By A. R. Bath

During the late 1970s, pilot mining tests carried out on manganese nodules in the Pacific Ocean and metalliferous mud in the Red Sea demonstrated the technical feasibility of deep sea mining operations. However, the production of manganese nodules on a commercial scale is subject to numerous technical problems. As a result, a German-French joint development project has been underway since 1985. This venture focused on three key points: nodule pick-up device, locomotion of self-propelled collectors and hydraulic lifting of nodules. This paper presents the scope of this research and development program, its main results to date and future prospects.

Jan 1, 1992

By E. J. Berentsen

The Turquoise Ridge gold deposit is located near the Getchell Mine, 72 km (42 miles) northeast of Winnemucca, Nevada. The deposit is owned by First Miss Gold Inc. The host rocks consist of Ordovician and Cambrian age shales and limestones. They have been crosscut by the northeast-trending Turquoise Ridge shear zone and northwest-trending shear zones. Gold mineralization occurs at depths from 427 m (1 400 ft.) to 671 m (2 200 ft.), along the intersection of these structures. Large tonnage, flat-lying deposits occur where folded, favorable beds are intersected by the faults. The carbonate within the beds has been replaced with silica, pyrite and arsenic sulfides.

Jan 1, 1996

By Peter L. Hofmann

Significant quantities of nuclear wastes were first generated in 1944 as a byproduct of the national defense program. To establish the current inventories and future projections of nuclear waste products is not a simple task. The Oak Ridge National Laboratory recently issued a report which now constitutes the official basis for nuclear waste inventories and projections. Radioactive wastes originate from five major sources (U .S. Department of Energy, 1980b) : (1) From the commercial nuclear fuel cycle related to the production of electricity , (2) From defense related activities, (3) From institutions such as hospitals, universities, and research foundations, (4) From industrial uses of radioisotopes, and (5) From mining and milling of uranium ores.

Jan 1, 1981

By R. K. Singhal, H. Sahay

Introduction In terms of the world's recoverable coal reserves, Canada ranks 10th, providing 0.6% of the world's total. The US is first with 27.8% and the Soviet Union follows with 24.1%. Figure 1 shows the principal coal mines in Canada. Several provinces contain substantial coal deposits, but the largest deposits are found in the western provinces of Alberta, British Columbia, and Saskatchewan. Conservatively, 90% of the lignitic, 80% of high volatile bituminous, and nearly 100% of subbituminous, and low and medium volatile bituminous coals are located in these three provinces. During the past decade, Canadian coal production of all types increased from 18.8 Mt (2 million st) in 1972, to 25 Mt (28 million st) in 1975, to 61 Mt (66 million st) in 1984. About 38 Mt (43 million st) of this output was classified at thermal and 23 Mt (25 million st) as coking and metallurgical coal (Table 1). The three western provinces currently produce 57 Mt (62 million st) of coal - 95% of Canada's total. The remaining 3.6 Mt (4 million st) (5%) is produced in Nova Scotia and New Brunswick on the east coast. The majority of western coal (98%) is produced by surface mining methods. On the east coast, though, mining is predominantly underground and only 15% is produced on the surface. In 1985, Canada exported close to 28 Mt (30 million st) of metallurgical coal and thermal coal. During the same period, 15 Mt (16 million st) of coal were imported, mostly from western US for use in Ontario and Quebec. Almost 60% of the imported coal was used for thermal applications. The remaining 40% was metallurgical coal for the steel industry. It is generally cheaper to import coal into central and eastern Canada from the eastern US to augment local supplies rather than from western Canada. This is mainly because of high transportation costs. Mining methods The suitability of mining methods in a particular area depends largely on the geological setting. Geology, therefore, simplifies or adds complexities to mining operations, directly affecting the economics. It also influences the flexibility required from the min-

Jan 9, 1986

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 D. Morin, J. Villeneuve, S. Foucher

The development of new processes has to follow "best practice" rules in order to be technically and economically as efficient as possible. However, innovations, new process routes and new rules are continuously emerging to minimize financial risk and maximize environmental compliance. Process simulation, which offers a complete overview of the flowsheet, makes it possible to cope with this new challenge-minimizing waste production and water consumption. Furthermore, simulation provides an estimate, at the early stage, of the cost of alternative technical routes. Four examples involving biotechnological circuits are presented, both at the design and commissioning stages.

Jan 1, 2000

By D. L. McClure

Gold mineralization at the Colosseum Mine is submicroscopic and associated with pyrite. Pyrite occurs in breccia clasts, replacing dolomite, in crackle breccia veinlets with traces of quartz, and as disseminations in two small, interconnected intrusive pipe complexes of rhyolitic felsite and breccias of felsite and wall/country rock. Breccia types grade from felsite plus wall rock of Pre-cambrian gneiss to cross-cutting breccias "of felsite, gneiss, and Paleozoic sedimentary rocks that are in contact with the Precambrian gneiss terrane one-quarter mile (40Om) southwest of the Colosseum pipes. Mineable reserves are estimated to be 8 million short tons (7.3 million metric tons) at 0.074 troy ounces of gold per short ton (2.3 g/metric ton) at a cutoff of 0.03 troy ounces of gold per short ton (1.0 g/metric ton).

Jan 1, 1988

By G. R. Addie

While the cost of transporting raw phosphate matrix from a pit to a processing plant via slurry pipelines is more efficient than it could be by rail cars, conventional trucks or belt conveyors, it still amounts to many millions of dollars, and in many areas there still exists much room for improvement. By taking advantage of pipeline test data on different slurries, it is possible to reduce costs by optimizing pipeline diameters, operating velocities and slurry concentrations. Better wearing, more efficient pump designs are now available which, if applied correctly, can lead to significant savings. The authors discuss what benefits are possible in relation to the electrical operating and wear maintenance costs and go into some of the factors associated with taking advantage of these benefits, identifying what they see as being practically possible.

Jan 1, 1998

By Ammar Henchiri

INTRODUCTION A current need of the phosphate industry is the development of process technology for treatment of high carbonate content ore. About 75 to 80 percent of the world phosphate reserves (1) are associated with carbonate gangue, which is not amenable to treatment by the existing techniques. Numerous laboratory and pilot plant studies have been devoted to carbonate-phosphate separation. Different techniques were involved (washing, sieving, attrition, flotation, calcination, and leaching). For technical and economical considerations, flotation appears to be an efficient process for this problem. Separation of carbonates (calcite and dolomite) from igneous phosphate is applied in industrial plants in Brazil, Finland, and South Africa. But, for sedimentary phosphate, no industrial realization exists at this time, with the possible exception of some plants in China. The main problems with sedimentary phosphates are: • high substitution by CO3-2 and F- for P04 -3 in the apatite lattice. • larger surface area of the phosphate particles because their surface is porous and irregular. • tendency of sedimentary minerals to produce more slimes in conditioning than the crystalline minerals, hence, larger dosages of collectors are required for sedimentary minerals. Investigations reported in the literature indicate that most processes developed for sedimentary carbonate-phosphate separation involved inverse flotation of carbonates using fatty acids as collectors (2), (3) associated with phosphoric acid (4), monosodium phosphate (5), F- (6), or SiF6 -2 (7) as phosphate depressants. Later investigations, conducted by A. Henchiri and G. Baudet (8), (9), (10), (11), (12), (13) in the BRGM technology department, of phosphoric esters revealed that these reagents are selective collectors for carbonate-phosphate separation. The above investigators developed a process which used phosphoric esters to collect carbonate minerals and sulfuric acid or sodium fluorosilicate as depressants for phosphate. Extensive comparative tests for different processes on the same phosphate sample show that the process developed at BRGM is one of the most promising methods proposed for sedimentary phosphate-carbonate separation. It should be pointed out, however, that phosphoric esters make abundant froths. The handling of these excessive froths will be a problem in an industrial-scale plant. This paper outlines test work performed in order to optimize and to improve the efficiency of the flotation process on a sedimentary phosphate ore selected from the Sra Ouertane orebody. The Sra Ouertane flotation process, illustrated on Figure 1, first removes carbonate minerals by inverse flotation and then recovers phosphate as a froth product, leaving quartz as a cell product.

Jan 1, 1993

By R. K. Rajamani

The theoretical model based on fluid mechanics, in conjunction with the laser-Doppler velocimetry (LDV) measurements, elucidate the size-classification mechanisms in an industrial hydrocyclone. The model has no adjustable parameters and involves solving the Navier-Stokes equations to predict the liquid-phase velocities. The spatial-concentration gradients were determined considering the particle phase in the Lagrangian frame and the classification curve was determined by balancing the forces acting on the particle. The force balance requires liquid velocities, which in turn depend on the local volumetric concentration of the particles. Hence, complete modeling work involves coupling both the concentration and liquid-phase velocity calculations until convergence is reached. Finally, the experimental and predicted classification curves were presented for 250-mm hydrocyclone operating at high-percent solids.

Jan 1, 1994

By Carl P. Maronde, William P. Barnett, Patricia A. Rawls

The commercial deployment of advanced fine-coal cleaning technologies depends on cost-effective approaches for efficient separation and ancillary operations in handling, dewatering, drying, and transporting coal fines. As a result of two solicitations under the High-Efficiency Preparation component of the Department of Energy Coal Preparation Program, several projects were initiated for testing and evaluation of emerging technologies and equipment that address operational difficulties associated with coal fines. This paper will update the status of those projects and discuss how the technologies they represent can ameliorate some problems associated with coal fines in today's preparation plants.

Jan 1, 1995

By W. R. Dearman, N. Turk

A seismic fissuration index (K) is defined as the ratio of the difference in the P and S wave velocities obtained when a dry rock specimen is tested both under a load equal to half the uniaxial compressive strength of the rock (Vo) and without an applied load (Vd) to the velocity obtained without an applied load (Vd), as K = (Vo - Vd)/Vd. A similar seismic fissuration index is also proposed for classifying the dry rock mass in terms of field seismic velocities. The field equation is extended by including the intact rock seismic velocities. K is found to be related to the porosity of rocks. The proposed equation can equally be used for characterizing saturated rocks, using S-wave velocities. However, the time average equation should be used for characterizing saturated rocks, using P-wave velocities, even though this equation gives upperbound estimates of the rock material and fracture porosities.

Jan 1, 1986

By Richard H. Kennedy, G. A. Swanquist, John W. King, Frank F. McGinley, Dale C. Mathews, Hans H. Adler, E. C. Peterson, Ralph M. Wilde

INTRODUCTION From the first historical records of the discovery of uranium as an element and the attempted classification of its minerals in the early 18th century-through its first uses in pigmentation and the coloring of glasses and ceramic glazes-until 1939 when it was discovered that the isotope U235, was fissionable, uranium oxide in the form of pitchblende ores and concentrates (produced mainly in Bohemia, Canada, and the former Belgian Congo) in recent times was the source of uranium compounds incidental as byproducts to the recovery of radium from this invariable associated source. In 1938 this byproduct production from pitchblende concentrates was about 471 st of U3O8, with over 90% from Canada and the Belgian Congo and only 25.85 st from carnotite ores in the United States.1 Under the impetus of the Atomic Energy Commission's (AEC now part of the Energy Research Development Administration) domestic and foreign production incentives and buying programs, and as an initial assurance of atomic armament capability of the United States and the Free World, the growth of the uranium mining and milling industry burgeoned from 1952 to 1962. After a short period of decline, in the second decade and in large commitments beyond, it has again extended its capacity to meet ever-increasing fuel demands of atomic power generation by the electric utilities industry. In 1961 the peak production in the United States alone was 17,758 st of U3O8. Peak aggregate domestic and foreign deliveries of 34,581 st of U3O8 to the AEC occurred in 1960.z Canada's maximum delivery of 13,506 st of U308 was made in 1959. These peak and continued productions in the Free World are largely from: the Mesozoic (Jurassic) and Tertiary (Eocene) sandstones in the United States; the quartz pebble conglomerates of Canada and the Witwatersrand; pegmatites, Jurassic limestones, and Precambrian complexes, with less but significant production; the phosphoria, where byproduct production is minor. This uranium production in the form of precipitated concentrates has come from the milling of ores from these sources, both directly and by retreatment of gold cyanidation tailings on the Witwatersrand. Milling of crude ore has followed these processes: conventional crushing and size preparation, ore drying when required, salt roasting for high vanadium ores and byproduct vanadium recovery, carbonate or acid-leaching processes, classification sand-dine separations or countercurrent decantation (CCD) circuits and complete liquid-solids separations, resin-in-pulp (RIP) or liquid-liquid (solvent) ion-ex- change extractions, clarification of pregnant liquors, precipitation, filtration and washing, sodium and vanadium removals, and drying or roasting and packaging of the high-grade, high-purity uranium concentrate commonly referred to as "yellowcake." Coupled with the hazards and control of dust generation incident to conventional crushing and milling operations, more stringent control of airborne respirable and ingestible radioactive particulates and the protection of personnel against definitive external radiation are inherent to uranium milling. Impoundment and control of tailings and other effluents of uranium milling are more restrictive than in conventional practice, be- cause long-term disposal and containment of the uranium series of radionuclides, whether in solution or in solid form, are requisite to uranium milling and are made manadatory under regulatory agencies of government. 2. GEOLOGY AND MINERALOGY OF URANIUM Early Uses and Byproduct Production of Uranium Uranium was discovered by Klaproth in 1789 but had little commercial importance until the discovery of uranium fission by Hahn and Strassman at the close of 1938. The well-known uranium ores of Joachimsthal, Czechoslovakia, the Congo, and the Colorado Plateau were early sources of radium. Minor quantities of uranium were used for small-scale technical and industrial applications, particularly in coloring glass and ceramics, but most of the uranium was discarded. The Colorado ores were also mined later, chiefly for vanadium. Impetus of Armament Capability and Fuel Demands for Atomic Power Following the discovery of atomic fission, uranium became critically important for military applications and, more recently, as a nuclear fuel. Prior to 1966 uranium was acquired in the United States almost solely for use in the weapons program of the AEC. By 1970 the AEC had procured approximately 325,000 st of U3O8 from domestic and foreign sources. Current and future marketability is primarily dependent upon commercial demand for reactor fuel. Estimates of

Jan 1, 1985

By D. F. Boyd

On April 10, 1958 a new 7500 long ton/day iron ore beneficiation plant went on stream producing an average of 3000 long-tons of high quality concentrate a day. Plant operates on two, 12-hour shifts is six days per week, The new mill end crust ink plant were built adjacent to the company's open pit dining operate on at Bomi Hills, Liberia. The mall is essentially a gravity concentrator employing crushing, and grinding to liberate the mineral values, followed by concentration in Humphreys spirals. The cleaner spiral tailings are re-ground and tabled to recover additional iron values. Ire addition to. this mills the company operates a crushing and screening plant for the high grade direct shipping ores

Jan 1, 1962

By J. H. Adkins

The goal of the project reported in this paper was to make recommendations for changes in roof bolting procedures and bolter design that would reduce roof bolter accident rates. To that end the project identified the major hazards associated with each task a roof bolter operator per-forms, normalized task accident frequencies. by the time spent on each task, reviewed equipment design features and operating procedures related to the identified hazards and developed recommendations for equipment and procedural changes that would reduce, if not eliminate, the hazards. The research steps completed during the project were: a. A review of related literature and re-search including roof bolting time studies b. The collection and analysis of 1975 accident data pertaining to roof bolter activities c. The normalization of the accident frequency data on the basis of time/task data d. A review of roof bolting equipment e. The development of a field data collection instrument f. The selection of mines for bolter observations g. The collection of field data h. Data analysis and problem specification i. The development of recommendations for corrective measures

Jan 1, 1978

By A. Afrouz, F. P. Hassani

The types of bulkhead that contain backfill in stopes under various pressures and mining conditions are outlined. Conventionally adopted theoretical and empirical techniques were integrated in the design and construction of each type of bulkhead utilized underground. Methods to monitor the performance of bulkheads are discussed.

Jan 1, 1993