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By George Gauci

INTRODUCTION The Broken Hill orebody was discovered in 1883. The richness of the deposit encouraged rapid development of the field and within fifteen years ten mining companies were operating. By 1940, several companies located in the centre of the field with limited reserves, had ceased operation. These leases have been acquired by Broken Hill South Limited and North Broken Hill Limited. The four companies currently operating in the field are, in order of increasing production rate:¬- Broken Hill South Limited (BH South) North Broken Hill Limited (North BH) The Zinc Corporation, Limited (ZC) and New Broken Hill Consolidated Limited (NBHC) The tonnages treated by each company since the present plants have been in operation are shown in Figure 1. The leases are located as shown in Figure 2, and an aerial view of Broken Hill showing the spread of the City on each side of the line of lode is shown in Figure 3. The present treatment plants date back to the early 1930's when the BH South plant was built. The North BH and ZC plants were built in 1939 and NBHC's in 1952. The three plants built before 1940 have similar crushing and grinding flowsheets. NBHC differs in that it includes rod mills with consequent differences in fine crushing equipment.

Jan 1, 1970

By Fukuichi K, Matsukawa H, Nakagawa M

The Myojin Tunnel, located on the Shikoku Expressway being constructed by the Japan Highway Public Corporation, is 3,770 m long with a cross sectional area of 80 m2. Kajima Corporation, the contractor for the northern construction section of this tunnel, adopted here its newly developed "mini-bench" method of excavation. The objectives of this method were 1. to be able to perform all tunnelling operations using the whole cross sectional area of the tunnel under any ground conditions, and 2. to be able to vary the length of the mini-bench within the range of 0 to 7 m according to ground conditions. In order to achieve these objectives, original, sophisticated equipment was developed and employed in the work. One of the newly developed machines is a special jumbo, a hydraulic crawler jumbo with five rotary type booms. This machine is capable of accommodating variation in the length of the mini-bench accompanying changes in ground conditions and is equipped with a special mechanism by which the positions of the booms can be controlled by means of hydraulic cylinders. Also developed was a shotcrete robot for use with the mini-bench method which has the control board near the shotcrete nozzle for close control of application.

Jan 1, 1987

By Churchill M

One of the significant changes which has occurred in the flotation sector of the minerals industry, over the last two decades, has been the successful development of the very large flotation machine. The last twenty years has seen the volume of the individual cell, available to the industry, increase by a factor of ten. Today, new mills, and existing mill modernization plans, can consider individual cell volumes as large as 85 m3 with the certainty that the metallurgical performance capability of the large machine is inherently as efficient as the smaller machine. The large flotation cell offers benefits to the user such as reduced floor space, lower total power, process control simplification, and reduced maintenance. However, the flotation machine size selection process, based on overall installation economics, must include such factors as process tonnage, flotation kinetics characteristics, and metallurgical performance objectives. This paper discusses the flotation machine size and circuit arrangement selection based on both metallurgical performance and economic considerations. A computer based flotation kinetic analysis technique, which has proven valuable in quantifying the metallurgical response of flotation circuits having different cell sizes and number, is utilized to illustrate the selection of cell size and arrangement best suited to a client's Requirement.

Jan 1, 1991

By Jon E. Bischoff

Construction of a secondary clarifier on the banks of Rainy River, Northern Minnesota, required the driving of H-piles 14HP102 to a sloping, very strong bedrock through thick deposits of soft and medium stiff soils. Pile toe protection, APF Hardbite HP 77750, was specified to prevent damage to the pile toe and to enable the pile toe to bite into the bedrock surface. The toe protection worked well for bedrock sloping less than 2H:1V. However, where the bedrock was steeper, the piles experienced damage and failed to reach bearing. In most cases, the also the replacement pile failed. Pile Driving Analyzer measurements showed that on encountering the bedrock, the pile toe reflection, which at first was sound, deteriorated indicating pile toe damage. Extraction for visual inspection showed that the failed piles were bent and had deformed pile shoes. In areas of steeply sloping bedrock and for replacement piles, an alternative shoe, the Scanpile Herkules rock shoe, was employed. This pile shoe proved to be able to secure the pile toe into the rock and to eliminate the problem. The costs of the Herkules rock shoe considering price, shipping, and attaching, were about equal with the Hardbite shoe.

Jan 1, 1993

By Mike Amick

As virgin coal reserves dwindle, more and more mines are being opened in areas with previous mining. As addressed in this conference before, there are solutions available for designing mines extracting coal from reserves with known underground workings above or below the target seam. Often times, however, mining begins with limited knowledge of the underground workings. Even with careful planning, the proposed design has limited success because the ?facts? as presented during planning turn out not to be as accurate as one would like. At National Coal?s Mine #14, mining the Walnut Mountain seam, after driving the main entries in some 34 crosscuts, it was found during routine mine examinations that the pillars had separated from the roof in a few areas of the mains. Immediate roof conditions proved to be sound but questions arose concerning the stability of the main roof and floor. Core tests were done to better determine the rock strengths and characteristics. The paper presents the ideology used to tackle the effects of mining over old works in an operating coal mine. This paper discusses the analysis of the symptoms observed and the steps taken to ensure that this pillar separation was caused by the underlying old workings and that the separation was expected and controllable.

Jan 1, 2009

By Jessica M. Wempen, Dallan J. Coons, Bailey S. Simmons, Michael K. McCarter

Gate-road yield pillars are subject to increases in stress as the longwall face advances toward the pillars. Increases in pillar stress can be inferred by measuring roof/floor convergence surrounding the pillar. This paper presents a case study of convergence measurements surrounding a two-entry gate-road yield pillar in the head gate of a coal mine. Convergence was measured over a six-month period, as the longwall face approached and passed the pillar. Measurements were collected at eight locations surrounding the pillar: four locations in the travelway and four locations in the beltway. In addition to convergence stations, the pillar was instrumented with an array of seismometers. In future analysis, convergence measurements will be compared to seismic interpretations. This study reports on the geology and geometry of the longwall panel, the roof and rib support, the change in convergence over time, and the physical properties of coal and parting. Additionally, the convergence measurements are compared to pillar safety factor distributions derived from a finite element model. The convergence measurements contribute to the knowledge of when yield pillar abutment loading, caused by the encroaching longwall, is first detected. Knowing when abutment loading begins to yield the pillars can help define when standing secondary roof supports are required for head gate entry support.

Production from a major, deep orebody requires the construction of two 6 m diameter, 1000 m deep ventilation shafts over the next three years. Further ventilation upgrades have foreshadowed an additional 1500 m of 6 m diameter shafts beyond that. After reviewing the construction alternatives it was decided to raisebore the first shaft in one pass using Western Mining Corporation's 121R raiseborer and the Wirth sequential head. The significant cost and speed of construction potential of 6 m raiseboring justified the risks associated with this new technology. Large diameter sequential head raiseboring has only been carried out in South Africa. Over the last three years many lessons have been learnt and the technology has progressed to being considered feasible. Operating practice and the optimisation of raiseboring performance for specific ground conditions are the areas requiring further work. The development of large diameter raiseboring in South Africa and the site preparation and initial operation at Z.C. Mines are described. Comment on actual operating experience includes the geotechnical investigations, the raiseborer foundations, cuttings disposal and the drilling of the pilot hole which has progressed to beyond 450 m. Unforeseen difficulties with the verticality of the pilot hole and with mud losses illustrate the types of problems that can be expected.

Jan 1, 1988

By Bruce W. Jack

An extensive underground roof-monitoring program was conducted in order to determine the roof strata behavior under various conditions. In total 29 sites at 5 different collieries were monitored using the sonic probe extensometer. Results showed that, in drill and blast sections, there are often pre-existing openings in the roof prior to the installation of the support. An estimated 42 per cent of the total roof displacement monitored in drill and blast sections took place prior to the installation of support. A comparison between roadways and intersections indicated that, for a 40 per cent increase in the span, taken across the diagonal of art intersection, relative to the roadway width, the magnitude of the displacement in the roof increased by a factor of 3. Total displacements measured were relatively small, only 2 reaching double figures of 12 mm. The remainder were all less than 7 mm. The results also showed no evidence of a substantial increase in the height of the bed separated, potentially unstable roof strata, as is the case in the high horizontal stress-driven beam-buckling mechanism experienced in for instance some Australian coal nines. Therefore, it was concluded that, in South African collieries, the effects of horizontal stresses is generally relatively small compared to overseas collieries.

Jan 1, 2000

Black coals occur in most of the major sedimentary basins in Australia. In addition to the better known Permian coal occurrences of the Sydney, Bowen, Oaklands and Galilee Basins, coals of Permian age occur in the Arckaringa Basin in South Australia, the Bonaparte Basin in Northern Territory and the Collie, Perth and Canning Basins in Western Australia and the Tasmania Basin in Tasmania. Coals of Triassic age occur in the Ipswich Callide and Tarong Basins in Queensland, the Tasmania Basin in Tasmania and the Leigh Creek area in South Aus- tralia. Coal bearing rocks of Jurassic age occur in the Mulgildie Basin and Maryborough Basins in Queensland and in both the Queensland and New South Wales portions of the Clarence Moreton Basin and Surat Basins. They also occur in the Perth Basin in Western Australia. Rocks of Cretaceous age known to contain coal occur in the Styx, Maryborough and Laura Basins in Queensland, the Gippsland Basin in Victoria and both the Queensland and New South Wales portions of the Surat Basin. The coal measures have been deposited in a variety of sedimentary environments and the coals vary widely with regard to thickness, extent, banding characteristics, maceral and ash content. However, they are generally of low rank and most are suitable only for steaming.

Jan 1, 1975

By John Hall

(New York Meeting, October, 1913.) THE Fremont test for measuring the energy consumed in breaking a notched bar of steel is not so well known in this country as it deserves to be. The test specimen used in this test is about 3/8 by 1/4 by about 11/4 in., notched with a hack saw on the lower side to cause the piece to break at a fixed point. A weight of 10 kg. falling 4 m., and provided with a knife or. chisel which strikes the specimen, breaks the test piece by impact. The residual force in the falling weight after it has broken the specimen is recorded by a suitable device, and the difference between the total energy and the residual energy of the weight (in kilogrammeters) is the force consumed in breaking the specimen. An experience of several years with the Fremont testing machine has shown its great value in readily detecting brittleness not revealed by tensile testing or slow bending testing. In this paper it is proposed to discuss (1) the supersensitiveness of the test as applied to cast steel and (2) its value in revealing the effect of heat treatment under certain conditions.

Jan 7, 1913

By Keith Heasley

As part of the initial investigation and validation of a new boundary-clement formulation for stress modeling in coal mines. the underground stresses and displacements at two multiple-seam coal mines with unique stress problems are modeled and predicted. The new program, LAMODEL, calculates stresses and displacements at the seam level and at requested locations in the overburden or at the surface. Both linear elastic and non-linear seam materials can he used: and surface effects, multiple seams, and multiple mining steps can be simulated. In order to most efficiently use LAMODEL for accurate stress prediction, the program is first calibrated to the site-specific geo-mechanics based on previously observed stress conditions at the mine. For this calibration process. a previously mined area is "stress mapped" by quantifying the observed pillar and strata behavior using a numerical rating system. Then, the site-specific mechanical properties in the model are adjusted to provide the best correlation between the predicted stresses and the observed underground stress rating. Once calibrated, the model is then used to predict future stress problems abead of mining. At the two case study mines, the calibrated models showed good correlation with the observed stresses, and also accurately predicted upcoming high stress areas for preventive action by the mines.

Jan 1, 1998

By J. M. Kuchta

The chemical and thermal criteria used for predicting the spontaneous combustion hazard are briefly reviewed and data are presented to characterize the gas desorptions and self-heating tendencies of 29 U.S. coals. Closed vessel desorption experiments showed that CO, CO2, and CH4 are the main gases evolved and that the CO, CO/?O2 index, and 02 absorption rate increase with decreasing rank and increasing oxygen content of the coal. In this Bureau of Mines report, the effects of temperature, moisture, and other variables are discussed together with the application of the data to the complex conditions encountered in a mining environment. An important finding is that the presence of CO alone in a mine is not necessarily an indication of a self-heating reaction of the coal. Based upon experiments conducted in an adiabatic-type calorimeter, the self-heating temperatures of lignite and subbituminous coals can be as low as 30° C, whereas the bituminous coals require a temperature of about 60° C or more. The self-heating hazard is greatest when the coals are dried and exposed to a high humidity condition, apparently as a result of the "heat-of-wetting." Generally, the hazard is greatest with the western coals of the United States.

Jan 1, 1980

FOR some years after the erection of the first chlorination plant at Mount Morgan the ore sent to the works for treatment was mined entirely from the oxidized zone; consequently, the bullion recovered at the refinery was of unusual purity, averaging about 972 in fineness, and, as no impurity in any way detrimental to the softness or toughness of the bullion was present, there was no necessity to subject it to any refining process.The charcoal from the filters was calcined to ash in small reverberatory furnaces of the usual type. The ash was mixed with suitable proportions of soda and borax to form a good liquid slag. This' mixture was then charged into salamander cruciblesand run to metal and slag in the ordinary wind furnaces-a slow and tedious proceeding in the Mount Morgan climate. The bullion, cleaned of slag, was re-melted under borax and poured into bars weighing from 350 to 400 oz.; these bars, after being dipped while hot into dilute sulphuric acid, were packed and sent to the mint. Of late years, however, the ore coming from the deeper ground of the oxidized zone became much lower in gold values, and contained variable but increasing quantities of sulphides, sulphates...

Jan 1, 1911

The need to solve the problems associated with spontaneous combustion, system of ventil- ation and methane drainage in gassy coal mines has brought about the development of mining and degassing methods which has made possible up to 80% gas recovery in retreating longwalls. Beneficial results also were obtained mostly in the double or multiple-entry systems, but for single-entry systems and for a seam thickness exceeding 3 m, gas recovery rate is still very low. With some single-heading systems, such as those where a return roadway is not maintained in the goaf behind the face line, a new methane drainage technology is practiced. Attempts were made to extract methane from roof holes drilled from offsets in the ribside of the longwall block. The inclinations and lengths of the boreholes were planned and designed on the basis of the geological and mining condit- ions encountered at the time and every second hole was terminated precisely at the point where the previous hole intersected the immed- iate roof goaf area above the face. There are mathematical relations approp- riate to the design of the above drainage systems to give optimum methane recovery under the given conditions. Some examples of drainage have reached 87% recovery and have attained 94% CH4 purity.

Jan 1, 1982

By Ancel St. John

DURING a session on coal and coke at the February, 1926, meeting of the American Institute of Mining and Metallurgical Engineers, the writer called attention to the important work on the X-ray analysis of coal1,2 being carried on in England by C. Norman Kemp and his associates. This aroused so much interest that a paper on the subject was requested for the October meeting. It has seemed advisable to make this paper a preliminary survey of the present status in the application of X-ray methods to coal problems and to follow it from time to time with further articles as the art develops. A survey of this sort naturally divides itself into two parts, radioscopic analysis of the distribution of constituents through the body of the coal, and diffraction analysis of the state of association of the elementary components. In this article the subject matter concerning radioscopic analysis has been drawn almost entirely from the writings of Kemp and his associates and the illustrations have been specially furnished by him. It is a pleasure to record here a great indebtedness for this courtesy and cooperation. The subject matter and illustrations concerning diffraction analysis are taken from the author's unpublished researches.

Jan 10, 1926

LITHOPROBE is a national, collaborative research grogram with the general objective of understanding the teotectonic evolution of the North American continent through multidisciplinary lithospheric studies in carefully selected areas of Canada. Six transect areas are investigating Precambrian evolution, although only in two of these is the research well evolved. The Archean Kapuskasing Structural Zone in Ontario is confirmed as an upthrust slice of upper to mid crust exposed at the surface. The Late Proterozoic Keweenawan mid-continent rift is shown to be the deepest known rift on Earth and the Grenville collisional zone of Ontario and Quebec involves crustal scale imbrication and ramping of deeply buried rocks to the surface. Two transect areas are investigating Phanerozoic evolution. In the Newfoundland Appalachians the geologically defined tectonostratigraphic domains do not coincide with lower crustal blocks defined by seismic reflection data. The Southern Cordillera Transect in western Canada is examining the nature, timing and dynamics of the assembly of the Cordillera, and particularly the role of accreted terranes. Work in the eastern and central segments has extended the known western limit of the North American craton at least IOO km westward and crustal-scale ramps associated with metamorphic core complexes have been identified.

Jan 1, 1990

Twenty field-scale tests were conducted in a 28 MW pulverized coal power plant in Healy, Alaska, to examine mill power consumption in relation to coal grind size. The intent in this field-scale study was to verify if grind size truly impacted power consumption by a detectable amount. The regression model developed from the data indicates that grind size does impact mill power consumption, with finer grinds consuming significantly more power than coarser grinds. However, other factors such as coal hardness (i.e., the lower the Hardgrove Grindability Index, or the harder the coal, the higher the power consumption) and mill throughput (i.e., the higher the throughput, the higher the power consumption) had to be included before the impact of grind size could be isolated. It was also observed that combining amperage and flow rate into a single parameter, i.e., specific amperage, hurt modeling. Cost analysis based on the regression model indicate a power savings of $19,972 per year if the coal were ground to 50% passing 76 mm rather than the industry standard of 70% passing 76 mm. The study also demonstrated that size reduction constituted a significant portion of the power consumption.

Jan 1, 2008

By Henry Kreisinger, WALTER T. RAY

This preliminary bulletin was written as the first of a series of several on the significance of drafts in steam-boiler practice, the succeeding bulletins to be along the same lines but of a more advanced character. The conclusions arrived at are tentative, and are the result of a study of one of the many problems growing out of a general plan of the United States Government to increase the efficiency with which the coals of the country are being used. Greater efficiency requires better boiler and furnace design. The experimental study of drafts on which the conclusions presented in this bulletin are based formed part of the fuel-testing investigations that were carried on by the technologic branch of the United States Geological Survey and have been transferred to the Bureau of Mines. The experiments made seem to indicate that it is possible to double or treble the capacity of a plant without making any radical changes the furnaces and boilers. These increases require about double and treble the quantities of air to be put through the fuel beds and boilers. It also seems probable that rebafHing the boilers will often permit the capacity to be doubled or trebled, while still getting more steam than formerly per pound of coal for uses outside the boiler room. These experiments were undertaken with the object of clarifying ideas concerning the passage of air through fuel beds and boilers. Measured weights of air were passed through two beds of lead shot, series, one of which remained always the same and represented a boiler; the other being varied as to size of shot and depth of bed, and representing a fuel bed. Careful observations were made of the weight of air passing through the beds per minute. All data were plotted in many charts, so as to permit the study of them from several points of view. A number of laws were deduced bearing on the relative amounts of power required to force air through fuel beds of various thicknesses, composed of various sizes of coal, and through boilers of various lengths and areas of gas passages. An important part of the discussion relates to an increase in the capacity of boilers by increasing the amount of power applied to pressure and exhausting fans and thus forcing several times as much air through the fuel beds and boilers. may be possible, as a result of these investigations, to raise the rate of working the boiler heating surface to three or even four times its present value. Such an increase would undoubtedly mean new designs of grates, stokers, furnaces, and boilers, especially fitted for high rates of working. Fan equipments designed to supply three or four times as much air under several times the pressure would be provided with more efficient engines, thus giving an additional factor favoring high-capacity working. It must be borne in mind, as stated above, that the results are tentative. It will cost money to force gases at high speeds through fuel beds and boilers, and there will soon be pressing need of such quantitative data as will enable the largest possible part of the energy imparted by the fans to be advantageously utilized. We desire, to thank our superiors, especially Messrs. L. P. Breckenridge and D. T. Randall, for their helpful criticism and suggestions.

Jan 1, 1911

By Stuart Coutts

"This paper presents an overview of the author’s experience related to the assessment of the base capacity of straight shafted and enlarged-base bored piles in sand. A design approach based on CPT qc is described which has been calibrated using a database of load tests. The importance of correct installation techniques with instrumentation are illustrated and a discussion is presented on the current use of high strain dynamic testing to validate compliance with design. An example of a recent project with high quality instrumented load test data illustrates the close match to the proposed best practice approach and also highlights the importance for consideration of the effects of stress relief for deep foundations installed in deep excavations.1 INTRODUCTIONContinuous Flight Auger (CFA) piles are the bored foundation pile of choice for sand deposits across Australia. The evolution of the determination of the base resistance of CFA piles has been shaped by available investigative techniques, calculation methods, and calibration of designs with laboratory and field testing. The Cone Penetration Test (CPT) has been widely used in Western Australia (WA) where the test has been commercially available via multiple contractors for more than 25 years. On the East coast, the adoption of CPT testing has been slower with a transition from traditional Standard Penetration Testing (SPT) still occurring. Dynamic pile load tests are often used to derive parameters. The influence of pile installation on performance is commonly misunderstood and is an important element on any discussion of pile capacity for CFA pile types. The interface between the base of the constructed pile and the in-situ soil has an influence on capacity such that a poorly constructed pile base will have limited (if any) contribution to pile performance within the normal working range, generally within a 10 mm movement. The research presented in this paper pertains to CFA piles (no drilling fluids) and enlarged base piles constructed using CFA techniques under drilling fluids such that clean pile/base interface is targeted. Developments in modern piling equipment and instrumentation allow the pressure and volume of delivered concrete/grout to piles to be accurately monitored at various stages of installation such that repeatable ‘best practice’ can be achieved. The changes in soil conditions that occur due to the disturbance of the install technique are also important.Although the results of this research are likely applicable to bored piles, the interface between the pile and in-situ soil (shaft and base) need to be considered for various installation techniques. The effects of stress relaxation (due to removal of soil above pile base and adjacent shaft), time to concreting, and the zone of disturbed soil around the pile shaft are paramount.2 INSTALLATION CONSIDERATIONS The pile mix (concrete/grout) and interface with the in-situ soil are also an important consideration. For example, coarse grained, poorly graded, dry, clean sand will be partially permeated by most pile mixes; such that the influenced soil will be enhanced and in instances the overall effective pile dimensions increased. Permeation of the disturbed zone of a pile or anchor shaft along with scale effects (Lehane 2009) can have significant effect on shaft capacity and shaft frictions significantly exceeding expected are not uncommon based on ‘theoretical’ dimensions. Advancements in mix technology and mix techniques also have a large influence on the pile/soil interface. The ability of the piling rig and augers to excavate a plumb and gauge hole can also have a large influence on the zone of soil disturbed adjacent the constructed pile with a resulting influence on capacity."

Jan 1, 1900

By Aner W. Erickson

"Preliminary examination of tungsten deposits on the Mountain View property near Hyder, Alaska, was made by Neal M. Muir, an engineer of the Bureau of Mines daring the summer of 1942. Fifteen samples were cut, rough esti¬mates of ore reserves were made, and it was proposed to extend the drift on scheelite-bearing vein 300 feet in a northwesterly direction.From May 22 to October 24, 1944, an exploratory project was conducted on the property by the Bureau. In the course of this work, the camp buildings were rehabilitated; the dam, hydraulic line, and machinery were repaired; 226 feet of drift was driven; 80 groove samples aggregating 3.9 tons in weight were cut; a 6,000-foot surface and underground traverse was run; and the area was mapped in detail.In its program of exploration of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to the national security and economy. It is the policy of the Bureau to publish the facts developed by each exploratory project as soon as practicable after its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts preliminary examinations, performs the actual exploratory work, and prepares the final report. The Metallurgical Branch, R. G. Knickerbocker, chief, analyzes samples and performs beneficiation tests. Both these branches are under the supervision of Dr. R. S. Dean, assistant director.Special acknowledgment is doe Neal W. Muir, project engineer, and Robert S. Sanford, acting chief, Alaska Division, Mining Branch, for their supervision of the field work and revision of the report.Acknowledgment is also made to Silbak Premier, Ltd., for rendering valuable assistance in the repair of equipment and for extending various courtesies to Bureau of Mines personnel during the conduct of this project.The Mountain View property is located at latitude 55° 59' north, and longitude 130° 03' west in the Salmon River mining district of southeastern Alaska, about 5 miles in a northwesterly direction from the town of Hyder, which lies at the head of Portland Canal, as shown in figures 1 and 2. Vein outcrops and surface workings are at an elevation of 950 feet and occupy the west flank of a low ridge between Skookum and Fish Creeks, as shown in figure 3. The portal of the long adit exposing the vein at depth is on Skookum Creek about 550 feet north of the confluence of Skookum and Fish Creeks.Access to the property is over a 4-foot wide trail built and maintained by the United States Forest Service. This trail is suitable for pack animals and is adequate for transportation of supplies and material for exploratory work. During the periods of camp construction and past exploratory operations a 4,000-foot, single-cable, aerial tramway, now in disrepair, served for transportation of materials and all machinery from the Salmon River Highway to the property. The cost of such hauling was high, amounting to $12 a ton. Topography is suitable for construction of a ""cat road"" 2 miles in length, connecting the property with the Salmon River Highway. It is estimated that such a road could be built for $5,000 a mile, and supplies, machinery, and concentrates could be haled over it at a cost of less than $2.50 a ton."

Sep 1, 1946