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By Edward A. Barrett, Roberta A. Calhoun

MORE THAN 30 MILLION EMPLOYEES each year are exposed to hazardous occupational noise, and approximately one-third of them develop permanent hearing loss (NSC, 2000). Possible explanations for the latter statistic include worker regard for noise as a mere nuisance rather than as an occupational safety and health hazard, and consequent neglect of established protective measures (e.g., hearing protection); lack of knowledge concerning noise; improper use of hearing protection; worker indifference; and inadequate training (Bauer & Babich, 2004). Many drill rigs generate high sound levels, which vary according to the type of machine, its location with respect to the physical surroundings, and the location of the sound measured around the rig. A NIOSH study measured noise output from several types of drill rigs during field investigations (Ingram & Matetic, 2003). Two types of data were recorded the actual noise generated by the drill rig at various positions around the rig and the noise to which the drill operator was exposed during the drilling cycle. For the latter, sound level measurements up to 120 dBA were recorded while hammering casing (metal on metal) in drilling a water well (Photo 1). Several types of administrative controls exist to address worker exposure to loud drill rig noise. Rotating duties to decrease exposure time and posting warning signs in high-noise work areas are two such controls. Another is the use of hearing protection. Worker use of hearing protection has been disappointing, however. One study by the University of Michigan found that construction workers used earplugs and earmuffs only between 36% and 61% of the time that they were necessary (Lusk & Kerr, 1998). In a 2001 study, OSHA reported a relatively low rate of 30.4% for use of earplugs among construction workers (Walker, 2001). Why are rates for hearing protection use so low? One explanation may be workers' lack of concern for noise in the workplace. They expect workplace noise to be a loud and in¬ evitable nuisance and, therefore, accept it as part of the job. As a result, they disregard proven measures that can protect their hearing. Other workers may use hearing protection, but do so improperly. They may misguidedly remain in high-noise areas for extended periods thinking they are protected when in fact they are not. Other reasons for low use and/or misuse of hearing protection include poor education, lack of awareness and inadequate training (Nash, 2003). To address the training issue, NIOSH developed two exercises from which drillers can learn about noise, hearing loss and hearing protection. The first is an invisible ink exercise, titled "Drill Rig Incident" (DRI) (Photo 2); the second is a 3-D slide reel training aid, "Wearing Hearing Protection Properly" (WHPP) (Photo 3). DRI is an instructor-

By Michel C. Frippel

This section of the Minerals Yearbook reviews the minerals industries of 29 countries: the 12 nations of the European Community (Belgium, France, the Federal Republic of Germany (FRG), Italy, Greece, the Netherlands, Denmark/Greenland, Spain, Portugal, Luxembourg, the United Kingdom, and Ireland); 6 of the 7 nations of the European Free Trade Association (Sweden, Nor-way, Finland, Iceland, Austria, and Switzerland); Malta; the 8 Centrally Planned Economies of Eastern Europe (the German Democratic Republic (GDR), Poland, Yugoslavia, Albania, Hungary, Czechoslovakia, Romania, and Bulgaria); and the U.S.S.R. Western Europe Western Europe [loosely defined to include the 12 nations of the European Com-munity (EC) and the 7 nations of the European Free Trade Association (EFTA)] is the single largest trading area and consumer of raw materials in the world. If Western Europe was at one time an important mining sector, it has now increasingly relegated the role of supplying minerals for its minerals processing industry to its ex-colonies in North and South America, Africa, and Australia. In this regard, Western Europe is the most important determinant of raw materials consumption (and thus raw materials production). There is an important reason for this since Western Europe lies somewhere between Japan at one extreme and the United States and the U.S.S.R. at the other extreme as regards the availability of natural resources.

Jan 1, 1992

By Gordon T. Austin

The combined value of production of natural abrasives, which include tripoli, special silica stone, garnet, staurolite, and emery, increased about 4% in 1990. The increase in the value of tripoli production was the result of an increase in the unit value. Emery increased owing to an in? crease in the volume of the material produced and an increase in the unit value. Special silica stone experienced a decrease in unit value and an increase in the quantity produced. Garnet showed a 10% in? crease in quantity and a 73% increase in unit value. Staurolite decreased about 8% in the quantity produced, and the value of production decreased about 10%. The fused aluminum oxide industry showed a 5% decline in the quantity produced and in the value of production. The silicon carbide industry saw a 10% decrease in the quantity produced and a 9% decrease in the value of production. Production for both industries decreased 7% in quantity and value compared with those of 1989.

Jan 1, 1993

By R. H. Grau

Researchers from the National Institute for Occupational Safety and Health have demonstrated that mine-wide ventilation in large-opening stone mines can be improved by using low-pressure, high-volume propeller fans and constructing stoppings in key locations to direct and control airflow. In light of these findings, a comparative study was conducted to determine if a portable diesel-powered propeller fan could per-form more efficiently for dust dilution and transport than an axial vane fan for localized ventilation. The objective of this study is to evaluate both fan types for ventilation efficiency at an underground dump/crusher facility in a limestone mine. Results showed an improvement with the propeller fan to dilute both the respirable dust and the respirable silica dust around the dump/crusher facility. Overall, an average reduction of 20% in respirable dust and silica was observed at the dump/crusher location with the propeller fan.

By C. O. Karacan

Underground longwall mining of coal causes large scale disturbance of the surrounding rock mass. The disturbance can increase the rock mass permeability through a reduction on the stress as well as formation of new fractures in the rock. Methane gas contained in the disturbed rock mass can migrate towards the low pressure mine workings and present an explosion hazard. This paper describes the application of a finite difference program to develop a geomechanical model that predicts permeability changes within the rock mass. The calculated permeabilities are used as input to a reservoir simulator that models methane desorption from the coal matrix, methane release from the rock layers and flow towards the mine excavations. The model also considers the basic characteristics of the mine ventilation network. The geomechanical model uses empirical relationships between fracture permeability and stress to calculate permeability changes around a longwall face. The extent of rock failure is determined using a strain softening model that considers both rock matrix and bedding plane failure. The cave rock (gob) is modeled as a compressible, granulated material. The calculated horizontal and vertical permeabilities around the longwall face are averaged and used as one of the inputs to the reservoir model. The reservoir model was developed and calibrated against records of methane flow at a study mine in southwestern Pennsylvania. Good correlation between actual gas production and model outputs has been achieved. The modeling approach provides a basis for estimating methane inflow and optimizing control measures.

By D. R. Babich, E. R. Bauer

Noise-induced hearing loss (NIHL) in mine workers, especially underground coal miners, continues to be a problem in the mining industry. The recently enacted MSHA noise standard, Part 62 – Occupational Noise Exposure (Federal Register, 1999), is aimed at reducing NIHL in the mining industry. The U.S. National Institute for Occupational Safety and Health (NIOSH) is conducting a cross-sectional survey of noise sources and worker noise exposures to address NIHL in various aspects of coal mining including surface mining, coal preparation plants and underground mining. In underground bituminous coal mining, noise surveys, consisting of full-shift worker noise exposure, time-motion studies and equipment noise profiling, have been completed on longwall and continuous miner sections in six underground coal mines. The studies revealed widely varying shift-to-shift worker exposures, with workers in certain occupations routinely exposed to potentially hazardous levels of noise. A summary of these studies is reported, including worker dose, source/dose relationships and equipment noise profiles.

By Dennis S. Kostick

Salt is a universal mineral commodity used by virtually every person in the world. Although a very common mineral today, at one time, it was considered as precious as gold in certain cultures. This study traces the material flow of salt from its origin through the postconsumer phase of usage. The final disposition of salt in the estimated 14,000 different uses, grouped into several macrocategories, is traced from the dispersive loss of salt into the environment to the ultimate disposal of salt-base products into the waste stream after consumption. The base year for this study is 1990, in which an estimated 196 million short tons of municipal solid waste was discarded by the U.S. population. Approximately three-fourths of domestic salt consumed is released to the environment and unrecovered while about one-fourth is discharged to landfills and incinerators as products derived from salt. Cumulative historical domestic production, trade, and consumption data have been compiled to illustrate the long-term trends within the U.S. salt industry and the cumulative contribution that highway deicing salt has had on the environment.

Jan 1, 1993

To allow routine measuring of the exposure of underground workers to N02 from diesel engines and residual gases from blasting. The Approach: A miniature sampler absorbs NO2 which can be measured using a simple method adaptable to both multiple automatic analyses or individual on-site analysis. How It Works: The NO2 sampler is encased in a plastic tube approximately half the length of an ordinary ball point pen and clipped to an underground worker's hard hat. Removal of the end cap activates the personal sampler. Air from the working place enters the open end and diffuses at a controlled rate down the tube interior. The diffusion rate is dependent on tube dimensions (ratio of cross-sectional area to length). The closed end of the tube contains stainless steel mesh which is coated with triethanolamine (TEA) for absorbtion of all NO2 reaching it. Other oxides of nitrogen are not absorbed. The amount

Jan 1, 1975

By Christopher Mark

Perhaps the most significant development in coal mine ground control during the last century was the introduction of roof bolting during the late 1940’s and 1950’s. From an engineering standpoint, roof bolts are inherently more effective than the wood timbers they replaced. Roof bolts promised to dramatically reduce the number of roof fall accidents, which then claimed hundreds of lives each year, and they were initially hailed as “one of the great social advances of our time.” Roof bolting also emerged at a time of rapid technologic transformation of the coal industry, and greatly accelerated the transition to trackless, rubber-tired face haulage. The U.S. Bureau of Mines quickly became the new roof support’s strongest advocate. Some state agencies and miners were skeptical at first, but nearly everyone was soon won over. Case histories were reported showing that roof falls could be largely eliminated while productivity increased dramatically. Little wonder that, in the words of one contemporary observer, “roof bolting has been adopted more rapidly than any other new technology in the history of coal mine mechanization.” Yet by the end of the 1950’s, it was clear that roof fall fatality incidence rates had actually increased. It would be another decade before the superior ground support provided by roof bolts would clearly save lives. The story of how roof bolting was implemented by the mining industry, but took so long to live up to its promise, is a fascinating example of the interaction between economics, technology, regulation, and science. It still has important lessons for today.

By Donald L. Siebert

This profile study of the commercial secondary aluminum industry examines not only the elements that form the industry but also the technological contributions of each toward industrial growth. Concise descriptions of processing methods trace aluminum scrap from generating sources to marketable industrial and consumer goods. Economic and marketing appraisals are used to illustrate the impact that recent technology has had upon the secondary aluminum industry. Price, supply, demand, competition, and substitutes are selected as components of an economic model of the secondary industry and are used to illustrate the aggregate effects of technological changes. The final section is a conceptual look at the future in which sensitive economic indicators (such as die casting in the automotive and appliance industries) are examined as well as the problems of conserving mineral resources by retrieving secondary aluminum from solid waste.

Jan 1, 1970

To predict the spontaneous combustion potential of bituminous coals using a simple expression based on an easily acquired coal property. Background Approximately 20% of underground coal mine fires in the United States since 1978 have been attributed to spontaneous combustion. Spontaneous combustion fires in underground mines are most likely to occur in gob area; and are difficult to detect and to extinguish by direct fire fighting methods. Often, sections of the mine or the entire mine must be sealed for long periods, at a great economic loss to the mine operator, mine employees, and the surrounding community. It is conservatively estimated that the cost of scaling a large mine is about $50 million.

Jan 1, 1989

By S. H. Lorain

Mechanized dirt-moving equipment has greatly increased the scope of prospect trenching by lowering the costs and increasing the speed of such work. Where the soil covering was more than 3 or 4 feet deep, operators were quickly discouraged and abandoned surface exploration in favor of shaft sinking, drifting, or diamond drilling; wildcat trenching was seldom undertaken, even where the soil covering was thin. Although power shovels, trench diggers, and draglines are useful under special conditions, caterpillar-mounted angledozers will usually do the same type of work and have a far wider range of adaptability. They are therefore incomparably the most generally useful equipment for the purpose. Since 199 the Bureau of Mines has been engaged in a widespread search for minerals useful to the war program; this work required a great deal of pioneer exploration in areas where known outcrops were marginal or subcommercial by pre-war standards. Engineers in charge of field operations were quick to perceive the applicability of mechanized trenching on a fairly large scale, particularly in the Northwestern States, where completely exposed vein-outcrops are rare. Probably no other organization to date has done a comparable amount of angledozer prospect trenching under such a wide range of conditions. The following comments and accompanying cost tables are based on work performed chiefly in Idaho, under a variety of physical and climatic conditions. The most important applications of the angledozer for such work may be described under three heads:

Jan 1, 1944

By Kray Luxbacher, Mario Karfakis, Erik Westman, Peter Swanson

Three-dimensional velocity tomograms were generated to image the stress redistribution around an underground coal longwall panel to produce a better understanding of the mechanisms that lead to ground failure, especially rockbursts. Mining-induced microseismic events provided passive sources for the three-dimensional velocity tomography. Surface-mounted geophones monitored microseismic activity for 18 days. Eighteen tomograms were generated and high-velocity regions correlated with high abutment stresses predicted by numerical modeling. Additionally, the high-velocity regions were observed to redistribute as the longwall face retreated, indicating that velocity tomography may be an appropriate technology for monitoring stress redistribution in underground mines.

By Gerald T. Homce, James C. Cawley

This paper updates an earlier report by the authors that studied electrical injuries from 1992 to 1998. The previous information is expanded and supplemented with fatal and nonfatal injury rates and trends through 2002. Injury numbers and rates were used to compare and trend electrical injury experience for various groups and categories. This information allowed identification of at-risk groups that could most benefit from effective electrical safety interventions. The data presented in this paper are derived from the U.S. Labor Department’s Bureau of Labor Statistics’ Census of Fatal Occupational Injuries (CFOI), Survey of Occupational Illnesses and Injuries (SOII) and Current Population Survey (CPS). Between 1992 and 2002, 3,378 workers died from on-the-job electrical injuries. Electricity remained the sixth leading cause of injury-related occupational death. From 1999 through 2002, 4.7% of all occupational deaths were caused by electricity, down from 5.2% in the 1992 to 1998 time period. The cause of death was listed as electrocution in 99.1% of fatal cases. Contact with overhead power lines was involved in 42% of all on-the-job electrical deaths. The construction industry accounted for 47% of all electrical deaths between 1992 and 2002, but showed overall improvement from 1995 through 2002 by reducing its electrical fatality rate from 2.2 to 1.5 per 100,000 workers. An additional 46,598 workers were nonfatally injured by electricity. Contact with electric current of machine, tool, appliance, or light fixture and contact with wiring, transformers, or other electrical components accounted for 36% and 34% of nonfatal electrical injuries, respectively. Contact with underground, buried power lines was involved with 1% of fatal injuries and 2% of nonfatal injuries. NIOSH research aimed at evaluating commercially available overhead power line proximity warning alarms is described. This research is expected to be the initial step for eventual development of a performance standard for such systems.

By M. E. Poad, M. M. McDonald, J. C. Johnson, W. G. Pariseau

A U.S. Bureau of Mines case study of pillar recovery in high-grade ore near the Ross shaft at the Homestake Mine, Lead, SD, has demonstrated the usefulness of the finite-element method for evaluating shaft pillar mining plans and shaft stability. This report focuses on mine measurements and calibration of the two-dimensional computer model and is the second in a series of three Reports of Investigations describing the Ross shaft study. In this study, borehole extensometers and other instruments were installed to provide data for model verification and to monitor the shaft. Results of the recalibrated two-dimensional model (UTAH2) confirmed the premining stability evaluation. However, after mining began, concern was expressed because cracks and other signs of ground motion appeared at considerable distances from the area of active pillar mining. In part 3 of the study, an intense three-dimensional modeling effort using UTAH3 was initiated. The results again showed that the observed effects were within expectations and that the shaft would remain safe. Three-dimensional analyses of alternative pillar mining scenarios indicated that more of the shaft pillar ore reserve could be recovered than previously thought.

Jan 1, 1995

Bag stackers who use semi-automated palletizing machines and air slides may be exposed to high concentrations of dust. To reduce dust exposure, use an exhaust ventilation system in conjunction with an envelope of clean air over the bagstacker provided by an overhead air supply. Description of Hazard Mineral processing plants in the United States and throughout the world process material that is finely ground and placed into bags for shipping to the consumer. These bags normally range from 50 to 100 pounds in weight. Once the material is placed in these bags, a bag stacker loads the bags onto pallets. A bag stacker is exposed to a lot of dust that is mainly released by the force from loading the bag onto the pallet. The two main sources are the dust on the outside of the bag and the dust that escapes from inside the bag as it is loaded. The Mine Safety and Health Administration's (MSHA) records indicate the bag stacker's dust exposure is one of the highest of all workers at mineral processing operations. Ways to reduce the dust exposure and strain to the bag stacker are in constant development. Recently, automated systems have been built. These systems range from fully automated, which totally remove the worker from the bag-stacking process, to semiautomated systems, in which the bag stacker still performs some of the functions. This Hazard Control deals with controlling the bag stacker's dust exposure during use of a semi-automated palletizing machine. The worker slides the bags into position on the palletizing machine. Once an entire layer of bags is positioned, the bag stacker operates the controls on the palletizing machine to lower the layer of bags onto the pallet. An air slide is built into the semi-automated palletizing machine so the bags are easier to move. This slide uses a metal table with air jets that exit through small holes at high velocities, similar to an air hockey game. The dust problem occurs because the air slide causes dust to blow up onto the bag stacker, significantly increasing the dust exposure.

Jan 7, 2001

By J. E. Chilton, T. Mal

Methane monitoring at the mine face is essential to assure a safe work environment in underground coal mines. Machine-mounted methane monitors must be used to continuously monitor methane levels during mining. Monitors used on mining machines must be approved by MSHA and properly maintained to provide protection for workers (30 CFR 75.342). To provide protection the instrument must give accurate readings of current methane levels. Accuracy is maintained by calibrating the instrument with a standard gas at least once every 31 days. Instrument “response time” determines how quickly measurements will change to reflect current concentrations. At present there are no criteria for measuring the response time for a ma-chine-mounted methane monitor while underground. This study examined a procedure for measuring the response time of a machine-mounted methane monitor. Response times were measured using methanometers obtained from three different manufacturers. The effects of the measurement technique and methanometer sensor head design on response time measurements are investigated. Techniques for reducing variation in response time measurements are discussed.

By W. R. Reed, J. A. Organiscak

Haul trucks have the potential to generate large amounts of respirable dust. This respirable dust has been shown to be a health hazard to personnel, especially if it has a high silica content. Lack of dust sampling data from haul trucks prompted the completion of a study to quantify respirable dust concentrations. These field studies were conducted measuring instantaneous respirable dust at stationary locations from passing haul trucks at a stone quarry and at a coal mine site. Fugitive dust levels from haul trucks were analyzed to characterize dust dispersion. This analysis indicates safe following distances for haul trucks and other heavy equipment to avoid overexposure of respirable dust from the lead haul truck.

By W. A. Young

To initiate this project a critical evaluation of the pre-sent phosphate mining industry in the Western phosphate field was conducted. Mines were visited, mine operators were interviewed and pertinent literature studied. Three phosphate mining enterprises were reviewed and mining cost estimates prepared. The report discusses the present state of phosphate processing, rock alteration and location. New ideas and concepts are proposed to improve the recovery of phosphate rock from the Phosphoria formation. The report evaluates two variations to the present phosphate open pit mining methods, which were developed to improve the economics of mining phosphate and to better accomplish necessary reclamation and accelerate the time for environmental recovery. A material handling system using conveyor haulage will eliminate the need for trucks. Terrace haulback utilizes safety benches to haul and dispose of waste in the mined out pit. Ore will be removed from the pit via an inclined, cable-supported mobile conveyor.

Jan 1, 1980

By Todd M. Ruff

The majority of fatalities that occur in road construction work zones in the United States involve a worker being struck by a piece of construction equipment or other vehicle. The Spokane Research Laboratory of the National Institute for Occupational Safety and Health, in cooperation with the Washington State Department of Transportation, is evaluating methods to decrease these accidents. One such method uses devices that assist equipment operators in monitoring blind areas around the equipment to prevent collisions with workers on foot or other objects. Several cameras and sensor systems are available for this application, and a study was conducted to evaluate these systems on various trucks used in road construction and maintenance. Tests were conducted using sanding trucks during the winter months, which allowed researchers to investigate the effectiveness and limitations of various technologies under the most extreme conditions. Tests were also conducted using dump trucks during the warmer months to study the effectiveness of the systems in highway work zones. Results show that many difficulties arise when using camera and sensor systems in cold, snowy climates. And, while the operation of these systems is more reliable during the warmer months, challenges still exist in using them on equipment in crowded work areas.

Jan 1, 2004