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By Sol Ribakoff

In 1973, the Subcommittee on Contracting Practices, U. S. National Committee on Tunneling Technology, National Academy of Sciences, under the able chairmanship of A. A. Mathews, Engineering Consultant, now residing at Kaunakokai, Hawaii, undertook the task of developing recommendations for improving the performance of underground construction work, reducing the costs of such work and minimizing the adverse atmosphere in which owners and contractors were performing their respective functions. The author of this paper and C. F. Palmetier, a highly qualified engineer, were thereupon appointed as staff assistants to the Subcommittee, to conduct a study of existing practices and relationships in Western Europe and in the United States, to formulate recommendations, for consideration by the Subcommittee and the participants in a future workshop, as to desirable improvements in United States contracting practices and relationships. The study, conducted during 1973 and 1974, involved personal interviews of a total of 162 owners, engineers, contractors, lawyers, and educators throughout the United States and in 7 European countries, the analysis of 178 replies to questionnaires sent to individuals and firms involved directly or indirectly in construction, and a workshop, near Napa, California, attended by 53 representatives of all segments of the construction community. The resulting report, entitled "Better Contracting for Underground Construction", was submitted by the Subcommittee to the National Academy of Sciences, which approved its publication in 1974 by the National Technical Information Service. It may be obtained from that Service at Springfield, Virginia, 22161, as Accession No. PB-236 973. It was recognized-during the course of the study that while contracting practices and owner-contractor relationships were the

Jan 1, 1981

By Vinton A. Garbesi

INTRODUCTION The placing of the monolithic concrete lining of the Bi-County water tunnel illustrates the state of the art in the materials, equipment, methods and productivity available to the industry for this type of construction. This paper describes the management and engineering rationale used by Clevecon, Inc., a subsidiary of S & M Constructors, Inc., Solon, Ohio, in developing the concrete mix designs, the design of the specialized equipment, and the methods used in the manufacture, transport, and placing of the lining. Also discussed are the changes to the reinforcing steel design instigated to facilitate its handling and placing, as well as to enhance the quality of the lining. The intent is to bring to the attention of designers the effects certain design aspects have on the construction of reinforced concrete tunnel linings, as well as indicate the areas where research and development effort should be expended to further reduce costs for this type of construction. GENERAL DESCRIPTION The Bi-County Water Tunnel West is a water transmission main owned by the Washington Suburban Sanitary Commission of Hyattsville, Maryland. The facility was designed by A. A. Mathews Division (formerly STRAAM Engineers, Inc.) CRS Group Engineers Inc., Rockville, Maryland. It is to be utilized as the central feeder of potable water for the northern suburbs of Washington, DC, extending some 4,597 meters from a riser shaft at its western terminus to the eastern interface, with a similar tunnel which extends eastward about 5,180 meters; the majority of its length being under Interstate Highway 1-495. The excavated and finished diameters are 3.8 and 3.05 meters respectively. The reinforced concrete

Jan 1, 1981

By Dewey W. Geary

Nast Tunnel is the first granitic rock tunnel to be excavated by a machine for the U. S. Bureau of Reclamation. The machine has excavated 7500 ft of the tunnel at this writing. There have been a few good performances; 31 ft in 1, 8 hr shift, and 75 ft in a 24 hr period, but generally, progress has been slower than that accomplished in the area with reasonable comparable conditions using conventional excavation techniques. Button cutters, now employed using compression as the means of fracturing the rock, gives an average cutting rate of 3 ft per hr. Disc cutters manufactured by the machine builders were tried briefly but the snap rings holding the discs to the hub failed. However, disc cutting rates of 6 ft per hr were recorded for short periods of time in a competent coarse grained porphyritic granite. The snuck was also considerably larger and more easily handled than that produced by the button cutters. Hughes Tool Co. is working on a disc type cutter and expects to have them on the cutterhead by mid June. LOCATION, DESCRIPTION AND BID OPENING Nast Tunnel is located 2 miles west of the Continental Divide and 39 miles east of the town of Basalt in Pitkin County, Colorado. The outlet portal is in the Fryingpan River Valley at an elevation of 10,000 ft. The tunnel is a 3 mile long, 10 ft diameter gravity flow water conveyance structure and a part of the west slope water collection for the Bureau of Reclamation, Fryingpan-Arkansas Project. The bids were opened July 9, 1970, with 8 contractors submitting proposals. The contractors were given the opportunity to bid

Jan 1, 1997

By Thomas E. Bruner

Today many small diameter tunnels are being constructed in Metropolitan areas and towns as transmission holes for utilities such as water, electricity, natural gas and sewage, to name a few. These tunnels function as utilities beneath the streets, highways, railways, and other structures where open-cut techniques are impractical for any one of a number of reasons. Many such bores range in diameter from 15 to 72 inches and in lengths from 100 to 500 feet. Auger drills with auger type heads have long been used to bore these "road crossings" as they are usually termed; however, many such crossings must be bored in rock with rock-boring heads. Rock with a compressive strength of 15,000 p.s.i. and higher seems to present the greatest challenge for the contractor. These rocks include most igneous and metamorphic rocks and some sedimentary rocks. In general, this grasps most granites, basalts, gneisses, slates, schists, quartzites, limestones, and cherts. In the past ten years boring machines have been developed and used to excavate road crossings through hard rock. Many crossings have been successfully excavated using these machines, and the degree of success has increased substantially in the last few years. A variety of machines have been built and manufactured to bore most rock in a range of diameters up to 72 inches. The machines vary in capabilities, size ranges, and designs but all perform the same basic task and function of boring horizontally. Incidently, here the term horizontal implies horizontal or within five degrees of horizontal. In addition, there is a wide variety of designs, sizes, and types of drill stems, joints, and pipe to meet the various conditions and

Jan 1, 1974

By Steve Kral

The Red Dog zinc-lead deposit, said to be the world's second largest, is located inside the Arctic Circle in northwestern Alaska - a location too harsh and remote for some mining companies but just right for Cominco Ltd. The complex has been in operation since November 1989 and is producing 508 kt/a (560,000 stpy) of zinc concentrate, 109 kt/a (120,000 stpy) of leadconcentrate and 45 kt/a (50,000 stpy) of an Imperial Smelter Feed, a combined zinc-lead mixture that is too small to separate. All of this concentrate production derives from a relatively modest mine production of 5.4 kt/ad (6000 stpd) extracted from a surface pit. Despite being a high-grade zinc-lead deposit, Red Dog's metallurgy is complex, requiring a very fine grind and use of column cells for flotation. The Red Dog complex is located in the DeLong Mountains. They are characterized by eight stack and folded thrust blocks that contain sedimentary and igneous rocks. The Red Dog deposit is located in the second lowest thrust and ist hosted by late Mississippian to Permian age black shale, the Ikalukrok member of the Kuna formation. The Red Dog mining complex is operated by Cominco Alaska, Inc., a wholly owned subsidiary of Cominco American, Inc, which, in turn, is owned by Cominco Ltd. In 1980, the deposit region was acquired by NANA Corp. as part of the Native American Claims Act Settlement of 1971. NANA is one of 12 such Native Corporations in Alaska. In 1982, NANA and Cominco American signed a develop¬ment agreement and formed Cominco Alaska to manage the project.

Jan 1, 1992

By Charles L. Kimbell

In 1989, worldwide total mineral industry activity registered advances from 1988. The advances may not have been as noteworthy as in 1988, but they can be regarded as a worthy theme for this article. The momentous political events throughout the centrally planned economy world had only a modest impact on actual 1989 industry performance. But these events have such potential for worldwide changes in economic activity in future years that they dwarf the actual happenings of 1989 in the minerals industry. Perhaps most significant factor here is the rapidity with which these changes have occurred. The end of World War II saw the almost immediate division of the world into major economic blocs. Since then, mineral industry activities and other industrial operations have been governed, to a considerable extent, by this partitioning. The developed market economy nations have operated as a group, the centrally planned economy states as another group. And these two groups essentially have vied for recognition in mineral industry operations in the developing economy states of Asia, Africa, and Latin America. The boundaries of these country blocs were fixed in the late 1940s and early 1950s. They were not markedly altered in the ensuing 40 years. We have seen the establishment of the Organization of Petroleum Exporting Countries, the continued Arab-Israeli confrontations in the Near East, the upheavals surrounding the rise of Moslem Fundamentalism in Iran, and the establishment of Soviet-oriented governments in Cuba and Nicaragua. These events have had notable effects on the world economy. But they have done little to change the pattern of market economy states functioning as a competitive bloc with the centrally-planned economy countries.

Jan 1, 1990

By Murray D. Lester

The relationship between bauxite and energy has two distinct aspects. On the one hand, since virtually all of the bauxite that is mined winds up as aluminum metal, the economic health and future of the bauxite industry and of the bauxite-producing countries depend on the continuing vigour and competitiveness of aluminum against alternative metals and materials. The price of aluminum is, in turn, particularly dependent on the price of energy. Hence, the need for bauxite is ultimately affected by the price of energy. The second aspect relates to location of the bauxite industry. There is no shortage of bauxite resources in the world. For various reasons, as we shall see, there is a growing tendency toward the integration of bauxite mining, bauxite refining and aluminum smelting in those countries that have the resources both of bauxite and of energy necessary to support the entire production chain. Thus, the availability of attractive energy supplies will increasingly favour development of bauxite mining: the traditional export of bauxite as a simple raw material is likely to diminish in relative terms. In short, both the amount of bauxite mined and where this mining will take place are related to energy considerations. Let us first have a brief look at the four basic activities that are involved in our integrated operations: A. The bauxite is mined and moved to an ore plant. This step does not require more than relatively modest amounts of energy normally associated with excavation, loading and shipping of any bulk material. We need about four or five tonnes of bauxite for every tonne of metal produced.

Jan 1, 1984

By M. J. McPherson, P. Mousset-Jones, J. Banik, F. Calizaya

Friction factors or coefficients of friction used to estimate the resistances of mine airways are, in the main, estimated from empirical measurements made in other airways considered to be of a similar geometry and type of lining. A somewhat more analytical approach, although still based on empiricism, is to estimate the ratio of the average height of the asperities to the hydraulic mean diameter of the airway (e/D ratio) and then to employ the Moody Chart or one of the equations that have long been established to represent the [coefficient of friction v Reynolds number curves] on that chart. Unfortunately, the Moody Chart and corresponding equations are based on pipes of uniformly distributed (sand grain) roughness whereas the asperities that exist on the surfaces of mine openings are frequently highly irregular both in their size and distribution. This is considered to be a major cause of discrepancies that have been found between coefficients of friction by the Moody Chart and those actually measured in mine airways. The work described in this paper examines an alternative method of estimating coefficients of friction for rough natural surfaces with uneven sizes and distribution of surface asperities. The technique utilizes the relatively recent developments in fractal analysis. A fractal dimension is determined from the topography of the surface. This has been correlated to coefficient of friction for a scale model of a mine airway. Further work is being carried out in actual mine airways. However, at this time, it appears promising that the fractal method may allow coefficient of friction to be predicted for given types of strata and method of roadway drivage.

Jan 1, 1993

By David K. Parrish, Duane A. Labreche

Analyses of jointed, cracked, and fractured rock masses are needed in a variety of applications, including estimates of reduced elastic modulus for damaged rock, estimates of permeability changes as a function of stress changes, and estimates of relaxed regions due to excavation. A numerical model of a jointed rock mass, the compliant joint model, was used to study the response of a jointed rock mass near a circular excavation. The joint constitutive model was linear elastic in shear and nonlinear elastic in the relationship between normal stress and joint closure. Initial stresses were geostatic and representative of stresses in a granitic jointed rock mass approximately 300 m deep. The joint properties were based on values that are representative of joints in granite. The results from numerical simulations were compared with analytical results for stress near a circular opening in an elastic medium having reduced Young's Moduli to simulate jointing effects on the rock mass. The differences in response between the two models resulted from the differences in the symmetry of elastic properties, the shear modulus of the continua, and the constitutive relations in the two models. For example, the non- linear anisotropic elastic continuum described by the compliant joint model resulted in vertical stress concentrations near the side of the circular opening that were 25 percent higher than the vertical stress concentrations in an isotropic linear elastic medium. The equivalent Young's Moduli in the vertical and horizontal directions of the compliant joint continuum deviated by as much as 50 percent from the values assigned to the modeled region prior to excavations. The perturbations of the elastic Young's Moduli extended to distances of two to three radii from the opening.

Jan 1, 1986

By d&apos, L. R. Fletcher, Andrea. D. V., M. A. Peltier

The Bureau of Mines analyzed coal mine blasting accident data obtained from the Mine Safety and Health Administration (MSHA), U.S. Department of Labor. The data were examined to determine the causes, frequency, and severity of accidents in an effort to point out the most dangerous aspects of coal mine blasting. Accident data for the 14 years from 1971 through 1984 show that there has been a total of 43 fatal and 926 nonfatal blasting accident victims in surface and under- ground coal mining. This is an average of 3.1 fatal and 66.1 non- fatal injuries each year. Underground coal mining accounted for 60.5% of the fatal and 78.7% of the nonfatal accidents involving explosives and breaking agents in coal mining. In addition, since 1970 there have been 53 fatal and 20 nonfatal injuries that occurred when explosives were the ignition source for dust and/or methane explosions in underground mines. Abstracts from 297 accidents that occurred from 1978 through 1984 were also examined to determine accident causes. Most accidents occur during scheduled blasting, and failure of the blast area security system is the leading cause. Blast area security problems in surface mining are failure to clear the blast zone, failure of personnel to follow instructions, inadequate guarding, and failure to retreat to a safe location and/or take adequate cover. Other common causes in surface mining include premature blasts, excessive flyrock, and misfires. In addition to the above causes, accidents in underground coal mining can be due to rockfalls triggered by the blast, unexpected breakthroughs, fumes, and incidents associated with Airdox-type systems.

Jan 1, 1986

By D. M. Bodily, M. D. Deo, E. M. Whitney

Field data from coalbed methane wells indicate a significant variation in composition as a function of flow rate and time. In particular, San Juan Basin wells have displayed an increase in C02 concentration over time. Prediction of gas quality is critical to the economic evaluation of any coalbed project. Previous models have forecast only pressure and production profiles, ignoring compositional variations. In this study a multicomponent model that incorporates binary isotherms for methane and carbon dioxide has been developed. An extended Langmuir isotherm is used for the adsorption representation and a constant separation factor (similar to relative volatilities in distillation) describes the phase distribution of the species. This separation factor depends both on the surface characteristics of the coal and on the adsorbing species. The chromatographic separation equations have been superimposed on Darcy's law flow. The formulation allows decoupling of the pressure and compositional partial differential equations. The equations have been cast in dimensionless form and solved for pressures and compositions. It is observed that the composition of the preferentially adsorbed C02 increases at the wellbore as a function of dimensionless time. The dimensionless time is directly proportional to the real time and coalbed permeability and is inversely proportional to the gas viscosity, coal porosity and the square of the length of the reservoir. As the separation factor increases, the compositional variation increases. This variation in produced C02 concentration is also greater when the initial C02 concentration in the reservoir is higher. A sensitivity study has been performed to identify the effects of important parameters such as isotherm variables and reservoir characteristics on pressure and composition profiles.

Jan 1, 1993

By Charles A. Weinstein

INTRODUCTION As a set of management practices, "Knowledge Management" (KM) has disappointed many of its early advocates. The core notion behind KM can be summed up in the oft- quoted adage, "If we only knew what we know." KM describes a set of tools, practices, and approaches for using data, information, and expertise-knowledge-resident in an organization to improve the performance of that organization. The idea was incubated, hatched, and grew among some the largest and most successful companies in the world. Some of these companies created "Chief Knowledge Officers." Many more collectively invested billions in a huge range of KM efforts, all designed to use their organizations' information and expertise to innovate, improve margins, sell, or accomplish any of a myriad of sound business goals. Some KM efforts were successful, and many were not.* Today, it is indisputably the case that KM as a named set of practices has fallen out of favor. Why, then, should KM be discussed at a conference on "Things that Actually Work" for plant operators? Because, in many instances, KM has actually worked. The practices that represent KM done right offer significant opportunities for plant operators to achieve real gains, especially in times of resource constraints and in the face of ever-increasing technical and commercial goals. The KM fad is all but over. The KM benefits continue to accrue to those who have applied the lessons learned from that fad, and implemented sound * Fair disclosure: I am not unbiased with respect to the potential impact of KM. Teltech has been a pioneer and leader in KM, both as a practitioner and as a leading consultant to other organizations.

Jan 1, 2004

By S. Orr

Flow in heaps and dumps is a two-phase flow phenomenon, though for many applications it could be simplified as unsaturated flow. Unlike saturated flow (typical of ground water flow), where permeability is independent of other hydraulic parameters, unsaturated flow permeability depends on the degree of saturation and/or on capillary pressure. Several recent field studies suggest that flows in heaps and dumps tend to concentrate in preferred pathways, bypassing much of the ore. Different preferential flow phenomena are triggered, promoted and influenced by different heap structures, by pretreatment, by the composition of the leach solution and by application rates and schedules. The structure of heaps and dumps is determined and affected by every stage of their construction -from blasting to crushing to conveying and stacking of the material. History of heap construction and operation combined with monitoring, mapping and certain field tests can reveal patterns of flow and transport in a given heap and can shed light on the physical mechanisms behind it. Such insight can provide a first cut on heap leaching enhancement by either eliminating or bypassing physical barriers to flow and leaching. Based on the understanding of the heap structure, advanced flow and transport models can be constructed and further enhance the insight. This insight is essential for understanding cause and effect and can provide a basis for decision making. Further, based on the physically-based models, an intelligent control agent, such as MRDS1, can learn and build a self-learning representation (or a model) of the complex heap leaching system, followed by dynamic optimization and planning of heap leaching and heap rinsing.

Jan 1, 2003

By Ross A. Scarano

It wasn't until late 1976 that the U. S. Nuclear Regulatory Commission (NRC) set about to address the uranium tailings issue in earnest. It was decided that a generic environmental impact statement related to uranium milling operations would be prepared to support formal tailings regulation. We recognized, however, that this was a task that would take many years to complete and we could not take a "business as usual" approach to tailings management in the interim; the issue was too sensitive. To facilitate licensing during the interim period, the NRC developed guidelines in May 1977, for the industry in the form of the following performance objectives for tailings management: Siting and Design 1. Locate the tailings isolation area remote from people such that population exposures would be reduced to the maximum extent reasonably achievable. 2. Locate the tailings isolation area such that disruption and dispersion by natural forces is eliminated or reduced to the maximum extent reasonably achievable. 3. Design the isolation area such that seepage of toxic materials into the groundwater system would be eliminated or reduced to the maximum extent reasonably achievable. During Operations 4. Eliminate the blowing of tailings to unrestricted areas during normal operating conditions. Post Reclamation 5. Reduce direct gamma radiation from the impoundment area to essentially background. 6. Reduce the radon emanation rate from the impoundment area to about twice the emanation rate in the surrounding environs. 7. Eliminate the need for an ongoing monitoring and maintenance program following successful reclamation plan. 8. Provide surety arrangements to assure that sufficient funds are available to complete the full reclamation plan.

Jan 1, 1980

By A. Davaliev, K. Hrkovic, V. Pavlovic

On the territory of Macedonia in South Yugoslavia primary and dory gold occurences were known since ancient times. Remnants of numerous goafs and remainders of washaries on river terraces and alluviums date right back to the times of Phillip II and his son Alexander of Macedonia and from Roman times, as well as from the Middle Ages witness exploitation of primary and secondary gold. More recent explorations on primary and secondary gold occurrences date from the period between two World Wars. Over that period a number of private companies, each on their own jointly, carried out gold exploration, particularly of alluvial occurrences on rivers emptying into River Vardar, starting from Skopje to the Greek frontier. The latest gold explorations carried out In the alluvium of River Konjska date back in 1976, and in 1978 old terraces of River Konjska were explored. The Visibility Study was prepared on possibilities of exploitation of gold from River Konjska alluvium. In the paper are collected the basic date an all known primary and secondary occurrences of gold, the results of the latest explorations, and the study itself. To-date geological explorations and analyses show very interesting potentionality of River Konjska and River Vardar alluvium, which proves continuing of he further explorations. For the moment, it is necessary to re-explore more complete view of the deposit. After that it will be possible to make complete techno-economical estimation of the auriferious alluviums and the conditions of the evaluations of the alluvial gold. 1. REVIEW OF PRIMARY AND SECONDARY GOLD DEPOSITS IN MAOEDONIA,YUGOSLAVIA 1.1. Primary deposits Scarse data are available for primary gold deposits in Macedonia` being unadequate for clear

Jan 1, 1988

By Darrell V. B. . McClarty

In 1996, Rio Algom, Denison Mines and the Elliot Lake Research Field Station (ELRFS) formed a consortium to implement a regional environmental information management system (REIMS) for the Elliot Lake area in Ontario, Canada. ELRFS is an affiliate of Laurentian University in Sudbury, Ontario, The discovery of uranium in the Elliot Lake region in post-World War II led to the development of 12 mines and 11 associated mills between 1955 and 1958. During the late 1980s, declining world demand for uranium, combined with the discovery of high-grade uranium ore in other areas of the world, made the Elliot Lake mines uneconomical. As a result, all area mines ceased opera¬tions by the end of 1996. The eight facilities and three tailings management areas operated by Denison Mines and Rio Algom's five mining waste management areas contain 150 Mt (165 million st) of potentially acid-generating tailings. The areas cover 13.2 km2 (3,265 acres) and receive drainage from an additional 13 km2 (3,212 acres). The primary objective of the joint initiative was to implement a personal-computer-based, regional, environmental-information management system for managing historical data and ongoing environmental programs in the Elliot Lake region. The Elliot Lake consortium decided it needed an information system with an integrated, process-oriented and requirements-driven approach to collect and manage the environmental information. Following a study of environmental information management systems currently used by the mining industry, the consortium decided to base REIMS on the "Envista" product. This is a commercially available, environmental information management system marketed by Envista Technologies of Saskatoon, Canada.

Jan 1, 1999

By A. Dale Wunderlich

With the price of precious metals at an 18-year low, every ounce of metal produced is important. The theft of metals from mining and refining sites can mean the diffrence between profit and loss for many mining companies. Low metal prices do not reduce the potential for the theft of precious metals. History has shown that the price of gold has little to do with the desire for employees to steal precious or base metals. There is actually evidence that the theft of precious metals increases when the price of this commodity goes down. Several of the major precious metal thefts in the past year took place at silver mines when the price of silver was less than 16 cents/g ($5/oz). How does the lowest gold price in 18 years affect the need for security at precious metals properties? There is no short answer to this question. One reason is because the exposure to theft of precious metals is unique to each property. This makes it important that each property be evaluated individually. More than 95% of all precious metals thefts can be attributed to those working at the mine site. So preventing employee theft is the primary concern. One consideration is the location of the property. Gold selling at any price is still an attractive commodity in countries where the employees are making between US$400 and US$600 a month. It is not uncommon for employees at mines in countries where low wages are the norm to consider the value of a gram or two of gold to be a significant amount of money. A gram or two of gold a day may not seem like much. But if 15 employees steal two grams a day, that equates to a significant amount of money during a year. The type of property where the precious metals product is being recovered is also important. For example, a property with a gravity circuit is more likely to suffer from the theft of gold product than a property where all gold is finely disseminated and the only gold seen in the ore body is through a microscope. Gravity circuits increase an operation's exposure to theft because the grinding circuit that is associated with a gravity circuit often becomes a giant concentrator. Areas such as the bottom of grinding-mill pump boxes, cyclone-feed-pump clean out traps and the sumps often become locations where precious metals concentrate (Figs. 1 and 2). Muck concentrations in these locations can be as high as 25% to 40% of gold or silver. Not long ago, muck was removed from a barren-solution sump at a Merrill Crowe circuit that had concentrated to more than 40% gold. At a milling site in the Pacific Rim, residents of the community adjacent to the mine learned about the value of the concentrates in the sump under the ball mill and committed an armed rob¬bery. While several of their co-conspirators held the em¬ployees at bay with machetes, the others emptied the contents of the sump into buckets and removed it from the site. Armed robbery is not as common as employee theft. However, while this article was being written, an armed robbery occurred at a gold property in Central America. Armed perpetrators took as hostages the night shift employees at a process plant and used cutting torches that were on site to cut into the high-security and gold-storage areas. The perpetrators then stole a company vehicle to remove the stolen gold buttons and sludge from the site. Unfortunately, this type of activity goes on regularly. But managements of most mining companies are reluctant to discuss theft scenarios. So information pertaining to the theft of precious metals seldom becomes a newsworthy item. An audit conducted at a mine site with a gravity circuit recommended that the gravity recovery area be shut down until adequate protection could be provided. Although it was not connected with the audit, it was necessary to shut down the gravity area for a pro¬longed period because of problems with the gravity table. In the two months that followed, gold production at the site increased by about 31 kg/month (1,000 oz/month). It is difficult to attribute all of this increase to the theft of concentrates. But there was a good chance that at least part of the increase was due to the fact that concentrates were being stolen from the gravity area.

Jan 1, 1998

By Robert F. Kaufmann

INTRODUCTION In response to the Uranium Mill Tailings Radiation Control Act (Public Law 95-604, Section 114c), a report has been prepared by the U.S. Environmental Protection Agency (1980) which describes the potential health and environmental effects associated with uranium mine wastes. The author was responsible for the geology, hydrology and aqueous pathways analysis portions of the report. All potential sources of contaminants, solids, liquids, and airborne emissions, which might cause adverse impacts upon the environment or health of nearby populations were considered. Wastes at both active and inactive uranium mines (Hans and O'Connell, 1981) are described and assessed with respect to dose and health effects (Blanchard et al. 1981). The emphasis of this paper is on the liquid emissions and the aqueous pathway. Model uranium mines were developed for surface and underground mines. The model underground mine was placed in New Mexico while the model surface mine was in Wyoming. Development of a generic assessment was complicated due to the inherent variability of uranium mines. Also, most information available relates to uranium mills rather than to mines, or reported measurements were often influenced (biased) by wastes from a nearby mill and did not specifically reflect mine discharges. Consequently, the assessment presented is often based on conservatve (maximizing) assumptions which are identified as such, and which were based on knowledge from field investigations, available literature, and consultations inside and outside the U.S. Environmental Protection Agency. Maximum use was made of available data, supplemented with limited field studies in Colorado, Texas, New Mexico, and Wyoming. PREVIOUS INVESTIGATIONS Stream survey work in Colorado by the Water Pollution Control Commission and the U.S. Geological Survey (Moran, 1974; Wentz, 1974) mentioned a portion of the Uravan Mineral Belt and uranium mines therein, but the work did not emphasize uranium mines. Significant amounts of acidity and total trace metal concentrations were found in streams from 18 different mining areas. Dilution and chemical precipitation below mine drainages decreased concentration and increased the pH. Given enough time and distance, the streams recover naturally, but the accumulations of trace metals in the sediments increase. Field observations in 1971-72 of streams in most of Colorado indicated that approximately 724 km of streams in 25 different mining areas were adversely affected by mine drainage (Wentz, 1974). Discussions of the impacts of uranium mining on water quality or quantity are incidental in numerous impact statements and environmental reports prepared by industry and (or) the U.S. Nuclear Regulatory Commission as an integral part of licensing or relicensing uranium mills. Coverage on mining is usually minor as the principal focus is on milling impacts. The same is true for the recently prepared generic EIS on regulation of uranium milling (U.S. Nuclear Regulatory Commission, 1979). Radiochemical assessment of surface and groundwater in uranium mining districts of New Mexico is done by self-monitoring programs associated with NPDES permits. Also, radiochemical assessment studies have been funded by the New Mexico Environmental Improvement Division and U.S. Environmental Protection Agency. Unfortunately, there has been no concerted effort to prepare broad assessments of the cumulative impacts of mining and milling in areas of interest in Texas, New Mexico, and Wyoming. Critical review and synthesis of these types of data can produce rather useful information. For example, the publication "Water Quality Impacts of Uranium Mining and Milling Activities in the Grants Mineral Belt, New Mexico" (U.S. Environmental Protection Agency, 1975) addresses the groundwater and surface water changes as the result of extensive uranium mining and milling production in a relatively confined area. A more recent report by the Wyoming Department of Environmental Quality summarizes 16 years of aqueous radium and uranium data. The study reports significant amounts of radium-226 and uranium were present in surface water in the Shirley Basin as a result of inadequate mine water treatment (Harp, 1978). In Texas, surface water and groundwater monitoring conducted by industry, as well as by State and Federal agencies, reveals little or no change of chemical quality attributable to uranium mining and milling (Gesell, 1977; Kallus, 1976). This conclusion is based on 586 samples collected from 198 stations over a period of 39 years, but primarily from 1961 to 1975. The State monitoring program by several agencies is continuing, but data reporting and interpretation is lagging. One survey (Itin, 1975) showed that none of the mine water from the 10 lakes that were sampled was suitable for human use. The lakes were also unsuitable for irrigation due to mineralization of the water by sulfate, chloride, and TDS. One of the 10 was suitable for stock watering.

Jan 1, 1981

By Stanley C. Suboleski, C. B. Manula

INTRODUCTION In any mining operation all possible steps should be taken to increase efficiency. One area for improvement is mine planning and design, particularly in the area of equipment selection for room-and-pillar systems. Be- cause of the availability of a wide variety of face machines, a fair degree of selectivity can be exercised in the choice of equipment for a particular job. However, this choice must be made on the basis of quantitative facts and forecasts related to the mining application. The purpose of this section is to develop and analyze the details of the mining process. Some specific areas studied include the relationship of system design to productivity, suboptimization as a result of equipment changes, and measurement of system performance. The plan of work leading to a quantitative description of these study areas is based on the growing interest in total system design using simulation as an analytical method (Manula, 1963). CHARACTERISTICS OF PRODUCTION OPERATIONS FROM ROOM-AND-PILLAR SECTIONS For a given mining method, raw production in a given section of a mine is primarily dependent upon the coal seam thickness, roof and floor conditions, methane emission, the mining methods, and the man-machine element. Average section production varies from 300 to 800 st per shift for conventional and continuous mining in high seams and from less than 100 to 300 st per shift in low seams. Since the reject varies from 0 to 40%, these figures must be decreased by the appropriate percentage to reflect the amount of clean coal mined. Personnel requirements per production section per shift for the various methods are listed in Table 1. Table 1. Production Personnel Method No. Method No. Conventional 12-1 5 Longwall 9-14 Continuous 9-1 2 Shortwall 9-12 MINING VARIABLES To evaluate the constraints and interrelationships for various mining methods, it is necessary to categorize the variables which underlie system production potential. Seven critical independent variables which determine production can be identified and categorized (Suboleski, 1978) : Seam Height The five categories are as follows: less than 36 in.;. 36 to 55 in.; 55 to 100 in.; 100 to 180 in.; and greater than 180 in. Floor Quality Floor quality ranges from : Excellent: Smooth, hard, grades less than 1 to 1 % % , and dry. Good: Smooth, soft but dry, with grades less than 3 % . The floor will deteriorate, but cautious operation can prevent it. There may possibly be heaving at some later time. Fair. Soft and damp. There is occasional interference with equipment operation; requires the use of four-wheel drive shuttle cars; ruts with regular use, and may have adverse grades of 5 to 7%. This may be coupled with slippery bottom and/or occasional steep rolls. Poor: Soft and wet. Requires blocking of the bottom to support equipment. There are frequent steep rolls and grades in excess of 7%. Roof Quality Roof quality ranges from : Excellent: Men are able to work under the unsupported top during the initial production cycle if legally permitted. Good: The roof is bolted on a 4 x 4 or 5 x 5 pattern with short bolts (442 in.) or <seam height if the seam >42 in., or requires posting with no bolts on a 4 x 4 or 5 x 5 pattern. There are no falls. Average: The roof is normally bolted on a 4 x 4 or 5 x 5 pattern, but with long bolts (>seam height or >6 ft.). There are infrequent minor falls or there may be an excellent roof which is difficult to drill. Fair: This type often requires spot bolting in addition to the regular pattern or bolting with planks. The roof conditions require shorter than planned cuts, or narrow cuts. Poor: This type requires bolts plus crossbars and posts, or installation of yielding supports or truss-type support. It is almost certain to fall if this is not done. Methane Liberation This ranges from none detected to low (no buildup at the face, even with minimum ventilation requirements) to moderate (the curtains must be extremely tight and tubing close to the face or methane will build up to 1 % during the loading of the car) to high (methane will build up to 170 if the miner is operated at the normal rate, even with proper ventilation). Hardness of Coal Coal hardness falls into the following categories: Soft: Soft coal is easily cut by a continuous miner. A plow could be used by longwall. Average: Coal of average hardness could be easily cut by a miner, and a shearer would be used in the longwall. Moderate: Moderately hard coal causes difficult cut-

Jan 1, 1982

By W. G. Pariseau

Joints may be taken into account when using numerical modeling as an aid to mine design by embedding joints in the model. When using the popular finite element method, say UT3PC, a pre-analysis step is necessary, Step 0. This step is for the computation of equivalent properties of a representative elementary volume of jointed rock (REV) in the model. This Step 0 is taken before Steps 1, 2 and 3 for specification of a rock properties file, generation of the mesh, and model analysis are taken. A brief explanation of equivalent properties and several examples aid in explaining the details of Step 0. Focus is on procedures, input files, and output to show ease of computation. Theoretical details are relegated to references (e.g. Pariseau 2022). Comparisons of safety factor distributions about example mine excavations with direct scaling from mine observations then offer some insights concerning equivalent properties, especially strengths.

Feb 1, 2023