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By Natasa Mitevska, Predrag Djordjevic, Zivan Zivkovic

This paper presents the results of an experimental investigation into the distribution of copper in the slag of an industrial reverberatory furnace sulfide concentrates smelting process in the copper smelter RTB Bor (Serbia). The influence of copper content in the matte, the temperature and the height of the slag on the content of copper in the slag was determined as Cuoxide, Cusulfide and Cutotal and was based on possible mechanisms for the loss of copper in a silicate slag from the smelting of sulfide copper concentrates. The greatest quantity of copper in the silicate slag was found in the form of matte particles, which were captured in the slag as a result of the “flotation” of SO2 gas which was formed by magnetite reduction with FeS at the slag–matte interphase boundary.

By Joseph R. Hatch

Previous studies of the Thompson and Temperly ore bodies show alteration aureoles in the Middle Ordovician host-rock limestones, dolomites and shales extending laterally as much as 60m from the ore. Thickness, texture, carbonate and clay mineralogy, major-, minor-, and trace-element contents; and carbonate carbon and carbonate oxygen Isotope compositions of the host rocks all have been significantly altered by hydrothermal processes. Organic geochemical analyses of samples from the basal 8-cm-thick carbonaceous shale bed and immediately overlying limestone bed of the Quimbys Mill Member of the Platteville Formation, collected from within the ore, the alteration aureole, and the unaltered country rock show: 1) solution of carbonates and residual concentration of organic matter, 2) decreases in the volatile (Si) and pyrolytic (S2) hydrocarbon yields In samples of the basal shale from within the ore, 3) decreases in the relative amounts of the lower molecular weight (<nC25) saturated hydrocarbons in samples from the ore, and 4) no changes in either the organic carbon isotope composition or the Rock-Eval or biomarker thermal maturation Indicators. In light of the 125-170°C depositional temperatures documented for the early marmatitic sphalerltes in these deposits by fluid Inclusion studies, the lack of thermal alteration of the organic matter suggests a relatively short mineralization episode, a conclusion supported by the relatively simple sphalerite band stratigraphy. The decreases in the volatile and pyrolytic hydrocarbon yields for shale samples from the ore supports a model for mineral deposition which obtains sulfide through reaction of brine sulfate and indigenous organic matter.

Jan 1, 2013

By David S. Bolin, Bruce Kennedy, Leigh A. Readdy, Graham Mathieson

INTRODUCTION The estimation of ore reserves is a process that begins with the earliest exploration stages on a property and continues throughout any subsequent evaluation and exploitation of the deposit. During exploration and preliminary evaluation, the results of these reserve estimates constitute the basic data for prefeasibility studies and economic analysis. The decision to continue exploration and development or to abandon a prospect is often based upon these studies. During the active life of a mine, reserve computations are continuously revised to assist in development planning, cost and efficiency analyses, quality control, and improvement of extraction and processing methods. Accurate reserve estimates are also required when financing a project, purchasing or selling a property, and for accounting purposes such as depletion and tax calculation. It is important to remember that the reliability of ore reserve estimates varies progressively through time as more and more information becomes available. The lowest order of reliability of estimation of reserves exists at the time of discovery. The maximum level of certainty concerning the ore reserves within a deposit is reached when the deposit is completely mined out. Between these two extremes are variable levels of certainty as to the tonnage and grade of the resource. This is particularly true of that portion of the mineral resource that constitutes the "minable reserve," as this portion is dependent upon economic as well as geological and technological factors. In the following discussion, several of the factors affecting ore reserve computation and some of the commonly used methods of calculation are presented. The first part of the discussion is confined to classical methods of hand calculation utilizing level maps and sections. The second part of the discussion presents an overview of somewhat more sophisticated methods of geostatistics which have been developed within recent Years. Geostatistical methods frequently provide the best ore re- serve estimates for many deposits. However, a digital computer is required for such geostatistically derived estimates due to the number and complexity of the cornputations involved. For many properties the classical nongeostatistical methods are adequate, particularly in the early exploration stages. In fact, it is the author&apos;s contention that even at those properties where the geostatistical approach is employed for reserve estimation, the geological and engineering staffs should prepare an estimate by traditional means. This provides an internal audit for the reserves and at the same time requires a continuing close appraisal of geologic problems that influence the presently known geostatistically estimated reserves and production at the mine.

Jan 1, 1982

By I. E. Odom

An electron optical and microprobe study was made to determine the physical and chemical nature of the silica minerals that occur as natural impurities in bentonite and montmorillonitic fuller&apos;s earth clay products (both granular and powder) and that occur in <10-µm dusts from plants that process these products. The purpose of the study was to determine if discrete "free" silica minerals, such as quartz, could be observed using SEM and EDS methods. No “free" silica minerals could be observed in the SEM images of the granular and powdered products, either among or on the surfaces of the particles. Also, no “free" silica could be identified by either SEM or EDS analyses of the dusts, even though quantitative X-ray diffraction analysis indicated that trace amounts of quartz occurred in all samples. It was determined that these quartz and other silica minerals were encapsulated or coated by montmorillonite. Vigorous washing, however, removed some of the clay coatings, so that small amounts of silica minerals could be seen by SEM and EDS analysis. It was found that all primary crystalline quartz grains in the bentonites have diagenetic overgrowths consisting of a mixture of montmorillonite, opaline silica and possibly microcrystalline quartz. Detrital quartz grains in the fuller&apos;s earth have thin diagenetic overgrowths of opaline silica, also containing montmorillonite. The clay encapsulation of the silica minerals in the products studied, as well as in the potentially respirable (<10-µm) dust produced during manufacturing of bentonite and montmorillonitic fuller&apos;s earth clay products, is considered to be an important factor influencing the potential health effects (e.g.. silicosis) of the contained silica. Even if clay dust containing silica should be inhaled, the montmorillonite encapsulating the quartz and other silica minerals would prevent direct contact of the silica with lung tissue. The clay encapsulation of quartz, as well as the highly hydroscopic nature of montmorillonite, may explain why not a single confirmed case of silicosis has ever been reported among plant workers in more than 65 years of production.

Jan 1, 1998

By J. Loredo

The region of Asturias, located in the northwest of Spain, has an extensive mining history; coal, gold, zinc, lead, copper, cobalt, mercury, iron, manganese, fluorspar and others have been extracted from the antiquity. In the Asturian Central Coal Basin, the closure of all open pit coal mines and their restoration, the progressive closure of underground coal mines that is happening from the 1980?s, and the restoration of spoil heaps, provides post mining lands for alternative uses. In relation to metallic mining, the abandonment of all mercury mines without restoration in the 1970´s, has left significant quantities of wastes and mining works. More than thirty years later most of them remain without restoration. In these sites the legacy of the historical mining activities is apparent in the form of shafts, galleries and transversals, old mining installations and spoil heaps. Mine wastes have eventually become important Hg and As pollution sources, resulting in a widespread contamination of the surrounding soils and surface waters. Abandoned mines of other metals such as copper, cobalt, iron, etc. and industrial minerals such as fluorspar, have also left a mining legacy to take into consideration. In this context of declining mining areas, some remedial options have been applied to specific areas resulting in alternative uses as pastures, agro-forestry, industry and socio-cultural activities.

Jan 1, 2008

By Scott G. Britton

This chapter is concerned with the construction of the dynamic component of belt haulage systems. The dynamic system includes the belt line and tailpiece extension and retraction movements in a production system where mine management is continually placing the belt in the most effective operating position. Correct installation of the belt and tailpiece during an extension is very important for many performance reasons. Two of the most important reasons are to eliminate spillage and safely operate the belt line. This chapter is divided into three major discussions. The first discussion looks at analyzing the parameters of effective belt line construction. This includes a review of the parameters and management tools needed for proper scheduling of a move-up. The second major discussion topic centers on efficient procedures for a belt line extension. Topics such as site preparation, tailpiece breakdown and setup, stringing the belt line and structure, plus operating and maintenance tasks needed after the belt line is installed and running, are covered. The third discussion presents a list of conveyor and conveyor component manufacturers who provide services and products to the coal mining industry. Again, any discussion on underground haulage systems must generalize much of the site specific design approaches to be practical. This text will mention, where applicable, some of the alternatives available to construction engineers in designing belt line systems.

Jan 1, 1983

By Mohammad Hossein Sadaghiani

"Construction of underground structures in urban areas is a very challenging work. There are generally two methods of construction, an open cut-and-cover and underground method. To eliminate the subsurface and surface disturbance and street traffic problems, underground method is preferred. The stress redistribution caused by underground excavation induces movements and deformation in the earth mass and ultimately at the ground surface. This is more pronounced in large space excavations. Generally pre-supporting system is used to control ground deformation and thus enhance its stability. In this paper an innovative pre-supporting system is presented. Concrete Arch Pre-supporting System (CAPS) is introduced in Tehran Metro in 2002. This method has roots in construction method of an Old Iranian small water tunnels, called Quanat. CAPS is an efficient method for stabilizing large span underground spaces constructed in shallow and soft ground. In this technique underground reinforced concrete elements are constructed around the proposed underground space prior to main excavation. This method is used successfully in over 50 large span underground structures in Tehran Metro stations and road tunnel intersections. CAPS has potential to be used to pre-support the large span underground spaces at any weak ground condition in an urban area.1. INTRODUCTION Underground subway stations can be constructed either by open cut-and-cover or underground construction. Due to the presence of subsurface utilities and street traffics in urban areas, underground construction is preferred to eliminate relocation of the subsurface utilities, and other urban disturbance. Underground construction in an urban area is a very challenging effort. The complexity of the work is more pronounced in a weak and shallow ground. The stress redistribution caused by underground excavation induces deformations in the earth mass and ultimately at the ground surface causing damage to adjacent structures. The need to control ground surface settlements in urban area is widely recognized and new construction methods are continuously developed. Settlements induced by underground excavation may cause serious damages to nearby structures and subsurface underground utilities, (Sekimoto et. al. 2001). In order to improve stability of underground excavation and reduce settlements, various ground treatment techniques are presented, Johnson, et.al., (1983), Carrieri, et.al. (2002), and Ocak (2008)."

Jan 1, 2016

By John A. Haggman

Philippines is a country that is richly endowed in mineral wealth. In 1988, Climax Arimco Mining Corp. (CAMC) geologists found the Dinkidi porphyry gold-copper deposit in Nueva Vizcaya province. It is the most significant mineral discovery in that country in recent times. To date, the company has defined indicated resources of 124 Mt (136 million st) of 1-g/t (0.029-oz/st) gold and 0.4% copper. This includes a high-grade core of 7.9 Mt (8.7 million st) of 6-g/t (0.175-oz/st) gold equivalent. Total contained metal is 124.4 t (4 million oz) of gold and 499 kt (1.1 billion lb) of copper. Dinkidi&apos;s discovery resulted from initial geologic reconnaissance and recognition of the intrusive complex that is exposed at surface and anomalous in its topographic expression. This was followed by systematic exploration. This includes extensive gradient array induced polarization (IP), ground magnetics, geochemical sampling and diamond drilling. This later defined a further 16 satellite porphyry targets in the Didipio region. Climax was been granted a Financial and Technical Assistance Agreement contract with the Philippine government. It allows 100% foreign ownership of mining projects. After four years of negotiations, Climax was the first company to have such an application granted. Some 120 applications from numerous international mining companies are waiting for approval following implementation of new Philippine Mining Act of 1995. Exploration history Didipio is located 200 km (125 miles) north of Manila at an elevation of about 700 m (2,300 ft) in the remote Sierra Madre mountains. This region remains mostly unexplored. The property is accessed by 25 km (15 miles) of logging track from the town of Cabarroguis, Quirino. The area experiences an average rainfall of about 3,000 mm (118 in.) a year. Most of it falls during the July-to-November typhoon season. Didipio was first recognized as a gold province in the 1970s when native Ifugao and Ilongot hunters discovered alluvial gold in the region. The region had been prospected over the years by local companies. They were mostly prospecting for alluvial gold. However, in 1988, Climax Mining geologists identified the potential of an obscure razorback ridge protruding from the alluvial valley floor. This ridge, later named Dinkidi by Climax, was the site of several small- scale tunnels. Locals had mined narrow quartz stockwork veining and sluiced soft argillic alteration zones, using irrigation canals and sluice boxes to catch free gold.

Jan 1, 1997

By Yi Luo

Bolting the mine roof is one of the noisiest underground mining operations. The main contribution to the high noise is the drilling of the roof bolt holes, especially in hard rock. A previous research shows that the specific energy consumed in drilling the bolt holes is inversely proportional to the bite depth (i.e., penetration per drill revolution). Less specific energy at a reasonably high bite depth means less energy is wasted in the drilling process to produce heat, bit wear and noise. Therefore, control of drilling operation to achieve a higher bite depth can provide an opportunity to reduce drilling noise from its sources as a proactive noise control approach. In order to explore the feasibility and to develop the proactive technology for reducing drilling noise, drilling tests have been conducted in laboratory settings. The preliminary results show significant reduction in noise dose can be achieved by drilling in medium hard rock at a reasonably high bite depth. This paper presents the findings from the laboratory experimental studies conducted so far.

Jan 1, 2013

By Howard G. Coopersmith

Kelsey Lake kimberlites are a cluster of eight diamondiferous pipes that occur in the northern State Line kimber lite district of the Colorado-Wyo¬ming diamond province (Coopersmith 1991, 1993) (Fig. 1). This is located at the southern margin of the Wyoming Archean province. Two relatively large pipes and a few smaller bodies define the cluster (Fig. 2). The Kelsey Lake kimberlite cluster has been developed as the first diamond mine in the United States. The cluster was discovered in 1987. Full-scale production began in the spring of 1996. Mining has produced gem-quality diamonds up to 28.3 carats in size. The 30 State Line kimberlites, intruded about 390 million years ago into Proterozoic crystalline rocks, were presumed to be underlain by Archean basement of the Wyoming Province. Nearly all the kimberlite pipes contain diamond but only the Kelsey Lake pipes are economic. The Kelsey Lake kimberlites contain predominately diatreme facies kimberlite, with minor hypabyssal and crater facies rocks locally occurring. Alteration and weathering of the kimberlites is extensive. Petrologic studies indicated an underlying lithosphere that has a largely Proterozoic signature and shows evidence of deep melt and metasomatic events. Current development has concentrated on the two largest pipes. These have been bulk-sampled after geological study (1987) identified the presence of small diamonds and mineral chemistry indicating favorable diamond conditions. A 10-t/hr (11-stph) rotary pan plant was established in 1992 to process thousands of tons of bulk-sample material. Grades and gem-quality diamonds to 14.2 carats in size were recovered. Early in 1995, it was decided to move from evaluation to commercial mining. Production began in early 1996. A 195-t/hr (215-stph) rotary pan plant was built. A water supply system and tailings disposal have also been incorporated. The project straddles the Colorado/Wyoming border. Existing mining permits were amended to incorporate the increased scale and new plant facility. The permits for this project included the following: Colorado mining permit, Wyoming dozing permit, Corps of Engineers Section 404, Colorado NPDES, Wyoming NPDES, Storm water Management Plan, Air Pollution Emission Notice, various Colorado and Wyoming State Engineer and well permits, Substitute Water Sup¬ply Plan, Larimer County Special Use Review, and US Forest Service road use permits. The temporary destruction of a wetlands area was a sensitive issue. It has been addressed through the Clean Water Act Section 404 permit administered by the US Corps of Engineers. This use will be mitigated by creating new, self-sustaining wetlands in the immediate drainage system. A comprehensive and bonded reclamation plan is incorporated in the permits. Diamond mining and ore processing is environmentally benign. No chemicals are used in processing the diamonds. The plant is a water wash facility. The kimberlite ore is inert, as is the granite wall rock. The exposure of the ore body and the subsequent ore processing and waste rock and tailings containments pose no threat of release, leaching or dispersion of any detrimental elements. There is no acid-forming waste. Even a prolonged acid rain environment will not produce a harmful leachate. Slimes containment and clarification ponds will prevent unacceptable levels of suspended solids in water discharge. The isolated, restricted access and nonvisible nature of the mine and processing has led to straightforward permitting. Geology The State Line district is located in the northern

Jan 1, 1997

By E. F. Young

An integrated steel company is an industrial complex ranging from raw materials mining, through pyrometallurgical smelting and refining, and hot shaping, to product finishing and coating. Within this complex is a great variety of operations which use vast quantities of water, and a variety of water uses which can result in pollution of many different types. The industry has recognized most of its problems for some time, and has spent a great deal of money and effort in reducing and eliminating pollution. A recent survey by AISI showed that the industry has spent, within the last 15 years, two hundred forty millions of dollars on water pollution control, and has authorized spending eighty-seven millions more on this type of non¬productive facilities. While much still remains to be done, I think the record to date is one we can be proud of. In this presentation, we will attempt to outline a number of the water pollution problems encountered in an integrated steel company and to show what types of corrective action have been and are being taken, using Jones & Laughlin Steel Corporation as an example.

Jan 1, 1968

By Robin G. Adams

The market prices received by producers of internationally traded commodity metals have been, and continue to be remarkably volatile and unpredictable compared with most other traded goods and services. This volatility results in an erratic financial performance on the part of producing companies, disruptive and often inflationary cost changes for consumers, unreliable tax revenues and export earnings for host governments and severe social and economic pressures on local, sometimes remote, communities which are dependent on the activity in question. Generally speaking, price volatility appears to be associated with the inability of the metal producing side of the industry to regulate the volume of supply in a manner that is consistent with metal demand, which in turn reflects broad macroeconomic and industrial developments around the world. This statement does not purport to apply to all metals or to all instances of volatility of course. Price movements may occur as a result of pure speculation or even illegal manipulation of the commodity markets. Embargoes, boycotts and other politically induced supply changes may contribute. Threatened or actual strikes also cause artificial swings in sales volumes and prices. How- ever, most of these developments are of a short-term nature. Yet metals price cycles may last for several years, as demonstrated by the extended copper price trough from 1981 to 1986. This paper deals with price volatility which reflects long-term economic cycles and the adaptive processes that exist within the industry in response to such cycles. Special emphasis is placed on the role of forecasts and forecasters in these processes. It should be said at the outset that this reflects the personal experience of one forecaster working in private sector commercial consulting practices that are independent of producers, consumers and host governments. However, the experience does cover the entire period since 1973 and has involved working with a substantial majority of the major companies that supply high volume commodity metals. By way of background it should be stated that the post-1973 world economy has provided a challenging environment for forecasters. One cannot be precise about the forecasting record of either industry insiders or outside consultants, financial analysts and academic forecasters because comprehensive records have not been kept, or if they have the results are too embarrassing to be published. Institutions such as the World Bank have published forecasts of the prices of major commodities on a regular basis and these have, presumably, had some influence on financing decisions in the industry. This record along with our own experience and numerous discussions with metal producers, major consumers and host governments permits certain generalizations to be made. The most important of these is that during the early 1980s. from about 1980 through 1985/6, the forecasters system- atically and substantially over- estimated metal prices. While some fore- casters did correctly anticipate a recession in the early 1980s and some consequential decline in prices, the magnitude and duration of the decline was far greater than anyone foresaw. This systematic forecasting "failure" appears to have occurred independently of the forecasting methodology employed. Moreover, its extent cannot be explained by obvious factors such as incorrect macroeconomic assumptions. There appears to have been some kind of structural change in the world mining and metals industry over this period

Jan 1, 1989

By Byron C. Hardinge, Michael Sokaski, Paul F. Sands, W. Loring III Mc Morris, David J. Akers

INTRODUCTION In the early days of coarse-coal cleaning by the dense-medium process in Europe, loess was one of the materials used for medium solids. Newly developed cyclones were used to reclaim and thicken the loess suspension. On occasion, when the cyclone thickener at the Maurits mine in the Netherlands plugged, the overflow was found to be filled with clean coal free of impurity. From this observation stemmed the concept of the cyclone as a cleaning device. Development took place during World War II in the laboratory of the Dutch State Mines under the direction of M. G. Driessen. A 15-tph (13.6 t/h) pilot plant was in operation in the laboratory by 1945, when, in September, Driessen made the first public disclosure of the process in a paper presented to the Institute of Fuel in London.51 In April 1945, operation of this pilot plant was observed by H. F. Yancey, who was so impressed with the potential of the cyclone process that, on his return to the United States, a research program on the cyclone was immediately started by the US Bureau of Mines (USBM). This work led to an AIME paper in 1946 in which the first details of cyclone operation on American coals were made available.52 Commercial adoption of the cyclone proceeded in Europe, initially in the Netherlands, Germany, and France. In the United States, where coal is less costly and most of the coals are easy to clean and respond well to simpler cleaning processes, the first cyclone plant was not built until 1961.53 THEORY Before discussing the theory of a dense-medium cyclone, a brief description may be helpful to some readers who are not familiar with its basic operation. In a typical dense-medium cyclone, illustrated in Fig.7-51 a mixture of medium and raw coal enters tangentially near the top of the cylindrical section, thus forming a strong vortical flow. The refuse moves along the wall of the cyclone and is discharged through the underflow orifice. The washed coal moves toward the longitudinal axis of the cyclone and passes through the overflow orifice, or vortex finder, to the overflow chamber. Washed coal is discharged from this chamber, usually through a tangential outlet.

Jan 1, 1991

By Eberhard Werner

Existing reports on the effects of mine subsidence on water wells and springs appear to be inconsistent. Some report quick and complete recoveries to pre-mining conditions while others indicate long-term or permanent effects. It is clear that topographic and geological factors as well as precise position with regard to the mine are important in determining probable effects of subsidence on aquifers. Ridgetop aquifers which are well above regional base-level are much more susceptible to disturbance by mining activities than those located topographically lower. Effects seen are attributed largely to increased permeability, both horizontal and vertical. of the aquifer rocks. The deeper aquifers usually show short term losses or water-table declines. but the effects on the ridge-top aquifers persist for longer periods or may be permanent. Subsidence enhances permeability. so that infiltrating water moves much faster to lower levels. causing pond and stream losses and declining levels in wells as well as declining flows of springs of the higher aquifers, while increasing levels and flows of the lower aquifers. Additional effects are shifts of spring locations caused by minor tilts due to differential subsidence and redirection of shallow flows by changes of horizontal fracture permeability. These effects are seen as mining of a panel progresses beneath the site. and are often repeated when adjacent panel mining fronts pass the site. Analysis of water well level and spring flow records indicates that the effects are greatest at the edges of longwall panels in the tensional regime. These effects are amplified for locations close to topographically steep terrain and in close proximity to fracture traces mapped from medium-to small-scale aerial images.

Jan 1, 1986

By Tim Cleary, Steve Skelhorn

The 9th Line / 16th Ave tunnels are part of a $700 million expansion of the York Durham Sewage System, north of Toronto. The 15 km of tunnels presented many challenges, including glacial and postglacial deposits, at depths up to 55 m. Due to high hydrostatic heads, the Owner specified EPB tunnelling, however, an alternate was proposed utilising rib and lagging tunnels, combined with a de-watering scheme. State of the art technology was utilised with a new Lovat TBM, incorporating PLC control, soft start water-cooled motors and a head designed to tackle the mixed ground expected. The 9th Line tunnels were completed in 2002. Subsequently the second section of tunnel along 16th Avenue has been awarded to the Joint Venture. This paper presents a case history of the soft ground tunnelling, including design elements, tunnel systems and TBM operations.

Jan 1, 2003

By Vladimir Adamek

Due to the variability of subsidence characteristics across the U.S. coalfields, it was concluded that it would be practically impossible to develop a universal predictive model for mining-induced subsidence based on theoretical assumptions. Therefore, an effort was made to find a procedure to develop an empirical subsidence predictive model based on a sufficient Mount of field data from one mining area (in this case the Northern Appalachian Coal Region). It was also thought that this procedure, if successful, could be used as the template for developing predictive capabilities for other coalfields with different subsidence characteristics given a reasonable amount of field data. It has been found, in the Northern Appalachian Coal Region, that the variability of subsidence characteristics can be expressed by a polynomial equation developed through regression analysis of the variable subsidence coefficient and derived directly from the field data. In this study, field data were obtained from 11 Bureau longwall panel studies (16 half profiles) for static subsidence and 14 panels for dynamic subsidence. The effects of lithology, expressed in the form of a variable subsidence coefficient, have been separated for each test site by introducing a correlation between hythetically homogeneous overburden and existing ithological conditions. For each longwall panel, the characteristic of the variable subsidence coefficient was defined along individual static profiles. The definition of mean values with acceptable deviations is the substance of the predictive method. The same procedure was used to develop a predictive model for dynamic subsidence, since it war discovered that the rate of longwall face advance is not a necessary functional parameter. This paper presents the theory, development, and application of the static and dynamic subsidence prediction models.

Jan 1, 1986

By Robert E. Blackett

To help local governments plan for long-term supplies of sand and gravel for buildings and infrastructure, the Utah Geological Survey is assessing natural aggregate resources (mainly sand and gravel) in the St. George, Utah area. Whereas much of the aggregate in the study area is adequate for road-base construction, high-quality aggregate for Port- land cement concrete is limited due to geology, and also due to land administration and environmental issues. Virgin River alluvial gravels southwest of St. George are generally poor sources of aggregate because they contain clasts of soft sediments and soluble minerals derived from Mesozoic rocks. Elsewhere, widespread secondary calcium carbonate (caliche), as rinds and matrix in gravel, lower the quality of material. Young river-terrace deposits in Fort Pearce Wash, and along the Virgin River above St. George are the primary sources of sand and gravel for the area. Alluvial fans on the east side of the Beaver Dam Mountains, and on the west side of the Hurricane Cliffs are also sources of aggregate. Stream-channel deposits associated with "inverted valleys" north of the towns of St. George and Hurricane, Utah, and older pediment gravels on the west flank of the Beaver Dam Mountains may be future sources of high-quality aggregate. Accelerated urban development during the 1980s and early 1990s has caused St. George and other communities in Washington County to encroach upon sand and gravel pits originally located in rural, undeveloped areas. Urban residents often view nearby sand and gravel operations as undesirable neighbors and pressure elected officials to close the pits. Pit closures effectively eliminate the remaining reserve from the sand and gravel resource base of the area. More- over, resources may also be lost as new homes are built upon undeveloped sand and gravel deposits. The St. George area is particularly susceptible to loss of aggregate resources because high-quality natural aggregate for construction is already in short supply. Moreover, most of the land in the study area is administered by the U.S. Bureau of Land Management and subject to various land-use restrictions. Much of this public land cannot be developed for mineral materials, such as sand and gravel, because of federal regulations protecting rare plants and animals, archaeological sites, and important watershed areas. Of particular concern to resource development are areas designated as Areas of Critical Environmental Concern, Wilderness Areas, and Wilderness Study Areas. Protection for Endangered Species is a critical element in all planning efforts. Those species present in the St. George area or in areas near- by include: the desert tortoise, southwestern willow flycatcher, Virgin River chub, and dwarf bearclaw poppy. As the St. George area is depleted and/or deprived of sand and gravel resources through extraction and urbanization respectively, construction costs will rise unless conservation measures are instituted. To avoid the loss of aggregate resources, the UGS is pursuing a program of data gathering and field surveying of surficial deposits to determine tonnage and quality of the remaining sand and gravel resources. The resource information from this program will help land planners, developers, and government officials make informed decisions concerning urban development throughout the region.

Jan 1, 2001

By R. J. Matetic

The impact of longwall mining on the local hydrological regime has become an important environmental focal point. Unfortunately, only a few studies have addressed the timing and range of well fluid level fluctuations and the associated ground movement. Furthermore, even fewer studies have determined the influence of longwall mining on water quality. The U.S. Bureau of Mines is providing insight into this environmental concern through a program of field case studies. One such study was conducted in Cambria County, PA where five observation water wells were drilled above two adjacent longwall panels. In this study, three wells were completed as nested piezometers and the remaining two served as producing wells. The piezometers were positioned along a line oriented subparallel to the longwall face and were located at the centerline of each panel and over the intervening chain pillars. The piezometers were designed to monitor fluid level fluctuations in both shallow and deep water-bearing zones. Slug tests were conducted before and after mining to characterize changes in hydraulic conductivity of the respective water-bearing zones. Pressure transducers and data loggers were installed to provide continuous fluid level fluctuation data as mining developed through the study area. The producing wells were drilled to provide water quality information. One well was located directly above the centerline of a panel and the other was positioned over the panel&apos;s set-up rooms. The wells were designed to simulate domestic use and were produced daily, for four hour intervals, throughout the study. Samples of the produced water were collected before and after mining progressed through the area. In addition, an array of monuments was installed near the study wells and was periodically surveyed to characterize mining-induced surface deformations. This study shows that: a) the observed changes in ground water chemistry did not affect the potability of the water; b) short-term major water level fluctuations occur at the approximate time of undermining; and c) water level recovery begins before the process of subsidence is complete.

Jan 1, 1986

The response of 174 domestic water supplies to longwall mining of the Pittsburgh coal seam was compared to various physical parameters. Sixty-four percent of domestic water supplies returned to service without the need for intervention, while thirty six percent required intervention to reestablish a suitable water supply. Domestic well response is strongly correlated with the topographic setting. Valley wells showed the least effect while hilltop wells showed the greatest effect. Well response was also found to be correlated to the location of the well above the mining with greater effects observed in zones of surface tension and compression, and fewer effects in zones which are stress neutral. Ground water supplies remained unaffected or were re¬established at 149 of 150 sites, indicating that ground water resources remain available to domestic wells after mining. Results of this study support the stress-relief model of ground water flow in the Northern Appalachian Basin. Longwall mining&apos;s effect on this system is to locally increase fracture connectivity in the near surface zone. This may shift the zones of saturated fractures to greater depths beneath hilltops and hillsides, and increase recharge and storage in valleys. General trends in well response are predict¬able utilizing the stress relief conceptual model, the topographic setting of the water sources, and their location over the mine.

Jan 1, 1986

By Wilbur C. (Original by) Helt

Throughout the history of mankind, the principal use of coal has been to produce heat through combustion. The heat is used in many ways: to warm air space for our comfort; to provide heat or energy to power industrial processes, such as cement and steel production; and to produce electricity. Because it is our nation&apos;s most abundant fossil energy fuel, coal in the late 20th century is on the threshold of becoming a significant source for synthetic liquids and gas energy fuels for this country. This is made possible by conversion processes which can change solid coal into various synthetic gases and liquids. These coal-derived fuels are nearly identical to the processed fuels and chemicals provided by natural gas and crude oils, which presently provide almost all the petrochemical feedstocks and energy fuels needed for the residential, light commercial, and transportation markets. A revolution is beginning to take place, not only in the United States, but in many other countries with a return to a coal-based energy economy. Also, new combustion and conversion technologies which are compatible with national health and environmental goals are rapidly emerging. These technologies will allow coal&apos;s use to be expanded not only in its traditional markets, but also to supply markets held by natural gas and crude oil. With the worldwide decline in natural gas and crude oil reserves, coal is being-looked upon to meet the energy demand. Because of these new coal conversion technologies, coal will no longer be only a combustion fuel, but a valuable raw material for production of a variety of clean fuels and chemicals.

Jan 1, 1981