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By P. L. Dunn

Automatic control of fine coal cleaning circuits has traditionally been limited by a lack of sensors. Although several nuclear-based analyzers are available, none have seen widespread acceptance. In this investigation, image analysis is used for on-line determination of ash content in fine coal slurries. The ash content of a flotation tailings stream is correlated to the mean gray level of the slurry. Based on a 90% prediction interval, an analysis of sensor performance indicates an accuracy of 73 ± 4% ash over a range from 65-90% ash. While this result is comparable to existing nuclear-based analyzers, the video-based system is only a fraction of the cost. The sensor is currently installed at the Middle Fork preparation plant owned by Pittston Coal Company.

Jan 1, 1997

By Kanaan Hanna

A joint research program between the U.S. Department of the Interior's Bureau of Mines and Cyprus-Yampa Valley Coal Company is being conducted at the Foidel Creek Mine, Oak Creek, Colorado. This program goal is to study the effects of state-of-the-art, high-speed, automated longwall mining on health and safety, and primarily, ground stability under various geological conditions. The Bureau installed an automated data monitoring system, known as the Ground Control Management System (GCMS), to monitor in real-time the effect of rapid mining on pillar and face loading, stress redistribution in and around the longwall panel, and caving characteristics of the roof. The Bureau's GCMS, combined with the company's existing monitoring systems, which include environmental monitoring, a computer programmable conveyor belt system, and gamma ray roof control thickness indicators, has been effectively used to improve safety at the face, increase productivity, and reduce production costs.

Jan 1, 1991

By C. Einberger

Groundwater Monitoring is typically required by regulatory agencies at potentially hazardous landfills or surface impoundments. Agencies have often required an arbitrary number of wells with limited evaluation of the effectiveness of the network to detect a leak. A Monitoring Efficiency Model (MEMO) has been developed to improve the design and cost effectiveness of monitoring well networks. MEMO 15 an analytical model that simulates the migration of hypothetical contaminant plumes from a site and quantifies the efficiency of alternative well network designs in detecting the plumes. The computed monitoring efficiency provides a quantitative measure of the well network adequacy based on hydrogeologic considerations. The model was recently used to design the groundwater monitoring well network for a heap leach pad at the proposed Beartrack Project.

Jan 1, 1993

By Giorgio Höfer-Öllinger, Peter Pointner, Manfred Stadlober

"SUMMARY Investigations from tunnel face are part of risk mitigation measures during the excavation works. With the tunnel equipment, percussion drillings of up to 30-40m can be achieved. Core drillings are state of art method for investigation exceeding 50m. At Koralm base tunnel, up to 270m deep percussion drillings were performed with drilling rigs and accompanied by an intensive investigation program. These investigations consisted of monitoring during the drilling, field tests (with packer, using the preventer, borehole imaging) and in laboratory. Percussion drillings are cheaper and save time of interruption of the excavation progress. INTRODUCTION As part of a proper risk management, horizontal advance drillings during excavation of underground works can be seen as state of art and meet wide acceptance. Core drillings, deep and shallow percussion drillings can be differed. The selection of the type of drilling, meanwhile, causes intensive discussions. On the one hand, only a core drilling allows a direct investigation of the rock mass expected during later excavation works. On the other hand core drillings are expensive in both cost and time – if there is no excavation progress during the investigation measures – in construction time. Percussion drillings can be performed as rapid investigation measure with the excavation equipment (“Jumbo”) allowing two dimensional image of the ground around the cross section. There is some limitation concerning a reasonable depth of approximately 30m and a borehole diameter of 76mm. The applications of preventer, packer or borehole imaging are hardly applicable. By use of a drilling rig depths of percussion drillings of several hundred meters can be achieved relative easily and there is less limitation of the borehole diameter. Installation of a preventer is possible, as well as packer tests and borehole measurements (imaging, gyroscope, borehole geophysics). The gap of information between core and percussion drilling cannot be closed completely, but it can be reduced substantially and sufficiently by combination of an intensive program of measurements and analysis accompanying the investigation works."

Jan 1, 2016

By Todd Wanless, Daryl Poduska, Prakash Donde, Mahmood Khwaja

"The proposed Minne Lusa Stormwater Conveyance Sewer is part of the Phase 3 Major Combined Sewer Overflow projects to be scheduled as part of the City of Omaha’s Long Term Control Plan (LTCP). The system features a 6,100 foot long, 14-foot inside diameter tunnel to provide for conveyance of separated stormwater from previously completed and future LTCP sewer separation projects to the expanded Storz West and Pershing Detention Basins and subsequently, the Missouri River. The tunnel will operate as a pressurized system and convey flows of up to 2,500 ft3/s resulting from a 10-year, 24 hour storm event. This paper provides a synopsis of the project with a focus on the overall design aspects related to siting the tunnel alignment in an urban environment, the hydraulic analyses performed to choose a pressurized system rather than an open channel system, and expected geologic conditions. Tunnel alignment and profile and geological profile are presented, as well as an overview of the construction related impacts considered during design. PROJECT BACKGROUND The proposed Minne Lusa Stormwater (MLSW) Conveyance System will provide for conveyance of separated stormwater from previously completed, and future, LTCP sewer separation projects to the expanded Storz West and Pershing Detention Basins and subsequently, the Missouri River. The project location is representatively shown on Figure 1; the overall conveyance system is represented in Figure 2. The MLSW Conveyance System consists of three separate construction contracts under Contract Numbers: OPW-52004 – The Storz West Detention Basin to 31st & Paxton Tunnel; OPW-52454 – The Storz West/Pershing Detention Basin Grading and Improvements; and, OPW-52752 – The Pershing Detention Basin to ML Outfall Channel. This paper focuses on the project covered under Contract OPW-52004: design and construction of an approximately 6,110 feet 14-foot inside diameter (ID) tunnel, constructed using a Tunnel Boring Machine (TBM). The tunnel will receive flows from the Paxton Boulevard (PB) and the John Creighton Boulevard (JCB) Stormwater Conveyance Sewers and convey the flows to the Storz West Detention Basin, resulting in CSO volume and flow rate reductions to the Minne Lusa Outfall Channel and the North Interceptor."

Jan 1, 2016

By Paul M. Jr. Musgrove, Donald C. Moore

Conventional Smelting Practice Conventional copper smelting practice varies from smelter to smel¬ter, but generally consists of some or all of the following unit processes: roasting, smelting, converting, and fire refining. Roasting. Copper sulfide concentrates can be smelted directly or after an initial roasting step. Roasting is used in some smelters because roasting prior to smelting increases smelting capacity, less energy is required to melt hot roaster calcines than wet sulfide concen¬trates, roaster off gases are high in Sot concentration, 5-15% SO2, and some volatile impurities are removed from the concentrate prior to smelting. However, many smelters do not use roasters, because the problems associated with handling hot dry calcines outweigh the advantages mentioned. Concentrate roasting is performed in multiple hearth or fluid bed roasters. If the moisture is low, roasting can be performed autogenously, usually at 500-600°C. High roasting temperatures are avoided because excess oxidation of the iron compounds may lead to magnetite formation. Magnetite is detrimental to reverb operation because mag¬netite can combine with refractory minerals to form a highly viscous slag. This slag prohibits efficient matte-slag separation and leads to excessive copper losses. Also, magnetite can settle through the matte layer, deposit on the furnace bottom, and consequently reduce furnace capacity. Roasting is carried out only on sulfide concentrates prior to smelt¬ing in reverb or electric furnaces. For smelting processes, such as the flash and continuous that rely on the exothermic heat of oxidation of the sulfur minerals, roasting is not practiced. Reverberatory Smelting. The predominate copper smelting fur¬nace for the past 50 years has been the reverb. These furnaces are typically 100-120 ft long, 30-35 ft wide, and 12-15 ft high. A typical furnace layout is shown in Fig. 2. Refractory brick linings cover all internal surfaces of the furnace. Originally the flame was directed to reverberate or reflect off the furnace ceiling and melt the feed material. Current practice is to direct the flame down the furnace length to melt the concentrate. A method of charging the concentrates or calcines, generally along the side walls to minimize refractory erosion, is incorporated in the furnace design. The copper concentrates, calcines, and fluxes charged into the reverb undergo a series of complicated reactions as the temperature of the mixture increases. The reaction of the iron and copper sulfides with the oxygen in the furnace produces a molten Cu25-FeS mixture called matte. Copper smelting metallurgy is based on the fact that sulfur has a greater affinity for copper than for iron and most other common metals. Therefore, in a system containing copper, the copper will preferentially remain as a sulfide compound until all of the other metals have been oxidized. The oxidized metals combine with silica to form a silicate slag that floats on the matte and is removed from the system. Reverberatory furnace smelting chemistry can be approximated by the following chemical equations: FeS2 + O2 - FeS+ SO2 (1) The formation of FeS ensures that any copper present other than as sulfides will be reduced by the relationship: CuO2 + 2FeS + O2 - CuS + 2FeO+SO2 (2) or 2Cu +FeS - Cu2S + Fe (3) As the molten charge travels down the furnace, continued oxida¬tion of the iron minerals and sulfurization of the copper minerals occurs. When all of the copper has been converted to sulfides, the iron sulfides can then be further oxidized as: FeS + (3)2 O2 FeO + SiO2 (4) The FeO reacts with the silica added as flux in the furnace charge. A simplified equation is: FeO + SiO2 -FeO SiO2 (5) The iron silicate slag formed is skimmed from the surface at the end opposite the burners. The copper content of reverb slag is usually less than 0.6% Cu and is discarded. Matte is removed along the side wall and is taken to the converter for oxidation of the remaining sulfur and iron. The main objectives in reverberatory smelting are to produce a molten Cu2S-FeS matte containing 30-60% Cu and a throwaway slag. Production of matte permits complete conversion of all copper minerals into copper sulfides, which can migrate because of specific gravity differences, through the lighter slag layer. Also, the molten matte droplets collect the noble metals, gold and silver, as the matte settles in the furnace. The large settling area of the furnace provides enough separation time to produce a low grade slag, which can be discarded without further processing. High heat losses are associated with reverberatory smelting be¬cause of the large volume of gases sweeping through the furnace. Therefore, an outside source of heat is required to keep the smelting reaction going. Natural gas, fuel oil, or pulverized coal are used as this heat source.

Jan 1, 1985

By L. Landryova

The Department of Control Systems and Instrumentation, VSB - the Technical University Ostrava, has been involved in a project dealing with utilization of landfill gases, when the methane gas utilization and minimization of its release into the atmosphere was the main concern. The landfill site is generally a place, where technology for energy production can be built. The conditions for this technology implementation vary and depend on various factors. This paper is presenting findings and experience gained regarding a method of methane gas utilization for energy production. This method is concerning building bioreactors at the landfill sites, which are already operated. Every bioreactor can be thought of as a process, which is controlled in order to maximize energy production and minimize the methane gas escape into the atmosphere. The bioreactor landfill can represent a number of environmental and cost savings and, at the same time, is able to comply with all legislative issues.

Jan 1, 2005

By Lawrence Tsang, Conrad Ng, Tim Leung, Peter Poon

"The Mined Tunnel is part of the Central-Wan Chai Bypass and Island Eastern Corridor Link (CWB), which is a strategic road along the northshore of Hong Kong Island targeted to alleviate the heavy traffic congestion. The objective of this paper is to review the performance of construction of a 160m long Mined Tunnel with a trinocular cross-section area of 460m3 and a combined span of about 50m underneath the southern approach ramp of the existing Cross Harbour Tunnel (CHT) by sequential excavation method (SEM) in hard rock. Mechanical excavation of tunnel by adopting the New Austrian Tunnelling Method (NATM), together with the application of NGI Q-system allows observational approach and optimization of temporary rock support design. Furthermore, the good performance of optimized rock support and the stability of CHT are confirmed through instrumentation monitoring review. This paper also discusses the selection of different tunnel plant and equipment to achieve the planned rates of tunnelling by mechanical excavation in competent granitic rock. INTRODUCTION The works of the CWB mainly comprise construction of 4.5km dual three-lane trunk road, of which a 3.7km section is a tunnel connecting Rumsey Street Flyover in Central to Island Eastern Corridor at North Point (see Figure 1). The Mined Tunnel runs from the ex-Public Cargo Working Area (ex-PCWA), underneath the existing CHT, and through the Causeway Bay Typhoon Shelter. The Mined Tunnel passes at an oblique angle beneath the southern portal of CHT over a length of some 50m. CHT is the primary sensitive receiver of this project and is utilized with a daily throughput of about 120,000 vehicles that far exceeds the design capacity of 78,000 vehicles per day. Hence it is necessary to choose the most appropriate tunnelling method to preserve the structural integrity of the CHT. Other sensitive receivers in the vicinity include structures to the north of the Mined Tunnel, the Royal Hong Kong Yacht Club (RHKYC); and to the south of the Mined Tunnel, the Police Officers’ Club (POC)."

Jan 1, 2016

By C. H. Bucknam

Acid neutralization titrations were applied to the characterization of soil and overburden for the control and prediction of acid rock drainage in the coal fields of the eastern United States in the 1970?s (1). These became known as the Sobek methods as a result of the early United States Environmental Protection Agency publication and the methods have been modified (2) to be adapted to many applications in the metal mining sector (3,4,5,6,), and, as a result, there are a large number of acid neutralization potential methods being used that are referred to as Modified Sobek methods. Standardization of neutralization potential methods for metal bearing ores and related materials based on carbonate carbon, rather than titration, commenced in the 1990?s through the American Society of Methods and Materials (ASTM) Committee E01 on Analytical Chemistry for Metal Ores and Related Materials Subcommittee E01.02 on Ores, Concentrates and Related Metallurgical Materials (7). A subcommittee section, E01.02.05 on Environmental Methods, was organized to coordinate the method and material standardization efforts of ASTM and the Acid Drainage Technology Initiative Metal Mining Sector (ADTI-MMS) Prediction Committee (8), which took on the project of standardization of the acid neutralization potential acidity titration method (ANPA) to supplement the carbonate carbon method in E1915 (9) for application to samples which have metal carbonates (10), in particular, which result in overestimation of the neutralization potential using the carbonate carbon methods (11).

Jan 1, 2010

By H. H. Richards, Ray L. Tobie, L. A. Thomas

GENERAL DESCRIPTION Since the beginning of operations, with the exception of a small tonnage mined by slushing, ore extraction has been by full gravity caving. Formerly, a checkerboard sequence of block undercutting was followed with the even-numbered blocks in one panel and the odd¬numbered blocks in the adjacent panel being mined. As these blocks were depleted, the intermediate or pillar blocks were mined (Fig. 1). Following this checker¬board, the mining sequence went through a number of changes, finally evolving into diagonal retreat panel cav¬ing by blocks (Fig. 2). The numbers in Fig. 2 indicate the sequence in which blocks were undercut. Gaps in the numbering sequence indicate undercutting on the level outside the illustrated area. Geology The ore body is a low-grade deposit of chalcopyrite mineralization disseminated throughout structurally weak, highly fractured, strongly altered granitic host rocks. It takes the shape of a gently dipping elliptical cylinder consisting of an ore shell of variable thickness surrounding an interior waste core. Major and minor axes of the mineralized cylinder are 1524 m (5000 ft) and 762 m (2500 ft), respectively, and length approximates 2438 m (8000 ft). Ore is sufficiently fractured to break readily into medium-coarse size. The igneous rock complex containing the ore body is covered by a wedge-shaped blanket of Tertiary con¬glomerate which was brought into place by faulting along the major regional structure of the San Manuel fault. Thickness of the conglomerate cap varies from only 9 m (30 ft) at the east end of the ore body to more than 610 m (2000 ft) at the west. Structurally, the con¬glomerate is much more competent than the igneous host rocks and, when caving, it breaks into massive chunks. Conglomerate boulders seen in drawpoints underground are very coarse. The total rock column over the initial mining area of the 1415 grizzly level was 354 m (1160 ft) of which 122 m (400 ft) was ore, 79 m (260 ft) was leached igneous capping, and 152 m (500 ft) was conglomerate above the San Manuel fault. Diamond Drilling: From 4572 to 7620 m (15,000 to 25,000 ft) are drilled annually from underground workings to delineate the ore body. MINE DEVELOPMENT Haulage Level In the south or main ore body (see Figs. 3-6), with the exception of the draw and transfer raises, all the extraction openings are concreted (Seaney and Tobie, 1965). The haulage panel drifts, which are 18 m (60 ft) below the grizzly drifts, are first driven with pre¬concrete ground support. The drift, which has an arched section, then is concreted using mobile collapsible steel tunnel forms. The haulage drifts leading from the pan¬els to the hoisting shafts are not concreted. After the panel drifts have been concreted, the raise stations from which transfer raises will be driven are constructed and the raise-station ore-drawing chute is installed. The chute is prefabricated of A-36 steel with undercut guillo¬tine gates made of abrasion-resistant 2.5-cm (1-in.) steel plate powered by 20-cm (8-in.) air cylinder installed on each side of the raise station. Transfer Raises The transfer raises are lined with 15 x 20-cm (6 x 8-in.) cribbing and are 1.22 m (4 ft) in the clear. Each cribbing is protected from wear by a high carbon steel angle which is nailed onto the cribbing. The transfer raises are driven from each side of the raise station on an angle of 1.1 rad (63°). Each raise con¬sists of a main and a backover branch. The transfer¬raise driving crew consists of two men working one shift only. Grizzly Drifts After the transfer raise reaches the grizzly level, the grizzly drift can be driven. The grizzly drifts are spaced at 10.6-m (35-ft) centers and are driven parallel to the long axis of the ore body (see Fig. 2). This drift is driven by a two-man crew working on one or more drifts at a time using feed-leg machines. The eight grizzlies in the 42.7-m (140-ft) long drift are spaced at 5.3-m

Jan 1, 1982

By Sean Peterfreund, Grant Finn, Ty Jahn

For urban underground development involving tieback anchors for excavation support, authorities having jurisdiction typically require tiebacks to be de-tensioned before project completion. This paper updates “A Proactive Approach to Tieback Anchor De-tensioning” (by Peterfreund and Finn, published in the 2017 RETC Proceedings), which discussed a new method employed in a cut-and-cover transit station project. Since publication of that paper, 237 tiebacks were successfully and rapidly detensioned from using a small-diameter drill to cut strands from the surface. To the authors’ knowledge, this was the first intentional large-scale use of a drilling method for this purpose.

Jun 13, 2023

By B. Waterman, R. Collins, V. R. K. Paruchuri, P. Gonzalez, H. Dijkman

"INTRODUCTION Mining and processing of sulfide ore bodies has the potential to solubilize sulfate. Gypsum in the host rock, as well as oxidation of sulfides during milling and processing can solubilize sulfate. Acid rock drainage (ARD) also has the potential to generate waters high in sulfate. Even after treatment of the ARD with lime, the treated water can have sulfate present in gypsum saturation levels. Most mine-sites reuse sulfate impacted water but as a mine nears closure, reuse options may be limited and water treatment becomes an option. Furthermore, sulfate discharge requirements, particularly for anti-degredation narrative standards, can be very strict. Freeport has investigated many new technologies to economically remove sulfate from these types of water. A Dutch company, Paques B.V. developed one of these technologies and it utilized biological reactors to convert sulfate into elemental sulfur in a 2-step process. In 1992 the first industrial reference of the SULFATEQTM technology was commissioned at the Nystar Budel zinc refinery in the Netherlands. PILOT PLANT TECHNOLOGY AND DESCRIPTION As shown in Figure 1, the plant contains several process steps, which can mainly be divided into the following sections: 1. Anaerobic biological system in which sulfate is reduced to hydrogen sulfide by sulfate reducing bacteria. 2. Aerobic biological system in which hydrogen sulfide is oxidized to elemental sulfur by sulfide oxidizing bacteria. 3. Solid/liquid separation in which sulfur, calcium carbonate and biomass solids are separated and dewatered. Sulfate impacted ground water is pumped to the feed water tank through a plate and frame heat exchanger to maintain the solution temperature around 95°F. A custom mix of micronutrients is dosed to the feed tank. This nutrient mixture provides essential elements for the growth of anaerobic and aerobic biomass. Urea is added to the feed tank and provides the required nitrogen source to the biomasses. The pretreated feed water is pumped into the anaerobic reactor. The reactor works on the gas lift principle. Sulfate reducing bacteria utilize hydrogen gas as electron donors and reduce sulfate to hydrogen sulfide. This reaction increases the alkalinity of the solution. Carbon dioxide gas is added in order to control the pH within working range of the reactor. Due to the low solubility of the hydrogen gas, the anaerobic gas mixture is recycled through the system. The gas mixture recycle also provides the gas lift for mixing within the anaerobic reactor."

Jan 1, 2016

By Robert G. Pinkerton

Boyles Bros. Drilling Co. and Gibbons and Reed Company, both of Salt Lake City, Utah, have successfully combined into two joint ventures on the San Juan-Chama project of the U. S. Bureau of Reclamation. The Azotea Tunnel is 12.7 miles in length; the inlet portal is on the Navajo River in Archileta County, Colorado, and the outlet portal is in New Mexico, about 10 miles south of the state border. The Oso Tunnel lies immediately to the north of the Azotea Tunnel and discharges water directly into it. We are presently driving both tunnels with mechanical boring machines from their portals at the Navajo River. Both tunnels are circular, fully concrete lined. The Azotea Tunnel has a finished diameter of 10 ft. 11 inches while the Oso Tunnel is 8 ft 7 inches in diameter. Both tunnels are supported with circular, structural steel rings as required by ground conditions. In good ground rock bolts and steel roof plates are used.

Jan 1, 1967

By J. A. Madonna

Universities and colleges in three countries, Australia, Canada and the United States, recognized the need to establish and/or reorganize geoscience programs at the vocational and two-year technical levels. To accomplish this goal, a cooperative study with industry in one state or province from each country was initiated. These include 1) Tasmania, Australia, 2) British Columbia, Canada and 3) Alaska, United States. Over one hundred mineral industry organizations cooperated in the study by providing information regarding their specific training needs for support personnel. The data gathered has been used to identify training areas for semi-skilled, skilled and technical personnel in geochemical mineral exploration, including, but not limited to, geological skills, geochemical skills, environmental skills and computer skills. With the areas of major educational need defined for geochemical exploration, an educational field skills model has been developed for the three levels of training. The depth of each level of education and the training objectives for the work force at each level will be discussed.

Jan 1, 1993

By Yongsik Jeong, Kwangmin Kim

Most tailings storage facility (TSF) failures occur in active, upstream-type TSFs, often due to extreme and unexpected weather conditions—specifically, heavy rainfall and strong winds. This case study of a TSF in southern Arizona examines the use of the optimum safe beach distance (Doptimal, the optimum distance between the crest and decant pond) as a tool for monitoring geotechnical stability and reducing catastrophic failures. A digital model of the TSF was used to determine the critical beach distance (Dcritical) under normal weather conditions, and Doptimal was then determined by adding incremental distances to account for the effects of heavy rainfall (Drainfall) and strong winds (Dwind). To overcome accessibility issues, a drone was used to map the TSF geometry and create a digital model. This model served as the basis for conducting a coupled stress-seepage, finite-element (FEM) analysis with a safety factor of 2.0 to assess geotechnical stability (Dcritical). The safe beach distance increments were determined using the PMP (probable maximum precipitation) and possible maximum wind speed. Based on this analysis, the optimal safe beach distance at the study site was identified as 202.2 m. Since the current beach distance (371 m) exceeds this value, the TSF was considered to be stable and satisfied the design safety factor of 2.0. However, this distance should be reassessed periodically to account for changes in the TSF geometry and other conditions. Furthermore, it applies only TSFs that are well-managed and feature a smooth, non-undulating beach surface with a consistent slope.

By R. J. Roman

During the refining of primary magnesium metal: a spent flux (sludge) is produced which is considered a dangerous waste by the Washington State Department of Ecology. Four years of research, testing and marketing has identified two beneficial markets for the spent flux: 1) as a fertilizer and soil admendment as a result of the material's high potash and nitrogen content and its high lime equivalence and 2), as a roadway deicing agent to clear roads of ice and snow as a result of both the salt content and the flux containing chemical compounds which exothermically react with water.

Jan 1, 1988

By Phillip J. Maddex

After the presentation of a co-authored paper, "The Cost of Transporting Ores and Raw Materials in World Markets", at the February SME meeting, one questioner commented, "You have been talking about the large shipper and ship loads. What does the small shipper do?" This paper will attempt to answer that question, at least in part. Probably the questioner hoped to hear about specific new tools and new techniques that he could apply. But one paper could only scratch the surface of the vast fund of information available; so rather than talk specifics we should take basics, that is, people, management and technology.

Jan 1, 1967

By John S. Egbert

Many of you are familiar with the Washington Metro Project. However, inasmuch as some may not be, and others may want to refresh their memories regarding certain facets of the project, I will cite a few summary details about the rail transit system we are constructing. That summary will also give each of us a common point for departure as I develop the principal thoughts that I want to leave with you. The Washington Metropolitan Area Transit Authority (WMATA) is an interstate agency established by Compact between the District of Columbia, Maryland and Virginia and approved by the United States Congress. Currently, the Authority has approval to build and operate a 101-mile (162.5 km) regional rapid rail transit system as shown on Appendix A. Of that total, 38 miles (61.2 km) will be in D. C., 32 miles (51.5 km) in Maryland and 30 miles (48.3 km) in Virginia. (Mileage figures, because of rounding error, do not add to 101 miles.) Referring again to the 101-mile total, 48 miles (77.2 km) will be underground, 42 miles (67.6 km) on the surface and 10 miles (16.1 km) on aerial structures. Of the 48 miles (77.2 km) that are underground, 15 miles (24.1 km) are rock tunnel, 14 miles (22.5 km) are earth tunnel, 0.5 miles (0.8 km) 9.s sunken tube and 19 miles (30.6 inn) are cut-and-cover construction. The system will include 86 stations, with 51 of them underground. Referring again to the full 86 stations, 43 will be in D. C., 23 in Maryland and 20 in Virginia. We currently have 37 miles (59.5 km) of line and 41 stations in operations as shown on Appendix B. Also shown on Appendix B is another 16 mile (25.7 km) increment and 13 stations which have been substantially completed, but are not yet in service. Additionally,

Jan 1, 1981

By Gordon T. Clark

The preliminary design of four mined stations and 7.2 km (4.5 miles) of tunnels for Seattle’s light rail transit system is described. Constraints that influenced the design and options that were studied are discussed. The hilly post-glacial soft-ground geology of the Puget Sound Region pushed the alignment deep. Mined underground stations at depths up to 75 m (250 ft) and shafts with excavated diameters of 20-m (65-ft) are required. A 460 m (1,500 ft) sub-aqueous crossing of Portage Bay and undercrossing of an active 12-lane multi-level freeway were two of the more significant design constraints.

Jan 1, 2001

By T. E. Wilson

The length of Alaska’s coastline, combined with the presence of a significant number of fjords, encourages consideration of marine disposal of mine tailings. However, since various factors govern the viability of the submarine tailings disposal (STD) option, the decision making process is complex. An expert system, called Submarine Tailings Disposal Expert System (STADES) that will help mining project planners explore the feasibility of STD, was developed. Existing literature, supplemented by engineering recommendations, on the various aspects of marine disposal of tailings was reviewed and formed the knowledge base for the expert system. The shell used to develop the expert system was LEVEL5®.

Jan 1, 2001