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By Stephen Njoloma, Ivan Hee, Ravi Jain, Mina Shinouda

"INTRODUCTION DC Water’s First Street Tunnel (FST) is comprised of a collaborative effort between DC Water, DC Water’s Project Consultants Organization (PCO) led by Greeley & Hansen and McMillen Jacobs Associates and the design-build team of Skanska, Jay Dee, and Parsons Brinckerhoff. The fast-track project includes elements that were designed by the PCO and released for construction by DC Water prior to Notice to Proceed (NTP) and elements designed by the Design-Builder from 30% to released for construction after NTP. This required effective communication and technical coordination for integrated engineering and efficient construction. The project, constructed in an urban residential neighborhood, included innovative construction methods such as multiple location ground freezing, utilizing a centralized freeze plant, to minimize community impact. The means and methods chosen for cast-in-place shaft linings, precast segmental tunnel lining, microtunneling, sequential excavation method (SEM) adits and near surface elements reflected the immediate and sensitive surroundings, which varied by construction staging area (CSA). Technical aspects of the project, relative to the evolution from pre-bid to construction documents, are discussed along with modified designs to suit means and methods. SCOPE OF WORK In 2012, four major storm events swept through the District of Columbia and hit the Northeast Boundary sewer shed particularly hard with the neighborhood experiencing severe flooding. The extreme nature of the flooding, the damage to private property, and the health risks associated with exposure to sewage led to a multi-agency response and community calls for answers and action. The Mayor assembled a Task Force to evaluate a range of potential actions to address combined sewer flooding including engineering, regulatory, code revision, and management improvements. The Northeast Boundary Neighborhood Protection Project was the outcome of the Mayor’s Task Force; it is a three-step infrastructure initiative designed to offload the undersized sections of the existing collection system that serves the Northeast Boundary drainage area by implementing the McMillan Stormwater Storage Project, First Street Tunnel Project and the future Northeast Boundary Tunnel Project. Until the Northeast Boundary Tunnel Project is completed, the First Street Tunnel Project will add 8 million gallons of combined temporary sewer storage in a new tunnel under First Street NW to relieve undersized sewers that traverse the Bloomingdale neighborhood."

Jan 1, 2016

By R. L. Miller

"Why should we care about diesel quality amidst the complexity of mining for minerals? Mining companies use a large amount of diesel fuel in their worldwide operations, both for moving ore from the mine to the processing mills or transportation hubs, and to generate power for onsite processing. This creates a large carbon footprint and poses both environmental risk with the production of emissions, and public perception of how those companies do their business as stewards of the environment while incurring a huge fuel expenditure. To improve diesel quality and create incremental value and greater environmental stewardship, the opportunity is broken down into several segments: 1. Mining industry diesel consumption 2. Fuel quality issues 3. Impacts on operations, economics, and emissions 4. Potential solutions 5. How improved fuel quality saves fuel expenditures 6. Economics of improved fuel quality 7. Recommended testing process 8. Fuel quality analysis checklist MINING INDUSTRY DIESEL CONSUMPTION The average grade of mined Australian ore bodies has halved, while the waste removed to access the minerals has more than doubled over the last 30 years, thus increasing energy consumption by 70%, (http://eex.gov.au/industry-sectors/mining/). Energy consumption and intensity in mining and mineral processing is rising at around 6% per annum. The mining industry is a huge consumer of diesel fuel worldwide, and the SRS Rocco Report of 4 August 2014 gives a better picture of recent trends. To better understand the reasons to reduce both fuel costs and consumption, we need to compare metrics on the amount of diesel consumed per each ounce of gold produced over the last decade. The rate of diesel consumption in gallons per each ounce of gold produced for the top five worldwide gold producers has doubled in the last 8 years from 12.7 gallons per ounce in 2005 to 25.8 in 2013 as shown in Figure 1 below.This is caused by 1) lower ore grades requiring more hauls to get same amount of finished gold product, and 2) haul trucks moving ore from deeper sources in open pit and underground mines. For one large multi-national gold mining company, the 2005 waste rock / production ratio was 52 metric tons/gold ounce; by 2013 that ratio had grown to 113 metric tons/gold ounce per the same SRSrocco 4 August 2014 report. Using the metrics above, the top 5 gold miners used over 591 million gallons of diesel fuel in 2013. The cost of diesel in dollars per ounce of gold has increased from $30.48 in 2005 to $101.14 in 2013, an annual appreciation of 16.2% as shown in Figure 2 below."

Jan 1, 2017

By Nasri Munfah, Steffen Matthei, Vojtech Gall

"Conventional tunneling as defined by ITA WG19 is also known as the New Austrian Tunneling Method (NATM) or Sequential Excavation Method (SEM) was transformed in the US to deal with challenging tunneling conditions as an alternative to the more traditional tunneling methods. It is being used more often in urban areas, under difficult ground and ground water conditions, and with limited cover. Often the tunnel is of a large and non-uniform cross section in soft soils or weak rocks. The intent of using this tunneling method is to minimize impact on traffic and utilities and reduce disruption of everyday life of people and businesses. To meet these challenges, the industry developed technical approaches and implementation techniques and established sophisticated contractual relationships and collaboration in the field among various parties for successful implementation. This paper examines the development of conventional tunneling (NATM/SEM) in the US to deal with these challenges using recent examples such as Russia Wharf in Boston, Northern Boulevard Crossing, in New York, and Chinatown Station in San Francisco. INTRODUCTION / HISTORY Conventional tunneling or NATM/SEM is a concept that is based on the understanding of the behavior of the ground as it reacts to the creation of an underground opening. In its classic form the SEM/NATM attempts to mobilize the self-supporting capability of the ground to an optimum thus achieving economy in ground support. Initially formulated for application in rock tunneling in the early 1960’s, NATM has found application in soft ground in urban tunneling in the late 60’s and has since then enjoyed a broad, international utilization in both rural and urban settings. In the US the NATM/SEM tunneling method has been used successfully to address challenging tunneling conditions in urban areas. A large number of tunnels have been built around the world using a construction approach which was loosely termed NATM. During the years of discussions and the application of NATM a variety of terms have been used for the same construction approach. These terms were primarily aimed at describing the construction approach rather than the region of its reported origin."

Jan 1, 2016

By M. Hepokoski, M. Klein

"Mine refuge shelters are designed to protect mine workers from hazardous environmental conditions after a mine disaster, but high temperature and humidity levels inside these shelters may pose a significant safety risk. Due to the safety risks associated with human testing, detailed thermal models of shelters and human occupants have been developed using TAITherm simulation software. These models are used to predict the temperature and humidity within the shelter resulting from metabolic heating, evaporation due to sweat and respiration, moisture and heat from the shelter’s carbon dioxide scrubbing system, and heat transfer within the shelter. A detailed human thermoregulation model simulates the sensible and latent heat generated by the shelter occupants, and predicts the occupant’s body core temperature and moisture lost due to sweating and respiration. This information is used to assess the safety of the shelter. In this paper we will review technical details of the human thermal model, validation comparing the human model to human subject test data, and results of a mine shelter analysis. INTRODUCTION Portable mine refuge chambers are used in US coal mines to provide protection to mine workers from hazardous conditions following a traumatic event. Although these shelters are designed to supply clean air and sustenance for up to 96 hours, prolonged exposure to the mine shelter environment itself can pose a substantial risk to human safety. Heat generated by the shelter occupants combined with heat from the carbon dioxide (CO2) scrubbing system can raise the shelter interior temperatures and relative humidity to dangerous levels that can lead to heat stress in humans. Unfortunately, the thermal burden associated with mine shelter exposure is not well characterized due to potential hazards associated with underground human subject testing. In order to assess the thermal burden on people within a mine shelter environment, a detailed thermal model was created to accurately predict the temperatures and humidity within the shelter, as well as the impact of these environmental conditions on human occupants. The model consists of a mobile inflatable tent-type mine shelter, 23 humans, and also includes the surrounding mine environment. The thermal simulations were performed using ThermoAnalytics' validated commercial heat transfer prediction code, TAITherm (v12.0). Additionally, TAITherm's Human Thermal Module (HTM) provided the capability to simultaneously model the thermo-physiology of 23 unique humans contained within the mine shelter. The human thermal models accounted for the thermal interaction with the environment and also provided a core temperature response prediction, which can be used to evaluate survivability in heat stress situations [1]."

Jan 1, 2016

By B. Y. Wong

In April 1989, Southern Company Services signed a 3.5 year contract with DOE-PETC for generic engineering development of an advanced physical fine coal cleaning technology known as selective agglomeration. This technology offers the potential for significantly higher pyritic sulfur removal (90% +) than conventional coal cleaning (30 to 50%) while maintaining high Btu recovery (90% +). Engineering development will include bench-scale process development; component development; adaption or modification of existing unit operations; proof-of-concept (POC) module design, fabrication, testing and evaluation; and small commercial facility conceptual design. The information obtained during POC operation will be sufficient to result in a technical and economic design base that can support construction and operation of a small commercial plant. The major goal of the research is to develop selective agglomeration technology to achieve 90% pyritic sulfur removal while operating at Btu recoveries above 90% based on run-of-mine quality coal. This objective will be accomplished in two phases: Phase 1 -bench-scale and component development, and Phase 2 -POC module operation and conceptual design of a small commercial plant. Currently, work is proceeding under Phase 1 (Tasks 1-7) of the project. A review of the status of Tasks 1-7 is presented in this paper.

Jan 1, 1991

By Liming Yuan, Wei Tang, RICHARD THOMAS, JOHN SOLES, DAVOOD BAHRAMI

The abstract discusses the issue of mine equipment fires caused by hot surface ignition of flammable liquids. The research investigates the ignition probability of liquid fuels (diesel, engine oil, hydraulic fluid) on different metal surfaces (stainless steel, cast iron, carbon steel) under various ventilation speeds. The results show that the type of metal and ventilation speed influence the ignition temperature, with diesel being the most easily ignited fuel and carbon steel requiring a higher ignition temperature. The study provides data for understanding equipment mine fires and developing mitigation strategies.

May 4, 2022

By Robert J. Collins

Computer-aided design drafting systems have been employed in plant design for nearly ten years. Current and future systems will include computer-aided engineering as well. This paper will explore the history and development of such systems including computer and workstation hardware, graphics software, and plant design applications software. The paper will also address future systems and will present both the system vendor and the mine mill designer's view. Specific examples of particularly successful applications will be included.

Jan 1, 1985

By Lech Bolinski, Joe Shirley

Over two dozen Resin-in-Pulp (RIP) plants have been in operation in the fonner Soviet Union since the beginning of 1970. Currently approximately 50% of the gold produced in Russia, Uzbekistan and Kazakhstan, which equates roughly to 10% of the total world output, is recovered using the RIP technology. An alternative to activated carbon, ion-exchange resin has several advantages for the recovery of gold. Resins are less prone to clay or organic foul­ing and do not require thennal regeneration. They also have poten­tially higher loading capacities, faster adsorption kinetics, and are more resistant to abrasion. The original Russian RIP process was based on engineering expertise developed for uranium ore pro­cessing and has a few major drawbacks. The biggest problem is an 18-30 day resin stripping process, which results in a huge gold lock-up. The problem was recently overcome by the development of a new stripping technology which cuts the time to 12-24 hours. Currently, there is rather limited practical knowledge of the Russian RIP process in the West, but often Western mining com­panies developing gold mines in the fonner Soviet Union are hard pressed by their local joint venture partners to take a serious look into RIP. It is probably only a matter of time before one of these companies will cross Soviet technology with Western engineering and develop a modem RIP process as an attractive option to the current CIP and CIL technologies.

Jan 1, 1996

By James R. Jones

The Surface Mining Control & Reclamation Act is a complex piece of legislation signed into law on August 3, 1977. It is the culmination of more than six years of debate by the Congress over the need for a national regulation of surface mining as opposed to the prior concept of regulation by each concerned state. It departs from the more normal type of law in that it includes very specific requirements, limitations and performance standards. In its procedural aspects, it is somewhat similar to the Clean Air Act and the Water Pollution Control Act in that it places primary responsibility at the state level, provided the state meets minimum national requirements. At the time of writing this paper, in late December 1978, the Interim Regulatory Program has been in effect for seven months. The proposed regulations for the Permanent Program, the draft Environmental Impact Statement, and the draft Regulatory (Economic) Analysis ware available for eight weeks before the close of the comment period on November 27. We are now awaiting issuance of the final versions of these documents. The states in which coal is mined, for the most part, have made sere revision to their state laws and are in the process of revising their regulations, or have just completed the revision, to comply with the Initial Regulatory Procedures. They are now faced with another new major effort to analyze and plan for compliance with the Permanent Regulatory Program, which is expected to be promulgated by the Office of Surface Mining of the Department of Interior by the time this paper is presented.

Jan 1, 1979

By Ande&apos, Bengt n

The first Model 480 SALA-HGMS R carousel high gradient magnetic separator was recently manufactured (Figure 1). The carousel's design was based upon the high gradient magnetic separation technology developed and owned by Sala Magnetics Incorporated, Cambridge, Massachusetts. After a short (approximately 300 hours) in-house mechanical and electrical test and break-in period, the carousel was ready for a long term demonstration test. This paper describes the demonstration plant and operational performance of the Model 480 HGMS treating a low grade iron ore tailings. A location convenient to Sala International's main office in Sala, Sweden was desirable because Sala engineers and technicians were to operate the demonstration plant. The Strassa iron ore mine in central Sweden was chosen because it fit most of the criteria that was important for a good demonstration site. The Strassa mine is part of the state owned Svenskt Stal AB. The mine produces about 320,000 tons of iron concentrate per year consisting of 200,000 tons of magnitite concentrate and 120,000 tons of hematite concentrate.

Jan 1, 1980

By P. A. Anderson

Innovative solution management is being used at Coeur-Rochester, Inc. to increase bullion production and decrease overall costs. New operating programs call for reduced solution application rates to the heap to increase pregnant stream values at a lower and less costly plant flowrate because silver and gold extractions are equal regardless of leach solution application rate. Solar heating is used in the summer months to increase the core temperature of the heap for use in the winter months thus increasing silver extraction rate. This paper outlines the programs now in effect and the savings incurred because of them.

Jan 1, 1989

By E. Wiewiorowski

A new technology for recovery of metals from spent catalysts containing aluminum, cobalt, molybdenum, nickel and vanadium was developed. The catalysts are decomposed in two consecutive pressure leaching steps. Sodium aluminate-sodium hydroxide systems are lixiviants in both leaching steps. Selective extraction of molybdenum and vanadium is achieved in the first leaching step. The leach liquor is processed for separation and recovery of these two metals. The residue from the first leaching step is further processed in a second leaching step where alumina is solubilized. The residue from this operation is a nickel-cobalt concentrate. Alumina is separated from the second stage leach liquor by precipitation; the depleted liquor, a sodium aluminate solution, is recycled to the first and second leaching step. This technology has advantages over other approaches for the recovery of metals from spent catalysts because no solid waste is generated.

Jan 1, 1988

By Peter Zhang, Mark Van Dyke, Ted Klemetti, Morgan Sears

Room-and-pillar mining is a mining method used in the United States to extract coal from underground, and pillar recovery is widely practiced for maximizing coal recovery and mining economics. Under certain conditions, room-and-pillar mining can create high stresses in coal pillars resulting in a coal outburst. These outbursts represent one of the more severe safety hazards in underground coal mines, potentially causing injuries and fatalities. Over the past ten years, coal outbursts have resulted in three fatalities in U.S. room-and-pillar mines. Though coal outbursts generally occur under deep cover, they are more likely to occur during pillar recovery and under multiple-seam mining conditions. Coal outbursts are generally associated with strong roof and floor and heavy loading of coal pillars, but it is difficult to predict whether, where, and when they will occur. In this respect, risk management provides a proactive tool to prevent coal outbursts in room-and-pillar mining by identifying mining areas with high risk of outburst and mitigating the risk accordingly.

Apr 26, 2022

By L. G. Stolarczyk, R. C. Fry

In coal-bearing formations, seams are often bounded by sedimentary layers of mudstone, claystone or shale. When the electrical conductivity of the surrounding sediment layers is greater than the conductivity of the seam, a natural parallel plate waveguide forms in the strata. For frequencies below the AM broadcast band, the waveguide can be used for the transmission of electromagnetic (EM) waves. In a uniform seam, the primary wave travels in the coal layer along paths between a radiating antenna and a distant receiving antenna. The travel distance increases with seam height and the conductivity of the surrounding sediment layers. The distance decreases with increased coal conductivity. In Cretaceous western bituminous coal, the distance may exceed 549 m (1800 ft). Anomalous geologic disturbance zones such as faults, shear zones, paleochannels, sills and dikes significantly alter the values of EM wave propagation constants (attenuation and phase) expected in a uniform seam. In the neighborhood of an anomaly, EM wave energy is scattered (reflected and diffracted). Scattering creates secondary waves in the seam wave guide. A receiving antenna at a remote location in the coal seam can be used to measure the magnitude and phase of the EM wave at the end of the path. The measured data can be processed to determine the average value of the propagation constants along each path. Paths with anomalous propagation constants are used to locate and image geologic disturbance zones. Radio Imaging Method (RIM) instrumentation, survey procedures and data processing (tomography) algorithms have been developed to image geologic structure in advance of mining. The survey is conducted between gate roads of a longwall panel. Data processing constructs contours of constant attenuation rate (phase constant) across the plan view of the panel. In anomalous zones, the contours rapidly change with distance. The shape of the contour lines generates a visual image of the anomaly and suggests the type of anomalous condition to be expected in the coal seam. This paper briefly discusses the depositional environment and the formation of the imperfect waveguide in coal-bearing strata. The linkage between sedimentary geology and EM wave theory establishes an understanding of how the propagation constants depend on the anomalous geologic conditions. A case study compares in-mine geologic mapping with the tomographic image of a longwall panel.

Jan 1, 1991

By Charles H. Greene

This paper will describe briefly the steps taken in the development of a Central Florida phosphate ore deposit from acquisition to mining. Further, the design and early operation of the mining and beneficiation facilities will be depicted. During the 1950's, with confidence in the continually increasing requirement for phosphate fertilizer materials essential for producing food, I'. R. Grace & Cc acquired the Hookers Prairie tract containing approximately 45 million metric tons o. (50 million short ton~ of potential phosphate rock product. In 1973, at a point when the Grace captive need for rock was being greatly enlarged by a planned doubling of its Bartow phosphate chemicals plant capacity, the decision was made to expand existing phosphate rock production by building a new mine and plant. The initial annual capacity was to be 2.3 million tons (2.5 million st); however, subsequent investigation pointed to a higher than estimated dragline operating factor 'and the forecast of annual capacity was set at 2.5 million tons (2.8 million st).

Jan 1, 1977

By Xinzhi (Thomas) Du

"A longwall mining method is a productive mining method of coal extraction that involves the complete removal of large, rectangular panels of coal. Since this method causes deformations through the overlying strata to the ground surface, the surface- and ground-water regime above the longwall panels may be adversely affected and drained into the lower strata. The purpose of this study is to determine the effects of longwall mining subsidence on surface- and ground-water systems.This study is a site-specific hydrogeologic analysis conducted before, during, and after panel retreat at a site located over two selected longwall panels in the Pittsburgh coal seam in Greene County of Pennsylvania. Mine subsidence causes fractures in the overlying strata and enlarges bedding plane separations, increasing the effective porosity and storativity of the overlying strata. Generally, the water in deeper aquifers located in the lower fractured zone drains into the mine void due to the vertical fractures. Moreover, the water level does not recover after longwall mining (but may recover when the mine is flooded). The upper aquifers over the thick aquitard layers may maintain the water level or drop slightly during longwall mining and recover very quickly. The reason is that the underlying aquiclude layer has less change in porosity and permeability after longwall mining (Carver, 1994).A groundwater flow model-MODFLOW was used to predict the water table contours for the periods of pre- and post-mining conditions. The hydraulic gradients of post-subsidence became larger outside the panels and smaller inside the panels than that of the pre-subsidence. The groundwater hydraulic heads above the longwall panel dropped a maximum 50 ft in the study panels. The shallows monitoring wells that were less than 50 ft deep from the surface were deeply affected by longwall mining subsidence. For the intermediate wells that were more than 85 ft deep from the surface, where strata movement acted as a unit during longwall mining subsidence, there were little impacts of longwall mining on the intermediate wells in the study area. For the deep wells that were located below the Waynesburg sandstone, the water was drained to the underlying strata or even into the mine gob."

Jan 1, 2019

By R. Q. Phillips

INTRODUCTION Since Canada commenced sulphur exports in the early 1960's, the volume of exports has grown steadily and by 1984 Canadian sulphur accounted for 45% of internationally traded sulphur. In 1984 a total of 7.6 million tonnes of Canadian sulphur was shipped to offshore markets and the U.S.A. Total shipments, including domestic sales, were 8.3 million tonnes. With a production of some 5.6 million tonnes, inventory was drawn down by nearly 3 million tonnes in order to keep pace with demand. Since 1979, world consumption has exceeded total world production and Canadian sulphur inventory has played a truly crucial role in balancing world supply and demand. Consequently, by the end of 1984 the Canadian inventory, which stood at 21 million tonnes in 1978, had been almost halved to 12 million tonnes. This inventory, however, is still by far the largest in the world and will continue to play a vital role in the world supply until expected depletion around 1990. Canada is the world's second largest producer of sulphur following the U.S.A.. The Current production level of between 5 and 6 million tonnes per annum is forecast to be maintained to 1990 with only a marginal fall in that production level in the following decade to the year 2000. This will ensure that Canada retains its position as one of the largest producers and most important suppliers of sulphur in the world market well into the future. CANADA AS WORLD SUPPLIER OF SULPHUR Since Canada commenced sulphur exports in the early 19601s, exports have grown steadily. (Figure 1) The rate of growth accelerated in recent years and in 1984 a total of 7.6 million tonnes was sold for export, compared to 3.0 million tonnes in 1975 and less than 1 million tonnes in 1964. World trade in sulphur also increased during this period, from 11 million tonnes in 1975 to 17.0 million tonnes in 1984 (Figure 2). Most of this increase in volume was accounted for by Canada and Poland. As a result, the importance of Canada as world supplier expanded from 28% in 1975 to 45% in 1984. The markets for Canadian sulphur can be divided into two broad categories, i.e., solid and liquid (Figure 3). The solid market is the largest, taking about 70% of Canadian output, virtually all of which is sold offshore. The U.S.A. and the Canadian domestic market take about 20% and 10% respectively, in liquid form. In 1984, (figure 4) total Canadian sulphur sales exceeded 8 million tonnes with offshore export sales at a record 5.8 million tonnes and sales to the U.S. of 1.8 million tonnes. Domestic sales accounted for only 0.7 million tonnes. The general trend for offshore export sales has been upward whereas there has been relative stability in domestic sales. The exceptional growth in offshore sales in the 1970's necessitated considerable capital investments by the industry in order to establish a logistics system capable of handling increasing offshore tonnages. Over 50 sulphur plants are currently operating in Alberta and British Columbia. Some of these are connected by rail, (Figure 5) the balance being generally connected by road. There are currently fourteen of the larger rail-connected plants designated as export plants, and these are equipped with sulphur forming facilities. The long distances between these plants and tidewater terminals in Vancouver is a very significant factor in complex logistics of Canadian offshore sulphur exports (Figure 6). Alberta and B.C. plants are located an average of 1,400 kilometers from tidewater.

Jan 1, 1986

By Jerrold J. Marcus

United states reserves of oil and gas have been steadily declining while consumption of petroleum products has continued to increase. The nut result has been an ever increasing shortfall between supply and demand. This imbalance has been made up by imports of both oil and gas causing a strain on the United States Balance of Payments. To complicate the situation further, exporting nations have recently formed a cartel and dramatically increased the selling price of petroleum products. To meet U.S. energy demand, increased attention has been drawn to the production of synthetic oil and gas from coal. To date, considerable research has been conducted and is continuing on various processes for liquefaction and gasification of coal. Some of these processes are now in the pilot plant stage and at least one demonstration plant has been proposed. The coal conversion complexes envisioned will be very large, requiring substantial capital investments and abundant reserves of coal. Coal production to feed these proposed complexes has been estimated on the order of 75,000 tons per day. With the viability of these projects becoming economically attractive, the Office of Coal Research initiated a contract with Fluor Utah to determine and define the problems of surface mining coal at very high mining rates, under varied physical, geographic, and climatic conditions. The flow of recent events in the Middle East has created a greater sense of urgency for this study.

Jan 1, 1975

By Nicholas C. Lias

Quartz crystals are the raw material from which are made the crystal units utilized in filters and oscillators so vital to the performance of all long distance communications systems. These devices act as the heart of equipment that permits a single telephone cable to carry hundreds of conversations simultaneously. Quartz crystals are of value in communications because of this piezoelectric nature, that is when an electric signal is applied to the quartz, there is a resulting mechanical motion and conversely, a mechanical stress results in an electrical output signal. A plate cut from a quartz crystal will oscillate at some specific frequency, which is determined by the physical dimension of the plate. During the early stages of telephony, all quartz plates were cut from natural quartz, which was imported mainly from Brazil. Since the source of this important raw material was based upon a foreign supply which is located at a great distance from the user and could be vulnerable in time of a national emergent, it became necessary to maintain a large inventory of this strategic material. Also due to the considerable cost of natural crystals of a size and quality suitable for Bell System use, an investigation was made by Bell Laboratories into the possibility of developing a substitute material. The effort was successful and led to a joint development program between Bell Laboratories and Western Electric. This program brought about the design of manufacturing facilities capable of producing large quantities of cultured quartz at Western's Merrimack Valley Works, No. Andover, Massachusetts.

Jan 1, 1973

By S. G. Britton

"INTRODUCTION Strategies to improve performance in mining production, maintenance and mineral processing operations has evolved over time from straightforward time studies of individual machine performance in the 1960’s-1970’s to more sophisticated and better focused statistical and financial tools that have emerged in the 1980’s-1990’s . These newer strategies fall under the broad descriptive category of “Operational Excellence”. Operational Excellence is the term that embodies a number of performance evaluating strategies, the most popular and relevant to mining includes the following: • Six sigma for addressing errors within mining or milling process and work standards • Lean manufacturing to optimize organizational and operational performance through continuous improvement. There are other strategies that can be applied as well and this paper is not focused on a review of the pros and cons of any one strategy. However, the common threads in these strategies embody the expectation that expected results from these efforts can be quantified and that value will positively benefit the targeted work process, organizational unit, equipment deployment or time schedule when applied to it as part of continuous improvement efforts. The priority for proceeding with any one or more of these efforts is based on the calculated net value of the required resources to affect the change versus the estimated value gained. The practice is identified as the value mapping process. This discussion summarizes the value mapping process methodology used at a mature uranium mine and mill in northern Canada to work through the myriad of potential improvement efforts available through the operational excellence process for continuous improvement.THE RABBIT LAKE MINE AND MILL The Rabbit Lake Mine and Mill are located in northern Saskatchewan, Canada on the shores of Wollaston Lake (Figure 1).The mine was discovered in the mid-1960s and was built by Gulf Minerals, Ltd. The mill began processing uranium ore into yellowcake in 1975 from an adjacent open pit mine. A whole ore acid leaching followed by solvent extraction and precipitation forms the basic milling processes. The operation continued to produce yellowcake through a succession of open pits and finally opened an underground mine in the early 1990s. Since beginning production, over 200 million pounds of yellowcake has been packaged from the site, making it the sixth highest producing uranium mine of all time."

Jan 1, 2016