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By Dean Workman

Long extensible conveyor systems are an important option for efficient tunnel excavation where intermediate access is impractical. The conveyor system designed for the Pula Subbaiah Veligonda Tunnel #2 in Andhra Pradesh, India will eventually extend to 19.35km. The Ø10.0m water diversion tunnel will be excavated under India?s largest tiger sanctuary using a Robbins Double Shield TBM. Once extended, the conveyor will be one of the longest single-flight systems ever installed in India, and is expected to offer increased system availability over comparable systems using muck cars. This paper will examine the engineering challenges of long-flight extensible conveyor systems in the areas of belt selection, component design, and equipment location in confined assembly and launch areas

Syncrude Canada produces a large part of Canada’s crude oil supply. The company processes about 225,000 bbl/day. The oil produced is used for jet and automobile fuel, home heating oil, plastics and other consumer synthetics. Crude oil is produced through a process of mining, extracting and upgrading bitumen. A rich supply of bitumen is contained in the Athabasca oil sands deposit in northern Alberta. Tailings from the bitumen processing are sent to a settling basin.

Jan 1, 2000

By P. Zhang

A multiyear, comprehensive study of flotation reagents used in phosphate beneficiation was conducted. The study involved the evaluation of pure fatty acid compounds, comparison of various anionic collectors and testing of iso-acids. Various C12 to C22 fatty acids were tested as Florida phosphate collectors. The saturated fatty acids were found to be very poor collectors when using the standard conditioning procedure, whereas the unsaturated C16 to C22 fatty acids showed fair to good phosphate collecting ability. The C18 fatty acids oleic, impure oleic and linoleic and the C20 eicosenoic acid were shown to be the best phosphate collectors. The best flotation results were obtained using Liqro GA tall oil and oleic acid. Four isostearic/iso oleic acid type fatty acid collectors were compared with a commercial grade oleic acid and with Liqro GA tall oil as phosphate collectors using standard laboratory conditioning and flotation procedures. The most selective collector evaluated was Century 1108, a high isostearic acid-type reagent. However, it was concluded that this excellent-performing reagent was too expensive for commercial use. Overall, the most promising reagent was probably Century MO-5. This collector is essentially an iso-oleic acid/stearic acid mixture (not isostearic acid), and it costs much less. This program laid a sound foundation for developing single collector, all anionic flotation processes.

Jan 1, 2009

By I. G. Gonçalves

For most industrial minerals, the color is directly associated with economic value. In terms of physics, the principal property that defines the term ?color? is the intensity of light reflected (or transmitted) by an object over the visible band, comprehended between 400 and 700 nm. This reflectance spectrum serves as the starting point for a variety of color-describing factors, the most common in the mineral industry being the brightness (TAPPI, 1977 and 1986) and the L*a*b* system (HunterLab, 2008). Quality specifications for mineral products are usually based on these colorimetric parameters. This market is becoming increasingly more selective and demanding over the quality of raw materials and alongside the traditionally controlled characteristics, such as particle size distribution and chemical composition, a trend exists towards the establishment of increasingly more strict specifications for the optical properties of these materials. This is due to the fact that most plants consuming these industrial minerals incorporate them into products in which the visual appearance is controlled. For these plants, most of them being the manufacturers of plastics, paper, paints, and ceramics, variations in the color of mineral materials result in difficulties to achieve the right color in the final product. Therefore, these plants set strict specifications for colorimetric parameters such as whiteness and yellowness, as well as colorimetric coordinates like L*, a*, and b*. For the manufacturer of industrial minerals, this translates into difficulties simply because many of these parameters are usually alien to the tradition of the mining industry. The main quality parameter in the kaolin industry is brightness, which is a weighted average of reflectance values over the range of 400-510 nm (TAPPI, 1977). Due to the lack of a better property, producers tend to use brightness to also assess the quality of the in situ ore and along the processing operations. However, the unprocessed kaolin is often accompanied by ?contaminant? minerals. For Brazilian kaolins, which are the object of this study, the most important contaminants are hematite (Fe2O3), goethite (FeOOH), and anatase (TiO2). Each of these contaminant minerals has a distinct color and behaves differently during the processing of the kaolin ore. Hematite and goethite in particular are particularly strong pigmenting agents and at concentrations as low as 100 ppm they can make the difference between a high-quality white pigment product for paper coating and waste material. As each Fe-bearing contaminant has a different color and responds differently to processing operations (for example, magnetic separation, chemical bleaching, selective flocculation, and/or flotation in the case of kaolin), the in situ brightness tends to show a poor correlation with the brightness of the final product. Brightness measurements are sometimes complemented with X-Ray Fluorescence (XRF) analysis of Fe and Ti, but the total oxide content provided by XRF is also poorly correlated with product quality because Fe may be in the form of goethite, hematite, or inside the crystalline structure of kaolinite. Thus, a more robust technique capable of distinguishing each mineral phase is desirable. Diffuse reflectance spectroscopy has been used to analyze iron oxide/hydroxide content both qualitatively (Torrent and Barrón, 2003; Liu et al., 2011) and quantitatively (Jiet al., 2002 and 2006). These authors correlate slopes and inflection points at characteristic absorption bands with oxide/hydroxide content in natural soils. The approach presented here involves the extensive use of the Kubelka-Munk (K-M) theory, which has been used for color matching (Schabbachet al., 2009 and 2011) and particle size determination (Otsuka, 2004) in a simplified version. Unfortunately, the scattering constant S is very difficult to measure for dry powders, because the equations require a thin layer of material. Attempts have been made (Gonçalves and Petter, 2007, and Gonçalves, 2009) but the experimental errors tend to be high. Thus, this paper aims to develop a tool for the quantification of contaminant minerals in kaolin based on the K-M theory without resorting to measurements over thin layers. This tool is based on a new two-constant approach, which takes into account differences in scattering between materials over the whole measured spectrum. The experimental dataset consists of the reflectance spectra of mixtures between a bleached kaolin and synthetic Fe pigments.

Feb 27, 2013

By D. F. O?Connor

The health & safety of all workers in an underground environment is paramount to the success of our operations. The diesel emission reduction projects are key to improving such an environment. However, care must be taken to reduce the risk to personnel during such tests and prevent exposure to other hazards. VALE Inco works in a close partnership with its unionized employees, manufactures, suppliers, researchers and government officials to ensure projects are done safely and efficiently to successful completion. The Creighton Mine Diesel Particulate Filter (DPF) project is an example of such a project that is currently under way to evaluate new and innovative technology that will further our search for improved environment for our workplace. This paper will discuss the issues and processes that are followed to ensure Diesel Particulate Filter (DPF) field tests are conducted safely and productively.

Jan 1, 2009

By Paul Sarnoff

The economics of precious metals -- depending upon who is involved --could be the economics of hope, of fear, indeed of profit and perhaps survival. For those investors seeking capital gains in a puzzling economy, precious metals involve the economics of hope. Those who are convinced that currency soon won't be worth the paper it's printed on turn to precious metals because of the economics of fear. Gold and silver have been a storehouse of wealth since biblical times. The economics of fear during the past 500 years on the Continent has caused almost every European family to make sure a private stockpile or hoard of gold, silver or coins is at hand in case the paper currency of their country undergoes the kind of disaster that came to the German Mark after World War I. Understandably, for mining companies involved in the production of precious metals, the elements of operations and management are directly concerned with the economics of profit -- and perhaps survival. To the American miner the price of precious metals in the marketplace is a matter of daily concern. After decades of selling silver to the US Government at 64.64 cents an ounce, producing silver mines suddenly became faced with prices breaking $5, $10 and $20 per ounce, and approaching $50 an ounce during the period 1978-1981. What should the miner expect one year in the future? Five years?

Jan 1, 1981

The Pogo Mine, near Delta Junction, Alaska is a 2500 TPD gold operation employing processes including grinding, gravity, rougher flotation, leach, CIP, and E/W. An OCS(Optimizing Control System) expert control system has been implemented on rougher flotation in early 2008. The OCS system communicates with the Plant DCS(Distributed Control System) through OPC(OLE for Process Control) communication. The initial strategy was to control the flotation cell froth level set points to achieve target froth velocities. This strategy was enhanced by controlling both level and air flow setpoints. The flotation cell air and level are adjusted to reach cell pulling rates (froth velocities). The pulling rate setpoints for each cell are determined based on downstream capacity (concentrate surge tank level). The effect of pH and upstream disturbances is also taken into account in adjusting the air and level setpoints. Feed forward compensation is employed down the flotation row to minimize disturbances.

Jan 1, 2009

By Michael Karmis

"In December 2011, the U.S. Attorney’s Office for the Southern District of West Virginia, the U.S. Department of Justice, Alpha Natural Resources (ANR) and Alpha Appalachia Holdings entered into a nonprosecution agreement related to the explosion at the Upper Big Branch Mine (UBB) that killed 29 miners. This coal operation was owned by Performance Coal Co., an affiliate of Massey Energy Co., which was acquired by ANR in June 2011, more than a year after the UBB explosion. Pursuant to the agreement, ANR agreed to:• Establish a trust within 120 days.• Pay a total of US$48 million into the trust to be used solely to fund and administer research and development (R&D) projects to improve mine health and safety.• Administer the trust by three highly qualified individuals with academic and/or professional backgrounds in mine health and safety.In April 2012, the Alpha Foundation for the Improvement of Mine Safety and Health was created. The three directors - Michael Karmis, president; David Wegman, vice presidenttreasurer, and Keith Heasley, vice presidentsecretary - approved a plan to expend both the interest and principal of the trust, aiming at an 8-10 year research horizon. The foundation also appointed David Belden, an experienced manager of nonprofits and professional associations, as the first executive director of the foundation. The IRS approved the foundation’s tax-exempt application, as described in Section 501c(3) of the Internal Revenue Code, on Dec. 18, 2012. The board established guiding principles of the foundation, which are as follows:• Mission: to improve mine health and safety through funding R&D projects to qualified academic institutions and other not-for-profit organizations.• Vision: to enable miners in the future to be free of work related injury or disease by the implementation of the results of the projects funded by the foundation and undertaken by the best researchers from any discipline that can contribute. The foundation is now approaching its third year and regularly posts updates, including semi-annual reports, to its website (www.http.alpha-foundation.org/), which serves as the main medium for communication with the broader stakeholder community"

Jan 1, 2014

The administration came on as a strong supporter of the mining industry in April of 1982 when President Reagan delivered his long-awaited minerals policy statement. He promised to reduce America's minerals vulnerability, and called for spending billions on meeting stockpile goals for strategic minerals, opening up federal lands for mineral exploration, elimination of barriers to deep sea mining, and regulatory relief. He defended the favorable tax incentives in the Economic Recovery Act as a stimulus to private research and development that would ensure the availability of materials essential to the nation's economy and national defense. But the administration just didn't seem to get anywhere. Congress, environmentalists, and even foreign governments fought White House-proposed legislation on all fronts, delivering the ultimate coup in forcing Environmental Protection Agency Administrator Anne Burford's resignation and the subsequent EPA staff house cleaning in early 1983. Anti-Reaganites scored victory after victory against Reagan's efforts to stimulate the minerals industry. Congress was stalemated on so many mining-related issues that not much was done either for or against the industry. And the US was not to get its way on the issue of sea mining either. Most of Reagan's mineral policy objectives failed to be met. Three months after the National Materials and Minerals Program Plan was presented and the Cabinet Council on Natural Resources and the Environment was made its coordinator, the head of the Cabinet Council James Watt blamed lack of progress in reviving the mining industry and creating a better strategic stockpile on the weak economy and the House of Representatives, which repeatedly thwarted efforts to open wilderness lands to mining. Congress The 97th Congress spent much of its time saying no in 1982-to the Reagan administration's deep cuts in energy and environment programs, to major changes in clean air and water laws, to oil and gas leasing in wilderness, and to killing the Department of Energy. Most of 1982 (and 1981) was spent in heated budget disputes. Some things that did not happen: • The administration and industry failed to get changes in controls of hazardous air pollutants and sulfur dioxide emissions that are implicated in the phenomenon known as acid rain. Industry had wanted to relax requirements for new industries building in clean air regions where the air act demands prevention of significant deterioration (PSD) of air quality, and to relax requirements tightening up the regulation of emissions of hazardous air pollutants. The air battle is expected to continue on five major fronts-acid rain, hazardous air pollutants, PSD, automobile pollution, and nonattainment. • Regulatory reform legislation to overhaul the way government carries out the law died a slow death last year. Business groups and the administration said federal agencies should be required to consider cost-effective measures of reaching regulatory objectives of protecting public health, safety, and the environment. Opponents, including environmentalists, feared such action would delay, weaken, or scuttle important regulations. • Congress turned thumbs down several times on proposals for oil and gas leasing in wilderness but could not agree on any new wilderness recommendations (see The Wilderness Battle). • Congress refused to open the door to the Reagan administration's plan to raise up to $4 billion a year from sales of federal lands. The administration identified surplus and excess federal lands, mostly obsolete buildings or isolated tracts of land, that could be sold by the General Services Administration (GSA) to help out the federal budget deficit. Congress took no action. Some things that did happen: • Congress extended the Defense Production Act (DPA) for six months through March 1983 without changing the 32-year-old law. That came after it failed to resolve sharp differences over proposals for critical minerals programs. Differences concerned both the amount of funds and the scope of programs that would be authorized under the DPA's Title III. Some proponents pressed for $5 billion in funding for loan guarantees or purchase commitments to spur domestic production of minerals such as cobalt. Other members of Congress wanted smaller amounts of funding, and the Reagan administration, until about November, had opposed any use of federal funds for strategic mineral programs. These measures were certain to come up again before the DPA extension expired in March. • House supporters of the Critical Materials Act of 1982 were unable to come up with the twothirds majority needed to pass the bill, so it died on the House floor in December. The bill proposed that a council be established with responsibility for coordinating federal materials research and development. The administration opposed the council creation contending that the Cabinet Council

Jan 5, 1983

By J. E. Friant

Until 1956, drill and blast was the only way to excavate rock. In that year, a tunneling machine using disc type cutters economically bored a small Toronto tunnel. Its amazing 105 ft/day set a new world record and set the stage for a new industry. The Disc Cutter Role in Excavation Mechanical excavation of hard rock is by now deeply ensconced in the heavy civil construction industry. All over the world, from the Swiss Alp Melange to Hong Kong Granite, to New York Gneiss, huge Tunneling Boring Machines (TBMs) create transportation, water and sewer tunnels. Powerful machines, boasting as much as 6000 hp, bore through rock, excavating in excess of 1400 tons per hour. The tool that makes this tunneling phenomenon possible is the single blade, rolling disc cutter. These hardened steel discs, from 15 1/2 to 19 inches diameter are arranged on a rotating cutterhead, to cut concentric circles in the rock. As the machine is propelled forward under great pressure, rock below each cutter is crushed. But the efficiency of the cutterhead is derived from the science of cutter spacing (distance between cutter paths). The majority of the rock excavated is not crushed, but flakes off in chips and chunks. No pick, tooth, or drag type cutting tool can duplicate the performance of a disc cutter. The economic use of drag type tools is limited to as low as 5,000 psi UCS rock strength in massive formations. In weakly bonded, foliated rock, drag tools do better, but are still limited to rock generally less than 15,000 psi.

Jan 1, 2002

A dedicated tunnel construction version of the Caterpillar 328D LCR compact radius excavator is proving highly productive on the A9 Autoroute construction project near Visp, in Switzerland. It is the first machine of its kind to operate on a Swiss contract and uses a special dedicated front attachment designed and constructed by German Caterpillar dealer Zeppelin. The machine offers a powerful, stable and compact solution for tunneling contractors. A rear overhang of just 305 mm (12 in.) provides a tail swing radius of just 1.9 m (6.2 ft). The 328D LCR is ideal for the restricted working areas within a tunnel construction site. The machine is equipped with the wide tracks from the 330D L conventional crawler excavator, ensuring maximum stability when operating. In addition, the boom mounting has been moved further toward the center of the machine for the tunnel model, creating an increased lift capacity over the front end compared with a standard 325D L. The boom itself features a robust box section construction, with high-strength steels, additional supporting struts and reinforced bearings for maximum durability. All pins have hard-chromium plating for optimum protection against wear. Stick digging force is a powerful 134 kN, with up to 212 kN of bucket digging force available, for maximum penetration in blasted material. The 328D LCR is also equipped with a heavy-duty dozer blade as standard. This ensures outstanding stability when working and providing a useful secondary tool for clearing and leveling within the jobsite. Two 45° tilting mechanisms in the boom construction, allow the boom to be swung to 45° on either side of the machine. So the specially designed attachment linkage provides increased rollback for access to the roof of the tunnel. A Caterpillar CW45S mechanical quick-coupler allows rapid changes between specialist tunneling attachments, standard Caterpillar buckets and a range of Caterpillar work tools. The machine is powered by a Caterpillar C7 diesel engine. This six-cylinder EU Stage IIIA diesel motor [ ] offers 8 percent more power than its predecessor, with 140 kW (190 hp) available at just 1,800 rpm. Caterpillar?s ACERT combustion technology results in lower fuel consumption and reduced exhaust emissions. However, the tunnel machine is also equipped with a diesel particulate filter as standard, to further cut exhaust gases within the tunnel working. The 328D LCR is designed for use in transport tunnels of 6.8 m (22.3 ft) in height. With the tunneling boom in place, the machine has an operating weight of 42,540 kg (93,783 lbs), yet retains a transport height with the tunnel boom of just 3.9 m (12.8 ft). Transport width with 600 mm (23.6 in.) track shoes, is just 3.2 m (10.5 ft). On the A9 tunnel contract, the machine is being used by a consortium of Swiss and Austrian companies working for the canton of Valais? Routes Nationals Construction (RNC) department. The 31.8-km (19.7-mile) A9 Autoroute construction project will connect Sierre in the west and the town of Brig to the east. The tunnel that is bypassing the town of Visp is just one of a number along the mountainous route.

Jan 1, 2009

By W. J. Spat

Political risk is an integral part of the mining business in northern Andean countries. Peru, Ecuador, Colombia and Venezuela all have a higher than average political risk compared with other South American countries. Successful operations require good political-risk information, a thorough political-risk-management plan and a strategy to deal with political-risk perception on the part of the investing public. Colombia is perceived as about the riskiest place in the world to do business. A selection of recent headlines reads: “Colombia on the brink” (Economist, 1998), “Colombia’s ship of state is sinking” (Insight on the News, 1998), or simply “Bad news” (US Catholic, 1998). The World’s Most Dangerous Places rates Colombia as “currently the most dangerous place in the Western Hemisphere, and perhaps the world” (Aral and Pelton,1998). And many prospective investors and analysts say to Greystar Resources: “Yes, we love your results, but Colombia?”

Jan 1, 2000

By A. Schaum

On average, there are approximately 10 fatal haul truck accidents per year. The most common causes for haul truck accidents include mechanical problems, inadequate training and insufficient road/berm maintenance. Due to the frequency and magnitude of haul truck accidents, new training methods are being investigated. With the widespread availability of computers and new technology becoming more reasonably priced, the ability to incorporate computer-based training for miners is becoming more possible. It has been shown that computer-based training is just as effective in knowledge acquisition as traditional lectures, and computer-based training can lead to a significant increase in the retention of material (Williams and Zahed, 1996). Studies have also shown that more engaging training methods lead to more effective knowledge acquisition (Burke et al., 2006). A supplemental system for current and new miner training to address the common causes of fatal accidents was developed. The training system is a virtual preshift inspection of a haul truck, and it can train new haul truck operators to identify parts that look defective. The training will increase an operator?s ability to recognize problematic parts and correctly identify the corrective action needed. Increasing the quality of training by providing an engaging, simulated hands-on environment will lead to safer behaviors by trainees, which will ultimately lead to fewer accidents and fatalities.

Jan 1, 2008

By Bill Cain, David F. Tsztoo, R. John Caulfield, D. Scott Kieffer

In 1994, the East Bay Municipal Utility District (EBMUD) commenced a system-wide Seismic Improvement Program to protect their facilities from catastrophic damage. A primary focus of this program has been on retrofitting the 75-year old Claremont Tunnel, which crosses the active Hayward Fault zone. A large earthquake on the Hayward Fault could generate enough right-lateral fault slip to effectively sever this important lifeline. The retrofit project involves construction of a new bypass tunnel through the Hayward Fault zone, together with systematic contact grouting and localized structural repair of the existing concrete liner. Several innovative design measures have been incorporated into the seismic retrofit design, including an oversized tunnel cross section, backfill concrete side drifts, seismic isolation of an internal structural pipe, and shear fuses in the final lining.

Jan 1, 2005

By Stavros H. Constantopoulos

Mediterranean regions such as Greece, Turkey, Cyprus, Corsica and New Caledonia have experienced epidemics of malignant mesothelioma as a result of non-occupational, ??domestic?? exposure to tremolite asbestos and fibrous erionite. This exposure to tremolite asbestos and fibrous erionite is typified ??domestic?? due to its prevalence in regions with natural deposits of tremolite asbestos (or fibrous erionite) where the material from tremolite asbestos or fibrous erionite is used for domestic applications such as whitewashing. However, these exposures may be useful in examining the potential consequences of even small amounts of amphibole asbestos fibers in the ambient air. It can also elucidate the effects of fibers that behave like amphibole asbestos. However, this type of exposure is not useful for studying the potential effects of small amounts of asbestos in the ambient air of big cities due to the differing nature of the fiber types and modes of exposure between the regions. © 2008 Published by Elsevier Inc. Keywords: Tremolite asbestos; Erionite; Domestic; Environmental; Exposure

Jan 1, 2007

By Rex E. Loesby

The marble deposits of Yule Creek were first discovered in the late1870s. Minor quarrying occurred between that discovery and the early 1900s. Major development occurred in 1905, when Channing Meek, with some help from the Rockefellers, raised $3 million to develop the Colorado Yule Marble Quarry. That is $50 million in today’s dollars. Some of the words used to describe the marble deposit were “gigantic, remarkable, flawless and immense.” Boosters proclaimed, “The marble age is here.” Obviously, dreams were big for Marble.

Jan 1, 2003

By Georgene Renner, Chee Theng, William Gleason

"In February 2018, drawn in part by the states’ proud mining heritage, SME took its Annual Conference & Expo to Minneapolis, MN for the first time. More than 5,000 people and 554 exhibitors converged on the Minneapolis Convention Center for three days of networking, exhibiting and technical sessions.The state’s mining legacy, one that continues today, is fueled in large part by its vast iron ore resources in the northern part of the state. The historical significance of the mines in the Mesabi Range, otherwise known as the Iron Range north of Lake Superior, cannot be understated. “Mining is a way of life here,” said U.S. Congressman Rick Nolan of Minnesota’s 8th Congressional District. A native of the Iron Range, the three-term U.S. congressman was one of the featured speakers of the opening keynote session. “We like to think we contribute enormously to the well-being of this country and the world. We were the source of the iron ore and steel that helped win two world wars. And we like to think that we are part of the progress that has taken place in the United States ever since.” Nolan kicked off the keynote sessionthat focused on innovation and its part in the mining industry. The session included Rene Aquilar, vice president of corporate affairs and sustainability, Antofagasta Minerals Group; Bob Anderson, vice president for research and development, 3M; Rolf Weberg, executive director, Natural Resources Research Institute, University of Minnesota-Duluth and Christopher Beck, executive vice president and president, Nalco Water. The panel session looked at U.S. and global minerals production, and the importance of the United States to maintain a major role in the minerals industry, both as a producer and as a technology leader. The panel also touched on the global mining industry and the issues that impact mining around the world. Sustainability, the use of water in mining and earning a social license to operate were among the topics discussed by the panel.Speaking of the importance of mining, Nolan conceded that talking about the benefits of mining to the crowded auditorium at the SME conference might be akin to a preacher speaking to the choir, but, following the adage that all politics are local, he continued to illustrate his point by emphasizing the importance of mining to the Great Lakes.“A study by Homeland Security concluded that 13 percent of the nation’s GDP comes out of Lake Superior through the locks at Sault Ste. Marie and most of that is iron ore,” said Nolan. “That study found that, if those locks fail, it would create a national depression. It would put millions of people out of work. That ore and those minerals supply the steel mills, the auto industry, the heavy industrials. They are the heart of our economy. The study concluded that if the states that make up the Great Lakes were a nation, it would be the fourth largest economy in the world.”"

Jan 5, 2018

By · J. B. Boisvert, O. Leuangthong, T. Acorn

Optimizing final pit limits for stochastic models provides access to geologic and economic uncertainty in the pit optimization stages of a mining project. This paper presents an approach for optimizing final pit limits for a highly variable and geologically complex gold deposit. A heuristic pit optimizer is used to manage the effect of geological uncertainty in the resources within a pit shell with multiple uncertainty rated solutions. The uncertainty rated pit shells follow the meanvariance criterion to approximate the efficient frontier for final pit limits. Stochastic dominance rules are then used in a risk management framework to further eliminate sub-optimal solutions along the efficient frontier. This results in a smaller set of final pit shells that could be further analyzed for production scheduling. Additionally, the original solutions are analyzed for changes in the mining limits and two regions are targeted as potential regions for further exploration.

By · J. B. Boisvert, O. Leuangthong, T. Acorn

Optimizing final pit limits for stochastic models provides access to geologic and economic uncertainty in the pit optimization stages of a mining project. This paper presents an approach for optimizing final pit limits for a highly variable and geologically complex gold deposit. A heuristic pit optimizer is used to manage the effect of geological uncertainty in the resources within a pit shell with multiple uncertainty rated solutions. The uncertainty rated pit shells follow the meanvariance criterion to approximate the efficient frontier for final pit limits. Stochastic dominance rules are then used in a risk management framework to further eliminate sub-optimal solutions along the efficient frontier. This results in a smaller set of final pit shells that could be further analyzed for production scheduling. Additionally, the original solutions are analyzed for changes in the mining limits and two regions are targeted as potential regions for further exploration.

By Clay Haynes

In 2005, Black & Veatch Corporation began designing a raw water conveyance system for San Luis Obispo County from Lake Nacimiento to the city of San Luis Obispo. The first element of the water transfer system will be a raw water pump station and lake tap. The wet well of the pump station will consist of a concrete lined shaft approximately 180 feet deep constructed in the very incompetent sandstone of the Vacqueros Formation. The lake will be wet tapped at approximately 172 feet below grade using a slurry earth pressure balance tunnel boring machine. The 48 to 72-inch finished diameter microtunnel will be approximately 500 feet in length. Construction is scheduled to begin in the winter of 2007.

Jan 1, 2008