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Keeping an eye on the future while honoring the past, Frank McAllister, chief executive officer of Stillwater Mining Co., and life member of the National Mining Hall of Fame and Museum, gave the keynote address to a packed house during the 23rd National Mining Hall of Fame and Museum Banquet in Leadville, CO on Sept. 11. McAllister?s company made news just days before the induction ceremony, when it was announced that Stillwater Mining would acquire Marathon PGM Corp. for $118 million (ME, Oct. page 14).

Jan 1, 2010

By L. A. Romo, J. A. Ferrer

INTRODUCTION The principle line of the Caracas Metro is located generally along the most important east-west traffic corridor of the city from the yards and shops in Propatria at the western extremity to Petare, and eventually beyond to Palo Verde at the eastern end, a route distance of 21 kilometers. There will be 23 stations along the alignment, underground, at grade and elevated, and the line is forecast to handle 1,209,100 passengers daily by the year 2000 with a travel time of 29 minutes between Propatria and Petare. This principle line was divided into three sections for design purposes: Propatria-Fuerzas Armadas, Section I, Fuerzas Armadas-Chacaito, Section II and Chacaito-Petare, Section III. These sections were further subdivided into subsections for construction purposes. The Venezuelan Government, through its Caracas Metro Office in the Ministry of Public Works, awarded design contracts in sections to PARSONS BRINCKERHOFF-TUDOR-BECHTEL for Propatria-Fuerzas Armadas, Section I, OCOIDESA-GRID-APM for Fuerzas Armadas-Chacaito, Section II and OCOIDESA GRID-APM for Chacaito-Petare, Section III. Construction contracts were awarded by international bidding and work is now underway, by joint venture organizations of Venezuelan and foreign firms. The first two sections are under the administration of a company of Engineer/Inspectors in each section. The construction supervision of contracts in the first section is under the administration of the Venezuelan firm, Gómez-Celis-Herrera, (GCH) Engineers, acting under contract to the new C.A. Metro de Caracas that replaced ' the former Office of the Metro. The Propatria-Fuerzas Armadas section, approximately seven kilometers long, consists in part of the 2,951 linear meters of twin-bore

Jan 1, 1979

By Jim Peregoy

INTRODUCTION Frontier-Kemper Constructors, Inc. is an Evansville, Indiana based heavy construction contractor engaged in projects for both the public and private sectors of the underground construction industry. Construction activities range from conventional shaft, slope, tunnel and chamber excavation through state-of-the-art mechanical excavation, ground freezing, standard support and structural concrete operations. Conventional excavation and concreting equipment, as well as raise boring machines, road headers, tunnel boring machines, and freeze plants are owned, operated, maintained and modified "in-house" to suit the needs of individual projects. The balance of this paper wilt present a general overview of the Frontier-Kemper planning and construction operations on the recently completed Phase II of the U.S. Army Corps of Engineers, John Day Dam, Juvenile Fish Bypass Project. General Project History The U.S. Army Corps of Engineers is responsible for designing, constructing and maintaining various navigation and impoundment structures on the nation's inland waterways. Maintenance involves both the work required to maintain the structure in fully-operable condition and the ongoing work required to maintain a positive impact on the environment. John Day Dam is located on the Columbia River approximately 95 km (60 miles) upstream of The Dalles, Oregon. It was constructed to: provide electric power to the Pacific Northwest; provide Locking for up-and-downstream bound commercial and private watercraft; act as a water impoundment structure to control flooding conditions; and to provide a source of irrigation water

Jan 1, 1987

By Staff

In 2012, the estimated value of mineral production increased in the United States for the third consecutive year. Production and prices increased for most industrial mineral commodities mined in the United States. While production for most metals remained relatively unchanged, with the notable exception of gold, the prices for most metals declined. Minerals remained fundamental to the U.S. economy, contributing to the real gross domestic product (GDP) at several levels, including mining, processing and manufacturing finished products. Minerals? contribution to the GDP increased for the second consecutive year. Trends in other sectors of the domestic economy were similar to those in mineral production and consumption rates (Table 1). After continued decline following the 2008-2009 recession, the construction industry began to show signs of improvement late in 2011 and throughout 2012, with increased production and consumption of cement, construction sand and gravel, crushed stone and gypsum, mineral commodities that are used almost exclusively in construction.

May 1, 2013

By Steven A. Savage

Agrico Chemical Company, as we presently know it, is the result of the coming together of several different fertilizer operations. The Williams Companies, our parent organization, first entered the fertilizer business in 1971, when it acquired the fertilizer operations of the Gulf Oil Company. This gave us, among other things, the manufacturing facility at Donaldsonville, Louisiana. In 1972, The Williams Companies acquired Agrico Chemical Company from Continental Oil Company, bringing in a manufacturing facility and phosphate mines at Pierce Florida. Our Florida Mines are in the region commonly known as the Bone Valley Region of Florida. The majority of the phosphate fertilizer produced in the United States utilizes rock mined in this region. The Donaldsonville Plant was originally built in 1967-68 on the site of the old Faustina Plantation at an approximate cost of $80,000,000. (This plant is commonly referred to as our Faustina Plant.) Until such time as Agrico was acquired from Continental Oil, the Donaldsonville Facility was solely used to upgrade phosphoric acid into finished granular products.

Jan 1, 1986

By David E. Thompson, Wesley E. Stimpson

The Massachusetts Bay Transportation Authority (MBTA) Red Line Extension Northwest is currently in the early stages of construction. The 3.1 mile extension of the Red Line from the existing Harvard Square Station in Cambridge, Massachusetts to Alewife Brook Parkway in Cambridge, Massachusetts will include a large, near surface hard rock, rapid transit station chamber at Porter Square in Cambridge (Figure 1). [ ]

Jan 1, 1979

By Ebrahim Tarshizi, Livernois Ryan, Emily Sarver, Zoe Scopa, Robert Setterlind, Leah Frost

"The mines of the future present a host of challenges, which may appear exciting or daunting, depending on one’s perspective. Whether some sectors of the public recognize it or not, the demand for raw resources is not going away any time soon. In fact, it is rising, as the global population grows, urbanizes and attempts to steadily increase quality of life. Yet, at the same time that much of the highly developed world is calling for greener goods, reduced consumption and cleaner production, in other areas there are cries for clean water and sanitation, consistent energy supply, access to health care and education, personal security and support for basic human rights. The balancing act for sustainable development of our global society is, indeed, precarious and the mining community is a key player. Fortunately, many industry members have accepted this role and the responsibility to provide leadership and a solid foundation for progress. Looking ahead, we need new generations of leaders, including many mine engineers who are ready to tackle all sorts of complex problems.There are tremendous needs just for technological innovations. Increasingly tough deposits will require that the industry continues to expand scale toward “mega pits” and “super caves;” fully develop unconventional recovery techniques like in situ leaching and gasification or deep-sea extraction and seriously consider off-earth endeavors. Such work will take entirely autonomous equipment, novel separations, processing and recycling methods, and systems that can withstand extreme physical conditions, just to name a few. It will also take a level of systems integration never-before seen in the mining industry, complete with big data issues, sophisticated predecitve analytics and modeling efforts and cyber-security challenges.Moreover, increasingly complex environmental problems will require creative solutions. Addressing issues like pollution control across multiple media, emerging contaminants, optimal management of wastes, selective mining and shared use of resources between mine operations and surrounding communities and ecosystems are among the top priorities. Really, a complete paradigm shift must occur, such that the focus is on overall improvement of environmental conditions, rather than minimization of impacts. A similar shift will be required in the social realm. How can miners be safer and healthier on-site and off? How can the industry contribute to communities such that they are better off, now and longterm, for having a mine next door? How can artisanal mining practices be transformed to also contribute to sustainable development? How can the industry’s work be a factor in increasing economic and political stability? How can the public understanding of raw resources and the need for mining enterprises be improved?Given the coming challenges, there is no doubt that the mine engineers of the future will need highly diverse skillsets — meshing traditional and contemporary competencies to a degree not previously considered in mining, or most others fields. To be sure, the scope and scale of mining projects make them wholly different than most other engineering work, aside from perhaps the largest civil and urban development projects. While on-the-job experience will continue to be essential, formal education programs (i.e., at post-secondary institutions) must lay critical groundwork."

Jan 6, 2017

By Jesse H. Auvil

In January of 1966, during the annual session of Georgia's General Assembly, Representative Paul E. Nessmith of Statesboro, Georgia, walked into my office and asked me what I thought of the advisability and feasibility of a law which would require the mining operators to reclaim their mined out lands. My answer to him was, as a one time mine superintendent and operator, that I probably would not think very highly of the added cost which reclamation would impose on the operation; but that since assuming the job of Chief Geologist and Assistant Director of the Georgia Department of Mines, Mining and Geology, and in retrospect, I could recommend it very highly, particularly in view of the increased pressure being applied by the Federal government along these lines. I stated then and still emphatically state that this sort of administration should be done on the State level rather than the Federal level. He asked me if I would conduct him on a tour through some of the mining country in which I had worked and to this I readily agreed. The result of this trip was that he was adversely impressed by the devastation which the mining operations had wreaked on that area of middle Georgia along the fall line known as the kaolin belt. Very little except talk was done for the remainder of 1966.

Jan 1, 1970

By L. Schlink

Impacted waters, often complex, are created in mining which at some point in the mine life cycle will need to be attended. The simplest and most cost effective method of handling impacted water is to reuse it as makeup water for operations. At the end of mine life, operational reuse will not be an option and the impacted water will require treatment to achieve alternative reuse goals. Conventional mine impacted water treatment is successful in removing unwanted constituents but create brine and sludge that may require special handling or additional treatment, resulting in additional liabilities and costs. Freeport-McMoRan Copper & Gold has taken an approach to water treatment that focuses on transformation not concentration. The Water Treatment Test Facility located at Sierrita Mine has three test plants that are piloting the mine impacted water transformation process. Two plants have been designed for the removal of calcium and sulfate with products of gypsum and sulfur. The third plant removes metals from process water and transforms them into marketable metal sulfides. The transformation, rather than concentration, of mine impacted water solutes greatly reduce long term risks.

Feb 23, 2014

By Thomas F. Stinson

Energy-producing states see severance taxes as attractive sources of increased revenues for otherwise tight budgets. Consumers in energy-poor states, however, protest that current rates are excessive and have moved to obtain a reduction. The US Supreme Court heard two cases questioning such taxes during its 1981 term, and Congress, in each of its last two sessions, has seriously considered measures placing a ceiling on severance tax rates. Although discussions usually focus on coal severance taxes levied by Montana and Wyoming, ramifications of changes in national policy are much larger, potentially affecting mineral taxes in all states. Severance taxes yield substantial revenues in some states, as illustrated in the accompanying table. In fiscal 1980, Texas collected more than $1.5 billion from such taxes, while Louisiana, Alaska, and Oklahoma collected $525 million, $507 million, and $436 million, respectively. Oil and natural gas production were the major items taxed. While the table shows only the 10 states with the largest severance tax collections, a total of 17 states had severance tax receipts exceeding $10 million in 1980. The enormous increases in severance tax revenue between 1970 and 1980 can be seen from the table by comparing columns A and B. For the 10 states shown, revenues increased from $650 million to $3.8 billion during that period, due to a combination of higher prices, increased production, and new or increased taxes. In most states, increases in prices and production were more evident than higher tax rates. Although the revenue increase is impressive, it understates the extent of changes occurring during the past decade. Since tax collections are shown for fiscal 1980, the full impact of the decontrol of domestic oil prices is not evident. Also, taxes on natural gas reflect controlled prices. When full de-control of natural gas occurs, significantly higher revenues can be expected in gas-producing states, even if tax rates, production, and world prices remain constant. These increases in severance tax revenues, coupled with further increases expected to accompany natural gas decontrol, have produced fears that a substantial transfer of income is taking place from residents of energy-poor states to those living in energy-rich areas. Others worry that increased severance tax revenues will be used to substitute for a substantial portion of state taxes that would have otherwise been collected from firms and individuals. The resulting improvements in tax climate, it is thought, may encourage firms and workers to migrate to energy-producing states. While these issues are often portrayed as pitting energy have-nots against the haves, such is not entirely the case. Much of the original impetus for limits on coal taxes came from Texas residents, the state collecting the most severance tax revenue. One way of gaining perspective on these concerns is by examining severance taxes per capita and as a percent of state tax collections (see columns C and D in the table). When this is done, Alaska, where 1980 taxes on oil and gas production totaled more than $1300 per capita (and 35% of all state tax collections), stands out as a special case. There, the state was able to eliminate some individual taxes, place revenues in a permanent trust fund, and consider offering a rebate of some previous income

Jan 4, 1982

By J. Guzman

Introduction The Carlin Trend is North America's premier gold producing district. It is located in northeastern Nevada's Elko and Eureka Counties along a northwest trending belt about 65 km (40 miles) long and 8 km (5 miles) wide (Thorstad, 1989; Jones, 1989). This trend is the worldwide reference site for epithermal, sedimentary rock-hosted microscopic gold deposits. At least 19 deposits have been discovered to date, varying in size from 933 kg to 1.08 kt (30,000 to 35 million contained oz) of gold (Fig. 1). Newmont Gold Co. and its parent, Newmont Mining Corp., jointly constitute the largest mineral right holders in the district. They own or control more than 1000 km' (386 sq miles) in and around the Carlin Trend and own all or part of I6out of the 19 mines and prospects identified to date. Since the initiation of Newmont's exploration activities in the Carlin Trend in 1961, 2.24 kt (72 million oz) of cumulative gold resources have been identified. Cumulative production from all mines since the start-up of Newmont's Carlin mine in 1965 to the end of 1989 was about 202 t (6.5 million oz) (Jones, 1989). The incentive of sustained high gold prices and innovation in processing technology resulted in a significant acceleration of gold output over the last few years. Newmont Gold alone produced more than 43.5 t (1.4 million oz) in 1989. That is equal to 22% of the cumulative 1965 to 1988 output, and an almost 200% increase over its 1986 output. The same incentives produced even more spectacular exploration results. In each of the last five years, net additions to reserves and resources outpaced current production by substantial margins. These facts demonstrate the spectacular past prospectiveness of the Carlin Trend and the success of focused, multi-disciplinary exploration methods that made it possible to more than offset the recent accelerated depletion of gold resources. However, is this situation sustainable? How long can the mining companies along the Carlin Trend keep on finding resources faster than they deplete them? These are some of the questions that motivated this study. The authors have not quantified the future potential for gold exploration in the Carlin Trend nor established a deposit discovery path. But strong indications were discovered that the [ ] Carlin Trend remains a relatively immature exploration district and that the potential for significant new discoveries is high. Methodology and data The approach chosen to address the above questions was simple. The authors compiled deposit size data, measured in contained ounces of gold resources, for all known deposits along the Carlin Trend (Table 1). The resource information was obtained by adding cumulative historical production (adjusted for mining losses and metallurgical recovery) to 1989 year-end published resource inventories. In a mature exploration area, where most deposits have been discovered, this distribution would be expected to approximate lognormality and would plot along a straight line on a lognormal probability scale. This result was found in previous work by Allais (1957) and recently confirmed by Cox and Singer (USGS, 1986) in regard to various types of mineral deposits in several regions of the world. It was also found to hold true for oil and gas pool size distributions (Arps and Roberts, 1958; Kaufman, 1962; McCrossan, 1969). [ ] The data used were compiled by Newmont Exploration geologists. The purpose of the study is to make inferences about the underlying geologic processes in the district and the maturity of the exploration effort. Therefore, deposits were not classified according to ownership but according to geologic occurrence as known from current information. Newmont's Post and Barrick's Goldstrike and Betze deposits, for example, are shown as a single occurrence to reflect the actual geologic setting. The cumulative frequency distribution of deposit sizes was plotted on lognormal probability paper (Fig. 2). The abscissa shows the cumulative fraction of deposits at or below a certain deposit size and the ordinate shows the deposit size in thousands of ounces of contained gold resources.

Jan 1, 1992

By R. D. Williams

INTRODUCTION In a very real sense, Butte, Montana is where the copper came from that won two world wars. The price for that unrestricted mining and smelting of copper came due in 1983 when Butte was declared a Superfund site. One of the most complex remnants of this mining history is the Parrot Tailings site. The Parrot Smelter operated from 1881 to 1910 moving Upper Silver Bow Creek to the south and depositing approximately 370,000 cubic yards of waste material adjacent to Upper Silver Bow Creek. Additional mixed waste from other processing sites deposited below the Parrot Tailings at the Northside Tailings, Diggings East and Blacktail Creek Berm total approximately 224,000 cubic yards of contaminated material. As part of the Superfund remedy, EPA proposed leaving all these wastes in place. This proposal prompted a detailed criticism by several geoscientists familiar with the site. The EPA’s 2006 Record of Decision (ROD) did in fact leave these wastes in place which set the stage for a series of studies which continue to refine how best to protect extensive completed Superfund Remediation downstream of Upper Silver Bow Creek. HISTORY OF THE PARROTT MINE AND TAILINGS Placer gold was discovered in Silver Bow Creek, the headwaters of the Clark Fork River only a few miles from the Continental Divide in 1864. This discovery lead to a stampede of placer and lode claims. One of the first lode claims located was the “Parrot” lode, located in the fall of 1864. Progress for developing a mine at the Parrott was slow and it wasn’t until 1876 that one of the original locators encountered a rich vein of chalcocite. Butte had its first copper mine! The Parrott mine was patented in 1879 and by 1881 the Parrot, having lost a “t”, concentrator and smelter were built. The smelter and concentrator were an immediate success with a considerable market for processing the District’s rich copper ore. In 1885 the employees of the Parrot Smelter bought the Butte Reduction Works, another smelter. In 1885 dams were built on Silver Bow Creek to contain various tailings and related processing byproducts (Figure 1).

Jan 1, 2019

By D. W. Mitchell

Planning today for what hopefully will never happen is one of the surest ways to decrease the chance of it happening. As Napoleon proved and Ian Mitroff wrote, "The heat and stress of battle is the worst time to make decisions of strategic importance." Mitroff also wrote, "The value of a plan is not that it will ever perfectly match reality, but going through the process of planning speeds the process of recovery. It allows the organization to emotionally work through the worst before it actually happens." This paper concentrates on things miners must consider; on the need for plans to be like a belt conveyor strong enough to carry the load, flexible enough to stretch a little; on the criticality of throwing away fax machines and telephones, and having certain officials at the scene rather than back in head-quarters; on the training of fire brigades and mine-rescue teams; on having company-controlled chromatographs; on having people who can look at trends rather than numbers. Some of the things in this paper might anger some readers; for that, I can only ask them to consider first the problem not their position.

Jan 1, 1993

By Lane White

Environmental regulations have become a decisive factor for many minerals industry operations. Managers face new liabilities as a result of environmental laws, and restrictive permitting requirements for new projects make mine development an increasingly difficult proposition. An abundance of federal, state and local environmental laws and regulations already confront on-going minerals operations, and complex new legislation and rule-making is always in progress. Acronyms and initials like RCRA, CERCLA, SARA and EIS become as familiar as reserves, tons, grades and recoveries. The growth of such regulation has created a new category of professional employees - environmental scientists and engineers-whose presence will influence minerals production activity from now on. The disciplines of environmental science and engineering are still being defined. While these definitions are being worked out, companies in the minerals industry have responded by hiring people with professional experience in existing disciplines and training them to their special needs. An environmental consulting industry of substantial proportions has developed to offer expertise where producing companies may not find it economic to hire full-time professionals. The mining schools have responded by introducing environmental course work, but these programs have yet to supply a significant number of environmental professionals to the minerals industry. To gain some perspective on where minerals producers now stand in their hiring of environmental professionals, ME recently surveyed 20 companies, with questions about how they go about the business of managing environmental compliance. Twelve companies re¬sponded to the survey, and the results

Jan 1, 1991

By Staff

"In 2014, the estimated value of total mine production of nonfuel minerals in the United States increased. The quantity of production increased for most mineral commodities mined in the United States, as did prices. Notable exceptions were the declines in prices for most precious metals. Minerals remained fundamental to the U.S. economy, contributing to the real gross domestic product (GDP) at several levels, including mining, processing and manufacturing finished products. Following the reduction in construction activity associated with the 2008- 2009 recession that continued through 2011, the construction industry continued to expand in 2014, with increased production and consumption of cement, construction sand and gravel, crushed stone and gypsum, mineral commodities that are used almost exclusively in construction. Other segments of the nonfuel minerals industries increased as well. Trends in other sectors of the domestic economy were similar to those for industrial mineral production (Table 1).Discussion of mine production is frequently segmented according to the type of materials produced within the broad categories of metals and industrial minerals. Industrial minerals can be further subdivided as construction aggregates and other industrial minerals. The materials with the highest unit values, usually metals, tend to have very low production rates compared with those of many low-valued materials, such as crushed stone or construction sand and gravel. Therefore, for discussion and analysis of the performance of the minerals industry in general, the value of production is used rather than tonnage produced. Although the value of metals and industrial minerals mined in the United States are similar, if tonnages are compared, construction aggregates dominate, dwarfing the production of all other minerals combined.Mineral industry performanceThe estimated value of nonfuel mineral raw materials, including metals and industrial minerals, produced at mines in the United States in 2014 was $77.6 billion, a 3.5-percent increase from $75 billion in 2013 (Table 2). Net exports of mineral raw materials and old scrap were $15 billion (Fig. 2). Domestic raw materials, along with domestically recycled materials, were used to process mineral materials worth $697 billion. These mineral materials, including aluminum, brick, copper, fertilizers and steel, and net imports of processed materials (worth about $41 billion) were, in turn, consumed by downstream industries with a value added estimated to be $2,530 billion in 2014.In the United States in 2014, mine production of each of 14 mineral commodities was worth more than $1 billion. These were, in decreasing order of value, crushed stone, copper, gold, cement, construction sand and gravel, iron ore (shipped), industrial sand and gravel, molybdenum concentrates, phosphate rock, lime, salt, zinc, soda ash and clays (all types)."

Jan 1, 2014

By J. E. Brownhill

After being closed for three years, Specialty Minerals Inc.'s Port Inland limestone facility reopened in the spring of 1992 as a commercial limestone producer. In 1990, Specialty Minerals, a division of Pfizer Inc., bought Port Inland's reserves and equipment from Inland Steel because of the strategic value of the limestone for the production of precipitated calcium carbonate (PCC). Specialty Minerals' project team faced many challenges in reconstructing the Port Inland facility. Many traditions and norms had to be overturned to achieve the productivity, flexibility and cost necessary to survive in today's competitive minerals environment. Port Inland's history Inland Steel built Port Inland in 1930. It was operated as a captive source of metallurgical grade limestone for the steel industry until its closure in 1989. The facility is located in the Upper Pen¬insula of Michigan on the north edge of Lake Michigan. Operations consist of a deep water port facility with crushing, screening and stockpile storage for 453 kt (500,000 st) of finished product at the port. Ninety-nine percent of the stone is shipped by lake boat to ports within the Great Lakes. The operation is unique in that both metallurgical dolomite and limestone are produced on site.

Jan 1, 1994

By Robert Smith

Deposits are global, said Barrick Gold's Smith. This means that the mineral industry, by necessity, is global. "Manufacturers have considerable freedom to decide exactly where they wish to produce whatever it is that they sell," he said. "What we sell, on the other hand, must be produced where nature chose to lay it down. The question is not so much, whether to go global, as when to do it and how to go about it." The timing of international expansion depends on external factors, often political, Smith said, and on internal ones that relate to the company's size and stage of development. "In deciding how to expand, a company is largely deciding how to adapt its existing business strategy to activity on the world stage," he said Barrick entered 1997 with 1.58 kt (51 million oz) of reserves, Smith said, annual production of 93.3 t (3 mil- lion oz) and cash flow of $463 million. Reserves in- creased 40% in 1996 and production will begin to rise again significantly in 1999. "We believe our fundamental strategy is responsible for our early development and subsequent success," he said. Barrick entered the gold-mining industry in 1983. Its corporate mandate was to create shareholder value, Smith said. From the beginning, the company took a different approach - businesslike, entrepreneurial, strategic and focused. "Many mining companies start out with a technical team and develop business and financial expertise thereafter," Smith said. "In 1983, Barrick had the business people, and then moved into mining." First, it acquired part interest in two small operations, one in Alaska and one in Ontario. Then, in 1984, it merged with Camflo Mines, which operated a low-cost underground operation in Quebec.

Jan 1, 1997

By Richard L. Nielsen

Early Models In 1906, Daniel Jackling demonstrated that relatively low-grade disseminated copper deposits could be mined profitably using mass mining technology. The ensuing years saw a gradual increase in activity aimed at defining ore targets for large reserves of disseminated supergene enriched copper ores. Prominent organizations, such as Calumet and Hecla, Phelps Dodge, and Asarco, established teams of geologists. They focused on interpreting oxidized and leached outcrops over supergene chalcocite ore bodies. Techniques to evaluate oxidized cappings and predict the presence of underlying supergene chalcocite enrichment ores were developed and put to practical use by the late 1920s and early 1930s (Locke, 1926; Blanchard 1939, 1968). Oxidized capping evaluation centered on recognizing oxidation products derived from the various sulfide minerals found in disseminated deposits. Chalcopyrite, for example, oxidizes to a characteristic reddish pitch limonite that exhibits characteristic boxworks. Chalcocite is recognized by earthy, powdery, indigenous, hematite-rich limonite. Pyrite weathers to characteristic cavities and yellowish jarositic limonites. Evaluation of cappings is a systematic effort of noting and estimating the preoxidation sulfide mineral content and copper grade in an oxidized outcrop using mineral composition and morphology of oxidation products. Several complications were noted early in this technology's development. For example, the associated pyrite content of protore greatly influences mobility of copper and iron during oxidation. High-pyrite disseminated sulfide assemblages, upon oxidation, mobilize iron as well as copper. This results in oxidized rock with many leached cavities, poorly developed boxworks, and poorly developed indigenous limonites. This effect was noted and used in a general way to identify possible development of supergene chalcocite. Indeed, strongly leached outcrops could be present over enriched ore. A second complication is the manner in which associated gangue minerals influence the products of sulfide oxidation. Reactive gangue minerals, such as carbonates, neutralize acids formed by sulfide oxidation. Thus, copper cannot be moved from oxidized outcrops. Relatively nonreactive gangue, such as quartz-sericite-altered schist or porphyry, neutralizes supergene acid very slowly. This allows copper to move out of the oxidized outcrop. Recognizing these features was closely allied to an early understanding of the processes involved in oxidation supergene enrichment of disseminated ores. Field observations and mineralogic mapping of oxidized cappings were important in discovering many important porphyry copper ore bodies during the 1920s. These include Silver Bell, Miami-Inspiration, and Morenci in Arizona; Tyrone, NM; and Ely, NV. Capping interpretation like-wise led to discoveries at Mineral Park and Esperanza in Arizona during the exploration surge that accompanied high copper prices in the 1950s. In the 1960s, Kennecott research geologists refined and quantified some aspects of oxide capping appraisal (Anderson, 1982). The ratio of jarosite plus hematite to the total limonite assemblage was shown to be proportional to amount of copper leached from the oxidized outcrop. Thus, if the limonite assemblege in an oxidized capping consists of 40% goethite, 20% jarosite, and 40% hematite, 60% of the original copper is leached. The amount of copper remaining in the capping, together with the limonite mineralogy, can then be used to estimate original copper grade in the outcrop, amount of leaching, and chalcocite enrichment grade (in feet/% copper) in the underlying supergene chalcocite zone (Anderson, 1982). Evaluation of oxidized cappings and prediction of chalcocite blanket ore targets were successfully used in the western US and South America through the 1950s. Discovery of new porphyry copper provinces in other regions during the 1950s and 1960s, however, underscored some limitations of capping evaluation technology. Porphyry copper systems in Australia generally oxidize and weather to hematitic cappings. Presumably, the semiarid monsoon environment and the long time that the sulfide systems have been exposed to oxidation on that continent lead to development of relatively stable hematite. It is now recognized that jarosite and goethite persist metastably in the limonite assemblage in all areas once sulfide oxidation is complete and acid generation ceases (Brown, 1971). The assemblage eventually converts to hematite. But, climatic conditions in arid southwest US allows metastable limonites to persist for a long time, thus providing information on former sulfide assemblages. Another problem occurs when applying capping evaluation techniques in extremely humid re-

Jan 12, 1984

By Paul Taurasi, Mahmood Khwaja, Anjuli Corcovelos, William Brick

California’s San Diego County Water Authority provides a safe and reliable water supply to more than 3.3 million residents through twenty-four member agencies. The 2nd Aqueduct pipelines, a critical infrastructure consisting of three large-diameter pipelines, are susceptible to natural threats including streambed erosion, channel migration, and seismic hazards within the 3,840-foot-long Moosa Canyon segment of the alignment. A state-of-good repair, hazard mitigation, and resiliency project is progressing to ensure uninterrupted water supply. For each pipeline, a segment will be replaced by tunneling. A high-level project development approach is presented, focusing on alternative selection, environmental and geotechnical considerations, and operations and maintenance constraints.

Jun 13, 2023

By Sally Gillies

During the 14 years since the last update to National Instrument 43-101 (NI 43-101), there have been many discussions between Canadian regulators and mining companies about mining disclosure deficiencies that arise from regulatory reviews. These discussions are not made public, and as a result, there has been some drift in how NI 43-101 is interpreted by the regulators, which in turn creates uncertainty for the mining companies trying to comply with the instrument. To reduce uncertainty in mining disclosure requirements, the Canadian Securities Administrators (CSA) has issued a notice to update the current NI 43-101 with a streamlined instrument and form. Changes and benefits are listed in the “CSA Notice and Request for Comment — Proposed Repeal and Replacement of National Instrument 43-101 Standards of Disclosure for Mineral Projects,” which is available on the Ontario, Quebec, Alberta and British Columbia Securities Commission websites. The public has been invited to comment, with the comment period ending on Oct. 10, 2025. The 43-101 Companion Policy (43-101 CP) provides an update to the views of the regulators on how the CSA staff interpret and apply certain provisions of the instrument. Collectively, some of the changes to NI 43-101, the form and 43-101 CP are likely to increase the financial and other burdens on the mining companies responsible for the disclosure, and the qualified persons (QPs) who create the disclosure. In other instances, there are missed opportunities to reduce the burden on mining companies and QPs without impacting the markets.

Sep 1, 2025