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By D T. Ribeiro, J F. C L Costa, J C. Koppe

Drilling and sampling are responsible for most of the costs during mineral exploration, especially in multi-elements and polymetallic deposits, such as iron, manganese and bauxite deposits. On these deposits, often it is necessary to estimate multiple attributes at several granulometric fractions, ie distinct particle sizes. This paper investigates the effect of sampling at a close spacing grid only the head grades for the multiple chemical species in iron ore deposits. The remaining required data at the various grain sizes are sampled at a sparse grid. The derived geological model is checked for precision and accuracy comparing the output obtained against a model obtained using a complete isotopic data set including head grades and chemical analysis at each granulometric fraction analysed at all sampled positions. Among the several tested alternatives, the best procedure for dealing with the posed problem involved utilising the correlation coefficients between the grades at distinct fractions to obtain an isotopic database prior to interpolation. Cokriging was the method used, based on the intrinsic coregionalisation model. Estimates were obtained with the quality needed for the proposal of the study. Results showed that at least 50 per cent of the blocks were estimated with errors less than ten per cent relative to the grades obtained at the reference model, using only 15 per cent of the granulochemical data employed to obtain the reference model. The methodology also preserved the correlations between the attributes in their several granulometric fractions on the estimated model.

Sep 26, 2011

By P Mulvey, M Stuckey

"Inter-aquifer leakage due to fractures caused by coal seam gas extractions or longwall mining is an important issue for both the gas and coal industries. Currently, predicting stress induced macro-porosity associated with hydraulic fracturing, depressurisation via dewatering or collapse of overlying seams to infill a void left by longwall mining, is problematic. If fractures can be located the fracture can be sealed. Locating fractures is difficult. The non-geophysical approaches to locate fractures has been to consider the mixing of different waters, particularly that of more recent shallower groundwater with older deeper groundwater, via differences in radio-isotopes integrated with geochemical models to predict likely mixing of waters. This approach is applicable under appropriately complex settings; however, it is an expensive technique and is based on the assumption that the daughter isotopes are equally non-reactive which may not always be the case.Potentially a cheaper and faster technique is to consider integrating geochemistry (mineral weathering) and hydrogeology. The chemistry of groundwater, controlled by the weathering of primary rock?minerals and?formation of secondary minerals, can not only be differentiated between geological strata but also within strata as different stages in weathering results in differing impacts on water quality (ie different reactants).Field analysis of pH, electrolytic conductivity (EC), oxidation reduction potential (ORP) and dissolved carbon dioxide together with laboratory analysis of dissolved constituents characterise the chemistry of the water. Collection of rock samples at the time of drilling for bore installation can provide the (only) opportunity to assess the media in which the groundwater resides and migrates through. An assessment of aquifer matrix chemical makeup, via bulk sample chemical analysis, X-ray diffraction (XRD) and petrographic analysis can achieve this.The chemistry of groundwater is dependent on the water velocity. Water at deposition and post-diagenesis dissolution of minerals by hydrolysis and oxidation will result in equilibria of the dissolved phase with the solid phase. Post-depositional fractures caused by either tectonic activity or weathering alter the rate of weathering and thereby the geochemistry. Slow water flow in microfractures results in water in equilibrium with the rock minerals. Faster flow in larger fractures results in water being in disequilibria with rock minerals.Fractures can alter groundwater chemistry by two pathways: changing groundwater velocity, which changes the rate of hydrolysis or oxidation mixing water from different geological strata.Both pathways cause subtle changes in the water chemistry.It is however, the dissolved phase chemical data, which can be observed over time at individual locations and/or at a point in time along a flow path, which allows the hydrogeologist to ælook up-gradientÆ and locate the zone of leakage. Hence, influences on rock/groundwater chemistry, from anthropogenic sources to natural mixing of waters, can be assessed via appropriate interpretation of geochemistry, hydrogeochemistry and flow data.This paper will use the example of the geochemical and hydrogeological characterisation of aquifers within the Hawkesbury and Bulgo Sandstone of the Southern Coalfields to the south of Sydney in New South Wales to demonstrate this approach.CITATION:Stuckey, M and Mulvey, P, 2013. Looking for fractures - integrating geochemistry with hydrogeology to find inter-aquifer leakage above dewatered or collapsed coal seams, in Proceedings Water in Mining 2013, pp 99-108 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Nov 26, 2013

By Wayne E. Kilker, Michael J. McBride, William P. Levy, Thomas J. Lamb

Between 1989 and 2004 the Massachusetts Water Resources Authority (MWRA)constructed several major wastewater and water tunnels associated with three major projects in the Boston area of eastern Massachusetts. There were many similarities and differences in the bedrock conditions encountered and among the contractual approaches for these independent projects. Through a clarification of the approach similarities and analysis of the contract differences, this paper addresses and presents what are considered to be valuable lessons learned. In doing so, the paper follows the evolution of such disparate issues as contract conditions, baseline reports and dispute review boards. The authors believe that the lessons learned even represent what, in certain cases, could be referred to as “universal truths” that are intended to have application to the next generation of tunneling contracts.

Jan 1, 2005

By Brian W. Mackenzie

"This paper briefly outlines the characteristics which should be considered in assessing the economics of mineral exploration, and illustrates such an assessment by using data from the Canadian base metal sector. Implications for the sector are found to include the following:(1) base metal exploration has the potential to create a substantial amount of new wealth;(2) investment incentive for exploration under current conditions is not unattractive over-all;(3) because of existing taxation policies, there is much more incentive for large companies to explore than for smaller enterprises;(4) succesful exploration is sensitive to the size, financial resources and organizational structure of the exploration entity;(5) the general level of recent exploration expenditures should be adequate to maintain the current rate of production and perhaps to support very modest growth; and(6) there is an important opportunity for growth in the sector.The findings of the study suggest that government policies should be made more flexible, in order to take into account the risks associated with exploration and with price fluctuations in the base metal sector. Recommendations are also made concerning improvements in provincial regulations for disclosure of exploration information."

Jan 1, 1981

By R. Rushforth

The surge of activity in the solar energy market, spurred by government incentives, has created new and more efficient solar technologies, but issues surrounding land- and water-use have backlogged the full-scale development of solar farms. This paper explores siting solar power plants on degraded or polluted lands, such as mine tailings impoundments. Historically, mining and has been integral to Arizona?s economy, but has dwindled in relevance due to urban pressures and environmental regulations. Currently, it is legal to site solar power plants on degraded or polluted lands, but the question remains whether the economics of this degraded lands solar development is more favorable than developing pristine land. Therefore, we explore economics of developing mine tailings impoundments at both the institutional and financial level. Methods of research for this paper were interviews with government regulators, environmental advocacy organizations, farmers, and mining company executives. Financial models using extant tax incentives show a positive net present value for the installation of solar power plants, even when accounting for the costs of land remediation.

Jan 1, 2011

By Walter Barnum

AS a member of the Institute and as the president of the National Coal Association, I come before you today in a dual role. As an Institute mem-ber I welcome the opportunity to make complimentary reference to the growing support which bituminous coal operators are giving to programs looking to the advancement of the engineering profession, and to suggest plans whereby these programs may be enlarged to mutual advantage. As a representative of the bitu-minous industry, it gives me special pleasure to express the appreciation of the industry for the services ren-dered to it by members of your profession. Needless to say, there is a close relationship between the engineer and the coal operator. With increasing frequency and in the interests of the industry, the engineer is becoming more of a factor in the business of producing coal. I need look no further for an out-standing example of this encouraging trend than to Samuel A. Taylor, who not only is a bituminous coal producer but also has risen to such eminence in the engineering profession as to have been chosen the head of this great body of technical men, the American Institute of Mining and Metallurgical Engineers. There are many coal operators whom I might mention as having achieved distinction in the engineering world, such as Howard. N. Eavenson, chairman of the .Coal and Coke Committee. And I would be guilty of a serious .oversight if I failed to make reference to Eckley B. Coxe, one of the founders of the Institute in 1871, a prominent anthracite operator and credited with several important inventions. While it is true that a. considerable number of execu-tives of coal-producing companies in this country came up through the engineering ranks. the proportion of mine executives in England, France, and Germany who are graduate engineers is much larger than it is in the United States. In France all members of the staff are engineers and such is the case in Germany up to the owner of the mine. In Germany the owner is not so frequently an engineer as is the rule in France.

Jan 3, 1927

By Chris Twigge-Molecey

Demand for metals will continue to grow as global population numbers and prosperity levels steadily increase. Consequently, there will continue to be a need to design and construct new metallurgical plants. Business success in general requires projects to be financially successful and return appropriate value to their owners. However, in the metals industry, private and public sector financing sources have become very sensitive to the perceived inability of projects to contain costs and meet other business objectives. Thus, the capital for projects has become more difficult and expensive to obtain. It is instructive to note that Ernst and Young (2011) identified that: “Delivery of predictable project results bestows competitive advantage and market confidence to those corporations who successfully instill this discipline”. The implication for future projects is that they must be systematically developed to minimize perceived risks—and more importantly—to demonstrate that the risks are managed to achieve the business case. Then, provided that the project has been developed in a well-structured way, project success can again be defined as a project with: a final cost within 10% of the budget approved at the end of FEL3, when the project is properly defined and the permit conditions are agreed upon; a start-up date within three months of the definitive, scheduled startup date; production levels at 85% of design capacity within a year of starting commercial operation; production meeting the target environmental restrictions; and with zero lost time accidents during construction and startup. The plant design is one of many integrated activities required to achieve these objectives. This book represents a valuable link between the existing engineering literature that encompasses a wide range of engineering fundamental textbooks and design manuals and the project management literature such as the Project Management Body of Knowledge, or PMBOK® (Project Management Institute, 2014). It is evident throughout this book, that the design team is a small but essential part of a much larger project team comprising the project management, construction management, and construction contractor staff. Design activities must be regarded and managed as part of the integrated whole, with two fundamental links throughout the design process:

Jan 1, 2015

By Leonid N. Shekhter, Corby G. Anderson, Esra Cankaya-Yalcin, Daniel G. Gribbin, Joseph D. Lessard, Larry F. McHugh

"A new process for smelting copper, Looping Sulfide Oxidation™ (LSO™) significantly and positively alters the smelting energy balance. This process uses copper oxide in conjunction with air for the desulfurization of copper and chalcopyrite concentrates. Copper oxide is regenerated in a flash type furnace and then ""looped"" back for the oxidation of the copper concentrate. Heat and material balances show that the Looping Sulfide Oxidation™ process requires significantly lower net energy than conventional technology. This process produces anode copper and higher S02 content off-gases for efficient formation of sulfuric acid. Additionally, the process yields slags with lower copper solubility as compared to the conventional technology.IntroductionBased on the positive results from LSO™ investigations [1], further lab investigations into co=on sulfides and metal oxides were performed. It was discovered that chalcopyrite (CuFeS2) is oxidized with copper (II) oxide. In this reaction over 98.5% of sulfur was removed as S02, while a significantly improved energy balance was observed. This paper intends to analyze both the conventional flash smelting process and the newly developed Looping Sulfide Oxidation™ process, comparing heat and material balance results. LSO™ yields improvements to the energy footprint for copper, opening the door to new copper processing opportunities."

Jan 1, 2013

By J. G. Henning, T. R. Yu, J. E. Croxall

"Test work was carried out to investigate the thermal response of loose and solid rock under varying environmental conditions. The primary interest was to develop a technique that could be used to increase the thermal variation between loose and solid rock for better detectability of loose rock underground with a thermal imaging infrared scanner.A variety of thermal enhancement methods were evaluated both in the laboratory and in the mine environment. Air temperature variation created by the exhaust from diesel driven, mobile mining machinery was studied in detail. When sufficient hot exhaust was supplied to the air, unsteady thermal conditions became more pronounced on the rock surf ace. This allowed a greater percentage of loose rock to be detected by a high-resolution infrared scanner within minutes.The degree of thermal enhancement of loose rock was found to be dependent directly on the thermal conductivity of rock, looseness, air temperature change, and inversely on the size of loose, airflow rate and distance downwind from the heat source. It was also found that an air temperature rise of at least r c, or rock temperature differential of1°C was necessary for minimal thermal enhancement required f or infrared detection."

Jan 1, 1990

By Chikaosa Tanimoto

INTRODUCTION Bratislava is located at the intersection of important traffic routes, including motor-ways, roads, railways, air traffic, trading, and inland waterway with an important harbour. The construction of the D2 Motorway Bratislava, Lamacska cesta Stare grunty was the last missing section of D2 Motorway and its completion linked the Czech Republic through Bratislava to the Hungarian Republic. Traffic was obliged until its completion to use the Lamacska Road and Mlynska Dolina, which were the most heavily trafficked roads in the city. The section of D2 Motorway to be completed in 2006 was 3,300m in length, of which the SITINA Tunnel was approximately half the length. After putting into operation the transit traffic(motorway) and urban traffic was separated. Transit traffic by passing the town was eased. The junctions D2 with Lamacska Road (Harmincova) and Mlynska Dolina also allowed better use of the motorway for the urban traffic The tunnel construction was specified by the features with the highly weathered and thermally altered granitic rock formation with the overburden of Quaternary sediment of 2?4 m thick, very thin overburden, severely controlled deformation limit and environmental protection. The tunnel had to be excavated beneath and nearby the academic complex area and the zoo, where sensitive facilities exist and animals live in. The tunnel consisted of two tunnels (Tunnel A and B) with the length of 1,415 and 1,440 m, respectively. The overburden thickness was in the range from 10?30 m. The standard cross-section and the one with invert arch were 79.5?81.5 m2 and 92.1?93.3 m2. The excavation took 21 months from September 2003 to May 2005. The construction was based on the concept of NATM. The SITINA Tunnel was the third application of NATM in Slovakia, following the BRANKISKO Tunnel (commenced in July 2003) as the first and the HORELICA Tunnel (in October 2004) as the second NATM practice. To protect the surrounding structures and citizens from tunneling operations, seismic monitoring was performed in association with blasting. The allowable limit of blasting vibration was fixed to be under the particle velocity of 15 mm/sec. The tunnel excavation cleared this limit as expected before construction. In driving through the difficult geological situation the excavation work hit 49 faults, and some of them occasionally caused serious face instability. In principle, the rock formation has been affected by the high hydrothermal effect and the resultant clay filing along faults and joints. The auxiliary reinforcement with the 4?8 m long pipe roofing was needed to protect the vicinity of mining face area. This operation extraordinarily required additional works and time which had not been expected before construction.

The Lornex mine is located in the Highland Valley area of British Columbia, Canada, one of the most,promising districts of low-grade porphyry-type copper mineralization in the world; Lornex is operated by Rio Algom Mines, Limited, a member of the Rio Tinto Zinc Group of London. Exploration from 1965 to 1968 disclosed an ore body of 293 million tons with a grade of 0.43% copper and 0. 14% molybdenum; this led to the decision to construct a 38,000 tpd operation, and production commenced in the fall of 1972. The ore is open-pit mined with 15 cu yd (11 5 m3 shovels, which load 100- and 200 -ton trucks. These trucks dump directly into a 60 in. by 89 in. Allis -Chalmers gyratory from two sides of the 14 ft 6 in. (4.42 m) deep dump pocket and across splitters mounted on the pocket sides. The unlined pocket would hold 1,000 tons level full. The crushedore discharges into a 300-ton surge hopper equipped with an automatic sonic level indicator to prevent over -filling. A 96 in. by 23 ft (2.44 m by 7 m) apron feeder delivers the ore from the surge hopper to a 72 in. (1.83 m) transfer belt equipped with a tramp iron metal detector. The transfer belt discharges to a 60 in. (1. 52 m) conveyor which conveys the ore about 3,000 ft (914 m) to the 475,000 ton ore storage pile located near the concentrator. Four 48 in. (1.22 m) pan feeders transfer the ore to the mill feed conveyors, which in turn supply the two 32 ft by 15 ft (9. 75 m by 4. 57 m) semi-autogenous mills, which easily accept the 10 in. (254 mm) product of the crusher. Each semi- autogenous mill is followed by a secondary ball mill. The unusually large open side setting of the crusher accounts for its 6,300 tph maximum capacity. Concentrator capacity is now 48,000 tpd. Eccentric removal is eased by the design of the door to the crushed ore pocket, which has the cart rails mounted on its outer surface and is lowered to a horizontal position in the pocket by an electric winch. The top of the door rests on wear bar covered concrete piers in the pocket. Another feature is a chute through the floor at the crusher base that extends into the crushed ore pocket. Dust and spills of ore on that floor during crusher repairs are easily swept into the crushed ore pocket. This feature is also used at Bougainville and Palabora and has been added to others after operation has commenced. The design follows the concrete rectangular box concept with four main service and maintenance levels shown in the sectional drawings, although a third additional section has been added at the maintenance

Jan 1, 1978

By Marie Kinzel

LOS ALAMOS, New Mexico, the birthplace f the atomic bomb, is one of the most famous-and mysterious-places in the world. It leaped into fame on Aug. 6, 1945, when the first atomic bomb burst over Hiroshima. Unheard of until that day, its present life is as hidden from most people as was its very existence in pre-Hiroshima days. Then, those who did know of it dared not breathe their knowledge. "What do you tell your wife when you go to Shangri La?" was the favorite quip of the few consultants who made regular trips from east or west to Los Alamos during the tense months when the bomb was in the making. Security regulations made it impossible even to hint at the rigid secrecy surrounding the project. The puzzled wives in question knew only that their husbands had top priority on airplane flights to Albuquerque. When they had verified the safe arrival of the flight, they undoubtedly breathed a sigh of relief. If they could have visualized the rest of the trip, the sigh of relief would have been replaced by a state of tizzy, until a telegram came saying "Arriving home on Flight X" (on a nice safe airplane).

Jan 1, 1946

JOINT convention week has become a feature of the year with western mining men. The first was held at Denver in 1926, the second at Salt Lake City in 1927, and the third is about to take place at Los Angeles. Holding in the same city in one week the meetings of a number of related organizations has been .found to permit the development of a well-rounded program at the same time that it economizes time and money for the members, many of whom belong to several of the participating organizations. For the third time, the American Mining Congress, represented by its Western Division, of which Philip Wiseman is chairman, is taking the lead and assuming the main responsibility. The A.I.M.E. is furnishing the papers for two sessions and the California Development Association for one. The Southern California Section, Robert R. Boyd, chairman, is host for the Institute, but the Northern California, Nevada and Arizona sections have each contributed papers to the program, and will be represented at the meeting. It will be a real reunion of the mining men of the Southwest.

Sep 1, 1928

By AIME AIME

NO MORE SUITABLE time and place than LOS Angeles on Thursday and Friday, July 28 and 29, could have been chosen for the Western Regional Meeting of the~1nstitutk. After attending two clays of technical sessions and enjoying the luncheons and dinners of the meeting, visitors, on the following days, could see the opening ceremonies and events of the Olympic Games, which started on July 30 and continued to Aug. 14. Such d spectacle can be seen only once in a generation in this country.

Jan 1, 1932

THE third annual Joint Western Mining Convention, held at Los Angeles, Sept. 10 to 13 inclusive, was a notable success both as to attendance and interest. Registration the first day amounted to 201, and the total crept up to 347 before the close. The American Institute of Mining Engineers was well represented, approximately 80% of those registered and most of the speakers being members. This illustrates largely the amount of interlocking membership and the reason for holding at one time and place meetings of the several related organizations. The plan has proved so successful that it is probable that Spokane will extend an invitation for next year that seems likely to be accepted. It is proposed that the convention be timed so as to permit visitors from the East to stop there Oct. 3 to 5, en route to the American Institute of Mining Engineers meeting at San Francisco, Oct. 7 to 9. Simultaneously, it is expected that the Petroleum Division will hold its fall session at Los Angeles, the two streams of travel meeting in San Francisco, just before departure of the party of engineers traveling to Japan to attend the World's Engineering Congress. The Los Angeles meeting opened Monday morning with a general session under the auspices of the Western Division of the American Mining Congress with Philip Wiseman in the chair. After a series of short responses to the welcome extended, Charles W. Merrill discussed the needs of the western mining industry. A complimentary luncheon to members and delegates followed.

Jan 1, 1928

By AIME AIME

FEATURES of the second fall meeting of the Petroleum Division for 1941, held at the Ambassador Hotel, Los Angeles, Oct. 29-30, were the forum on the Paloma Plan on Thursday after- noon, the large attendance from east of the Rockies, and the dinner on Wednesday evening sponsored by the Southern California Section and at which President Suman spoke on the strategic minerals and metals situation. The attendance was large and the technical fare uniformly good ; the presiding officers had the proceedings well in hand at all times and kept things humming. Some- times it was necessary to taper off the discussion because of pressure on time. All this was due to careful groundwork before the respective sessions. These presiding officers deserve citation: L. W. Huebel, Howard Pyle, E. K. Parks, Carlton Beal, E. G. Trostel. R. W. French, Jr., John Dodge, and H. N. Marsh. The Los Angeles local commit- tees and the Southern California Section deserve much credit for the arrangements, which were recognized by suitable resolutions at the end of the meeting.

Jan 1, 1941

By Christophe Bragard, Brett Robinson

This paper reflects the challenges encountered during the construction of the light rail tunnels under Boyle Heights, in Los Angeles, California. Equipped with two state-of-the-art EPB TBMs, the construction team undertook the mining of twin bored tunnels in the Los Angeles alluvium. The gassy underground conditions dictated many aspects of the design of the tunnels, as well as the tools and means used for their construction. This paper will detail the challenges encountered during construction, as well as the means, methods and logistics used on the project. Discussion includes: EPB TBM machines with some very unique/specific features; complex assembly sequence due to limited shaft access; final precast concrete liner with double gaskets; NATM cross passage excavation in soft ground and below the water table; compensation grouting; mucking shaft arrangement.

Jan 1, 2007

By James A. Strosnider

INTRODUCTION The Metro Rail Project is approximately a 20-mile initial portion of Southern California's planned 150-mile transit network and will provide transit service to the dense population and employment centers within the Los Angeles regional core. The Southern California Rapid Transit District (SCRTD) has defined, as the first segment, a 4.4-mile five station rail line, which extends from the yard and shop area near Union Station to the Wilshire/Alvarado Station. Design packages are completed; utilities are currently being relocated; demolition is underway; early construction contracts have been awarded; and construction has started. This paper will describe the current status of the Metro Rail design and construction, after first briefly reviewing its history, objectives, and main components. PROJECT HISTORY The California State Legislature created the SCRTD in 1964 with a legislative mandate to design, construct, and operate a rapid transit system within the Los Angeles County area. To obtain the monies required to support this program, in June, 1974, Proposition 5 was passed by a solid majority, allowing a portion of state gasoline taxes to be used for rapid transit development. This measure provided a local source of funds for SCRTD to begin its rail rapid transit development program in Los Angeles.

Jan 1, 1987

By James E. Monsees, Richard J. Proctor

INTRODUCTION Los Angeles is one of the world's largest cities in area with a span of 70 km between its north and south limits. The population in the Los Angeles Basin exceeds 11 million people. Los Angeles is second only to New York City in density of U.S. urban population and it operates one of the largest city bus fleets in the world, 2,500 buses. After many years of planning and many consultants' reports, it is planned to initiate a 30 km (18.5 miles) starter line subway -- the "Wilshire Corridor" (Figure 1). Construction is to start in 1985. In several locations, subway routes ultimately will skirt or cross old oil fields, which may cause gassy tunneling. Of particular note are the La Brea Tar Pits, which overlie a part of the old Salt Lake oil field. Tunneling through tar sands for about 3 km will be unique for subway construction and will occur on the starter line. Experience with previous gassy tunnels in the greater Los Angeles area shows that tunnels can be completed safely if precautions are taken. Abundant ventilation is the main solution, although other precautions are discussed herein.

Jan 1, 1985

By Krishniah N. Murthy, James E. Monsees

BACKGROUND The development of public transportation in the Los Angeles Metropolitan area is, as in other cities, closely tied to the development of the area because of increases in population and commercial and industrial activity. Local transportation first appeared in the area in the 1870s when the population was fewer than 10,000 residents. Around 1910, after many consolidations of competitive interests, two large railway companies were formed: The Los Angeles Railway, which provided urban transportation in the Los Angeles City area, and the Pacific Electric Railway, which primarily provided suburban and interurban transportation. These two entities continued with their operations until after World War II, when the ownership passed on to the Los Angeles Transit Lines and the Metropolitan Coach Lines, respectively. By then the railroads needed new equipment, track rehabilitation, and, of course, more money-paying patrons. Lack of grade separation of railway facilities from other traffic increased commute times and encouraged travel by private automobiles. The romantic era of hopping on a Pacific Electric Company "Big Red Car" was coming to an end. As early as 1917, in fact, bus lines were substituted for unprofitable rail service. The Los Angeles Metropolitan Transit Authority (LMTA) was established in 1951 by the California Legislature to study and plan for improvements in the public transportation facilities in the Los Angeles area. In March of 1958 the Los Angeles Metropolitan Transit Authority took over the operation of the two lines.

Jan 1, 1989