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By D. J. Beeby

California's Surface Mining and Reclamation Act (SMARA) was passed in 1975 to identify and protect mineral resources in areas of high land use conflict and ensure reclamation of mined lands. Under SMARA, aggregate resource availability is quantified and compared to forecasted demand in specific market regions. Fifteen regions studied thus far cover 51,800 km2 (20,000 sq miles) and contain 45 Gt (50 billion st) of high-quality aggregate resources that have been legally designated as "regionally significant," providing a measure of protection previously unavailable. SMARA reports and state testimony at local hearings have supplied objective information and helped reduce conflict in mine permitting decisions.

Jan 1, 1987

By H. Huang, R. N. Gow

Acidic treatment of enargite (Cu3AsS4) dissolves both arsenic and copper from the mineral and then attempts to separate them in the leach solution. The reactivity of enargite was examined in acidic to neutral solutions, over the pH range 1-7, to determine a potential range for co-dissolution. Enargite mineral samples from Butte, MT and Quirivilca, Peru were used as working electrodes in a cyclic voltammetry corrosion cell setup, which were then cycled multiple times over -1000 to 1000 mV. Surface reactions and transitions were characterized using in-situ Raman spectroscopy, which were then compared to updated EH-pH diagrams for the copper-arsenic-sulfur-water system from a previous study done under alkaline conditions. The region of co-dissolution is limited to > 600 mV vs. SHE and pH < 1 under the proposed diagram.

Jan 1, 2014

Cretaceous volcanic activity (Hauterivian Albian) in the Peruvian Andes can be found along the coast of Peru and the western edge of the Andes mountains between 15o30&apos;S and 5o30&apos;S, extending discontinuously in south to Chile and north to Ecuador and Colombia. This volcanic activity formed in three aborted marginal basins; the NNW-trending volcanic Ca±ete and Huarmey, and NNE-trending Lancones basins. These volcanic rocks are predominantly andesitic and basaltic in composition, of calc-alkaline and tholeiite affinity with subordinate dacitic and rhyolitic rocks. One notable feature is the appearance of æocoitasÆ from Ica (14oS) south to Santiago de Chile. These rocks have a calc-alkaline to alkaline affinity. From south to north, the continental crust gradually becomes thinner, allowing mantle material to rise towards the surface. Ophiolitic sequences of this type form a marginal basin in Colombia. Very low-grade regional metamorphism which affects the volcanic rocks also varies gradually from south to north. Between Santiago de Chile and Ica this takes the form of burial metamorphism, with moderate geothermal gradients (20o-30oC/km). Metamorphism in the Huarmey basin is transitional between burial and ocean-floor metamorphism, with very high geothermal gradients (>3000C/km). High geothermal gradients are also apparent in metamorphism of the Lancones basin, though less than the other basins. Ocean-floor metamorphism is present in the ophiolitic sequence in Colombia. Associated mineral deposits in the Huarmey and Lancones basins, and in the north, are of the volcanic massive sulphide-type (VMS). The principal deposits in Peru are Leonila Graciela (20 Mt Zn and Pb) and Tambogrande (40 Mt Cu and Zn). There are also smaller mines and prospects. To the south of Lima, manto-type Cu deposits (CuMT) are found with a mineralogy of chalcopyrites, pyrites, magnetite, actinolite and apatite. The main example is Raul Condestable (10 Mt Cu). Other prospects are present to the south and Chile has some very large mines of this type (El Soldado, Lo Aguirre). The notable differences between the CuMT and the VSM deposits are thought to be the result of the prevailing conditions in the earthÆs crust during the Hauterivian Albian. To the south, calc-alkaline and alkaline volcanic activity in aborted marginal basins, with thicker crust, was thick, produced moderate geothermal gradients associated with burial-type regional metamorphism and deposits of CuMT. In the north aborted marginal basins associated with calc-alkaline to tholeiitic volcanic activity and a gradually thinning crust, produced transitional regional metamorphism between burial-type and ocean-floor type, associated with high to very high geothermal gradients and VMS deposits. In Colombia these conditions led to ophiolite extrusive rocks, ocean-floor metamorphism and also VMS deposits.

Jan 1, 1999

By V. O. Tenorio, K. P. Hague

Mines are constantly trying to improve production processes by optimizing work cycles, reducing operational delays, minimizing costs, controlling equipment utilization, and preventing occupational hazards. Currently, advances in digital mining technologies within the concepts of 5G and Industrial Touch Internet are allowing better control and monitoring of underground mining equipment, with centralized control systems that unify data analysis for proper decision making. A wireless 5G-based platform for controlling and monitoring systems for underground mine operations can be designed over a comprehensive layout in where bandwidth selection, sensor location, Wi-Fi repeaters and power distribution are put together to build a successful supervisory system. In order to confirm the validation of these concepts, a case study is proposed for a medium-sized underground mine with a multi-level network which includes tablets managed by production supervisors, along with other data collection devices installed in semi-autonomous mining equipment, collecting, and distributing data in near-real time, with interconnection to support and services areas on the surface.

Mar 2, 2022

By B P. Scott

Podsol soil horizons developed on Pleistocene glacial sediments overlying the Coronation Mine orebody were analyzed for copper and zinc spectro-photometrically, using biquinoline-isoamyl alcohol and dithizone carbon tetrachloride reagents. Copper and zinc are concentrated in the A. and C horizons, whereas the A1, A2 and B horizons are leached. Of economic significance is the fact that the C horizon contains a copper anomaly, in excess of 100 times back-ground, directly over the orebody. Due to the erratic distribution of high copper concentrations in the Ao horizon with respect to the orebody, that horizon is not considered as a reliable prospecting datum. U NDER certain conditions, metallic ore deposits are accompanied by primary halos of trace elements in unweathered rock surrounding the orebodies or by secondary halos in weathered rock, alluvium, soil, or vegetation above or near the mineralized zones. Where such halos occur, chemical analysis, as applied to the detection of trace elements, is a valuable prospecting aid, permitting the detection of mineralization of possible economic value.

Jan 1, 1965

By Yiming Zhang, Yunpeng Li, Chun Feng, Ruyang Cao

In the past, the selection of the number of empty holes between blast holes heavily relied on the subjective experience of practitioners, leading to unsatisfactory blasting results. The number of empty holes between blast holes is particularly important for the perforation of explosive cracks. In order to determine the optimum number of empty holes for inducing the propagation of explosive cracks, a two-dimensional numerical model of two-hole blasting was established based on the continuous-discontinuous element method (CDEM) using polymethyl methacrylate (PMMA) as the medium, and numerical simulation of various working conditions was conducted; the simulation results are basically consistent with the PMMA model test. Through the analysis of blasting parameters, the optimal number of empty holes with a certain hole spacing is fitted. The following conclusions are drawn: (1) There is a threshold for variable x. When x exceeds 50, the presence of empty holes cannot lead to the perforation of explosive cracks between the blast holes. (2) When x is below 50, the optimal number of empty holes inducing the propagation of explosive cracks can be determined through fitting an empirical formula. By adjusting the number of empty holes between blast holes, a significant spacing between adjacent blast holes was achieved, allowing for effective penetration, so as to effectively “induce” the direction of the fracture zone and make full use of the energy of explosives. The research results of this paper are conducive to the research of directional blasting technology and provide certain references for the optimization of precision blasting parameters.

Dec 19, 2023

By James Westfield

This publication covers the work of the Division of Coal Mine Inspection, Bureau of Mines, as performed under provisions of the Federal Coal Mine Safety Act. It presents background information and data since 1952 when the Act became effective and includes up-to-date statistics for the calendar year 1962. During that year, approximately 9,704 coal mines were active in the United States, and the Bureau made 12,810 regular inspections. BACKGROUND The Federal coal-mine inspection program was established to carry out the provisions in Public Law 49, 77th Congress, (H. R. 2082) approved May 7, 1941. This act has since been amended as Title I, Advisory Powers Relating to Health and Safety Conditions in Mines, under Public Law 552, 82d Congress, approved July 16, 1952, which also included Title 11, Prevention of Major Disasters in Mines. Public Law 552 is known as the Federal Coal Mine Safety Act.

Jan 1, 1963

By Tracy Brettmann

In recent years the Augered Cast-In-Place (ACIP) Pile industry has seen a substantial increase in the quality control options available to Contractors, Engineers, and Owners. Quality control methods range from the simple, manual techniques that have been used for years to new computerized installation monitoring equipment and nondestructive testing methods. Our ability to monitor and test ACIP piles has grown to such a degree that the industry is struggling to determine how much quality control is enough. This paper reviews the many options available and describes the pros and cons of each. The various nondestructive testing methods, in particular, have been difficult to apply reliably due to misapplications of methods and misinterpretation of the results. ACIP piles have unique properties that require the various nondestructive testing methods available be considered very carefully in determining the method most appropriate for a particular use. Some nondestructive testing methods, as well as automated monitoring equipment, potentially can be applied effectively to increase the level of quality control for ACIP piles. The experience gained on real projects using these new methods, in conjunction with the old procedures, provides valuable information for future applications.

Jan 1, 2000

By J. K. Brimacombe, I. V. Samarasekera, B. G. Thomas

"Mathematical models have been developed for the processing of static cast steel ingots and are app1ied to investigate the mechanisms for the formation of panel cracks. Panel cracking is an intermittent but persistent defect that causes affected steel ingots to be scrapped. A two-dimensional, finite-element, heat-transfer model was formulated and employed to calculate the temperature distribution in both large and small steel ingots during the various processing stages from initial casting to the start of rolling, including solidification, cooling in the mold and in air, reheating in the soaking pit, and subsequent air cooling. The stress state in the ingot arising from the calculated temperature variations was then determined. This involved the development of a transient, elasto-visco-plastic, finite element, thermal stress model, including the effects of phase transformation volume changes and kinetics creep, and temperature-dependent, mechanical properties. The results of the mathematical model predictions of temperature and stress were then used to determine the mechanisms and to suggest solutions for two different types of panel crack formation. Mid-face panel cracks apparently form during air cooling when the mid-face surface temperature is between the Arl and 500~C. Off-corner panel cracks appear to initiate internally during the early stages of reheating but do not propagate to the surface until much later. IntroductionPanel crack formation in static-cast steel ingots is a defect that has been plaguing the steel industry for several decades. Although the problem is intermittent, it is also serious since affected ingots must be scrapped. Panel cracks are manifested as two distinct types of cracking problems. ""Mid-face"" panel cracks are found exclusively in small, 2 to 6 ton, medium carbon steel (0.3 to 0.7% C) ingots and usually exhibit a single, continuous, longitudinal crack down the center of one of the ingot faces as shown in Fig. l (l). ""Off-corner"" panel cracks often form roughly oval, discontinuous crack patterns on the wide faces of large, 20 to 30 ton ingots as seen in Fig. 2 (2). They affect only low carbon steels (0. l to 0.2% C) with high manganese content. Both defects affect only aluminum-treated steels and are caused by a combination of intermediate temperature ductility loss involving aluminum-nitride precipitation and thermal stress generation. The ductility problem has received a good deal of attention which was the subject of a recent review (3). The present study was undertaken to investigate the thermal stress aspects of the problem through the development of mathematical models of heat transfer and stress generation in static-cast steel ingots. The ultimate objective was to elucidate the mechanisms of formation for both types of panel crack and to evaluate possible solutions to the problem."

Jan 1, 1986

By James Pile

Long, high capacity, highly tensioned, cable bolts (strand bolts), stiff enough to be installed with resin like a solid bolt, yet flexible enough to be used in any lengths, have been widely used in Australian coal mines since the early 1990?s. A brief history and update on recent developments of this technology is provided. The first major US trial of this Australian technology, has recently taken place at BHP Billiton?s San Juan longwall coal mine in New Mexico. Thirty-five foot long, high capacity, highly tensioned, post-grouted cable bolts are being used to provide active secondary support of intersections in areas where operator safety and life of mine considerations are paramount, and standing support cannot be installed for reasons of equipment access. The cable bolts are resin anchored into overlying sandstone channels, tensioned, and post-grouted. The installation procedure and support results for these highly tensioned cable bolts are given.

Jan 1, 2007

By R A. Pax

Operational grinding mills emit significant acoustic emissions which are a consequence of the dynamic environment prevailing inside them. From a technical perspective, the noise presents an opportunity to determine some details of the processes occurring inside the mills. The noise generated is not random and can be attributed to a range of events that occur inside these mills, consequently non-contact acoustic determinations of in-mill behaviour provide powerful insights into the operation of primary comminution tumbling mills. To enable a logically coherent picture to be formed of the processes inside a mill, arrays of microphones have been used. This approach allows a clearer picture of the in-mill behaviour of the charge to be accessed. In contrast to single microphone approaches, usually located near the expected charge toe position, an array of microphones allows much more useful information to be obtained from grinding mill noise.This paper will discuss and present data obtained from microphone arrays positioned at the toe and shoulder locations of a mill, and how this information can then be used for the optimisation of grinding mills in real-time.CITATION:Pax, R A, 2012. Determining mill operational efficiencies using non-contact acoustic emissions from microphone arrays, in Proceedings 11th AusIMM Mill OperatorsÆ Conference, pp 119-126 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 29, 2012

By M. R. Geer

The Bureau of Mines examined the washability data for 25 Appalachian coals requiring low-density washing to reduce sulfur content to 1 percent, using the distribution-curve method. The purpose was to estimate how closely theoretical sulfur values could be approached, what yields of washed coal could be expected, and the recovery efficiencies that might be achieved. Assuming that the run-of-mine coal would be crushed to 3/8 inch and cleaned in dense-medium cyclones, the calculations indicate that theoretical sulfur contents could be approached closely when cleaning at a specific gravity of separation as low as 1.30. With coals that have favorable specific gravity compositions the recovery efficiency anticipated for cleaning at 1.30 specific gravity is surprisingly high. Similar calculations for cleaning with concentrating tables at intermediate specific gravities indicated that theoretical sulfur contents at 1.50 specific gravity could be approached closely with some coals but not with others. The calculations suggest that operating a table at a specific gravity of separation much lower than about 1.50 probably would be unsatisfactory with most coals.

Jan 1, 1968

By Dusan Ilic

Conveyor system wear of belts and transfers attribute to a significant proportion of the maintenance costs and lost productive hours when handling hard abrasive ores at high unit rates typical of the iron ore industry. The recent growth phase has seen a rapid increase in mine and export capacity, with many new and upgraded plants operating at high throughput and utilisation. Subsequently, the industry has progressed to an optimisation phase, seeking to maximise production capacity and reduce maintenance costs with minimal capital spend. To support this, a programme of modifying designs was executed to improve conveyor transfer chute and belt life, which identified a need to challenge the industry practice for specification of designs to improve the functionality of the installed equipment. While acknowledging the importance of selecting the highest wear resistant materials for the intended application, this paper investigates design criteria related to decreasing conveyor transfer and belt wear. Of focus is a shift in the manner in which designs are specified, from specifications primarily governing geometrical constraints, to those meeting technical and functional requirements aimed at producing optimum geometry for a given set of material handling parameters. An assessment of transfer design criteria is presented.

Aug 17, 2017

By Edward Roberts

This is a progress report of an investigation by personnel of the Bureau of Mines from June to September 1951 to introduce preservative chemicals into growing timber. It also describes in detail the impregnation process, known as the collar method, developed by the United States Department of Agriculture2/ Twenty-eight trees were treated by this method, and a complete record was kept of each individual tree and of each timber cut from it. These timbers have been placed in a coal mine, and their tendency to decay is compared to that of adjacent untreated sets. Although several years will be required before final conclusions can be drawn, this report explains the appearance and encouraging results of the treated timber to date. Also included are some comparative costs of untreated timber, treated timber by the commercial pressure method, and treated timber by the collar method. INTRODUCTION In the hope of increasing the useful life of cut timber, experiments to impregnate growing trees with wood-preservative chemicals by utilizing the natural flow of sap have been carried on for centuries. None of the various methods used in these experiments has ever gained any widespread use because they have been commercially impractical.

Jan 1, 1953

By T. L. Carstensen

The Miami In-situ mine of BHP Copper is located in Globe-Miami, Arizona. The mine leaches mineralized leach capping over a supergene enriched sulfide deposit, and has produced over 500 million lbs of copper during the last 50 years. The Miami unit has identified several opportunities to enhance and expand in-situ production. A computer block model consisting of strict geologic controls, mineralogy, and metallurgical data was developed to assist in the determination of the leachable copper resource. An understanding of the accessibility and solubility of the resource to leaching solutions and the integration of hydrogeologic and hydrometallurgical information was necessary for completion of this project.

Jan 1, 1997

By Kevin J. Melong

"Redpath Canada Limited and joint venture partner Thyssen Mining and Construction Canada have recently completed the sinking of the Scissors Creek service in Saskatchewan through its joint owned company, Associated Mining Construction (AMC). The Scissors Creek service shaft was sunk at Nutrien’s Rocanville mine. The following paper outlines the shaft sinking plant and the methodology related to sinking and shaft lining. KEYWORDS Hydraulic shaft jumbo, Hydraulic shaft mucker, Potash shaft sinking, Shaft lining, Sinking galloway INTRODUCTION The sinking and lining of shafts at mines to access mineral deposits has always been one of the great mining challenges for owners, engineers and contractors. Over the course of history in Canadian mining, the sinking of potash shafts through the notorious Blairmore formation of Saskatchewan has proved to be some of the most challenging shaft sinking projects on record. There is no doubt that today’s shaft sinking business demands the utmost in safety performance while delivering projects within schedule and budget. Given these requisites, Redpath and TMCC (executed under the joint venture company, Associated Mining Construction or AMC), were taxed with developing the shaft sinking system to deliver this program in the safest and cost effective manner, with due regard to schedule and quality. Traditionally the potash shafts sunk in Saskatchewan involved a significant level of manual labour, owing to the methodology of excavation by means of chipping the frozen shaft sections with hand held pneumatic machines, and manually placing tubbing segments or steel liners of the shaft lining system. Most certainly, the AMC team wanted to make a step change from those earlier sinking programs and develop systems for sinking this potash shaft that removed the high level of manual work, thus making this project inherently safer, while endeavoring to sink more efficiently. With that in mind, the team embarked on a design program to improve its overall shaft sinking systems without the requirement for excessive capital and methodology flexibility to adapt to potential changing conditions expected to be encountered during shaft sinking. This was especially important should the new approach be met with less than expected success, and retrofitting of the system was required. The concepts were developed to provide for a much improved work environment, while easing the manual labour burden on the workers with innovative equipment and approach to the work."

Jan 1, 2019

By John Wightman

LOCATION OF PROPERTY THE property of Caribou Gold Mines, Limited, is situated in the north-eastern part of Halifax county, seven miles south of the Canadian National railway line at Upper Musquodoboit. Approach to the village is by a secondary road, improved recently by waste rock from the mine dump. A two-wire telephone line, seven miles long, built and owned by the present operators, provides communication to the nearest telephone exchange, Parker&apos;s Corner. HISTORY In 1870, the Caribou area was recognized as a proclaimed gold district. From then on, operations were intermittent, with periods of considerable activity by small companies until there were no fewer than seven mines in a district two miles long by three-quarters of a mile wide. These were the Holman, Truro, Caffrey, MacDonald or Elk, Lake, Dixon, and Hilchey properties, all of which have had separate stamp-mills, and have produced gold for varying periods. Depths of the workings range from 100 feet to 1,000 feet. Power was generated at each property by means of steam boilers. At the present time, the Consolidated Mining and Smelting Company of Canada, Limited, controls all the leased areas, approximately 800 acres, and is operating by means of one central vertical shaft. GEOLOGY The district in and about Caribou Mines has an elevation of approximately five hundred feet above sea level. The area is fairly well wooded, with rock outcrops here and there. These outcrops, along with information from test-pits and shafts, have been the basis for the very excellent geological map of the district prepared by E. R. Faribault some years ago. The rock structure, which is one of the best examples in Nova Scotia of an elliptical dome, has its anticlinal axis in a northeast-southwest direction, and flat plunges in the same directions.

Jan 1, 1938

By M. Abumiya, N. Onodera

"The synthesis of large scorodite particles in non-ferrous metallurgical industries usually requires a high-cost operation involving heating and high-pressure autoclaving. To overcome these obstacles, an atmospheric-pressure process for scorodite synthesis (DMSP®) was developed, in which ferrous ions were oxidized by oxygen gas in the presence of pentavalent arsenic ions. This process gives scorodite of good crystallinity with particle sizes as large as 15-20 µm. The solutions used for scorodite synthesis in the DMSP® are prepared from various residues containing arsenic from non-ferrous smelters. The solutions may be contaminated with Cu, Sb, and Bi, for example, and therefore the effects of such impurities on the formation of crystalline scorodite need to be investigated. In this study, the effects of Cu, Sb, and Bi contaminants on the formation behaviors of scorodite particles in the DMSP® were investigated systematically.INTRODUCTIONThe synthesis of crystalline scorodite (FeAsO4·2H2O) is a suitable method for arsenic (As) stabilization and storage of As-containing by-products such as flue gas dusts in non-ferrous smelters. It is expected that the formation of large, highly-crystalline scorodite particles would be an ideal method for avoiding the release of arsenic to the environment. Generally, autoclave methods under pressurized oxidation conditions at temperatures above 100°C have been used for the formation of arsenic minerals such as scorodite. However, the autoclave method requires sealed vessels that are resistant to high pressure, heat and acids. This process is also unfavorable on account of the high construction expenses, and high running costs as a result of vapor heat loss. Processes for synthesizing scorodite under atmospheric conditions at temperatures below 100°C which do not need an autoclave have therefore been extensively investigated (Demopoulos, Droppert, & VanWeert, 1994; Demopoulos, 1996; Demopoulos, Lagno, Wang, & Singhania, 2003; Droppert, Demopoulos, & Harris, 1996; Filippou & Demopoulos, 1997).Recently, Fujita et al. (Fujita, Taguchi, Abumiya, Matsumoto, Shibata, & Nakamura, 2008a, 2008b, 2009; Fujita, Taguchi, Kubo, Shibata, & Nakamura, 2009; Fujita, Taguchi, Shibata, & Nakamura, 2009) developed a new method for producing large scorodite crystalline particles with improved filtration and washability properties at normal atmospheric pressure and temperatures below 100°C. In the new method, oxygen gas (O2) is blown into solutions containing a high concentration of arsenic ions (As(V)) and ferrous ions (Fe(II)). The Fe(II) ions were subsequently oxidized to ferric ions (Fe(III)), resulting in the formation of large scorodite particles. High supersaturation of solutes such as Fe(III) will result in excessive nucleation, and the formation of poorly crystalline phases. The scorodite formation must therefore be conducted in a manner that avoids the critical supersaturation level being exceeded. It is supposed that the oxidation of Fe(II) to Fe(III) by O2 gas in the new method suppressed the supersaturation of Fe(III) during scorodite formation. The low Fe(III) supersaturation resulted in formations of highly crystalline scorodite particles of size of around 20 µm. In June 2008, based on the developed process described above, DOWA began experiments to verify the industrial capability of a plant with a capacity of 30 MT/month of As. It was successfully proven that it is possible to produce crystalline scorodite industrially on a commercial scale. This process was named and trademarked as DMSP® (Kubo, Abumiya, & Matsumoto, 2010)."

Jan 1, 2012

By E. W. Dean, W. A. Jacobs

"The petroleum division of the Bureau of Mines in its laboratory investigations, has had occasions to develop a number of types of electrical heating equipment. It was found that electric heaters could be used to particular advantage in the standard distillation test for gasoline. (Dean, E.W., Motor Gasoline, Properties, Laboratory Methods of Testing and Practical Specifications, Bureau of Mines Technical raper 214, 1919, 33 pages.) In order to assist in rendering this type of heater available for general use, a description of the apparatus developed by the Bureau was published. (Dean, E.W., A convenient electric heater for use in the analytical distillation of gasoline,. Jour. Ind, and Eng. Chem., Vol.10, 1918, page 823.) Shortly after the article was printed a chemical supply house undertook the manufacture of an electric heater suitable for gasoline distillation. A preliminary model was examined and tested by the Bureau and modifications were suggested that were incorporated in the type of heater that was finally marketed.Description of the Bureau of Mines-heater: The electric heater developed by the Bureau has an inverted conical resistance Plament surrounded by a layer of heat-insulating material and mounted in a metal case having a top of hard asbestos (Transite) board. The resistance element is a helix of nickel-chromium alloy wire held by a molded core of alundum. The Bureau heaters are generally of about 330 watts capacity and are used with stock types of regulating rheostats capable of reducing the effective wattage to about 43 the full-load maximum."

Jun 1, 1920

By Dennis E. Peterson

Land subsidence had been observed in recent years throughout the Southwest. Particular examples of this phenomenon that have gained wide publicity axe in the Long Beach and Central Valley areas of California and, the Houston area of Texas. Less well known is the fact that the land surface Is subsiding in many parts of Arizona, including the Phoenix area. The causes of this problem vary from place to place, as do also the rates of subsidence. In Houston it has been related to pumping water from artesian aquifers; in Long Beach to the development of oil fields; and in the Central Valley to both the lowering of artesian pressures in deep aquifers and the wetting of poorly consolidated surficial deposits. The mechanism by which subsidence occurs in southern Arizona, even though it can be correlated with the continued lowering of ground water levels, is not as apparent as in these other cases. It is the purpose of this paper to examine both the causes and affects of land subsidence in southern and central Arizona.

Jan 1, 1965