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By D. C. Sharpstone

THE Polaris-Taku mine is a new gold property, situated in the far north-west corner of British Columbia. Production was started in November, 1937, at the rate of 150 tons a day, and recently has been increased to 200 tons. The property, which promises to become one of British Columbia's important gold mines, was developed and brought into production in twenty-nine months after work was started on it as a virtual prospect in June, 1935, by Edward C. Congdon and associates. Inaccessibility, extraordinarily complicated geological problems, and difficult metallurgy retarded development of the property before acquisition by the present interests, an::l, in fact, discouraged two companies that had spent substantial sums upon it from continuing development. This paper is concerned with reviewing the development of the property and describing the principal features of the geology, the mining and metallurgical practices, and the equipment employed. Acknowledgments The writer is indebted to Mr. Edward C. Congdon, President of the Polaris-Taku Mining Company, and to various members of the mine staff for their assistance in assembling the data for this paper. Special thanks are due to Mr. George G. Griswold, Jr., of Butte, Montana, who generously and painstakingly prepared the section dealing with milling and power. Microscopic studies of ores were made by Professors Frank Grout an::l G. M. Schwartz, of the University of Minnesota, and by Mr. Griswold.

Jan 1, 1938

By W. L. Hunter

This report describes results of beneficiation and smelting studies conducted by the Federal Bureau of Mines on chromite samples from the Emma Belle and Seiad Creek prospects in the Seiad Creek area, northern California. Samples were chosen from this area because the ore is typical of disseminated types that represent a sizable domestic reserve. The two samples were similar in composition, and both responded in like manner to gravity beneficiation. As the ore was banded, considerable coarse gangue was rejected in laboratory sink-float from a minus-3/4-inch, plus-6-mesh fraction without excessive chromium loss at a medium density of 3.32. An average of 85.6 percent of the chromium was recovered in the sink product, which analyzed 35 percent chromic oxide (Cr203). Tabling yielded concentrates containing 49 percent or more Cr203; however, recoveries, ranged from only 33 to 45 percent. A combination of tabling and electrostatic separation of the table middlings showed that the chromium recovery could be increased to about 73 percent; the composite concentrate averaged 53 percent Cr203.

Jan 1, 1960

By G. S. Knoke

This report presents the results of a demonstration of the technical, economic, and environmental feasibility of hydraulic borehole mining of shallow oil sands. Borehole mining offers a method for extracting the oil sands with minimal disturbance to environmental quality because (1) no overburden is removed, (2) no waste rock piles are required, (3) the tailings can be backfilled into the borehole cavity, (4) the ground water quality should be undisturbed, (5) a closed-loop water system can be employed so that no surface streams are polluted, and (6) surface subsidence can be minimized by backfilling the mined cavities. This project consisted of two concurrent tasks: mining operations and environmental monitoring. To generate the environmental impact, nearly 1000 tons of oil sands were mined from two boreholes. Water quality and ground subsidence were monitored. No significant changes occurred in the chemical composition of the process water, indicating that the borehole mining process does not dissolve the mined material. The average subsidence in the immediate vicinity of the boreholes was about 1/2 inch, although some points were noted to be slightly elevated. In general, the amount of subsidence increased with time and decreased with distance from the bore-hole. A mining cost analysis was used to project an estimated cost for production mining of about $38 per barrel of oil.

Jan 1, 1980

By J. Davis, M. G. Reading

"INTRODUCTIONInternational Minerals and Chemical Corporation (Canada) Limited operates two potash mine/refinery complexes near Esterhazy, Saskatchewan. Annual production of approximately 4.2 million tons is sold in the United States and overseas in five grades according to size and quality.Ore grading 25% K2 0 equivalent is mined from a horizontal bed by continuous boring machines, crushed, and hoisted at 8 inches. The refinery operation consists of the eight basic steps shown in Figure 1. Particle sizes handled are similar to those experienced in other forms of mineral beneficiation: 8 inches to 100 mesh. The ore is crystalline and particles are angular. Fortunately the major mineral constituents, sylvite (KCl) and halite (NaCl), demonstrate relatively low hardness at 2 to 2.5.Therefore, while simple abrasion must be acknowledged, it is not a major problem except, of course, in circuits carrying magnetite.Corrosion, as represented by the classic equations of Figure 2, occurs in all its various forms."

Jan 1, 1983

By F. C. Canney

Geochemical prospecting seeks hidden mineral deposits by sampling for variations in the chemical composition of naturally occurring materials. Usually the samples are of soils and other products of weathering and erosion—surface materials extremely susceptible to contamination by human activities. Except when a survey is conducted well away from populated areas, contamination is an ever-present hazard. The program's success is particularly endangered when the contaminants are the elements sought; if these occur erratically throughout an area, spurious anomalies completely unrelated to mineralized areas can be formed. Evenly distributed contamination can be dangerous too, if it raises the background to such a level that true anomalies can no longer be easily detected. Suppose, for example, that in an area where the lead background is 20 parts per million the soil over a lead vein contains 1000 ppm of lead. Here the contrast would be 50 to 1, which is very satisfactory for geochemical surveying. Now if 1000 ppm of lead from some source were added evenly to the soil in this area, the contrast would be reduced to about 2 to 1, and the anomaly would no longer be readily detectable because a threshold of significance twice the value of the background is the minimum generally used for interpreting geochemical data. Of the many possible sources of contamination, probably most important are smelter fumes, which may distribute large quantities of metal contaminants over many square miles of ground. For several reasons, the investigation reported here was begun in the Coeur d'Alene district in northern Idaho: 1) a lead smelter has been operated in this district since 1917 and an electrolytic zinc plant since 1928, and presumably the contamination patterns are strongly developed; 2) to evaluate the usefulness of certain geochemical techniques, V. C. Kennedy and S. W. Hobbs of the USGS had already studied the distribution of copper, lead, and zinc in the soils (both in background areas and other veins) and in the water and plants, providing a criterion for measuring the magnitude and effect of soil contamination; 3) one of the economically important parts of the district lies south of the South Fork of Coeur d'Alene River and within a radius of five miles of the reduction plants near Smelterville (Fig. 1). In this area, and in the entire district, conventional methods of prospecting are hindered by heavy vegetation and thick soil cover, and the possibility of contamination by smelter fumes has discouraged geochemical prospecting. Should data reveal that geochemical prospecting could be done successfully in such an area, a particularly useful tool would be available to mining companies and prospectors searching for concealed orebodies in this economically important part of the district. The field work on which this report is based was done from July 28 to 31, 1955. It should be emphasized that this was reconnaissance study only, and therefore far from exhaustive. Previous Investigations in U. S. : The first geochemical survey known to have been affected by contamination was conducted in 1940—a geobotan-ical reconnaissance made in the Michigan copper district by a private company. Geologists found striking variations in the copper content of oak and maple leaves, but unfortunately the high copper isograds of the study seemed to be related more to the Calumet and Hecla copper smelter fall-out than to mineralized ground.' The leaves of one oak tree near the smelter contained 0.4 pct Cu. Similar contamination was reported by Clarke (Ref. 2, p. 41), who conducted experimental geochemical soil and botanical surveys at Ray, Ariz. He found that the leaves of oak trees growing in unmineralized ground near Superior, Ariz., contained more copper than the leaves of oak trees growing on the capping of the Ray orebody and attributed this fact to contamination from the fumes of the Magma smelter at Superior. According to H. E. Hawkes,3 soils and stream sediments in the Superior area are also severely contaminated. Hawkes' work there has shown a copper content averaging 0.5 pct in the surface horizons of soils within one mile of the smelter stack. Samples taken only a few inches below the anomalous surface samples showed only background copper values. In 1950 L. C. Huff' of the USGS made a geochemical survey in an area near Jerome, Ariz., and found considerable zinc and copper in the soils over unmineralized basalt close to Clarkedale, Ariz., and over limestone close to Jerome. As the amounts were notably greater than could reasonably be expected to be derived from the underlying rocks, Huff suspected airborne contamination from the smelter at Clarkedale. Description of Area: The area sampled in detail (Fig. 1) for the study presented here is one of strong relief. The dominant watercourse is the westward-flowing South Fork of the Coeur d'Alene River. East of Kellogg the South Fork flows in a rather narrow canyon, but its valley floor widens considerably to the west where much of the flood plain is covered by an extensive veneer of mining, milling, and smelting debris. South of the South Fork and between Big Creek and Pine Creek is a mountainous area where

Jan 1, 1960

By P Guj, J A. Bell

The valuation of early-stage exploration projects requires a valuer to take into account a large number of uncertain value drivers, the interplay among which may be non-linear. This paper examines some of the key value drivers including geology, target metrics, project area and maturity, the market and the psychology behind the decision-making process. The commonly accepted valuation methods and their underlying logic are outlined, including a view on why they evolved, what value drivers they attempt to address and their potential shortcomings. These methods include the multiple of exploration expenditure, geoscience rating, expected values and market based methods. The potential future valuation methods of replacement values and neural networks are also introduced along with how to minimise heuristic bias and error within the market-based approach.CITATION:Bell, J A and Guj, P, 2012. Exploration value drivers and methodologies, in Proceedings Project Evaluation 2012 , pp 17-28 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 24, 2012

By Yushiro Hirai

Saganoseki smelter & refinery had operated two flash smelting furnaces from 1973, attaining 330,000 mtpy of copper production in 1989. In 1996, however, it carried out a "integration of two flash furnaces". That is, it doubled the feeding capacity to one flash furnace to shut down another furnace while maintaining the same production. Single flash furnace operation has successfully started in March 1996 accomplishing a great reduction of the total production cost. The production had reached to 350,000 mtpy in 1997, and further increased to 450,000 mtpy by executing the expansion program with single flash furnace in 1998. This paper introduces results of the single flash furnace operation and describes about an outline of the expansion.

Jan 1, 1999

By O. Bernal, G. Velarde

Sociedad Minera Cerro Verde, majority owned by Phelps Dodge produces 200M lbs per year of LME Grade A copper from low cost leaching of secondary sulfides and SXEW processing. Central to the success of Cerro Verde has been the continuous improvement of leaching practices which currently yield over 80% recovery of the contained copper in the ore. This recovery has been achieved by careful attention to operational practices and leaching process fundamentals. This paper details the development of the concept of “Lixiviant Request Rate” where by solution is applied at an optimal rate for the grade, mineralogy, and the point in the leach cycle. Also paramount to the success of Request Rate technology has been the development of irrigation practices such as drip irrigation and irrigation grid design. These developments have ultimately resulted in improved copper production, decreased sulfuric acid and water consumption, decreased pumping cost, and more consistent PLS grades.

Jan 1, 2004

By Hiroyuki T. Takeshita

Ca-Ni based alloys were investigated on structures, hydrogenation properties and the effect of additive elements on hydrogenation properties. CaNi, samples were decomposed to form a new hydride with a CsCl-type structure on the constituent metal atoms at high temperatures such as 673K in a hydrogen atmosphere. The candidate of the third element which was added to stabilize the original compound was investigated by using the Miedema's semi- empirical model and, as a result, Pd was chosen. The hydrogenation of CaPd was conducted with a Sieverts' type apparatus and the synthesis of Ca-Ni-Pd ternary alloys was performed by high frequency heating.

Jan 1, 2002

By Andrew Brown

"In recent years operators of brown-ore mines have shown increasing interest in .the reclamation of ore heretofore lost in tailing ponds. In January and February.1945 the author made a preliminary survey of the ponds in the Russellville district, Franklin County, Ala. The Russellville district (fig. 1) was chosen for the preliminary work because it contains many large ponds in a comparatively restricted area. All important properties in the district were visited with Charles R. Wilson of Russellville, who has been familiar with the Franklin County brown-ore industry since 1890; with Edmund Craddock and W. S. Blackburn, managers of the two washers now operated near Russellville by Shook & Fletcher Supply Co., and with S. A. Britton, manager of the Sloss-Sheffield Steel & Iron Co. washer. The larger ponds were measured roughly and tonnages estimated. and samples taken from different areas were analyzed and beneficiated at the Southern Experiment Station of the Bureau of Mines; Tuscaloosa, Ala.The ponds explored were the Sloss No.1 (Ensley); the Sloss No. 8, and the Sloss No. 4-5, which are among the largest in the district and so located, within an area of .three square miles (see fig. 2), that ore from all of them could be-treated,one centrally located washer.Actual work was begun on May 9. Between that date and June 30, when field work was completed, 246 holes in ponds were drilled and sampled, and 15 additional holes were put down primarily to test the drill .in different types of ground with a view to its possible utilization in other types of prospecting. Samples from all holes were analyzed for iron content; samples from 13 holes were sized and analyses made for each size fraction, and six large samples have been composited for beneficiation tests.Brown iron ore has been mined in the Russellville district since 1815, when the first blast furnace in Alabama was built in NW1/4 sec. 10, T. 7 S., R. 12 W., about 3 miles southwest of Russellville (19).-J The furnace was abandoned before the Civil War, and mining continued on a small scale until 1888, when Enoch Ensley began to mine the ridge between Russellville and Pain Creek. His first washer, Ensley No. 1, was about 300 feet south of the junction of the present Tharptown road with the Waco spur of the Southern Railway."

Aug 1, 1946

By Nikolaos Polysos, Holger Witthaus

INTRODUCTION The classification system for German coal mining is the result of approximately 100 years of experience in roadway development and longwall mining. It is also based on different research projects covered by national and European research programs. Over the past 30 years, more then 600,000 m of road-ways have been driven and employed for mining activities. To properly describe the German rock mass classification system, therefore, it is useful to take a look at the main geomechanical preferences and common support systems. The decision about the most effective development technique and support system is based on a synthesis of rock mass classification and geomechanical analysis. The properties of surrounding rock, the in situ stress, and the influence of mining activities in several seams at each German mine must be considered for the evaluation of the expected deformation of the roadway. The mine layout, the requirements of ventilation and fire prevention, as well as the need to maintain emergency escape routes for the miners, require that the gate roads remain usable after the passage of the longwall face in most cases. Moreover, the gate roads must be maintained despite the high stresses that are applied during longwall retreat mining. Therefore, gate road design must address a broad spectrum of potential deformation environments. In the past, when gate roads were supported solely with yielding steel arches, lithologic descriptions of the surrounding strata conditions were adequate for the dimensioning of support and the prediction of the roadway deformation. The current conditions of multiple-seam mining at depths of up to 1,700 m require combined support systems, including pattern bolting and backfilled steel arches. Rock bolt support is used for development, after which (typically 50–100 m outby the face) the steel arches are installed and backfilled with building material (concrete) in order to achieve an optimized development rate. The rock mass classification system described below was developed especially for the conditions of German hard-coal mining. It includes the stress distribution caused by multiseam workings (including crossing goaf edges of former longwalls), as well as in situ stresses due to greatdepth and the presence of tectonic faults. It is based on the evaluation of four parameters: • Geotechnical analysis of drill cores • Geotechnical observation of the development face • Geotechnical classification of tectonic structures (faults) • Standard classification derived from geotechnical assessment and evaluation of stress conditions (using numerical modeling for stress calculation) ROCK STRENGTH One of the most important input parameters for describing strata conditions is the strength of the rock. The German classification system is based on a description of lithotypes. This method has been used successfully since the 1950s and is based mainly on the uniaxial compressive strength (UCS) of the material. An evaluation of the rock strength observed in a survey of approximately 82,500 samples of rock core yielded the results shown in Figure 1. The three most common coal measure rock types are mudstone, siltstone, and sandstone. Each shows a specific mean UCS level and a different spread between the minimum and maximum values. Sandstones, in particular, have a wide spectrum of compressive strength, ranging from approximately 40 MPa to greater than 130 MPa, with an average of 85 MPa. The causes of this wide range include different sedimento-logical preconditions, facies, and digenetic processes. [ ]

Jan 5, 2007

James Barnes is Managing Director of James Barnes & Associated Ltd which is a company that has invested ten years of development to provide developers with a transparent, user friendly consultation framework that identifies who needs to be consulted, how they are to be consulted and procedures required to manage the risks associated with getting all the wrong! Despite the assertion above, this paper is not about to provide delegates with the answer to whom they ought to consult or identify the expectations that Maori might have in regard to the consultation process. It would be a very brave person indeed who would venture an opinion on such a sensitive subject. There are no short cuts to finding out what expectations Maori might have on any given situation. Nothing can be taken for granted. What this paper will attempt to do however is provide practical insights into what might be on the minds of Maori interests as they deal with the issues associated with mineral resources, particularly those under Treaty of Waitangi Claim. The Treaty of Waitangi has a significant bearing on the current debate between Maori and the Crown regarding ownership of mineral resources in New Zealand. The Waitangi Tribunal is currently hearing a case presented by a number of Iwi over the ownership of oil and gas resources in Taranaki and Hawkes Bay. Others will follow. The Crown and Maori have never been able to settle differences over ownership rights without resorting to legal action and it looks like this scenario is about to be repeated in regards to minerals. The Crown has a duty to actively protect the Maori interest. This is a fundamental expectation in the relationship between Maori and the Crown. In the case of minerals, Maori have yet to see the Crown do its duty. The impact on developers has become evident through Maori objections to consent applications as the issues of mineral right remain unresolved.

Jan 1, 2000

By Congcong Chen, Bo Ma

When assessing the safety of a tailings dam, the constant weight method (CWM) is one of the most commonly used methods. However, when the evaluation indicator value suggests serious defects, the evaluation value is often inconsistent with the actual situation. To address this issue, the variable weight method (VWM) is introduced to assess the safety of the tailings dam. Initially, a three-layer indicator system for dam failure safety assessment is built, and individual indicator values are divided into four grades. Then, an appropriate state variable weight function is constructed and relevant parameters are determined. Finally, a case study is illustrated to verify the effectiveness of the model. The assessment results of the VWM more closely represent the actual situation than that of the CWM, which is more helpful for decision makers and technicians to take scientific and reasonable precautionary measures, thereby improving the safety management of the tailings pond.

Oct 8, 2022

By S. J. Rodgers

This report presents the results of in-mine studies to determine the severity of dust sources in conventional mining operations. Three underground coal mines were surveyed using gravimetric samplers and GCA RAM-1 continuous dust monitors. Two additional mines were surveyed using only GCA RAM-1 monitors. Data on dust control methods were acquired during the survey, also. The results indicated that cutting/drilling and loading out were the dustiest operations during a conventional mining cycle. Roof bolting, shot firing and product transport were less severe dust sources.

Jan 1, 1983

By M I. Roberts

As Australia’s mining industry painfully retrenches, mining executives and managers strive to remain viable by seeking significant productivity increases directly through process improvement and indirectly by improving leadership and workplace culture, the most powerful determinant of productivity. Culture is the combination of people’s attitudes and behaviour, together with leadership values and focus.Comprehensive new and automated data collection and management systems promise much for improving productivity, yet despite rapid advances in measurement and sharing of data, the use of data can reduce productivity unless behavioural aspects are considered and designed as part of implementation. This is because systems drive behaviour that in turn shapes attitudes to determine culture.Experience from many mine sites and other industries in three countries confirm that the most powerful drivers of people’s behaviour are the Measurement-Analysis-Reporting system and business leadership.This paper discusses fundamentals of practical, statistically valid process measurement, analysis and reporting systems before discussing associated leadership considerations for sustained improvement in safety, productivity, employee retention, leadership, accountability and commercial returns.The key to productivity improvement is improving core processes and important support processes. In turn, the key to process improvement is identifying the major process components and their interaction by measuring and then analysing their variation and level of performance. Understanding variation is often neglected yet is usually highly significant. It is essential that the fundamentals of statistically valid yet practical process and data analysis are understood and incorporated into system design to ensure productive, informed behaviour.The design and use of Measurement-Analysis-Reporting systems influences behaviour most profoundly and determines people’s effectiveness. Behavioural aspects are detailed by focusing on six primary drivers of human behaviour and five basic systems for managing businesses. These are integrated in a seven-step process and productivity improvement methodology that combines statistical, analytical, systems and behavioural factors.The paper includes development, implementation and tracking of a project plan for improving management and leadership systems to drive aligned behaviours. This key leadership responsibility is essential for improving performance to get the most from capital while providing people with the opportunity to develop greater autonomy, which is essential for self-discipline, responsibility, initiative and accountability.CITATION:Roberts, M I, 2015. Integrating measurement, systems and leadership to build safe, productive cultures, in Proceedings Third International Future Mining Conference, pp 73–82 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 4, 2015

By O&apos, M. W. Neill

Mini-piles have been found to be a practical, technically correct remedial underpinning method. They can be constructed in limited access areas with very little disruption. Experience indicated that mini-piles installed using a down-the-hole soil displacement hammer would be particularly effective in the "bottomless" Beaumont Clay formations in the Houston, Texas, U.S.A. area. The University of Houston Foundation Testing Facility was ideally suited to perform tests on mini-piles. The availability of extensive geotechnical data and previous pile test results was invaluable in evaluating the mini-pile test data. As expected, the mini-pile test results were consistant with test results from large sized driven piles in the same soil formation.

Jan 1, 1989

By Q. G. Reynolds

DC arc furnaces are widely used for steel scrap melting, and are increasingly being used for smelting applications as well. The electrical resistivity of slags varies widely, from highly conductive slags in ilmenite smelting, to highly resistive slags in applications such as cobalt recovery from non-ferrous slags, and nickel laterite smelting. Models have been developed to predict the electrical behaviour of the DC open plasma arc and the molten slag bath. These models allow the voltage and current ranges of furnace power supplies to be specified.

Jan 1, 2004

By William G. Pariseau

Solvay Chemicals Company mines trona in south-central Wyoming and has done so for many years. The mine is one of several in a mid-continent sedimentary basin that hosts the largest trona resource in the world. Trona is an evaporite, a sesquicarbonate that occurs in several seams of varying thicknesses and depths. Trona is processed into soda ash which has a number of industrial uses in the manufacture of glass, detergent, paper and chemicals. Figure 1 shows the location of the Solvay Mine. A ventilation shaft was recently excavated at Solvay Chemical Company’s mine in the trona patch. In fact, a 22 ft (6.7 m) diameter shaft (inside diameter) was bored upwards from the 1500 ft (457 m) level to the surface. The first bored section was 26 ft (7.9 m) in diameter that allowed for a 2 ft (0.6 m) thick concrete liner. This section began at a depth of approximately 1500 ft (457 m). A second bored section was 24 ft, (7.3 m) in diameter that allowed for a 1 ft (0.3 m) thick concrete liner. This section began at a depth of approximately 750 ft (229 m). This shaft is the #5 Shaft. Figure 2 shows the cutter head used to excavate the shaft.

Feb 1, 2025

By Francis Foley

IN examining steel under the microscope, one is constantly confronted with structures that are difficult to interpret. Recently, in a collection of samples for exhibition purposes, the writer found apiece of open-hearth runner metal, 2 in. (50 mm.) in diameter, that had been fractured for use as a sample of cast-steel structure. On polishing and etching a section for the purpose of photographing a field to typify the microstructure of steel in the "as cast" condition, a variety of structures was found (Fig. 1) so arranged as to arouse interest at once. For a distance of about 0.065 in. (1.6 mm.) from the skin of the runner, normal ingot structure was found (Fig. 2); this was followed by a zone, about 0.215 in. (5.5 mm.) wide, of considerably lower carbon content in which occurred a most pronounced Widmannstättian structure (Fig. 3); from this point on to the center of the runner, the metal was again of normal ingot structure (Fig. 4). Representative samples taken from the metal in the three zones showed the following analysis: C Ni Cr Metal from skin 0.34 1.26 0.63 Widmannstättian zone 0.21 1.18 0.63 Metal from center 0.34 1.32 0.67

Jan 7, 1919

By R Blair

The Domain and Burnley Tunnels, which are major features of the Melbourne City Link Project, are MelbourneÆs first road tunnels. They are 1.6 km and 3.5 km in length respectively and are being constructed through a variety of ground conditions. Deeper sections of the tunnels have been driven through the Silurian mudstone which underlies Melbourne. Other shallower sections of the tunnels pass through a variety of ground conditions including silts, sands, clay and rock and have been constructed using both top-down and bottom-up cut and cover construction techniques. The Yarra River Crossing is a 140 m length of the Domain Tunnel which crosses under the Yarra River on a relatively shallow alignment. The crossing of the river using cut and cover techniques was identified in the early stages of design development as being one of the most challenging stages of the works on the Southern Link. The prevalence of varying geological conditions combined with the need for maintained traffic and stream flow conditions provided a demanding and often conflicting set of criteria for which there appeared to be no one clear solution. A team of designers, constructors, estimators and specialist contractors were involved in a concept evaluation and risk analysis study spanning a period of approximately 12 months. During this study, four concepts were considered as likely contenders. This paper provides a brief outline of the four concepts addressing their relative merits, disadvantages and risks followed by a detailed description of the adopted solution, namely top-down construction using secant pile walling (east bank) and bottom-up in situ construction (west bank).

Jan 1, 1999