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By Friedrich Steinhäusler

RADON SOURCES AND CONTROL MEASURES IN THE MINING ENVIRONMENT Most of the contamination of the mine atmosphere by radon 222 is due to radon emanating from solid or fractured ore surfaces of walls, roof and floor. Also radon gas emanates from broken ore either from storage in backfilled mined-out areas as applied in e.g. shrinkage stopping methods or from ore spillage along intake airways mainly due to the use of trackless haulage. To a lesser extent water itself can represent an additional source of radon, which emanates into air from open drainage ditches or seepages along intake airways. The contribution from water can be controlled effectively by isolating the water from the primary intake air system, e.g. by diverting the water through pipes and/or sealing of seepages by grouting. However, control of radon emanating from rock surfaces creates a major technical problem with significant impact on the economic aspects of mining operations, if adequate radiological conditions must be maintained. Basically this can be achieved by suppressing the emanation process itself, confining already emanated radon or by removal of radon from the mine atmosphere. Extensive research has been carried out on the rate of radon emanation as a function of barometric pressure changes (Pohl-Rüling and Pohl, 1969). It could be shown that the radon supply consists of a permanent and variable component. The former results from the surface of the rock and depends mainly on the emanating fraction of its radium 226 content; the latter originates from within the rocks and is a function of the suction effect of decreasing barometric pressure, rock porosity and fissures. The practical application of this barometric pump effect for depressing the rate of radon emanation, e.g. by pressurizing the mine atmosphere, is limited due to high costs for providing a sink for absorption of radon and air as well as lack of permeability in most uranium ore bodies (Schroeder et al., 1966). Mine air cleaning by removal of radon can be achieved with the use of cryogenic methods, chemical removal, adsorption into charcoal beds, use of a gas centrifuge or general ventilation techniques. Technical problems have so far prevented the application of any of these methods other than ventilation. It is common practice to use the age-of-air concept, i.e. fresh air is delivered to the worker as directly as possible and removed quickly afterwards thereby maintaining the air "young". Engineering principles for quantity distribution of air through underground working areas are straightforward for general mining situations where radon constitutes an environmental contamination problem. However, in cases of high uranium ore content this concept may result in high costs with regard to installation and energy requirements for effecting both frequent air changes as well as sufficient heating of the air in cold seasons. Taking into account that the investment in ventilation systems is a major cofactor for the overall ore production costs this can be a limiting and decisive component in the assessment of the economic feasibility of specific mining operations and mineral reserves in general. Effective control of the radon flux from the rock surface prevents the initial contamination of the mine air with radon directly at the source. A radon diffusion barrier for practical application in mining requirements should fulfill the following requirements: - reduction of radon emanation rate by at least an order of magnitude - high mechanical strength - ease of sealant application onto surface to be coated - water resistant - low fire hazard - resistant to temperature changes encountered in mines - high cost efficiency in relation to exposure reduction achieved (direct and indirect costs) - low degree of maintenance. In the past several materials have been tested as sealants for controlling the emanation of radon from surfaces of rock and building materials. Epoxy paints reduce radon emanation rate only by a factor of 2 to 6 (Auxier et al., 1974; Eichholz et al., 1980; Keith Consulting Engineers, 1980). Although it is possible to prevent the escape of more than 99 % of the radon to the environment with gel seals over 80 mm thick (Bedrosian et al., 1974), practical applicability is very limited. Multilayer coatings of epoxy resins with various additives require meticulous preparation and flawless application of seamless four-layer coatings in four days to impede radon diffusion (Culot et al., 1976), otherwise results from this method have not been totally satisfactory (Leung, 1978). Aluminium foil laminated with polyethylene and paper on each side is under test as radon barrier but results are not available yet (Ericson, 1980). However, this method has the inherent disadvantage that possible malfunctioning electrical installations can cause fire or electrical shock through the sealant. Polyurethane foam coatings have been used on stoppings as very effective sealants. It does, however, represent a potential danger of spontaneous ignition and it is expensive (Rock, 1975). Thus, there is still need for a material which has similar properties as outlined above. In the following results are reported from investigations on the suitability of various materials as radon diffusion barriers.

Jan 1, 1981

By Francesco Chiappalone, Marco Invernizzi, Franco Gasperin, Fabrizio Fara

As part of the Ship Canal Water Quality Project, 2.7-mile Combined Sewer Overflow tunnel is excavated with a 21.5-foot diameter EPB Tunnel Boring Machine. Due to the difficult geological and hydrogeological conditions, the tunnel is excavated maintaining a ground support pressure between 1 and 3 bar imposing significant challenges to the projects. The first part of the paper describes the general characteristics of the project while the second part focuses on the challenges and technical details of the pressurized breakthrough that took place in a deep shaft excavated in urban environment as part of the project.

Jun 23, 2024

By Michael E. Lively

DOUG HALBE: We've talked about copper operations and gold operations. For our third section on the topic "Operating Ideas That Have Saved Me Some Bucks," we'll turn to the coal fields. Our featured speaker is, I'm almost embarrassed to say, a mining engineer, Mike Lively. Mike has 25 years' experience in the coal industry. He is currently superintendent of surface operations for Southern Ohio Coal Company, Meigs Division (AEP Company). I've read his paper, and there's some really great information here. Mike.

Jan 1, 1998

By R. R. Graham

Echo Bay Minerals operates a 650 tpd gravity float gold circuit at their Manhattan facility. The objective of this paper was to document the gold recovery by size distribution. This was accomplished by studying the material balance of each size fraction as it progressed through each gravity Circuit separator. It proved to be an impossible task. Figure I depicts the gravity circuit. The gravity cyclone underflow goes to two duplex Pan American type jigs. The jig overflow reports to the OK Flash Float Cell. The cyclone hutch product is reground and goes to a full size wilfly table. The rougher table concentrate reports to a pilot size Wi1fly cleaner table. The cleaner and rougher table tails circulate back to the jig feed. The gravity circuit was composite sampled for two to four hours per day for four days. Each sample was taken every 20 minutes. Each composite sample was filtered, dried, repu1ped, and screened through a wet/dry screening procedure. Each size fraction was checked for gold value by fire assay fussion technique. A material balance was run on each size fraction. The tables listing the results are enclosed.

Jan 1, 1989

By Daniel G. Ganey

Kerr-McGee Coal Corporation has used diesel face haulage and support equipment at its dual-seam Galatia Mine in Southern Illinois since production activities commenced in 1983. The mine began production from its lower seam, the Harrisburg No. 5 coal seam, in October 1983 and from the upper Herrin No.6 coal seam in April 1985. Before production began, the company developed a program designed to make use of the flexibility offered by diesel equipment. While productivity was an important goal, the top priority of the program was to provide a safe and healthy work environment for the miners. Management believed that high productivity would naturally follow. History has proven this belief to be true.

Jan 1, 1990

By William J. Ferguson

At Henderson Operations the 24-kilometer conveyor system consists of three main conveyors with lengths of 1.2 km, 16.7 km and 6 km. Upon commissioning of the conveyor system, the Henderson maintenance department was challenged with the inspection and monitoring of over 50,000 idlers. To take a proactive approach to idler maintenance, an idler tracking database system was developed. Using the idler tracking program, the Henderson Crush & Convey department now has the ability to provide data for engineering solutions to idler problems and to manage thousands of idlers for priority replacement work and warranty purposes. Recognizing the potential for injury to Henderson employees in the process of idler handling, Henderson approached idler replacement as a material handling process. Material handling solutions have resulted in failed idlers being replaced and discarded from the underground environment without ever touching a human hand. This paper will detail how Henderson tracks idlers in all primary conveyor belts and how an innovative idler handling system can result in reduced risks to conveyor maintenance employees.

Jan 1, 2004

By Rimas Pakalnis, Lyndon Clark, Tom Brady

A major focus of ground control research presently being conducted by the Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) is to incorporate data on weak rock masses into existing design relationships, with an emphasis on updating the span design curve for manned entries and the overbreak curve for longhole entries. Both curves were originally developed at the University of British Columbia, Vancouver, BC. The original database has been augmented by information from mines throughout the United States, Canada, Australia, and Europe. The common factor in all these mines is the presence of a weak back and/or walls. In most cases, the ore zone is the weakest rock unit and must be stabilized so that the mineral-bearing rock can be extracted safety. The current NIOSH research attempts to provide rock mechanics tools to assist a mine operator in making economic decisions that will also ensure a safe working environment. This paper documents the Nevada database with a special emphasis on Nevada underground gold mines.

Jan 1, 2005

By Victor F. Hollister

This section describes two exploration models currently used in the search for porphyry exploration deposits: the hood and the vertical cylinder. Each has alternate names within industry and in the literature. The hood is also known as the Climax or Henderson and the vertical cylinder has also been called the Mt. Pleasant model. The paper by Hollister (1978, abstract herewith) refers to the vertical cylinder as the zoned model in reference to the horizontal sulfide and silicate zonation evident in and peripheral to the vertical cylinder of molybdenite mineralization. The distinct ore body geometry in each model type necessitates differing drilling and exploration strategies. Drilling for a hood shape is clearly different from drilling for a vertical cylinder type target. The paper by Wallace et al. (1968, abstract herewith) on multiple intrusion and mineralization at Climax, CO, well describes the hood model. That description is supplemented by the paper by Wallace et al. (1978, abstract with Chap. 37) on the geology of the Urad and Henderson deposits. The paper by Hollister (1978, abstract herewith) describes the vertical cylinder model.

Jan 1, 1991

By Howard A. Jongedyk, Jerry Wachtel

Advancements in tunneling technology and underground construction, plus rapidly rising costs of land, and a higher priority being placed on urban esthetics, make tunnels a more attractive option for certain portions of the highway construction program. Recent emphasis placed on fuel conservation reinforces the need for tunnels as a means of shortcutting circuitous routings designed to avoid potentially undesirable environmental impacts on any given area. Larger and more complex tunnels which have been constructed in recent years attest to this greater interest. More than 100 major highway tunnels are in operation in the United States. Highway tunnels commonly have much higher initial cost compared to surface routes. Where extensive cut and cover is involved, temporary disruption of the surface area may prove costly. In exchange for these costs, certain environmental advantages result. The purpose of this paper is to discuss some of the environmental advantages of highway tunnels and some of the unsolved problems related to obtaining maximum use of highway tunnels and research underway to help solve these problems.

Jan 1, 1974

By B. P. Boisen

INTRODUCTION Application Measurement of rock deformation is essential to stability and behavioral monitoring of underground openings. The difficulties of obtaining adequate sample distribution, density, and orientation can frequently be overcome by the use of single and multiple position borehole extensometers. In its simplest form, a borehole extensometer consists of an instrument head, usually anchored in the collar of a borehole, and a number of in-hole anchors, each of which is fixed in place at a known distance from the collar. As rock adjacent to the borehole deforms, the component parallel to the borehole direction causes a distance change between adjacent in-hole anchors, as well as a distance change between individual anchors and the instrument head. These changes are measured by means of a mechanical link (usually wire or rod) extending to the instrument head from each anchor. The resulting data can be used to compute the distribution, magnitude, rate, and acceleration of deformation in the material intersected by the extensometer's borehole. Wire Vs. Rod Extensometers Since the early 1960s myriad varieties of borehole extensometers have become available through the combination of various special features of two basic instruments, the wire and rod versions of borehole extensometers. Recent publications have recommended shallow depth limitations for wire extensometers, and favor rod extensometers for a broad range of borehole inclinations and depths. There are three main reasons for using a deep wire system: its cost effectiveness; the fact that tremendous depth means tremendous rod weight which will cause the rod to buckle or rub against the borehole or casing wall; and users' attitude and proper understanding of how to install and apply a wire-type extensometer. Here experience plays a big role. Over the years, many have learned the hard way that untensioned rod extensometers are simple and inherently inexpensive, but limited to vertical up holes where sensitivity is not influenced by friction between the rod elements and the borehole wall or protective conduit, the inertia of the rod elements, or the direction of the movement to be measured. In deep, horizontal, or inclined holes, and in instances where compressive as well as tensile strains or displacements are anticipated, tensioned rod or wire systems are preferred. System Components Borehole extensometers are made up of at least the following five principal components: the instrument head; the collar anchor assembly; the downhole system of anchors and rods or wires; the signal cable if the head is equipped for electronic readout; and the readout apparatus, whether mechanical or electronic. These components are shown in Fig. 1. Borehole Requirements Most extensometers are designed for installation in nominal 75 to 57-mm (3.0 to 2.25-in.) diam drill holes. Either a diamond drill or a percussion drill hole is satisfactory, provided the variation in drill-hole diameter is within the tolerance of the standard anchor design. The basic system may be modified for other hole diameters by changing the dimensions of the collar anchor and downhole anchor assemblies. Some instrument heads and collar anchor assemblies require enlarged borehole collars, though usually not over 150 mm (6 in.) for a depth of 1 m (3 ft). It is desirable, although not essential, that holes be free-draining. Holes must be clean and free of debris before installation. Depth/Orientation of Extensometer Boreholes Extensometers are designed to measure axial strain components in the instrumented drill hole. As the drill hole is axially deformed, the distances between individual downhole anchors and the instrument head change, as do the distances between adjacent anchors. The distance changes measured by a multiple position borehole extensometer, for example, are reduced to functions of time, hole depth, anchor position, or other parameters of significance in terms of the structure under investigation.

Jan 1, 1982

By Michael Brittan

For every million ounces/year of gold produced by mining and process operations, each 1 % loss to tails represents 10,000 oz/year of production sacrifice. Recovering this lost gold would generate aditional revenue of $3 million/year at $300/oz. Similarly, if the average recovered grade is say 0.15 oz/st, every $0.45/st reduction in operating costs will result in equivalent annual savings of $3 million. This paper describes the application of a technique to realize such cash flow benefits for milling operations.

Jan 1, 1999

By R. Krishna

The basic ventilation equation of power equal a constant times quantity to the power three (P=constant x quantity3) makes it an extremely costly palliative as a long term measure. Provision of increased airflow is also limited by maximum tolerable levels of air velocity, the effect upon respirable dust and, in case of coal mines, spontaneous combustion. The paper high lights amelioration measures for climatic improvements at a lower cost. The paper has also shown a method for monitoring air pollution using laser technology.

Jan 1, 1997

By Ellis L. Armstrong

Welcome to Chicago and to the first North American Rapid Excavation and Tunneling Conference. It is a great privilege for me to serve as the Chairman of the Executive Committee of such a Conference. We are here because of the rapidly mounting interest of technicians the world over in turning the potential use of underground space into sensible and economical benefits to people. This Conference certainly provides a major forum of international importance and scope for the exchange and dissemination of up-to-date knowledge on the technology of underground excavation and tunneling. The discussions will also surely delineate the immediate and longterm challenges we must approach in multidisciplinary force. We must exercise leadership in the problems we are trying to solve. Your program shows the breadth of the technical discussions which are going to be underway here during the three days of this Conference. I am not going into technical aspects or detailed discussions of the many uses to which underground space may be devoted. I also will leave to the technical meetings the outline of the state of the art. But I do want to tell you of the progress being made in channeling the expertise of many of the world's foremost authorities on rapid excavation and tunneling to consider the problems, laying the ground work for needed research, and provide the leadership in converting unused subsurface potentials to improve the quality of life. This first conference of its kind for North America is sponsored by the American Institute of Mining, Metallurgical, and Petroleum En-

Jan 1, 1997

By Richard Newcomb

Since the report of the 1972 Rapid Excavation Conference in the city of Chicago, speculation has continued concerning the estimates of tunneling demand. Little has been published that would persuade me to modify substantially the rather tentative estimates that originated with the National Academy of Sciences-National Academy of Engineering (NAS-NAE) study of 1968 which were recomputed by the United States in the survey of the Organization for Economic Cooperation and Development (OECD) in 1970. The OECD estimates, of course, hedged the really difficult question of forecasting civil construction tunneling demands. In the United States contribution, this was done by predicting both an upper and lower bound for important categories of demand. A discounting procedure was then applied to each of the major sectors of expenditures, permitting a forecast that reflected the current subjective assessment of how extensively and how likely cities were to adopt plans that required tunneling. This was done for water, utilities, transportation and other novel underground facilities. The purpose of this paper is a modest one. In it I wish to describe the efforts made since 1972 to generate more thoughtful and more robust estimates of urban sector demands, and to apply what has been learned to the most difficult category of predictions: those for urban mass transit systems. The estimates of the Underground Construction Research Council funded by the National Science Foundation have been described at an earlier panel of this Conference. The principal effort I am familiar with is that of

Jan 1, 1974

By William P. Barnett

In 1988, the US Department of Energy's (DOE) Pittsburgh Energy Technology Center identified three coal cleaning options for achieving flexible environmental control strategies aimed at reducing energy-related SO2 emissions. These are selective agglomeration, advanced froth flotation and advanced cycloning. Each relies on maximum liberation of pyrite and other mineral matter through feed coal comminution to fine and ultrafine sizes. The National Energy Strategy (NES) and the Clean Air Act Amendments (CAA) of 1990 are examples of the nation's commitment to a clean environment. The need to use the nation's energy resources in an environmentally sound manner presents critical challenges and opportunities for coal preparation during the next decade, particularly regarding the control of SO2 emissions. The principal challenge is the development of cost-effective coal preparation approaches for sulfur removal beyond currently achievable levels. Opportunities are provided in the form of incentives associated with a novel system of SO, allowances and a policy environment based on the proper functioning of familiar market forces. An allowance, as defined in Section 402(3) of the Amendments, is "an authorization ... to emit ... one ton of sulfur dioxide." To achieve the objective of the Clean Air Act Amendments, SO, emissions will be eventually capped at 8.12 Mt (8.95 million st) annually by controlling the number of allowances issued nationally. By permitting allowances to be bought and sold once issued, the law encourages "overcompliance" as a source of profit for owners of excess allowances. Many details concerning the administration of allowance trading are not yet written.

Jan 1, 1992

By F. C. Eberhardt

Systematic planning of underground work is increasingly important in this era of advancement of rapid underground excavation techniques. The day when planning consisted of deciding which men would shovel and which would push wheelbarrows - and the answer to any problem was more men - has faded into the past. The modern underground constructor faces economic and competitive conditions which demand exacting planning, logistics and scheduling; the most efficient operating methods and equipment known; and realistic, comprehensive, analytical risk evaluation with adequate contingencies or other protection. Proper planning to cover all these elements - plus one other element: old fashioned "good luck" - will insure a successful underground project. Underground work, because of its inherent characteristics, is among the most risky types of construction. The forecasting of underground conditions is at this time only educated predictions based on sometimes faulty data, insufficient data, or no data at all. The predicted conditions of numerous operations have deviated far from the actual conditions encountered. Opportunities for error exist in profusion seldom present for surface operations. Other than this unusual risk factor, the planning for underground work does not differ greatly from planning for surface work. In planning and starting an operation there is seldom available the information or time to thoroughly analyze all unknowns. It then becomes necessary to develop a plan predicated on assumptions and trade-offs that appear to be safe and economical and to add time and cost contingencies that will provide some degree of protection. On competitively bid fixed price work, choice of markup on estimated

Jan 1, 1974

By G. Norman Owen, Roger E. Scholl, Tor L. Brekke

INTRODUCTION Underground structures are generally regarded to be safer than surface structures during strong seismic motion, except when crossing a causative fault. Recent studies of observed earthquake damage to tunnels generally support this view, although instances of severe damage and, occasionally, collapse are reported. For proposed underground construction of sensitive structures such as nuclear power plants, liquefied natural gas facilities, and nuclear waste repositories, a verification of the seismic response of underground structures will be required.. This paper discusses the stabilization recommendations used in a study of additional costs required to protect tunnels against ground motion caused by earthquakes and underground nuclear explosions (1). The study is a part of the site investigations for possible construction of a nuclear waste repository. The additional costs estimated in the study are not presented here; only the stabilization measures are presented in the present paper. The tunnels, which would constitute the underground facilities of a possible repository, are assumed to be 5.5 m (18 ft) in diameter and to be located at a depth of 600 m (2,000 ft). Three candidate geological materials are considered: argillite (shale), granite, and tuff. Several peak ground accelerations are used: 0.3g, 0.5g, and 0.7g for earthquakes, and 0.5g, 0.7g, and 1.0g for underground nuclear explosions. Potential damage due only to shaking is considered here. This paper does not discuss problems that result from creep or sudden rupture of intersected faults or from ground failures at portals.

Jan 1, 1979

By A. Fiszer

One of the major problems with deep Polish hard coal mines are deformations of close-to-wall galleries since they are necessary and must he kept open for emergency situations and are largely responsible for work disturbances. In order to ensure safe and effective working operations, it is necessary to often rebuild galleries which, apart from the inevitable stoppage of operations, is greatly disadvantageous for the operation of a mine. The largest problems with maintaining the galleries open occur in Lower Silesian Coal Field mines where sometimes it is necessary to reconstruct the galleries several times [(Fig. 1)]. In light of what has been said above, the aim of this article is to present the reader with methods and ways of determining deformations occurring in close-to-wall galleries. Squeezing or convergence of headings is only a portion of the entire process of ground movement caused by ground disturbance due to workings. The term "squeezing of headings" is to be understood as a shortening of the distance between a point set on the roof of a heading and the corresponding one on the floor. It is very important to know the rules governing the process of squeezing in a particular mining system since it affords possibilities to define changes of the process and its parameters at any moment for a given system. This is of utmost importance because convergence of a heading is one of the most significant manifestations of ground pressure which has already been proved by studies performed by Everling (1). On the basis of those studies it has been observed that there exists an almost linear relation between the rate of convergence and loading [(Fig. 2)]. This, in turn, means that the deformations of the already exploited portion of heading are proportional to the pressure changes.

Jan 1, 1982

By G. Le Bel

Discussion by G. Le Bel The paper proposes three methods to determine optimum lifetime of a mining project 1. The conclusion is that the three methods arrive at the same optimum production rate (by coincidence). It is also stated that: "The stochastic and option pricing models, in addition to providing a more realistic optimum mine life than the traditional NPV (net present value) calculation, showed that the example project has the potential for substantially higher return. By explicitly considering a project's potential risks, the stochastic or option pricing techniques can more accurately describe its probable investment performance." This discussion is intended to demonstrate that: •It is no coincidence that the three methods arrive at the same optimum production rate. • The stochastic and option pricing models do not provide a more realistic optimum mine life than the traditional NPV calculation. •The potential for a substantially higher return is misrepresented. First, a review of investment decision theory in mining is needed. Net present value is the preferred performance measure because of the flexibility offered when comparing various alternatives. However, it presents the following disadvantages: • The discount rate selection is not straightforward. • The NPV obtained represents a deterministic characterization of the variables included in the cash flow calculations, i.e. a single-point estimate. Discount rate selection The opportunity cost of capital represents the rate of return that would be obtained if the capital was instead invested in other opportunities considered to exist. Such opportunities must be bypassed if the available capital is invested in the project studied 2. If these other opportunities carry risk similar to the project under analysis (for example, if they are other mining projects), there is no need to add incremental [ ] risk factors. On the other hand, if these opportunities are represented by the acquisition of government bonds yielding 7%, a risk premium factor must be included. The types of risks associated with a mining venture are shown in Table 1. Together they represent the "business risk" of being a mining company. The individual project risk is important to investors if it differs substantially from the business risk of the company and that of the other investments in mining ventures that we must pass up to invest in this particular project. A risk premium or discount would then be required. This can be illustrated by the following example. Consider that a company has two investment alternatives: one is the Cavender hypothetical project located in Nevada, and the other is the same project located in a civil war zone of central Europe. The second project requires a risk premium factor on the discount rate. Conversely, a project showing highly uncertain returns that are negatively correlated with the returns of the firm's other assets may decrease the company's corporate risk. Deterministic character of NPV calculation The cash flows used in NPV calculations are obtained from a set of variables. These variables are estimated using one parameter obtained from the engineering studies. Each parameter is thus a single value that is often termed a "realistic" or "best estimate" as opposed to "optimistic" or "pessimistic." However, considering that each variable can assume a range of values between the

Jan 1, 1994

By J. E. Stephens

US Borax began exploration in southeast Alaska in the summer of 1971 with a staff of two, Barry Watson and Jackie Stephens, based in Spokane, WA. After several years of prospect examinations in the islands west of Ketchikan, AK, and with the able assistance of prospector-pilot Kenny Eichner, Jackie Stephens proposed and organized a boat-based, helicopter-supported, stream sediment sampling program to explore the western contact of the Coast Range intrusive complex on the mainland. The rationale for this included: the extension of known mineral trends from Canada into southeastern Alaska along favorable geologic zones; the western contact area of the Coast Range intrusives with metasediments and metavolcanics was a favorable target for metals exploration as shown by numerous small prospects. Knowledge gained from mineral exploration of the island areas indicated that they were well mineralized, but already well explored, and that the known mineral potential was probably present in subeconomic quantities (Brooks, et al.). Publications of the US Bureau of Mines and other scientific agencies were gathered and every prospect within the southem southeastern Alaska area was plotted. This in itself lent a tremendous amount of knowledge to the total exploration program. US Borax's McLean Arm copper property on Prince of Wales Island was drilled and dropped while this compilation of data was proceeding. We found that many companies had followed one another around the island areas, but little or no exploration had been done on the west side of the Coast Range, and that many explorationists flatly stated that the west side of the Coast Range was barren of mineralization. In summary, although some of the shoreline and near shoreline areas of the mainland had been explored, no organized boat-helicopter exploration program had been done along the favorable western zone of the Coast Range Intrusive complex. We decided to use a boat as a floating hotel for the crews that were to be helicoptered into the back country from tidewater for our initial stream-sediment sampling program.

Jan 1, 1991