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By Edwin A. Blackey, Joseph G. Engels, James T. Cahill

An extensive geotechnical instrumentation program was undertaken during the construction of a 6.7 m (22 ft) inside diameter tunnel to monitor the ground-structure response and to check assumptions made for design. The tunnel was advanced through sedimentary and igneous rock using a fully shielded tunnel boring machine (TBM) with both temporary support and final lining provided by precast concrete liner plates erected in the tail section of the TBM. The parameters measured and evaluated include rock deformation, strain in the precast concrete liner, changes in tunnel cross section and groundwater response. In addition, an automated camera system is described which was mounted on the TBM to provide a continuous photographic record of the bedrock conditions exposed at the tunnel springline. The performance of various types of instrumentation equipment in an underground construction environment is also evaluated.

Jan 1, 1981

By Bhawani Singh, A. K. Dube, B. Singh

At least three hydroelectric tunnels constructed during the last decade through the lower Himalayan region in India have met with serious problems of supporting in squeezing ground conditions. Steel ribs under went intolerable deformations requiring rectification to provide space for concrete lining which delayed the projects inordinately. In an attempt to choose a rational method of predicting rock load, the authors have compared rock loads estimated from various classification systems and elasto-plastic theory with observed values. The deficiencies of the classification systems have been highlighted to show that the combination of elastoplastic theory and tunnel instrumentation programme provides better guidelines for the design of tunnel supports in squeezing ground conditions.

Jan 1, 1981

By Drupad B. Desai, C. C. Ku

INTRODUCTION The Laurens Street section of the Northwest Line of the Baltimore Region Rapid Transit System, located along Pennsylvania Avenue between Pitcher Street and North Avenue is situated in material which cannot be definitely categorized as soil or rock. However, in the area of residual soils in which these tunnels were constructed, considerable attention was required to determine the character of the ground so that the designers and the constructors could properly evaluate the behavior of the ground and plan their respective efforts accordingly. The Laurens Street sections structures consist of twin rock tunnels, station structure, traction power substation, vent shafts at both ends of the station, the midline vent shaft, and the twin mixed-face tunnels. This paper concentrates on the mixed-face tunnels which extend from Station 99+67.03 (O.B.) to Station 102+49.00 (O.B.) at the southern end of the section. Since the completion of the design of this project, the Laurens Street section has been renamed the Upton Station. (See Figures 1 and 2). SUBSURFACE INVESTIGATIONS At early stages, three preliminary studies were performed by the General Soils Consultant (Ref. 1, 2, & 3). The purpose of the first study was to ascertain the generalized geological and subsurface conditions which might be encountered in the region. No borings were performed for this study. A limited number of test borings were performed for the second study, which included subsurface data for the Northwest and South Lines of the Transit System. Three borings were

Jan 1, 1981

By H. Beecher (Original by) Charmbury

Water is a most remarkable substance, essential for life of all kinds. As well as needing water to survive, man has always used it for agriculture, transportation, recreation, and many other things. When our country was young and inhabited by few people, the streams, rivers, and lakes were able to provide all the clean water needed by man and take away all the wastes created. However, with our growing population and an ever-increasing demand for goods and services, the public, industry, and government at all levels have become acutely aware of the need to manage the nation's water resources more efficiently. Abundant energy from many sources has helped this nation to become the greatest industrial nation in the world. Coal has contributed a major portion of this energy, generating electricity, running railroads, and maintaining national security during wartime. The result has been the highest standard of living in the world and a time of widespread economic prosperity. The use of water in coal mining is somewhat different from its use in most industries. With the exception of water used in cleaning plants, for underground dust control, and for fire protection, most of the water en- countered in coal mining operations serves no useful purpose. In other words, it is an undesirable element and must be removed, otherwise it will interfere with operations, cause potential water quality problems, and may even stop operations by flooding. In the past, removing water from working areas of most mines was usually a fairly simple matter. Pumps with piping were installed at sumps or low spots in the mine and the water was pumped to the surface or to drainage control facilities constructed for the operation. Ditches were often used to collect and drain the water by gravity to the outside or to main sumps for pump discharge. In either case, the water was allowed to flow into the nearest stream or river. The concept of "water is water' was generally accepted without too much concern for what was in the water since low-cost products and services, rather than clean water, were the public demand.

Jan 1, 1981

By James E. Monsees, Wayne A. Carbiener, Michael R. Wigley

This paper illustrates an approach to quantitatively document the degree of technical conservatism to be incorporated into the design of a waste isolation system in bedded salt. It is anticipated that for an actual repository site the key performance constraints and/or design bases identified in this paper will be reviewed, and modified or supplemented as required. Ultimate acceptance of a repository will be dependent upon scientific peer input and scrutiny of the demonstrated conservatism inherent in each specific repository site and design.

Jan 1, 1981

By R. F. Holub, P. J. Dallimore

Basic to solving the problem of the role of radon transport on radon concentrations in mines is to establish whether it occurs primarily as diffusion and forced flow through porous rock or through fissures in the rock. The laboratory experiments performed involved measurements of diffusion and emanation coefficients, porosity and permeability of representative rock samples. Significant differences have been found when comparing the results of the laboratory permeability determinations to those of the mine determinations. Considerations of underlying principles, however, suggest that the diffusion and emanation coefficients are the same in laboratory and mine. It was also found that moisture content plays a dominant role in radon transport through rock. Using these concepts and findings, some conclusions about the radon concentrations in mines have been drawn.

Jan 1, 1981

By Ben Benally, Joseph M. Hans

INTRODUCTION The decontamination of the former Shiprock uranium millsite and the interim stabilization of its tailings piles began in March 1974, and ended in June 1978. Personnel monitoring for whole body gamma ray exposure was conducted for selected individuals working at the mill site throughout most of this period. The millsite and exposure conditions are briefly described to develop a basis for interpretation of the exposure data. Millsite The Shiprock uranium millsite is located in the community of Shiprock, New Mexico on a bench overlooking the San Juan River (Figure 1). Both Shiprock and the millsite are located on the Navajo Indian Reservation. About 1.5 million tons of tailings were produced on the millsite during its operation from 1954 to 1963. The tailings were pulped with waste process fluids and water, and discharged to form two tailings piles. The piles (ponds, dams) were formed with earth starter dikes and the dikes were then raised using the separated sand fraction of the tailings. The slime fraction of the tailings were discharged into the diked impoundment. The mill was shut down and partially dismantled before the lease expired in 1973, and the remainder of the mill and tailings reverted back to the Navajo Tribe which was the lessor. Portions of the millsite were then occupied by the Navajo Engineering and Construction Authority (NECA), a tribal enterprise. In addition to its regular activities, NECA established an on-site training school for heavy equipment operators. The trainees principally used the south tailings pile as a practice area and spread the tailings into a 10 hectare row of raffinate ponds located along the southwest side of the millsite. Overall, the training activities inceased the effective area of the tailings piles from 20 to 35 hectares. Another 56 hectares were contaminated with wind and water eroded tailings. Exposure Conditions Persons decontaminating a millsite may be subject to radiation exposures from several sources. Only whole body gamma exposures are discussed in this report. These exposures are arbitrarily divided into three levels: high, intermediate, and low. The levels are related to areas in which the decontamination work was being done and have no connotation concerning imminent hazards. High exposures would result when persons were working with raw tailings, and intermediate exposures would occur when persons were working in the ore storage and mill yards. Low exposures would result from working in areas where surface contamination exists from wind and water erosion. [ ] The millsite and its contaminated environs were divided into major areas to facilitate the decontamination work (Figure 2). Areas A, B, and C are defined as perimeter areas containing surface contamination. Work in these areas was expected to result in low exposures. Areas D, E, and F are the

Jan 1, 1981

By w. Chruscielewski, T. Domanski

INTRODUCTION Concentration of radon 222Rn and its decay products occuring in the Polish mines of metal-ores call for the necessity of systematic radiation control /Do8la/ both of the working environment and of the miners' personal exposure. The attempts at introducing a system of radiological protection in mines, similar to the ones existing in X-ray or isotope laboratories, took several years and consisted of development of the methods for control of concentration of radon and its progeny in the air, as well as the methods for measuring individual exposure. It was accepted that the assessment of both transient concentration in the air and of personal exposure are basic elements of the control system, which should be implemented independently of each other. Concentration measurement serves to detect and to determine those areas in mines where there is intensive radon emanation, and where current control of the effectiveness of technology introduced to deacrease the concentrations is necessary; personal dosimetry results in the assessment of the actual exposure of miners to radiation. PRINCIPLES OF THE SYSTEM The assessment of working environment is based on concentration measurements of the potential radiation energy of radon alpha decay products. Decentralized assessment is carried out by the special dosimetric service operating in each mine. Dosimetrists are equipped with portable radiometers, type RGR-11, made by the institute of Nuclear Research, Warsaw. The radiometer is presented in Fig. 1. Measurement of filter activity is performed automatically according to Markov's method /Ma62/ or any other method. Simultaneously to potential energy measurement the dosimetrists are measuring the dust concentration in the air and ventilation rate. Ventilation service looks for correlation between those indices and the concentration of radon daughters in the air. Derived Air Concentration /DAC/ for concentration assessment was accepted to be 6.25 10-6 Jm-3 /0.3 WL/ according to ICRP recommendation /Publication No. 24/ /ICRP77/. If environmental measurements reveal potential energy concentration exceeding the value of 0.3 DAC at working places, the miners employed there are subject to individual control of personal exposure. Individual exposure measurement is carried out centrally by the Institute of Occupational Medicine in [Lodz] for all metal-ore mines. Miners who are to be included in the control scheme are referred by a mine management to the Institute where they are registered and assigned a dosimeter. A passive dosimeter with

Jan 1, 1981

By Robert W. Buechley, Charles R. Key, Jonathan M. Samet, Marion V. Morgan, Arnolfo A. Valdivia

INTRODUCTION The Uranium Epidemiology Study at the University of New Mexico was initiated in 1977 with the objective of assessing health effects of uranium mining in the Grants, New Mexico, area. The planned approach was a cohort study of mortality that would capitalize on the availability of health records at the Grants Clinic. During the first year, emphasis was placed on determining the feasibility of the proposed study: Were adequate records available? What was the quality of available information? Could a cohort be established? The first year's work confirmed the study's feasibility (Buechley, 1979). Subsequent efforts have focused on the health and exposure data base and comprehensive follow-up. A retrospective cohort study of early miners is in progress; a prospective cohort study of miners who began working under the current Federal standard is planned. This report will summarize the current status of the Uranium Epidemiology Study. A chronology of the study's activities follows (Table 1). TABLE 1. Uranium Epidemiology Study Timetable 12/77 Official start of study. 12/77-8/78 Abstracted Grants Clinic records of 21,780 persons examined for mining companies from 7/57 through 12/76. Checked company personnel records to establish who had worked underground 1 year or more through 12/76. 7/78- Obtained physical exam and mining history information on qualified miners from Grants Clinic and companies. 9/78- Obtained working level month information from companies and other sources. 12/78- Checked qualified miners list with New Mexico death tapes and New Mexico Tumor Registry files. 9/80- Submitted qualified miners list to Social Security Administration for search of its records. 12/80- Obtained copies or abstracts of early State Health Department and Mine Inspector's reports. 3/81-4/81 Conducted Pilot Respiratory Disease Survey. 3/81- Verified underground status of qualified miners via company personnel records. 3/81- Verified smoking and mining histories of qualified miners via Grants Clinic records. 3/81- Began establishing cohort with first underground experience after 1970. 4/81- Checked qualified miners list with Post Office, Voter Registration Office, Motor Vehicle Division, telephone directories, city directories, and other sources. BACKGROUND Uranium Mining in New Mexico The Grants, New Mexico, uranium belt measures some 110 by 25 miles in Cibola, McKinley, and Sandoval counties (Kelley, 1963). The three chief mining districts are, from east to west, Laguna, Grants, and Gallup. Average annual production was about 5,500 tons, or 45% of United States uranium, from 1966 through 1978. Despite a drop in this figure in 1979, to 40%, New Mexico still leads the nation in uranium reserves and production (Hatchell, 1981). In 1918 carnotite, a yellow uranium vanadate, was identified in the Shiprock area (Chenoweth and Learned, 1980; N.M. Energy and Minerals Department, 1981). It received little attention at the time because of its apparently limited volume. In 1950 an important uranium outcropping was discovered by chance in limestone at Haystack Butte, northwest of Grants. In 1951 deposits were discovered in sandstone at Poison Canyon, north of Grants, and at Jackpile, northeast of Laguna. In 1955 finding of radioactive cuttings at an abandoned oil test site near Ambrosia Lake led to drilling and discovery of the first underground deposits (Melancon, 1963). Ore bodies were also found near Church Rock in the 1950's (Rautman, 1977). A uranium rush followed. At various times during 1952-1962, 60 mines and 5 mills were in operation (Gay, 1963). In the early 1960's the price of uranium fell, and many miners left the area. Subsequent market fluctuations have produced shutdowns and consolidations, development and expansion. Many early uranium miners came to New Mexico with

Jan 1, 1981

By J. D. Scott

This paper consists of a review of the development and application of spherical charge blasting at Inco Metals Company. Topics will include the Livingston Strain Equation, the field data required for its use in full scale operation, the type of ground in which mining has been carried out, explosives in use and their characteristics and finally, an overview of actual production applications. These applications include Primary Stope Mining, Secondary Mining Against Fill, Mining a Faulted Ore Zone and Drop Raise Blasting. INTRODUCTION Crater blasting in itself has been in use for over twenty years, but only recently has the technique been combined with a spherical size charge to form the Vertical Retreat Mining Method. This article endeavours to put the Livingston Strain Equation in a practical light, to describe several actual hard rock applications, and the results achieved in each case. THE LIVINGSTON STRAIN ENERGY EQUATION C.W. Livingston put forward the following equation as a standard means of determining the optimum burden required for full crater production blasting. The constant "E" is included in an attempt to recognize secondary breakage caused by strain waves.

Jan 1, 1981

By Wm. J. McCracken

HISTORICAL REVIEW OF BOARD OPERATIONS The Ontario Worker's Compensation Board was established in law enacted by the legislature of the Province of Ontario in 1915. It was designed to pay insurance benefits to injured workers, and at the same time to protect employers from legal suit. It was based upon an enquiry system rather than an adversary system such as that used in the courts process. Initially, the system was designed to pay compensation benefits and subsequently, to pay for the cost of medical treatment and pensions for disability and disease resultant from the effects of traumatic injury. In 1947, the Act was changed to include industrial or occupational generated diseases, not specifically related to traumatology. Such occupational diseases were therefore accepted and benefits paid subsequent to that date. As will be discussed in several minutes, even today the vast preponderance of compensation claims with the Ontario Board continues to be related to the effects of trauma. HISTORICAL REVIEW OF EXPOSURE TO RADON GAS DECAY PRODUCTS In some areas of Ontario, especially in Northern Ontario, there is a natural leaching of radon gas from the underlying rock formation. This constitutes very low levels of radon gas decay product radiation exposure to those persons coming in contact and inhaling these substances. This paper however is designed to discuss the occupational generated types of radon gas exposures. For many years dating back to the 1930's, partially refined ores were being shipped from Northern Canada to a refinery located at Port Hope, Ontario, still in operation and currently operated by Eldorado Nuclear Limited of Canada. Initially, the purpose for the operation was extraction of radium to be sold on world markets for medical treatment purposes. With the advent of World War II, this market collapsed. Subsequent to World War II, the availability of other sources of radiation for medical radio-therapy generally replaced the requirements for radium. During World War II, a new market opened up for the Port Hope refinery however as work into nuclear chain reactions and the development of the atomic bomb identified the need for uranium and enriched uranium. During the period of operations where radium was being extracted at the Port Hope refinery, it is now known that an identifiable radon gas hazard did exist. This hazard disappeared when the production line for extraction of radium ceased operations. In 1954, uranium mining operations opened up in Ontario at two locations, Bancroft and Elliot Lake. At the peak of operations, 16 mines were operational and 11,000 workers were employed in these mining operations. A high level of mining activity continued over a 10 year interval with the Bancroft Mines closing permanently in 1964 following a 10 year life of operation. The other mines in Elliot Lake closed about the same time with the exception of two uranium mine operations which have continued to be operational up to the present time. By 1965, due to a dramatic drop in world demand for uranium, the total work force had fallen to 1/10 of the peak work force, and approximately 1,300 workers remained in employment. It is of interest to note that one significant difference in the work environment between Elliot Lake and Bancroft was the high silica content of the Elliot Lake ore. This gave rise to a number of cases of silicosis developing in relatively short intervals of time in the Elliot Lake miner population. No cases of silicosis were identified from the Bancroft operations. Based upon the experience in investigating and evaluating actual cases of lung cancer in the uranium miners over the years, the medical staff at the Ontario Board also developed the impression that radiation levels were much higher in the Bancroft operations, especially in the earlier years of operation, than at Elliot Lake. This resulted in accumulation of higher levels of Working Level Months (WLM), usually over a shorter exposure interval in many of the cases. This aspect will be further evaluated in this presentation. Subsequent to 1965, the work force remained quite static in numbers until 1975. At that time, there began to develop an increase in the work force, and this increase is continuing at a moderate rate up to the present. INITIAL METHOD OF HANDLING LUNG CANCER CLAIMS The first lung cancer claims in Ontario from uranium mining operations were accepted on the perceived cause-effect relationship. This relationship was based upon the data from the Colorado observations and the Czechoslovakia data. Initially, a series of regression equations on mortality were developed and used to estimate the effect of exposure to low cumulative doses of radon daughters as it might relate to the frequency of occurrence of lung cancer at any particular cumulative exposure level. A probability of cancer being radiation induced as against it being caused from other factors was calculated. This method was discontinued subsequent to 1972 due to problems encountered in carrying out this complex evaluation. Thereafter, each case was dealt with on an individual basis, being based upon whether or not the tumour was of the oat cell type, a cumulative exposure in excess of 120 WLM; latency periods in excess of 10 years, commencement of mining prior to

Jan 1, 1981

By William L. Young

I think I should let you in on one of Canada's best-kept secrets, if you will promise not to tell it all over the place. Believe it or not, good, honest, enterprising capitalism is still alive and flourishing north of our common border, and I am living proof that capitalism is still working for the little guy. My personal story of mining development in Canada isn't all that rare -- you've probably heard something like it from other areas and other days several times -- but my case brings it up-to-date. I would like to Tell you briefly the history of Northumberland Mines Limited, a contemporary case of individual enterprise getting a mining operation underway. And if I can do it you probably can too.

Jan 1, 1981

By Robert A. Westin

Polychlorinated biphenyls (PCBs) are a group of chlorinated chemicals that were used in many different fire resistant hydraulic fluids, heat transfer fluids, and in electrical equipment as dielectric liquids. PCBs were manufactured primarily by Monsanto Chemical Company under the tradename Aroclor, and were used by many different electrical equipment manufacturers. PCBs are noted chiefly for their extreme chemical inertness. This resulted in exceptional fire resistance and long life in applications involving exposure to high temperatures and intense electrical fields. This combination of properties resulted in PCBs being widely used in electrical equipment used in mines, including transformers, capacitors, and some electric motors. PCBs were also used as working fluids in some heat transfer and hydraulic sys terns. The same chemical resistance that gave PCBs long life in industrial applications give PCBs essantially eternal life when they are released into the environment. PCBs are not highly toxic in the sense that exposure does not cause immediate health problems. However, PCBs accumulate in the human body and neither degrade nor are eliminated from the body, and long-term exposure to PCBs can result in changes in liver function which may increase susceptibility to the carcinogenic effects of other chemicals. PCBs also accumulate in the food chain; the concentration of PCBs in fresh water fish may be several hundred thousand times as high as in the water the fish are taken from.

Jan 1, 1981

By Victor E. Archer

INTRODUCTION Man is exposed to many agents which induce mutations in germ cells and/or cancer at work, at play, and at home. In this total mix of mutagenic and carcinogenic agents, how important are radon and its daughters? Before man moved into caves and other permanent dwellings, the principal mutagenic and carcinogenic agent to which he was exposed was natural background radiation--cosmic rays, radium and potassium-40 in his food, plus gamma rays and radon from the soil and rocks. When man moved into caves, captured fire, and began to preserve and store foods, his exposure to carcinogens and mutagens took a quantum leap. Carcinogens and mutagens appear to act in the same way, that is, by altering the DNA or nuclear proteins of cells. Most mutagens are carcinogens, and vice versa, so when I say mutagens from here on, I will be referring to both. The relationship of the two is emphasized by the fact that administration of a carcinogen to a group of animals not only increases cancer rates among the exposed animals, but also among their progeny (Tomatis 1979). Environmental Mutagens Smoke from man's fires, overheated foods, and foods preserved by smoking, resulted in ingestion and inhalation of many polycyclic aromatic hydrocarbons--many of which are mutagens. Caves and houses with tight windows and doors tend to collect the radon which is constantly emanating out of soil, rocks and concrete, so man's exposure to the radon daughter component of background radiation increased several fold. Preserving food by salting or pickling with material that contained nitrites and nitrates led to increased ingestion of nitrosamines, which are potent mutagens. When his grains and other foods were stored in slightly damp rooms, fungi or mold would grow on them. Several of these fungi are now known to produce very potent mutagens. The best known of these is aflatoxin B (Ramachandra 1979). It may seem strange that a living organism would produce a mutagen. One might think that it would scramble its own genetic heritage. The reason it does not is that it produces the mutagen in an inactive form. It can be activated only by an animal's enzyme systems after being eaten. When man moved into cities, the collective smoke from wood and coal fires further increased his exposure. That particular smoke has now mostly disappeared, but has been replaced by smoke from automobiles and industry. When man moved into the age of technology, his exposure to mutagens again increased dramatically. Many mutagenic chemicals, from benzene and beta naphthylamine to a long array of pesticides and tobacco products have been added to our environment. Excess deaths from cancer are now being observed among chemists in most industrialized nations. Mutagens are even found in much of our wine, beer, and whiskey (Keller 1980). Some of the chemical mutagens were widely used in food or in other commercial products before their potential was discovered. Striking examples of this is the original butter coloring agent and the polychlorinated biphenyls that have been widely used in brake fluids and electrical transformers. Large quantities of them have been discarded or disposed of in a careless manner--in such a way that many of them have contaminated our food, our ground water and air (Landrigan 1981). In this nation, with the help of several recent laws, we were just beginning to get control of the industrial chemical mutagens. With the relaxing of these laws that is currently going on, it appears that it will be many more years before we really bring chemical mutagens under control. Many nations have yet to come to grips with this problem. On top of this massive array of chemical mutagens we have now added radiation from many artificial sources. For most of us this means medical X-ray and fallout from nuclear weapons testing. Ionizing radiation is one of the most potent mutagens, so it has caught the public eye, and its contribution cannot be ignored. Fortunately, by the time we started using radioactive materials in quantity with the Manhattan Project, we had experience with radium and X-ray (some of it bad); we knew enough radiobiology and enough about methods of radiation protection so that most nuclear laboratories have had a phenomenal record of radiation safety. Radiation is one new technology with great potential for harm that has not exhibited that potential except for a few isolated situations like that of radium dial painters, uranium miners and atomic bomb victims. Uranium miners slipped into this list almost by accident. We could have protected our uranium miners just as well as we did the workers in nuclear laboratories; but we failed to do so. Why didn't we? The reason is simple. The Atomic Energy Commission was charged with protecting the health of their workers. They did not wait for a pile of bodies before they introduced controls. Congress appropriated the money, and taxpayers were willing to pay for the protection against radiation. Miners unfortunately did not work for the Atomic Energy Commission. Although mine operators were ignorant about radiation, the key item was that in the 1950s nobody was willing to pay the extra costs of adequate ventilation to control the high levels of radon and radon daughters in uranium mines. Control was not achieved until new laws and regulations were passed which made it compulsory. BIRTH DEFECTS AND CANCER

Jan 1, 1981

By Carl (Original by) Hrovatic

Land is a precious resource and should be treated as such by all members of our society. The soil covering this earth is only a very thin outer layer, varying in thickness from a few inches to a few feet and covering the rocks and minerals lying beneath the surface. The wise use of this valuable commodity is the responsibility of everyone. Many everyday activities disturb e earth's surface. Examples are highway construction, housing and commercial developments, agriculture, and various types of mining. This chapter discusses the relationships of the environment to land as it applies to surface operations in the coal industry. Mining by surface methods disturbs, for a brief period of time, thousands of acres of land annually. In addition, refuse piles, slurry ponds, abandoned mine structures, unprotected mine openings, and unsightly cleaning plants can also adversely affect land unless properly handled.

Jan 1, 1981

By Tor L. Brekke, Alberto Marulanda P.

The paper describes hazardous water inflows during construction that have taken place over the last three years in tunnels in Colombia. The projects involved are the Chivor II Hydroelectric Power Project (penstock tunnel), and the Chingaza Water Project (two tunnels). In all cases, loss of face control led to significant loss of ground; in one case some 70,000 m3 of slide material was involved, much of which came out through the portal situated 1.6 km from the face. Emphasis is given to: (a) the geologic setting, (b) the remedial measures taken, and (c) the main efforts that can be made to prevent hazardous conditions from developing.

Jan 1, 1981

By Martin C. Kuhn

The use of tritium in manufacturing and its subsequent loss to the local environment in Tucson, Arizona resulted in a great debate relative to the physiological effects of low level radiation. This paper reviews some of the facts of the release and attempts to quantify the degree of hazard encountered by the local community. Some of the difficulties in assessing the true degree of absorbed dose and the assumptions necessary for calculation purposes are presented.

Jan 1, 1981

By James Charles McHardy

During 1980-2000, the Florida Phosphate industry will deplete its Central Florida Polk County reserves. As a result, new mines will be built in the ?so-called? Southern Florida Reserve areas. These new mines will require new mining, beneficiation and tailings disposal technologies in that the southern reserves have different characteristics than have been encountered in the Central Florida deposits furthermore, government regulations will necessitate the development of new tailings and clay disposal methods. This paper reviews these challenges for the phosphate industry and how these opportunities can be expected to effect plant design and plant operating practices.

Jan 1, 1981

By Vas P. Srinivasa

This paper examines the role of the heavy media separator in the mineral industry. Procedures used in selecting the separating vessel, developing the process flowsheet, and designing a heavy media circuit are discussed. For comparative purposes, the capital investment and operating costs of different types of operation are included.

Jan 1, 1981

By James H. Boettcher

In the second quarter of 1979, ASL Inc. inquired whether Crocker National Bank ("CNB") would provide $4 million in term loan financing to help ASL acquire the outstanding shares of the S&S Coal Company in West Virginia. ASL had, prior to approaching CNB, sought financing with the assistance of a financial advisor from a number of commercial banks without success. A summary of the initial terms requested by ASL is shown in Table I compared with the actual terms the transaction closed with. It is not difficult to note that the two sets of terms differ significantly. This is often the case when financing requests based on the expectations and vision of a mine developer are juxtaposed with more pragmatic requirements of a commercial bank. The "art" and fun of structuring financing plans for mining ventures (highly leveraged acquisitions or grass roots) comes in working with mine developers to arrive at a final financial structure that meets their objectives and constraints as well as those of the bank or other financial institution providing much of the financing. This article briefly describes the process we went through with ASL beginning with the terms they requested initially and ending with the ones on which the transaction was finally closed.

Jan 1, 1981