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By Janet A. Johnson, T. B. Borak, K. J. Schiager

INTRODUCTION In the USA regulatory agencies have adopted standards which limit the allowable concentration of ore dust in underground uranium mines. The American Conference of Governmental Industrial Hygienists has recommended a threshold limit value for silica which has been incorporated by reference in federal regulations (30 CFR 57, 1980). The Nuclear Regulatory Commission (NRC) imposes a limit for unprocessed uranium ore dust for reducing the exposure to radioactive materials from inhalation (10 CFR 20, 1980). We have been unable to trace the origin of the NRC standard. Recently the ICRP has published recommendations concerning limits for intakes of radionuclides by workers (ICRP, 1979). We have used the ICRP methodology to compute the dose equivalent commitment to lung and bone from inhalation of insoluble ore dust particles. These values were used to derive air concentrations which would provide an acceptable risk for induction of cancer from occupational exposure. Results indicate that the new ICRP recommendations are more restrictive than the present NRC standard for radioactivity. The maximum allowable dust load in a uranium mine will depend on both the concentration of silica (% Si02) and the amount of radioactivity (% U308). We have combined these standards assuming complete independence of biological hazard to establish boundary conditions for which either silica or radioactivity is the dominating factor. Based on these results we present suggestions for analysis of ore dust to insure compliance with regulatory agencies. SILICA STANDARDS Silicosis, fibrotic lung disease produced by crystalline silica, was one of the earliest forms of occupational disease to be recognized. The pulmonary lesions caused by silica, silicotic nodules, consist of concentrically arranged bundles of collagen fibers. Fusion of these nodules results in progressive massive fibrosis causing alveolar changes which decrease ventillation and blood flow in the lungs. The current Threshold Limit Value (TLV) for mineral dusts is based on the concentration of free silica. The standard is expressed in three forms: (1) Particle count standard: TLV (mppcf) = 300/(% Si02 + 10) (mppcf = million particles per cubic foot) (2) Respirable dust mass standard: TLV (mg/m3 ) = 10/(% respirable Si02 + 2) (3) Total dust standard: TLV (mg/m3 ) = 30/(% Si02 + 3) The most commonly used form is the respirable mass standard. These curent values for silica are based primarily on epidemilogical studies of Vermont granite workers and other occupationally exposed workers. In the Vermont study no cases of silicosis were seen in individuals employed after dust control measures were initiated and whose subsequent exposure averaged less than 5 mppcf. The free silica concentration in the airborne dust to which these workers were exposed averaged 25%. A concentration of 10 mppcf of granite dust is considered equivalent to 0.1 mg/m3 quartz. The current respirable mass standard allows a maximum silica concentration of 0.1 mg/m3. NIOSH (1974) has recommended a reduction in the current TLV for respirable silica to 0.05 mg/m3 Si02. As with radiation standards, the TLV for mineral dusts is an upper limit for time weighted average exposure. It is recommended that dust concentrations be maintained as far below the TLV as current practices permit. RADIATION STANDARDS The present concentration limit for airborne natural uranium in ore dust prior to chemical separation is 75 µg of uranium per m3 of air ( 10 CFR 20, 1980) . This corresponds to 1.85 Bq/m3 (50 pCi/m3 ) of natural uranium, U-238, U-235 and U-234 and is equivalent to 3.7 Bq/m3 (100 pCi/m3 ) of gross alpha activity with radioactive equilibrium between the long-lived alpha progeny through Ra-226. The origin or basis for this standard is not known, but it presumably includes both chemical toxicity and risk from somatic radiation injury. Recently the International Commission on Radiological Protection (ICRP, 1977) has published recommendations concerning the objectives and criteria for limiting radiation exposures. This was followed b y a revision of the limits for intake of radionuclides by workers (ICRP, 1979; ICRP, 1980). The previous compilation of limits for internal emitters was published by ICRP Committee II in 1959 (ICRP, 1959). The latest version includes new methodlogy outlined in ICRP Publication 26 (ICRP, 1977) as well as extensive metabolic information

Jan 1, 1981

By D. W. Agers

This paper is an extension of previous work evaluating a new extractant, LIX®-64, for recovery of copper from dilute acidic solutions. Large scale pilot plant operations have confirmed the technical and economic feasibility of the process and, with minor exceptions, scale up parameters obtained by previous laboratory work. Operating problems encountered in the pilot plants are discussed. Design parameters for-scale-up to commercial plants are presented and discussed along with a revised capital cost estimate. The future pilot program is discussed, including minor design changes and the effect of entrained organic on dump leaching efficiency.

Jan 1, 1967

By John Newby, Ulf Gwildis, Ken Massé, Guillaume Roux

How to connect an effluent conveyance tunnel to riser shaft and diffuser arms of an outfall system is dictated by the ground conditions, which ideally include rock or soil strata of low permeability. Where such favorable conditions are beyond reach, both the complexity of designing and the risk of constructing this crucial system connection increase disproportionally. This paper describes the considerations that went into the approach of connecting a 5-m-diameter TBM drive with the in-river riser shaft of the Annacis Island WWTP New Outfall System in the highly permeable Fraser River sands at hydrostatic pressures exceeding 3 bar.

Jun 23, 2024

By R. D. Coursen

Tin has been one of the very few commodities which has been covered by an international commodity agreement. It is the only metal so covered. The reason behind tin's prediliction for an agreement has been the inconsistency of the price pattern for tin during the entire 20th century. It is not surprising in view - of the wide and wild fluctuations in its price that tin has been called the Cinderella metal. An examination, for example, of prices in 1977 alone attests to the erratic behavior of the tin markets. The high was recorded on October 27 at M$1,895 per picul and the low on January 3 at M$l,314 3/8, on the Penang market, a spread in Malaysian dollars of $581 for a picul weighing 133 1/3 pounds. The first steps in international cooperation on tin were taken after the price bonanza of the First World War. Despite a lack of increased consumption, and in spite of the fact there was no shortage of mining production during the war, prices boomed. Shipping shortages and thinning stocks brought about a situation where in the U.S., industrial stocks were only 1/6 of what they had been in 1914. The boom busted early. In 1921 the tinplate industry of the world had cut its output in half and total world consumption of tin fell by 1/3. Tin producers became so concerned that they created what was called the Bandoeng Pool. It accumulated stocks held by countries now known as Indonesia and Malaysia, amounting to 28 percent of the combined production of the two countries and about 15 percent of the total world for 1921. The pool holdings were shortly exhausted and thereafter in the years 1924 to 1928, general boom conditions existed for tin.

Jan 1, 1978

By Ing. Ludwig Schlebusch

The significant growth of the world population and its demand for an increasing standard of living leaves no other choice than continuously augmenting industrial production and making available steadily greater quantities of raw materials at still better qualities. Therefore, any raw material has to be utilized to the greatest possible extent and processed at optimum economy on large mechanical equipment. The layout of processing facilities of large throughput rates can be based on multiple or single lines. The latter enables the application of large machines of optimum size. Proven equipment for homogenizing, classifying, separating superfine material, sorting and dewatering are-now available in optimum sizes. By the use of these large machines operating cost of pit coal preparation plant can be significantly lowered by reducing the specific requirements regarding space, capital investment, energy, operation and maintenance.

Jan 1, 1980

By R. L. Virta

Ball Clay -- Four companies - H.C. Spinks Clay Co. Inc. (owned by Lhoist Group), Imerys Group (formerly Kentucky-Tennessee Clay Co.), Old Hickory Clay Co. and Unimin Corp. - mined ball clay in four states during 2010. Production, based on preliminary data, was 910 kt (1.11 million st) with an estimated value of $42.9 million. That was a 10-percent increase in tonnage from 831 kt (916 million st) with a value of $37.7 million that was produced in 2009. Tennessee was the leading producer state with 61 percent of domestic production. It was followed by Texas, Mississippi and Kentucky. About 70 percent of production was airfloat, 20 percent was crude and 10 percent was water-slurried.

Jan 1, 2011

By W. F. Mullen

Within the scope of this discussion, artificial dimension stone is defined as any manufactured product used as a substitute for natural dimension stone. The history of the development of these substitute materials is reviewed briefly, representative characteristics of each product are listed, several analyses of their market position are presented, and suggestions are made for recapturing markets lost to these products and preventing additional inroads.

Jan 1, 1959

By Ross A. Scarano

It wasn't until late 1976 that the U. S. Nuclear Regulatory Commission (NRC) set about to address the uranium tailings issue in earnest. It was decided that a generic environmental impact statement related to uranium milling operations would be prepared to support formal tailings regulation. We recognized, however, that this was a task that would take many years to complete and we could not take a "business as usual" approach to tailings management in the interim; the issue was too sensitive. To facilitate licensing during the interim period, the NRC developed guidelines in May 1977, for the industry in the form of the following performance objectives for tailings management: Siting and Design 1. Locate the tailings isolation area remote from people such that population exposures would be reduced to the maximum extent reasonably achievable. 2. Locate the tailings isolation area such that disruption and dispersion by natural forces is eliminated or reduced to the maximum extent reasonably achievable. 3. Design the isolation area such that seepage of toxic materials into the groundwater system would be eliminated or reduced to the maximum extent reasonably achievable. During Operations 4. Eliminate the blowing of tailings to unrestricted areas during normal operating conditions. Post Reclamation 5. Reduce direct gamma radiation from the impoundment area to essentially background. 6. Reduce the radon emanation rate from the impoundment area to about twice the emanation rate in the surrounding environs. 7. Eliminate the need for an ongoing monitoring and maintenance program following successful reclamation plan. 8. Provide surety arrangements to assure that sufficient funds are available to complete the full reclamation plan.

Jan 1, 1980

By d&apos, L. R. Fletcher, Andrea. D. V., M. A. Peltier

The Bureau of Mines analyzed coal mine blasting accident data obtained from the Mine Safety and Health Administration (MSHA), U.S. Department of Labor. The data were examined to determine the causes, frequency, and severity of accidents in an effort to point out the most dangerous aspects of coal mine blasting. Accident data for the 14 years from 1971 through 1984 show that there has been a total of 43 fatal and 926 nonfatal blasting accident victims in surface and under- ground coal mining. This is an average of 3.1 fatal and 66.1 non- fatal injuries each year. Underground coal mining accounted for 60.5% of the fatal and 78.7% of the nonfatal accidents involving explosives and breaking agents in coal mining. In addition, since 1970 there have been 53 fatal and 20 nonfatal injuries that occurred when explosives were the ignition source for dust and/or methane explosions in underground mines. Abstracts from 297 accidents that occurred from 1978 through 1984 were also examined to determine accident causes. Most accidents occur during scheduled blasting, and failure of the blast area security system is the leading cause. Blast area security problems in surface mining are failure to clear the blast zone, failure of personnel to follow instructions, inadequate guarding, and failure to retreat to a safe location and/or take adequate cover. Other common causes in surface mining include premature blasts, excessive flyrock, and misfires. In addition to the above causes, accidents in underground coal mining can be due to rockfalls triggered by the blast, unexpected breakthroughs, fumes, and incidents associated with Airdox-type systems.

Jan 1, 1986

By D. R. Rathburn

Jan 1, 1962

By Kirk Carlton

This paper deals with a group of subjects so familiar to all of us that we might question the need for discussion. Even so, nearly every day's business turns up expensive examples of differences in understanding, misdirected assumptions and incomplete technical purchase documents. As our international activities increase, so do these problem areas. Their expense in both money and embarrassment gives rise to this attempt to focus a little extra attention on technical criteria and specifications. The two terms ?criteria? and "specifications" are, we believe, worth separating with respect to meaning. They should not be used interchangeably, although they often are. Criteria are by definition "standards for judging", whereas specifications are "enumerations of particulars". In relation to plant or project engineering, the criteria are the general rules and data which apply to the whole project and the specifications are the further listing of detailed requirements for specific contractual items or pieces of equipment. We'll look a little more closely at specifications after we give another minute or two to this "criteria" subject,

Jan 1, 1973

By Sol Ribakoff

In 1973, the Subcommittee on Contracting Practices, U. S. National Committee on Tunneling Technology, National Academy of Sciences, under the able chairmanship of A. A. Mathews, Engineering Consultant, now residing at Kaunakokai, Hawaii, undertook the task of developing recommendations for improving the performance of underground construction work, reducing the costs of such work and minimizing the adverse atmosphere in which owners and contractors were performing their respective functions. The author of this paper and C. F. Palmetier, a highly qualified engineer, were thereupon appointed as staff assistants to the Subcommittee, to conduct a study of existing practices and relationships in Western Europe and in the United States, to formulate recommendations, for consideration by the Subcommittee and the participants in a future workshop, as to desirable improvements in United States contracting practices and relationships. The study, conducted during 1973 and 1974, involved personal interviews of a total of 162 owners, engineers, contractors, lawyers, and educators throughout the United States and in 7 European countries, the analysis of 178 replies to questionnaires sent to individuals and firms involved directly or indirectly in construction, and a workshop, near Napa, California, attended by 53 representatives of all segments of the construction community. The resulting report, entitled "Better Contracting for Underground Construction", was submitted by the Subcommittee to the National Academy of Sciences, which approved its publication in 1974 by the National Technical Information Service. It may be obtained from that Service at Springfield, Virginia, 22161, as Accession No. PB-236 973. It was recognized-during the course of the study that while contracting practices and owner-contractor relationships were the

Jan 1, 1981

By Alastair R. Biggart

ABOUT BENTONITE TUNNELLING Much has been written and many learned papers given on this subject whose generic term is Slurry Tunnelling. This paper is about the particular form of slurry tunnelling known as the Bentonite Tunnelling System. This method. of tunnelling was invented by J.V. Bartlett of consulting engineers, Mott Hay and Anderson in 1964. The general principles are incorporated in British Patent No. 1083322. It was not until the early 1970's that serious experimental work was started to prove the technical feasibility of the process. In the U.K. in 1971 Edmund Nuttall Limited started on an experimental length of 3.8m diameter tunnel at New Cross in London. In Germany at about the same time Wayss and Freytag were starting on a 3.7m diameter collector sewer tunnel in Hamburg. In Japan early slurry tunnelling work was carried out in the 1960's. In the early 1970's a large number of slurry tunnels of various diameters were carried out in that country. This paper is being presented at a time when this system of tunnelling has become an accepted method throughout the developed world. As a result of the work carried out so far there is now a large amount of data existing regarding the effects on the ground in the immediate area of the tunnel, settlement at the surface and the ability of the system to cope with ground varying from clays to coarse gravels and containing large erratics such as granite boulders. The decade of the 1970's has therefore seen a very rapid pace

Jan 1, 1979

By D. F. Malott

The Michigan Department of State Highways makes extensive use of geophysics for subsurface surveying which would be applicable for uses in other fields. Examples of resistivity surveys are given which include a proposed large volume excavation with suggestions for land use after excavation, subsurface evaluation for engineering design, and a subsurface survey for land appraisal. An example of a combined refraction seismic and resistivity survey is shown where the resistivity is used for outlining the unconsolidated soils, while the seismic method Is used to outline bedrock and to evaluate it for rippability. A refraction seismic survey at the bottom of bridge caissons for evaluation of bedrock uniformity and a relative aid In assessing rock strength is reported.

Jan 1, 1968

By W. S. Fyfe

The future environment of our planet, with the concept of sustainable development, has moved to centre stage of all future plans for development. This global view is new. It presents great opportunities and challenges for the Earth Sciences. We have the tools to describe our environment on all scales - planetary to molecular levels. We must respond to this great demand by world society.

Jan 1, 1990

By Josh B. Taggart

Some twenty to twenty-five years ago we saw the beginning of mechanization in our coal mines, It has now progressed to the point Chat as instruments of production the pick and shovel are things of the past, They had to give way to better and more efficient methods--so mechanization, followed by and combined with automation, has become common-place in our mines. Our coal could not keep its competitive position without this progress Without it our industry could not look to the future with any degress of confidence. Today we lock back and see cases of regained and salvaged markets. We see better coal products being produced at decreasing costs. We see better utilization of manpower and a stronger, more confident industry, Our hats arc off to those mining men, equipment manufacturers, labor leaders, and others who had the foresight to work toward these ends and the ability to bring them about.

Jan 1, 1962

By W. J. Turbeville

The subject of this discussion is timely. The U.S. phosphate industry is suffering the throes of depression. It's plight is a matter of widespread concern. The future role of the U.S. industry in world markets is of particular interest. If we should prognosticate phosphate supply-demand on the basis of recent history, we would face a puzzling choice of scenario. In 1980, perhaps the best year ever for U.S. phosphate, 54.6 million metric tons of phosphate rock entered the market place. Of this, more than half was exported -- divided almost equally - as rock or phosphate fertilizer. During the last half of 1981 the situation had begun to change.

Jan 1, 1983

By D. W. Olson

The estimated value of natural gemstones produced from U.S. deposits during 2004 was $12.9 million. This was a 3-percent increase from that of 2003. U.S. gemstone production included agates, amber, beryl, coral, garnet, jade, jasper, opal, pearl, quartz, sapphire, shell, topaz, tourmaline, turquoise and other gem materials. More than 60 varieties of gemstones have been produced commercially from U.S. mines. But commercial mining of gemstones has never been extensively undertaken in the United States. Most of the deposits have been relatively small compared with other mining operations. In the United States, much of the current gemstone mining is conducted by collectors, gem clubs and hobbyists rather than business organizations.

Jan 1, 2005

? The economic health and national security of the U.S. depends on the continued availability of, and access to, reliable and affordable energy and mineral resources. However, America is hindered by a costly, inefficient and often redundant regulatory structure that thwarts domestic investment, expansion and job creation. The annual cost of federal regulations in the U.S. increased to more than $1.75 trillion in 2008; averaging $8000 per employee.(The Impact of Regulatory Costs on Small Finns, SBA, 2010) ? The complexity, uncertainty and delays within the current permitting system places the U.S. at a competitive disadvantage with many other countries that have both abundant mineral resources and a more welcoming business and regulatory climate. As a result, American and international mining companies often move overseas or across borders to invest capital, create local employment, and produce the critical minerals America must then import at higher cost, while sacrificing employment and economic stimulus. ? According to Behre Dolbear, the U.S. is ranked lowest globally due to the lengthy permitting period required before mine development can commence. (Where not to Invest, 2010).

Jan 1, 2011

By Jr. Winters

The United States continues to be the largest producer and consumer of copper in the world. Table 1 on the following page shows several production statistics for 1974, the most recent year which the non-communist world copper industry might consider a good year, and for 1976 and 1977. In 1974 an estimated 24 percent of the non-communist world's newly mined copper was mined in the United States, and. 87 to 89 percent of that was from the western porphyry coppers. In 1976 U. S. new mine production was down to 22 percent of the non-communist world's newly mined copper, and the percentage of U. S. new mine production supplied by the porphyry coppers had risen to 89 to 91 percent. In 1977 the statistics remained the same as in 1976. U. S. porphyry copper production represented about 65 percent of U. S. refined copper consumption in 1974, rose to 75 percent in 1976, and dropped back to 61 percent in 1977 as imports of foreign copper into the United States began to swell.

Jan 1, 1978