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By J. H. Kempton

The scrutiny given to model predictions of pit-lake water quality has focused attention on the uncertainty associated with long-term predictions. Although comparison of probabilistic predictive modeling of water quality in existing pit lakes indicates that short-term predictions can bracket most parameters, uncertainties in wall-rock reactions and the stability of groundwater composition and climate remain unquantified. This overview of the uncertainties associated with longer-term predictions is presented as support for those considering policy decisions that must be made in the absence of reliable estimates of future conditions.

Jan 1, 1998

By Robert W. Carn

This paper presents the concepts which are presently being utilized in the design of coal export terminals. Criteria for selecting a viable site and establishing the terminal plan are presented. Factors affecting the design of the terminal as well as the present techniques and procedures in use today to determine the optimum use of equipment will be discussed along with the current trends in export terminal control systems. Finally capital and operating costs for a typical export terminal are reviewed.

Jan 1, 1982

By Brian E. Davies, Bobby G. Wixson

INTRODUCTION The mining, extraction and refining of metals into useful materials is an honorable profession with an ancient and productive history. Civilizations have long depended upon metals for their implements, structures and machinery necessary for survival, growth, and development. Today, as in the future, metals and minerals are essential to the progress of mankind as we approach the 21st century with technologies and concepts that will require new concepts and production from the metal mining and processing industries. Today is the tomorrow we talked about yesterday and the implementation of new ideas is essential if we are to achieve "Frontier Technology in Mineral Processing". Unfortunately, the state-of-the-art mining, processing, smelting and refining methods historically employed were less than desirable environmentally, which has caused todays public to view the metal mining and processing industry with concern. Presently the ancient rock and chat tips connected with old Roman lead-zinc mines which were worked in Wales are causing stream contamination problems that must be corrected at considerable expense to the local governmental agencies (Firth, J.N.M., et al., 1981). However, improved progress has been made and the environmental control and clean-up procedures utilized by modern lead-zinc operations in the "Viburnum Trend" or "New Lead Belt" of South East Missouri may serve as a model to illustrate how alternative technologies, environmental concerns and cooperative efforts contribute to efficient mineral production within the confines of a U.S. National Forest region without significant environmental impacts. This area received international attention when it was opened within the boundaries of the Clark National Forest in the mid 1960's. By 1970 it ranked first in the world by producing 432,576 short tons of lead ore and has since continued in this position producing 451,153 short tons of lead ore in 1983 representing 91% of the total United States lead production (U.S. Bureau of idines, 1983). This production comes from a mining area approximately 40 miles long by 10 miles wide extending in a north-south direction. Geologically the lead is disseminated throughout the Cambrain age Bonneterre Formation, mostly a dolomite, at depths ranging from 700 to 1200 ft. (213.4 to 365.8 m). Galena (lead) is the principal ore mined with lesser quantities of sphalerite (zinc), chaleopyrite (copper) and silver being recovered as economic co-products. This new mining development in one of Missouri is most scenic areas could have led to a classic confrontation between industries and environmentalists. Instead, through the cooperation of industries, governmental agencies and university researchers, the Ozark environment has been protected, and may serve as a model for future coexistence of the mineral industry with the environment. Cooperative Program Development As early as 1965 five new mines and two lead smelters were being prepared for production and environmental concern was an essential part of that planning. All the mining companies became acquainted with representatives of the various federal and state agencies and scientists from the University of Missouri-Rolla (UMR). During the next six years, St. Joe Minerals Corporation, American Metal Climax, Inc., Cominco American Incorporated, Ozark Lead Company (Kennecott) and American Smelting and Refining Company participated in cooperative research efforts. The companies also participated in information exchange meetings, the development of improved analytical methods and the utilization of research findings in the modification or construction of pollution-abatement facilities. Early on research was carried out to determine background values and to establish natural baselines of trace metals in the surrounding environment. The unusual topography and drainage pattern of the mining area were helpful since it was possible to establish control sites and test sites below individual mine-mill operations to study waste-water effects on the receiving streams. The location of the ‘New Lead Belt', mines, mills,

Jan 1, 1985

By E. I. Jurgens, K. E. Hanney, D. C. Comrie, R. H. Fletcher

Introduction The reclamation of mine/mill tailings areas is undertaken for a variety of objectives including safety, appearance, economical use of lands and forests and long term storage of a future resource. The establishing of criteria for these objectives at any site is a shared task of the government and mining company. Our attention in this paper is directed to uranium mine/ mill tailings as they are handled in the Canadian industry and in the unique Canadian climate. We focus our attention on the state of the art. Uranium is a ubiquitous mineral forming an average of 4 g per tonne of the Earth's crust. Ores are mined at about 500 g per tonne so that the residual content of uranium in tailings is comparable to average background levels. However, as in most mine/mill operations, the ore contains other minerals that become readily mobile after milling operations. Thus the main objective of tailings impoundment is the stability both physically and chemically of the mobile materials. Since the requirements for the operation and construction of tailings areas in Canada have changed considerably over the past decade, there exists a great many mine/mill tailings areas which while considered adequate in their day, would not meet modern criteria. However, most of these installations pose no concern or hazard to the public. The proximity of mine/mill development to inhabited land areas has necessitated more stringent modes of tailings operations and provisions for tailings site reclamation. The more important of these have been: 1) the prevention of dyke failure, with large liquid-solid outflows onto adjoining lands, and 2) the prevention of seepage from the tails of pollutants such as chlorides, sulphides, heavy metals and radionuclides. Uranium mill tailings are discharged as a slurry from the concentrator after the removal of generally only about 1000 g, or less, per tonne of uranium from the as-mined ore. As a consequence, a great volume of low level activity waste is generated. The amount of tailings is expected to grow in quantity in the future even faster than the increase in yellowcake production, as the demand for energy

Jan 1, 1980

By Michael J. Humenick

A laboratory experimental research project was conducted to evaluate the use of chlorine for the oxidative destruction of residual ammonia which may remain in ground water after in-situ uranium solution mining operations. The work tested the idea of the injection of high strength calcium hypochlorite solution into the mining zone to convert ammonia to nitrogen gas as a final clean-up process for ammonia removal from the ground water system. The paper details ammonia removal efficiency as a function of chlorine dose, reactant and product material balances, and how the concept may be used as a final ground water restoration process.

Jan 1, 1982

By M. J. Shulman

The exploration geologist is frequently confronted with the problem of allocating his resources, i.e., exploration effort, among various areas. Although geologic, financial, and logistic considerations influence the allocations, no objective criterion is usually given that determines the optimal allocation. Maximizing the expected gain in information, subject to the constraint of a limited exploration budget, is used as the objective criterion to allocate airborne reconnaissance effort. The information function, I(x), quantifies the expected gain in information, where x is the scale of exploration. To calculate the information function, the following probabilities are required: the probability that an area contains a deposit; the probability that an anomaly is produced by the target; and the probability that an anomaly is produced by a barren area (false signal). Alternatively, the barren areas can be replaced by other targets. To illustrate the allocation method, the optimal number of line kilometers, i.e., the optimal line spacing per area, is determined for an aeromagnetic survey for iron in Egypt.

Jan 1, 1987

By D. W. Park

Longwall mining is popular in underground coal production in the United States due to higher production rates and safety concerns. Because of the extreme complexity, it is necessary to plan an adequate design to achieve a safe and efficient working place. The proper sizes of yield and abutment pillars and panels can be determined by simulation using numerical modeling techniques. By means of three-dimensional modeling, stresses to be imposed on the pillars, panels, gob, and powered supports can be analyzed. In this study, an initial three-dimensional finite element model was developed and then modified into four different models. Using these models, the numerical outputs of distributed stresses on three different sizes of yield pillars, three different sizes of panels, and two different sizes of abutment pillars were compared and analyzed to determine the most adequate pillar and panel sizes. Progressive failure theory based on the Hoek and Brown failure criterion was used to determine redistribution of stresses in the yielded and failed areas in the longwall mine.

Jan 1, 1992

By R. N. Chakravorty, R. J. Kolada

Introduction Spontaneous combustion in coal mining is recognized as a major hazard in terms of safety and economics. A survey by Olaf (1979) revealed that 80% of coal mine fires were caused by spontaneous combustion. Modern mining methods demand a high capital investment. Closure of a working face may then result in a huge loss. Even a short production interruption can prove expensive. Spontaneous combustion may also produce lethal amounts of carbon monoxide, thus posing a serious threat to the health and safety of underground miners. The worldwide recession in the early 1980s resulted in a number of mine closures and production cutbacks. So large stockpiles at mine sites were common. Experience has shown that stockpile fires are difficult to extinguish. Critical factors influencing spontaneous combustion There is no simple method of predicting whether a particular mining method applied to a specific coal seam will result in spontaneous combustion. Under favorable conditions of heat accumulation, spontaneous combustion can occur with any type of coal. It is known that subbituminous coals are more susceptible compared to low volatility bituminous coals, and that a high ratio of exinite increases the risk. However, the inherent moisture content of the coal and the exposed surface area may be more significant. Actual mining and ventilation conditions also strongly influence susceptibility. In practice, the experience gained with the mining method applied to a particular type of coal seam must be carefully evaluated with respect to the factors responsible for spontaneous combustion. Feng, Chakravorty, and Cochrane (1973) summarized the critical factors influencing spontaneous combustion in coal mines (Table 1). Prevention methods and strategies Mine layout is the most important factor preventing spontaneous heating. Working districts should be designed so that a particular section can be isolated on short notice without affecting production in others. Sites for preparatory seals should be identified and marked during planning. With coal seams that are highly susceptible to spontaneous combustion, the retreat method of working is preferred. This is because the gob is not subjected to a large difference in ventilation pressure. Coal pillars should be designed to resist excessive crush. The panel system of working is preferred, particularly for mining coals susceptible to spontaneous combustion. The size of each panel is calculated based on the incubation period and the rate of extraction. Controlling air leakage is also important for controlling spontaneous combustion. This is usually achieved by minimizing ventilation pressure difference, proper siting of doors, and avoiding unnecessary stopping and starting of fans. Air leakage is also reduced by sealant coating, injection of cements in cracks and crevices, and by maintaining good gateside packs. Application of inhibitors to control spontaneous combustion met with limited success. Chamberlain and Hall (1973) concluded that borate solution or Montan powder sprayed in the gob area or infused into a low rank coal would reduce the possibility of spontaneous combustion. Early detection of heating Significant research is being conducted worldwide to develop methods for early detection of heating. Monitoring combustion products during the early stage of heating is the most suitable method for detecting spontaneous combustion. The major gaseous products resulting from low temperature oxidation of coal are carbon dioxide, carbon monoxide, and water vapor. In mining operations, carbon dioxide monitoring is considered unsuitable because there are sources other than spontaneous heating from which this gas may originate. Carbon monoxide, however, is a more specific product of combustion during low temperature oxidation of coal. Over the years,

Jan 10, 1988

By J. B. Yianatos, G. S. Dobby, J. A. Finch, A. R. Laplante, R. Espinosa-Gomez

The question is posed as to why columns typically have a collection zone 10 m high (H) by 1 m in diameter (D). Three geometry dependent factors are considered: degree of mixing, Np; volumetric bias rate, B; and volumetric gas rate, G. Increasing H:D decreased Np and B, which improves performance but decreases G, which causes the column to approach overloading. Taking typical column operating conditions, it is concluded that a collection zone H:D of 10:l is a reasonable compromise.

Jan 1, 1987

By Andrew B. Allen, Charles W. Robinson, Robert L. Schneider

In April, the US Synthetic Fuels Corp. broke a three-year silence and made its first financial award by approving a $820,750 loan for the First Colony peat-to-methanol project in North Carolina (ME, May, page 403). Peat Methanol Associates (PMA), a partnership between Koppers Co., ETCO Methanol Inc., Transco, Peat Methanol Co., and l. B. Sunderland, broke ground at First Colony last year and plans to begin production in Dec. 1985. Although the award is only a small part of Synthetic Fuels Corp.'s $15-billion budget, it does signal the corporation's intention to move aggressively ahead. It also is a positive indication that First Colony will be completed and operated successfully. This article describes the methods and equipment that will be used to harvest peat at First Colony, as well as how the peat will be converted to methanol. Introduction Peat deposits found along North Carolina's coastal plain contain high-quality fuel-grade peat with an average heating value of more than 23.3 MJ/kg (10,000 Btu/lb) (dry), with a low sulfur and ash content. The deposits differ from other US peats in that they contain large, sound Atlantic White Cedar and Cypress logs, stumps, and roots that may extend throughout the full depth of the deposit. A second difference is that these deposits are much more highly decomposed and, in the raw state, have the appearance and feel of a heavy, reddish-brown grease. These factors make it impractical to use standard production equipment so a new line was developed. Also, because of these conditions, techniques were modified to facilitate production. First Colony Farms, located near Creswell, NC, developed and evaluated a milled peat program. Equipment for this production method was designed and built, production rates were established from field operations, drying rates were established, weather data were analyzed, and total operating and capital costs were estimated. The method depends on the sun and wind for drying peat to the desired moisture content, in this case around 40%. Therefore, field preparation is actually the construction of a large solar collector to dry the peat so it can be harvested and stockpiled. It is essential that this collector be properly profiled initially and maintained during production to prevent precipitation from ponding. Initial Field Preparation Initial field preparation includes cleaning existing canals and constructing ditches and water control structures for proper drainage of rainwater run-off, building adequate roads for site access, removing surface vegetation, and profiling and sloping the fields. At First Colony, the 60.7-km2 (15,000-acre) harvesting area was divided into 129.5-hm2 (320-acre) blocks about 1.6 km (1 mile) long and 805 m (0.5 mile) wide. This was accomplished by cleaning main outfall canals with adjacent roads built from canal spoil at 1.6-km (1-mile) intervals. Existing intermediate canals that feed into main outfall canals at 805-m (0.5-mile) intervals also are cleaned. Headland roads are constructed from canal spoil along each side of each intermediate canal. This 129.5-hm2 (320-acre) block is then divided into 32 harvest strips by small V-ditches constructed at 50-m (165-ft) intervals. At the end of the field with the lowest elevation, corrugated steel pipe culverts are installed under the headland road in each V-ditch to control rainwater runoff into intermediate canals. Runoff water from the fields is diverted to a holding pond to prevent any increase in peak water runoff rates and to allow for more uniform drainage rate than experienced to date. After the drainage system is installed, harvest strips are ready for grinding and sloping operations. Surface vegetation, made up of small, waxy-leafed shrubs such as Gallberry, Bayberry, Magnolia, and scattered pond pine, can be effectively ground and incorporated into the upper surface of the peat layer. Here, it will rapidly decompose and have little effect on overall peat quality, thus eliminating the standard practice of pushing the vegetation and upper wood layer into long windrows with bulldozers and hauling this debris from the fields. Incorporating vegetation into the upper surface is known as the initial 102-mm (4-in.) surface vegetation grind and is accomplished by using a modified Bros Rota Mixer. Following this operation, and by using the same unit, a sec¬ond grind with a depth of 200-255 mm (8-10 in.) is made. This reduces the debris to a finer consistency, mixes it with the upper peat layer, and grinds any wood found in the upper 200-255 mm (8-10 in.). After initial grinding operations are completed, the augering or sloping operations can be accomplished with little or no hin-

Jan 7, 1983

By J. David Lowell

This paper describes the geology of the Kalamazoo copper orebody discovered in the course of an exploration project carried out by Quintana Minerals Corporation under the author's direction in an area immediately southwest of the San Manuel mine, Pinal County, Arizona. In the period 1943-1947, exploration projects were carried out in the San Manuel area by the U.S. Bureau of Mines and Magma Copper Company which resulted in the development of the San Manuel underground block-cave mine which is now in production at a rate of 41, 000 tons per day. Mining claims covering the area immediately west of the San Manuel orebody were staked in 1946 by Frank F. Salas, R. A. Buzan, H. G. Buzan, and W. C. Buzan of Mammoth, Arizona. These claims were optioned to Martha Purcell in 1946, and in the period of 1947-1958 seven churn drill holes ranging in depth from 1,400 to 2,950 feet were drilled by Mrs. Purcell. These holes did not intersect ore and no further deep exploration was attempted prior to the Quintana Minerals project which began in August, 1965, and which is described in this report. The Kalamazoo deposit is in Sections 3, 4, 9, and 10, T 9 S, R 16 E, Pinal County, Arizona, and it is reached by driving seven miles east from Oracle, Arizona (Figure 1) . The writer is indebted to Corbin J. Robertson and Ronald B. Thompson who participated in the exploration planning of this project and to a number of other individuals who contributed to its execution and management. Petrographic work by J. M. Guilbert was used as a basis for rock and alteration classifications.

Jan 1, 1968

By E. F. Schnitzer, C. Lidstone, D. Cramer, P. J. Wampler

The River Island mining site is located at approximately river mile (RM) 15 on the Clackamas River, a large gravel-bed river in northwest Oregon. During major flooding in February 1996, rapid channel change occurred. The natural process of meander cutoff, slowed for several years by dike construction, was accelerated by erosion into gravel extraction ponds on the inside of a meander bend during the flood. In a matter of hours, the river cut off a meander and began flowing through a series of gravel pits located on the inside of the meander bend. The cutoff resulted in a reduction in reach length of approximately 1,100 m. Erosion by bed lowering, knick point retreat and lateral erosion of upstream river banks occurred quickly. Within two days of the peak flow, 3.5 hectares of land and 105,500 m3 of gravel were eroded from the river bank just above the cutoff location. Much of this gravel moved a short distance downstream into the excavation. Reach slope increased from 0.0022 to approximately 0.0035 in the cutoff reach. Between 1996 and 2003, the knick point from the meander cutoff has migrated 2,290 m upstream, resulting in increased bed load transport, incision, and local lowering of the water table. In 1993, prior to the meander cutoff, transects were surveyed in the River Island reach upstream of the cutoff location. Resurvey of these transects and aerial photo analysis indicates that 96% of the knick point migration occurred during the first winter following meander cutoff. Connection of the flowing river to the off-channel ponds has had minimal effect on water temperatures in the mainstem Clackamas River. It is likely that this minimal change in temperature will decrease as ponds are isolated from active river flow by gravel bar deposition. Fish net-ting in spring 2002, suggests that salmonid use of the pond in the spring is minimal. The most abundant native species netted were large-scale sucker and northern pikeminnow. The most abundant non-native species netted was brown bullhead. Early regulation by state and federal agencies did not adequately evaluate potential impacts to the river and the floodplain; nor did it evaluate future impacts related to geomorphic processes and sediment transport. New permit evaluation methods, currently implemented by both Oregon and Washington, incorporate 1) river dynamism through historic river migration analysis; 2) stability of human structures in light of river dynamics; and 3) sediment transport and its impact on channel stability and dynamics. The gravel pit capture at River Island highlights the potential risks of mining in an active secondary channel of a large gravel-bed river. Mining deeper than the depth of the adjacent channel, within the active migration zone, may increase off-site impacts. In locations where multiple gravel excavations are present within the meander zone, a comprehensive reclamation and restoration plan should be developed which provides long-term channel stability within the natural variability of the entire river reach.

Jan 1, 2006

By W. A. Cincilla, S. C. Tadolini

INTRODUCTION Resin bolting systems continue to gain popularity in underground coal mines in the United States, and their general success under a wide range of geological and operational conditions is well documented. In 1984, 36% of all bolts used were resin-grouted systems. However, many questions dealing with basic support mechanisms and the influence of various factors on bolt effectiveness in situ remain only partially answered. The Bureau of Mines' Denver Research Center conducted a major research project to investigate the influence of installation procedures on the effectiveness of resin-grouted roof bolts. The project consisted of two main studies: the first dealing with the contribution of bearing plates to the load-carrying capability of the bolt; the second examining the relationship between installed grout column and the anchorage capacity as measured by the standard pull-out test. Additionally, a finite-element computer model and other analytical and empirical techniques were applied to aid in the basic understanding of the test procedures and to examine the load transfer mechanism in resin-grouted bolts, which to date has not been comprehensively assessed. The plate study includes field test results from two mines (Fig. 1). At these test sites two behavioral parameters were measured: the actual loads that bearing plates were subjected to when installed in conjunction with full-column resin grouted bolts, and the roof movements generated by the applied loads. Results indicate that bearing plates are subjected to varying degrees of loading, which range from conventional installation pressures of 2.2 kN (500 lb), up to a measured load of 142.4 kN (32,000 lb) when the immediate roof is shifting and deforming. These measured loads indicate that the bearing plate is an integral part of the support system. Differential sag stations, installed to monitor roof displacements in the test sites, show the highest degrees of loading occur in conjunction with the largest amounts of movement. The column-length study addresses possible reductions in anchorage capacity of "full column" bolts. These reductions could result from such factors as the loss of grout to surrounding strata, or improper mixing of catalyst and resin. Field test sites were established at eleven mines located in major coal mining districts throughout the United States (Fig. 1). Four major roof-rock types were represented in the study: shale,

Jan 1, 1986

By David D. Rabb

Leaching or solution mining, a relatively simple and economical process for beneficiating metallic ores, is likely to find increasing application in the treatment of low-grade ores that are impractical to mine by any other means. This process may be carried out in two different ways: 1. Dump leaching, where the ore is moved from its original location to be leached at another site. 2. In situ leaching, where the ore is leached in place by introducing the leach solution at the top, letting it flow down through the ore under gravity, and then recovering it plus the dissolved metals it contains.

Jan 1, 1969

By W. E. Sabina

In the short period of one mans? career we have seen specifications for bulk material handling systems and equipment grow from two or three pages to as much as two or three volumes for a single contract. The old 'short form' described what the purchaser expected the equipment to do. The long form does the same but also includes nut, bolt, and lockwasher depth of detail. What are the events that led to this proliferation of verbiage, and does it benefit the buyer in the final analysis? Is there a better way to purchase complex equipment while ensuring the highest quality for the dollar spent?

Jan 1, 1986

By Henri Letient, Tom Aley, David Evans

Antamina is a large open-pit copper and zinc mine located within the Central Andes of Northern Peru at an altitude of 4300 masl. The facilities are situated within the headwaters of several watersheds, within the Amazon basin. Nearby villages rely heavily on springs and streams for drinking and irrigation water. The principle source of baseflow during the dry season is from Cretaceous karstic limestone aquifers. Antamina will produce nearly 1.4 billion tonnes of waste rock over its mine life. Finding suitable sites for storing large volumes of waste rock is often a challenging task – especially in karstic, alpine terrain. Detailed hydrogeological investigations are essential for delineating the karstic hydrogeologic watersheds associated with the proposed waste facilities, which are often very different than topographic (hydrologic) watersheds. Contamination vulnerability mapping at Antamina consisted of geological and karst mapping, geophysical surveys, geochemical testing, dye-tracer studies, drilling and aquifer testing. Detailed mapping followed by dye-tracer studies proved to be the most cost-effective methods for characterizing the karst aquifer systems. The results were used to optimize waste rock management at the site to minimize potential impacts on groundwater resources.

Jan 1, 2005

By K. Perry, R. Eades

"Highwall miners continue to be implemented by operations to increase recovery, improve margins, and justify higher stripping ratios as high quality surface reserves become increasingly rare. Many times, operations facilitate projected underground operations by leaving an intact highwall for development purposes. These facts result in larger highwalls that are left standing for increased periods of time prior to reclamation. As a consequence, worker exposure and risk is also elevated, resulting in higher potential for accidents or fatalities relating to surface highwalls. Highwall stability is a complex issue, dependent on both geologic and mining factors. Dynamic numerical modeling offers the capability to assess possible stability issues related to blasting-induced ground vibrations. Research has been conducted to evaluate the effect of highwall stability due to ground vibrations from blasting events. Additionally, the relationship of amplitude and frequency, and their impact on highwall stability is investigated. The results of this modeling indicate that amplitude has little impact on stability. However, frequency has a significant impact on highwall stability. INTRODUCTION The number of mining fatalities has declined since 2010, and 2016 is currently on pace to continue this trend (MSHA 2016). This decline can be directly correlated to the decline in surface mining activity and the overall decline of the coal industry. However, since 2002 the percentage of surface coal mine fatalities associated with highwall activities remains relatively high, constituting approximately 15% of all surface mine fatalities. 2014 was the first year with a highwall failure fatality since 2011. Most recent surface coal mining fatalities are associated with machinery and haulage. Table 1 provides a summary of the total surface coal mining fatalities, and the number of highwall failure fatalities dating back to 2010.Highwall stability is a complex issue, dependent upon geology and geologic discontinuities within the rock mass, along with highwall geometry, standing time, and applied stresses. Another possible concern that has not been previously investigated is the effect of blasting-induced stresses on highwall stability and the stability of web/barrier pillar systems as a result of ground vibrations from blasting events. Many modern surface coal mines employ numerous extraction fronts that rely on blasting for primary rock breakage. This results in highwall and highwall pillar systems experiencing blasting-induced stresses of many different types and magnitudes."

Jan 1, 2017

By Niels Jonassen

INTRODUCTION The occurrence of the radioactive element radium, [2gg~a], often in trace amounts, in the crust of the earth gives rise to a flux of the daughter product radon, ['ii~n], across the earth-air interface. This so-called exhalation process has been studied by many investigators [KO 45, Kra 64, Pe 66, Wi 741] over several decades. In the earlier investigations the exhalation process was studied in a purely geophysical context, but over the last 20 years it has been realized, that under certain conditions the exhalation may be intense enough to also have radiological implications. This is for example the case where relatively radium-rich wastes or by-products, like uranium mill tailings and phospho-gypsum, are stored in larger quantities. In order to be able to predict the radiological impact on the environnent it is necessary to know the rate of exhalation of radon from the surface of the exhaling material. Usually the determination of these exhalation rates has been done by measurements in situ directly upon the accumulated material [~le 74, Ha 791. Although such field measurements have the obvious merit of dealing directly with the full scale problem, the results are often lacking in generality, making predictions for other situations difficult or even impossible. The present paper describes some results of an investigation where it is attempted from laboratory measurements on samples of limited size to obtain material parameters, which are suited for extrapolating and predicting the radiational behaviour of larger accumulations of the material. THEORY Let us consider a sample of a radon exhaling material enclosed in a container with a dead space volume, Vd, and initially containing radon free air. If the total exhalation rate (number of atoms per unit time) is c, the radon concentration (number of atoms per unit volume) N will initially grow with the time t according to the equation [ ] where [R] is the decay constant of radon. As the concentration (or activity) in the container grows, the net exhalation rate will slow down because of back diffusion, and, furthermore, radon atoms may be removed from the container, not only by radioactive decay, but also by diffusion leakage [JO 81 ]. If, however,only the initial. part of the activity growth curve is considered, the total exhalation rate, c, is given by [c = r•Vd(2) where r is the initial activity growth rate in the container. Let the container be cylindrical with an inner cross-section S and filled to a height L with a radon exhaling material with the specific mass p, the porosity E, the radon pore production rate f and the diffusion length i. When the container is left open,i.e. the radon exhalation takes place into a virtually radon free room, the radon area exhalation rate, E, can be written [Jo 80] E = Ef?t tanh L.R (3) assuming the exhalation only takes place in one direction, towards the surface of the material. It appears that for values of L > 2•ithe area exhalation rate becomes E a = Efi (4) independently of the sample dimensions and the total exhalation rate c is then c = E •S (5) For L ;~ 0.5•i, tanh P _ k and equation (3) may be written E ~ EfL (6) then c = EfL•S = p•m= Em •m (7) where m is the mass of the sample and Em = P (8) is the mass exhalation rate. It thus appears that the radon exhalation rate from a given amount of material may often be conveniently expressed by c = E •Sfor L z 2•I (5) a orc = Em •mfor L0.5•i (7) where S is the total exhaling area and m the total exhaling mass, E and E the area and mass exhalation rates respectively defined by equations (4) and (8).]

Jan 1, 1981

By Don Reining

The sand and gravel industry in Southern California has made a sizeable contribution to the construction development of the 15 County area in this part of the State. Facing this mineral extraction industry, in the next decade, is a problem of meeting the market demand. The question is, "how can sand, gravel and rock operations be made compatible with goals for sound and attractive community development?" Three basic principal characteristics of the land needed for this-mining industry are: 1. The land must have workable sand, gravel or stone deposits. 2. The land must be properly located for transportation purposes close to the market in order to sell the aggregate at a minimum cost. 3. The land must be zoned so that it will be permissible to mine.

Jan 1, 1967

By S. L. Bessinger

In the design and specification of a ventilation system for an underground mine, it is necessary to make reasonably accurate estimates of the pressure losses in the various airways of the mine. These estimates can be made with little difficulty for open airways with simple geometric cross-sections, such as those cut by continuous miners or tunnel-boring machines. The situation is much different on a longwall face, where the airway's complex geometric cross-section and the presence in the airway of obstructing equipment having a variety of shapes make it difficult, if not impossible, to estimate pressure loss using traditional methods of calculation. Headlosses in mine entries are calculated using Atkinson's Equation (1). [H = (English) H = (SI) (1)] where H = pressure ,loss, in. of H20 (Pa) K = friction factor, lbf min2/ft"4(Kg/m3) P = perimeter, ft. (m) L = airway length, ft (m) Q = airflow quantity, ft3/min (m3/sec) A = flow cross sectional area, ft2 (m2)

Jan 1, 1987