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By Jacques B. Wertz

Although fracture intersections and "domes" seem at a number of places to be the basic structural combination for the occurrence of a mining district, of the porphyry-copper type particularly, this situation is, of course, not always to be expected. For instance, the group of mines comprising Superior, Ray, Miami, Globe, Christmas appeared from the beginning of these structural studies as typical exceptions, and there are others. One had to expect additional parameters to allow for any mineral concentration to occur. One of these apparent parameters is here considered. From the result of stratigraphic studies related to ancient formations in Southeast Arizona, the Martin limestone (Devonian in age) was retained as having a possible relationship with the structure-economic studies in progress, as evidenced for instance by the mineralized O'Carroll bed located at the base of the Martin. This limestone formation has been rather extensively investigated in the past and there are many known sample localities. For this work, the isopach map was drawn by computer to insure more objectivity and, in addition to the available data points, a number of dummy points with a zero value were added around the assumed form-

Jan 1, 1971

By John Heter

An alum/sulfur deposit (USDA organic registered) was mined underground for alunite (K,Na) Al3 (SO4)2 (OH)6 from the early 1900s to the 1930s. It is now being mined as an open pit quarry. A larger assemblage of minerals is included with this method (Alunite, Potassium?Alum, Jarosite, Gypsum, Native Sulfur and K-feldspar). This assemblage of minerals provides the necessary requirements as a Volcanic Soil Conditioner Sulfur-Potash. Heart of Nature? Company has been marketing this product to farmers on the west coast as a (1) pH reducer, (2) soluble sulfur and potassium source for plant growth and (3) soluble calcium. Recently, a new market has been tapped. This product has been found to solve many odor, bacteria and algae problems faced in the dairy industry.

Jan 1, 2008

By Leonard Sugin

As we approach the end-of the 20th century we are made more aware of the tremendous role that energy plays both directly and indirectly in our varied way of life. The industralized nations of the world have already established industries and economies which are greatly dependent upon the availability of energy. The underdeveloped and developing nations of the world are slowly and surely moving to the same utlimate requirements. The world wide need for distribution of energy sources is continuing to grow. At the present time there is a great imbalance between the sources of energy and the consuming economies In order to bring about greater equality between supply and demand major efforts and large capital expenditures are constantly being made. Industralized areas are seeking their own independent sources of energy whereas those areas of the world which contain great reserves of energy are limiting its export as well as developing its own industralized capacity. Nevertheless, energy bearing materials are still transported great distances in order to satiate the appetites of power hungry economies.

Jan 1, 1975

By Ken Deter

I have some general comments on optimizing profitability based on working in heap leach operations in tropical environments. Many of my planned comments this morning have been stated earlier in the Conference. I get the opportunity to say only a few words, and follow up on some specific comments and concerns. In normal operations, stack the ore higher, where possible. The surface area of the stacked ore controls the total solution volume that can be sprayed on the pad at a specific time period. With higher lifts, solution will contact more ore particles as it percolate through the lift, and therefore the solution grade flowing through the base will be increased, whether it is freshly stacked or almost completely leached ore. This also allows more tonnage to be stacked per lift on the pad, decreasing conveyor movement and downtime. Increasing from 6 to 8 meter (20 to 26 feet) lifts have worked successfully, and some mines are using 10 meter (33 feet) lifts in 10,000-15,000 dmtpd plants. The same concept will work with smaller plants, but initial 6 meter lifts should be used until the start-up period has shown the leaching is working as planned. As the stacked ore lifts get higher, the solution flowing through the highest lift is diluted by solution retained in the lower ones. Eventually no real increase is noted from putting fresh ore in service, and gold production rate suffers. To address the dilution problem, an HDPE liner should be installed between each 2 to 4 lifts, depending on each site specific lift height, recovery, % slump in the lift, recovery rates, and grade treated, among others. The surface of the previous lift should be leveled and sloped to control the effluent draining from the planned lift, then the liner is placed, including berms and discharge pipes. The intermediate HDPE liner does not need to be completely sealed as would be the case with the base liner, and can accept some solution penetrating into the lower lifts. A one-mm (40-mil) thickness liner can be used. This intermediate liner allows the upper lift(s) higher-grade effluent to report to the pad discharge point. This will maintain higher gold solution grades going to the ponds. The slopes of the previous lifts should not be covered with HDPE in this concept, and precipitation falling on the lower lift slopes and benches can be directed to barren or surge ponds.

Jan 1, 1999

Mine planners must select a single pit for design with the knowledge that the grades on which this selection is made are uncertain. This uncertainty is often ignored through the use of deterministic models of grade. This makes the mine planner?s job simpler but does not necessarily lead to the ?correct? or ?best? selection. Grade uncertainty is typically modeled with conditional simulation, which generates multiple possible realizations of grade that are equally probable (or improbable). M ethods for incorporating grade uncertainty into mine planning to date have either been perceived as being too complicated, not accessible or too time-consuming. This paper proposes a simple and efficient modeling approach to incorporating conditional simulation into pit optimization, which would be able to be applied in currently commercially available software. An example for R esolute M ining Ltd.?s Syama gold project in M ali shows the range of ore, grade and value outcomes associated with generating pits through a variety of methods.

Jan 1, 2013

By Leo Gentile, David Selhorst

The $528 million Toledo Waterways Initiative (TWI) was implemented by the City of Toledo in 2002 and completed in August 2020. Toledo is one of many US cities required to implement a Long-Term Control Plan (LTCP) but one of few to have completed its plan. TWI consists of three storage and conveyance tunnels, four below grade storage basins ranging from 4 to 36 million gallons (MG), miles of sewer separation and interceptor improvements, green infrastructure and other appurtenant structures to dramatically reduce combined sewer overflows to the Maumee River, Ottawa River and Swan Creek. All three rivers flow into Lake Erie. The City’s 180-year history as a Midwest shipping, manufacturing and transportation hub provided design engineers and contractors no shortage of unknown underground challenges to complete the projects. The City will begin its 5-year Post-Construction Compliance Monitoring in 2021 to satisfy the final LTCP requirement. A program overview and experience from tunnel and underground basin construction in urban areas with buried active and legacy infrastructure will be discussed.

Jun 13, 2021

By Jack E. Fraley, Robert E. Simpson

INTRODUCTION Spokane Mining Research Center (BuMines) is researching sealants for underground coal mines to: 1. Reduce sloughing of shale roofs. 2. Reduce sloughing of coal ribs. 3. Seal block stoppings against air losses. 4. Construct stoppings by spraying over jute cloth or metal lath. 5. Render incombustible in-place polyurethane foam. Originally the work was directed towards reducing sloughing of shale roofs. Many underground coal mines have shale directly over the coal which weathers severely after exposure to the mine atmosphere. Lab investigations(l, 2, 3, 4) have shown that many shales separate into layers when immersed in water or stored in a high relative humidity environment. Upon drying or after removal from high humidity, the shales continue to separate. Underground coal mines become wet in the warmer months from condensation of the ventilating air. Conversely, the mines become dry in the cooler months from evaporation. The mines experience severe shale break-up during the summer and much less break-up during the winter. Figs. 1, 2 and 3 show weathered shale roofs. in underground coal mines. Fig. 4 shows fallen shale on the entry floor. Sealing the shale reduces this sloughing problem.

Jan 1, 1974

By R. C. Timberlake

An understanding of the Florida Phosphate Industry, the mining practices and extraction processes and the historical development of the Industry, is essential to any consideration of reclamation. In the earliest days of the Industry, phosphate rock was produced by screening the phosphate pebble from the matrix. The waste, which consisted of overburden, clay, sand and fine phosphate, and was called "debris", was disposed of onto, either the adjacent surface area, or into mined-out pits. Since the Central Florida area was sparsely settled in those early days, there was no complaint from residents about contamination of streams or the resulting spoil piles - environmental concerns were non-existent. The development of the flotation process in the 1930's and the implementation of the flotation process in the early 1940's was a significant technological breakthrough in the Industry. This technique made possible the extraction of fine phosphate particles, and doubled the recovery of phosphate values from the matrix. However, the implementation of the flotation process produced a new waste disposal problem.

Jan 1, 1978

"The 35th Annual American Mining Hall of Fame Awards Banquet and Fundraiser, sponsored by the Mining Foundation of the Southwest (MFSW), will be held at the JW Marriott Tucson Starr Pass Resort & Spa on Saturday, Dec. 2, 2017. This year, the Foundation will honor one living Hall of Fame inductee, two Medal of Merit recipients, four honorees from Mining’s Past and an Industry Partner for their respective contributions to the mining industry.Gary J. Goldberg will be the 2017 Hall of Fame Inductee and will serve as the keynote speaker at the awards banquet. Goldberg was appointed president and chief executive officer and joined the board of directors of Newmont Mining Corp. in March 2013. Prior to this appointment, he served numerous companies in key positions including Rio Tinto Minerals, US Borax and Coal & Allied Industries. At every appointment, he was able to improve safety concerns and reduce injury rates. While serving as chairman of the National Mining Association, Goldberg launched the CORESafety initiative and US Borax was the first mining company to receive the California Governor’s Environmental and Economic Award.The Medal of Merit will be awarded to John C. Lacy, a shareholder of DeConcini McDonald Yetwin & Lacy, P.C. and a director of the Global Law Center at the University of Arizona’s Law School. Lacy’s law practice concentrates on mining and public land law and encompasses transactional and title consideration involving acquisition of mineral rights. He played a crucial role in the revisions to the mining law of the Republic of Bolivia and the English translation of the mining laws and regulations of Mexico. Lacy’s expertise in mining law impelled the University of Arizona James E. Rogers College of Law to approach him to head the new Global Mining Law Center in 2015. The program now partners with the Lowell Institute for Mineral Resources and offers cross-listing of courses"

Jan 10, 2017

By F. N. Kissell, H. K. Sacks

This study examines the accuracy of area sampling for measuring the dust exposure of mining machine operators in coal mines. The specific objective of this research was to find locations where an area sampler might work better than earlier studies have indicated. The results show that fixed-location area sampling cannot accurately predict the dust exposure of a machine operator, even when the best fixed location is sought, the fixed location is quite close to the operator and the bias due to the dust concentration gradient is corrected. Industrial hygienists have known for many years that area sampling is unsuitable for measuring air contaminant exposures in the workplace. Near contaminant sources, the dilution air and the contaminants are not evenly mixed. Therefore, when workers are near contaminant sources, exposure measurements must be taken from the worker's breathing zone to be accurate.

Jan 1, 2003

By D. M. Bodily, M. D. Deo, E. M. Whitney

Field data from coalbed methane wells indicate a significant variation in composition as a function of flow rate and time. In particular, San Juan Basin wells have displayed an increase in C02 concentration over time. Prediction of gas quality is critical to the economic evaluation of any coalbed project. Previous models have forecast only pressure and production profiles, ignoring compositional variations. In this study a multicomponent model that incorporates binary isotherms for methane and carbon dioxide has been developed. An extended Langmuir isotherm is used for the adsorption representation and a constant separation factor (similar to relative volatilities in distillation) describes the phase distribution of the species. This separation factor depends both on the surface characteristics of the coal and on the adsorbing species. The chromatographic separation equations have been superimposed on Darcy's law flow. The formulation allows decoupling of the pressure and compositional partial differential equations. The equations have been cast in dimensionless form and solved for pressures and compositions. It is observed that the composition of the preferentially adsorbed C02 increases at the wellbore as a function of dimensionless time. The dimensionless time is directly proportional to the real time and coalbed permeability and is inversely proportional to the gas viscosity, coal porosity and the square of the length of the reservoir. As the separation factor increases, the compositional variation increases. This variation in produced C02 concentration is also greater when the initial C02 concentration in the reservoir is higher. A sensitivity study has been performed to identify the effects of important parameters such as isotherm variables and reservoir characteristics on pressure and composition profiles.

Jan 1, 1993

By H. K. Lin

Elemental sulfur is founded to be the predominant sulfur-containing species in a leaching residue resulting from ferric chloride leaching, under given conditions, of a chalcopyrite concentrate. The mineralogical study of the leaching residue which consists of 52% elemental sulfur reveals that the sulfur formed at the end of leaching process is in the form of discrete crystal rather than coating film. Flotation has been applied to recover the sulfur successfully using xanthate as a collector. Dispersants arc needed to prevent the mechanical entrapment of silicate and quartz by sulfur. Very high recovery of sulfur with satisfactory grades can be achieved with a relatively simple notation scheme.

Jan 1, 1991

By Michelle L. Ramos

INTRODUCTION The Ballard Siphon was built in 1935 and consists of two 91.4 cm (36-inch) diameter wood-stave pipes. These pipes convey sewer flowsunder the Ship Canal from northwest Seattle and the Ballard Regulator to the North Interceptor and the West Point Treatment plant. The siphons were constructed using open cut construction, are now buried in the sediment on the floor of the canal, and have severely limited ability to be dewatered, inspected, or cleaned. The existing siphon is 394.7 m (1,295 feet) long from the junction structure on the southern shoreline to the regulator structure on the north. The location of the Ballard Siphon is shown in Figures 1 and 2. The area around the Ballard Siphon has become more populated and developed since the siphon was built. Additionally, the Ballard Siphon is subject to high flows that are greater than the capacity of the pipelines. This has resulted in predict-able Combined Sewer Overflows(CSO?s) whenever a large, long duration rain event occurs. The aged pipeline of uncertain viability has become a critical piece of the sewer system infrastructure. Because of the age of the pipelines and their importance, a sonar survey was completed on both barrels of the Ballard Siphon in December of 2005. The sonar images appeared to indicate crown intrusion of the wood-stave pipes, which suggested that the pipes were in imminent danger of collapse. As a result, an Emergency Declaration was executed by King County and the Ballard Siphon Replacement Project was initiated. Staheli Trenchless Consultants was retained to perform feasibility studies to deter-mine the viability of using microtunneling and horizontal directional drilling (HDD) for replacement of the Ballard Siphon. For the evaluations, the preferred site location was determined to be at or near the site of the existing Ballard Siphon in order to minimize the ancillary sewer work which would accompany moving to a new site. To meet flow demands and hydraulic requirements, the replacement siphon needed a mini-mum equivalent diameter of 182.9 cm (72 inches). This could be accomplished with a number of different siphon diameters and configurations including, but not limited to, three 106.7 cm (42-inch) diameter pipelines, two 152.4 cm (60-inch) pipelines, or two 91.44 cm (36-inch) pipelines and a 121.9 cm (48-inch) pipeline.

By H. M. Conger

I'm really very pleased to be talking with you today about the environmental impacts of gold ore processing as part of this symposium on emerging process technologies for a cleaner environment. But before I talk about some of the newer developments that are coming, I would like to set the stage by reviewing some of the recent past. Over the last decade or so the U.S. gold mining industry has experienced remarkable growth, primarily in heap leaching operations, and not surprisingly there has been parallel growth of environmental regulations. At Homestake, we have had the excitement of bringing on-line a new mine embodying state-of-the-art technology and environmental planning, and during the same period the flagship of our company, the Homestake mine, has been brought into modern day compliance through the application of innovative environmental technology. This has been a learning process; in both cases we found that we had to develop new ways to meet our objectives. At our McLaughlin mine in California a major achievement was pioneering the use of pressure oxidation, or autoclaves, for refractory gold ores, and at the Homestake it was the development of a unique bio-treatment plant for wastewater. These projects were developed balancing operational goals, environmental concerns and costs, and I would submit that being cost-effective is our greatest challenge in the development of new, environmentally sound, process technology. In meeting that challenge, our job has not been made any easier by the myriad environmental laws and regulations that directly affect the design and operation of our facilities. Most of these constraints have evolved through the political process more or less independently, but in their application there often are over-lapping provisions. Adding to this complexity is the fact that action takes place in both state and federal arenas. As a result, state and federal roles sometimes become intertwined, and a good case in point is provided by various cyanide issues faced by gold producers. The vast majority of U.S. gold mining takes place in the so-called "mineral States," the western States that come under the Mining Law of 1872 as amended. This is the basic statute that provides for access and tenure to develop mineral resources on federal lands in those states. There is gold mining outside the defined mineral States, and there is also gold mining in the mineral States on private lands. Our own Homestake mine in South Dakota is one of the best examples of the latter category: located entirely on private land, it is nevertheless subject to at least 13 federal environmental statutes and some 29 federal regulatory requirements. There are also nine significant state statutory and regulatory requirements that apply. On federal lands in the mineral States there are numerous federal statutes and regulations which affect mining, over and above the current Mining Law. These, which are in addition to the laws applying to private land, include the National Environmental Protection Act and the Federal Land Policy and Management Act, among others. Still, those who advocate radical changes in the basic Mining Law would have us believe that sweeping environmental protection and reclamation provisions, not to mention new land use restrictions, are needed. Such changes could effectively prohibit mining on the federal public lands. Strict enforcement of our current Mining Law would have presented most of the abuses cited by the critics but if the Law is to be changed at all, I believe that, at a minimum, the principles of self-initiation and security of tenure embodied in the present statute should be maintained. These are critically important concepts, but there are other statutory and regulatory issues constantly before us as gold miners. Let me cite a few examples: Reauthorization of RCRA There are several bills being considered by Congress to amend the Resource Conservation and Recovery Act (RCRA) that have as their theme

Jan 1, 1992

By A. Papandreou

Industrial wastes nowadays constitute one of the most serious threats for the future of our planet. Researchers around the world have very often proposed many kind of solutions in the management problem of industrial effluents. However in most cases suggested solutions are either too expensive to be applied in industrial scale, or they just transfer the problem (e.g. precipitation creates dangerous sludge) and so they create an even greater problem and threat. In the present study the exploitation of valuable hydraulic and adsorption properties of fly ash is studied. Fly ash can easily and cheaply be shaped into stable pellets. After ageing for a sort period of time, these structures can be used as adsorbents for the removal of heavy metals from industrial effluents. Experiments in aqueous solutions have shown excellent adsorption behavior concerning the removal of cadmium, copper, lead, chromium (III) and zinc. The advantage of this technology, except low cost, is that after saturation the pellets can be easily removed from the liquid phase and stabilized in concrete structures without any problem of desorption or leaching. Moreover in these structures a significant amount of cement in the concrete can be replaced by raw fly ash. (Ashcrete as it is called). The utilization of an industrial byproduct as fly ash in the form of pellets as adsorption means and their stabilization with concrete (or ashcrete) combines the useful properties of a solid waste in the treatment of liquid effluents and constitutes a green low cost technology.

Jan 1, 2006

By C. Green, J. Uhrie, C. Filippone, A. Guzman

A central aspect of heap leach management and recovery optimization is solution control. Insofar as each heap is unique in physical and metallurgical properties, it is essential to understand the hydraulic parameters that control the migration of solution on a case-by-case basis. Water Management Consultants, as part of an ongoing research effort for Phelps Dodge Process Technology Center, have adapted techniques of parameter estimation for application to data typically resulting from metallurgical column testing. The parameterization is completed within the context of a variably saturated flow model that allows interpretation of available hydraulic information collected during hydrometallurgical column tests. A novel interpretation approach is introduced to extract the necessary hydrodynamic parameters from typical hydrometallurgical data sets. Results from the application of the approach to standard metallurgical test data will be presented together with a discussion of the application of information gained to the design and operation of a heap.

Jan 1, 2002

By D. Earley

High metal prices and new world trade standards and accounting for environmental liability in financial disclosures are creating markets for metals commodities that are produced using ?green technologies?. A promising "green" gold leaching system uses a polysulfide based lixiviant which is non-toxic and non-polluting. Laboratory testing has demonstrated selective gold extraction rates comparable to those of cyanide. The polysulfide lixiviant is a dilute aqueous solution which can be inexpensively produced from readily available chemical reagents and even mining wastes. The reagent system is self-buffering and maintains the optimal chemical environment for leaching. Treatment of residual leach solutions is not necessary because the lixiviant itself is not toxic, and breaks down as the system equilibrates. Simple closed system boiling is used to recover gold from process solutions. The polysulfide lixiviant can then be readily renewed and recycled back into the system, forming a closed loop system that conserves reagents and energy which minimizes operating costs. Economic projections have shown that the system can be used profitably for standard ore types and grades.

Jan 1, 2009

By J. W. Wilson, P. C. Graham

SUMMARY The Witwatersrand quartzites in which South African gold mining operations are moat exclusively conducted, are notoriously difficult and costly to drill. Despite this situation, however, with the high cost of developing new mines and extending existing mines, together with the rising cost of labour and mining problems resulting from the ever-increasing depths of workings, the demand for raise-boring in these formations is increasing rapidly. Not only is the demand for raises and shafts increasing, but also the length and size of these excavations. Raise-boring studies carried out in South African gold mines have indicated that increased penetration rates and possibly reduced costs could be obtained if higher thrusts were available at the reaming head. Until fairly recently there has been no raise-boring machine suitable for underground use that possessed the thrust and torque characteristics necessary to achieve high penetration rates in hard abrasive quartzite formations and the cutters available were not really developed for high loading. In response to these requirements a raise-borer, the Robbins 83R was designed and built in Seattle, U.S.A. for the Anglo American Corporation. This machine is operating in South African gold mines and is currently being used at a depth of 12 000 ft below surface in one of the. Group's mines. The initial raises bored have substantiated that increased penetration is attainable at high thrust and it is now apparent that the machine is sufficiently versatile to drill raises of up to 12 ft in diameter in quartzite formation over a length of 2 000 ft.

Jan 1, 1974

By Jürgen Brune

This is a shortened version of the paper ?The Methane-Air Explosion Hazard Within Coal Mine Gobs published in the 2013 volume of SME Transactions (Brune, 2013, pp. 376-390). This paper analyzes the explosion hazard resulting from the formation of methane-air mixtures in the mined-out gobs of underground longwall coal mines. Evidence from numerous mine explosions suggests that explosive methane zones can form within longwall gobs. Explosions and fires resulting from these methane accumulations have led to severe and fatal injuries to the miners, including the explosion of the Upper Big Branch Mine in West Virginia, where 29 miners lost their lives April 5, 2010.The paper also reviews current research on numerical modeling of gas flows in longwall gobs and outlines how targeted injection of nitrogen into gobs can effectively reduce the volume of such explosive methane zones. The paper concludes that comprehensive monitoring of gas compositions, along the accessible fringes of the gobs along with inertization, improved ventilation schemes and further research are necessary to control this explosion hazard and make mining operations safe. Keywords: Longwall, gob, methane, EGZ, explosive gas zones, underground, coal, explosion, fire

Feb 1, 2014

By Jay S. Silhanek, Vernon E. Andrews

[Introduction] Section 122 of the Clean Air Act Amendments of 1977, Public Law 9595, directed the Administrator of the Environmental Protection Agency, to review all relevant information and determine whether emissions of radioactive pollutants into ambient air will cause or contribute to air pollution which may reasonably be anticipated to endanger public health. In August 1979, EPA published a preliminary report on assessments of public health impact resulting from emissions of radionuclides into air from a broad spectrum of major source categories (1). A section of this document presented a theoretical analysis of the radioactive airborne emissions from several non-uranium mines including iron, copper, zinc, clay, limestone, fluorspar, and phosphate. Since 1978 EPA's Las Vegas Laboratory has been gathering field data on actual radionuclide emissions from these mines to support the earlier theoretical analysis. The purpose of this paper is to present the results of those field measurements in comparison with the assumed values for the theoretical analysis. Data were presented in EPA's preliminary report on both gaseous radon-222 and particulate uranium-238 emissions from non-uranium mines. Most of the emissions data were rough estimates based upon the uranium content of the ore. Preliminary data from a few field studies were also used. Although both the theoretical and field studies by EPA were concerned with radon-222 and radioactive particulate emissions, this paper will concentrate only on the radon effluents. Radon from mines seems to have the greatest potential for possible health effects due to radiation. Data on particulate emissions are presented in other technical reports (2-5). [Theoretical Study] The theoretical emission data are presented in Table I. The estimates for the iron, zinc, and clay mines are based upon preliminary measurements taken by the Las Vegas laboratory. The estimates for the other mines were made assuming that 20% of the total radon-222 in the ore was released during the mining process and the radon release rate from the exposed ore surface was a factor of two greater than that resulting from mining. [ ] Dose assessments for radon from these mines were carried out using model facilities located on generic sites (1). The AIRDOS-II computer code (for estimating dispersion of airborne pollutants) with some minor modifications was used to determine working level exposures to a maximally exposed individual and a regional population. A conversion factor for risk/WL-year(O.021 fatal cancers/person-WL-y) was developed primarily from information on uranium miner exposures (6). This computer code and conversion factor were then applied to the assumed emission rate of radon-222 from each type of mine to develop estimates of working levels, lifetime risks and number of fatal cancers. A summary of this data is presented in table II. [ ] The highest estimated number of cancer deaths per year of operation is 0.05 cancer deaths or 1.0 death due to radon during the 24 year life of a phosphorous mine. For comparison, EPA estimates that underground uranium mines would cause .03 cancer deaths per year of operation in a regional population(1). [Field Study] As a followup to the theoretical study, EPA's Las Vegas laboratory began making measurements in 1978 of actual emissions of radon-222 and radioactive particulates from mine vents at several facilities for each of the industries listed in Table I and II. They were intended to verify general information and radon emissions from EPA's theoretical estimates.

Jan 1, 1981