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By John E. Tilton

Looking back on the second half of the 20th century, future historians, I believe, will be fascinated by two major political upheavals. The first is the environmental revolution in the 1960s. It erupted in the United States and parts of Western Europe and then swept across the rest of the globe like a wild fire. The second event is the collapse of the Soviet Union. It was the last of the world's great imperial empires. With its demise went central planning as a viable economic system. History, I suspect, will see this second revolution as an offspring of the first. This is because economic and environmental issues were largely responsible for the unraveling of the Soviet Union.

Jan 1, 1994

Rheology is the science which deals with the deformation and flow of matter. Thus rheology is concerned with the flow of any material. The mining industry is concerned with digging things out of the ground, extracting the good stuff and throwing away the bad stuff. In the upgrading processes associated with mining, ie mineral processing, wet techniques are used where the primary material being handled is a particulate fluid, ie a suspension. After the processing operation, with the concentrates extracted, what is left behind generally is a wet material in suspension form, which may or may not contain reagents harmful to the environment. The amount of waste generated in any of the mining processes is large, in fact, the mining industry is the largest generator of solid waste in Australia. In order to minimise the waste generated within the industry it has become of interest to handle the particulate fluid wastes, or suspensions, at high concentrations, thus removing water and some of the reagents which may be harmful to the environment. The resultant highly concentrated suspension is a non-Newtonian fluid. Rheology deals with the flow of non-Newtonian fluids; therefore a combination of rheological understanding of high density suspensions, in conjunction with an understanding of the environmental problems being faced by the mining industry, can and has led to improved methods of waste disposal in the industry, ie waste minimisation. This paper describes the progress that has been made in the development of dry disposal technology in the mining and minerals industry in Australia.

Jan 1, 1998

By DV Boger

Rheology is the science which deals with the deformation and flow of matter. Thus nccology is concerned with the flow of any material. The mining industry is concerned with digging things out of the ground, extracting the good stuff and throwing away the had stuff. In the upgrading processes associated with mining, is mineral processing, wet techniques are used where the primary material being handled is a particulate fluid, ie a suspension. After the processing operation, with the concentrates extracted, what is left behind generally is a wet material in suspension form, which may or may not contain reagents harmful to the environment. The amount of waste generated in any of the mining processes is large, in fact, the mining industry is the largest generator of solid waste in Australia. In order to minimise the waste generated within the industry it has become of interest to handle the particulate fluid wastes, or suspensions, at high concentrations, thus removing water and some of the reagents which may be harmful to the environment. The resultant highly concentrated suspension is a non-Newtonian hold Rheology deals with the flow of non-Newtonian fluids; therefore i combination of rheological understanding of high density suspensions. ill conjunction with an understanding of the environmental problems hero' faced by the mining industry, can and has led to improved methods of waste disposal in the industry, ie waste minimisation. This paper describes the progress that has been made in the development of dry disposal technology in the mining and minerals industry in Australia.

Jan 1, 1998

By S. J. Swart

This paper discusses the principles and application of risk assessment and management as the basis for environmental management within the mining industry. Unlike in other industries, mines are required to obtain closure certificates in terms of section12 of the Minerals Act, which should ultimately release them from further environmental responsibilities. It is emphasized that the concept of environmental risk assessment and management, when applied correctly will mean that the mine will be identifying and managing environmental issues beyond those set by current legal requirements and management strategies. The focus shifts from conventional minimum legal compliance management to management of real environmental risks. The advantage of this approach is that the perceived ?shifting of legal and management goal posts? due to changing environmental laws or management principles, will not influence or dictate the mine?s short or long-term management objectives or actions, mine closure funds can be more accurately determined and mine closure should become a relatively simple procedure. The risk assessment approach has been applied to the planning of mine closure at Iscor?s Durban Navigation Collieries (Durnacol) in Kwa-Zulu Natal and certain key risk issues such as the long-term risk of water pollution from coal discard dumps have already progressed to fully quantitative risk assessment. This paper will discuss the process, which has been followed to date, with particular emphasis on the most recent phase, namely quantitative risk assessment and management of pollution from coal discard dumps. It is believed that the approach that is being pioneered at Durnacol and which overcomes some of the more obvious deficiencies of both the EMPR and the traditional IEM process will ultimately serve as the model for all responsible mines in South Africa. It is also believed that this approach will enable the authorities to issue closure certificates with the confidence that there will be no unforeseen surprises in the years after closure.

Jan 1, 1998

By Voorhees JS, Bureau G

To operate a mine in California requires compliance with State environmental regulations, including assessment of risks and associated financial assurances for postulated worst case catastrophic event scenarios. Carson Hill Gold Mine, an open pit, heap leach operation, completed new risk assessment catastrophic event analyses in 1988. The risk assessment was performed at the same time that a new leach site (Leach Site 3) was being designed. Leach Site 3 is located about 400 m upslope of New Melones Reservoir, which is a public recreation facility and a source of drinking water. Release of leachate (pregnant solution) or ore containing cyanide and metals from Leach Site 3 into New Melones Reservoir was considered to pose the largest risk of environmental damage.Flow failure of the ore heap, potentially induced as a result of liquefaction of the saturated portion of the ore, and/or overtopping of the leach site containment embankment due to excessive precipitation were found to be the most plausible leachate release scenarios. Yearly combined probabilities of various downstream release volumes were estimated. The release volume corresponding to a yearly probability of 0.05 percent was then used to estimate potential environmental impacts and mitigation costs. The costs include earthwork to restore the geometry of the ore heap and repair the fill slope below the Leach Site 3 containment, and impacts on New Melones Reservoir.

Jan 1, 1990

By X Sun, L B. Zhou, H Yi, X Tang, P Ning

The rapid industrialisation in China has consumed large amounts of various industrial raw materials, which has left behind large quantities of industrial solid wastes produced from the processes of mining, mineral processing and smelting. The storage of huge quantities of industrial solid wastes is an obvious risk to the environment and human well-being. As the first step to fully appreciate the scale of this risk, it is necessary to carry out research for developing a pollution source environmental risk assessment system (PSERAS), especially for the typical staple industrial solid waste (TSISW). This paper aims to discuss the frame of the PSERAS for TSISW for large scale production. This system consists of two aspects: predicted factors and accidental ones, which involve physical, chemical and biological risk assessments, on-site and during transportation process. Two analysis methods, the analytic hierarchy process (AHP) and fuzzy logic assessment (FLA) were used to handle the complexity of environment and non-quantitative data. The risk assessment system for such a complex objective is difficult and the assessment of relative factors is problematic through the usual quantitative analysis. With the proposed PSERAS, it is possible to define the risk class of pollution sources. Furthermore, the risk assessment results will be helpful to the decision-maker, especially when facing unknown risks in the environmental management of industrial solid wastes. In addition, by means of the PSERAS, risk factors can be ranked against their contributions to environmental risk, in order to calculate their relative priorities in decision-making.CITATION:Sun, X, Ning, P, Tang, X, Yi, H and Zhou, L B, 2012. Environmental risk assessment system for typical staple industrial solid wastes, in Proceedings Life-of-Mine 2012 , pp 301-304 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

By Hjalmar Thiel

Since industry is progressing into the deep sea, marine scientists have expressed their concern about environmental disturbances which will be introduced by using the deep seafloor for mining metalliferous resources or as a repository for wastes. Environmental studies have been conducted on national levels and in bilateral or multilateral cooperation in the development of manganese nodule mining, as this is generally achieved in marine research. These investigations were partly large-scale and experimental approaches aiming at the assessment of the impacts expected to occur in commercial mining. The results elaborated till today and expected to be acquired in the foreseeable future may remain limited. Reliable impact evaluation will result from monitoring a Pilot Mining Operation (PMO). The lecture will present the broad outlines of a possible program and a preliminary calculation of approximate costs for such a combined industrial test and environmental monitoring event. Although the extent of necessary efforts for the environmental risks evaluation can only be estimated rather vaguely, it will become evident that the required human, technical, logistical, and financial resources to be mobilized will exceed industrial capacities and go beyond national funds. Therefore, such assessment of environmental risks is calling for broad international cooperation. While industrial developments for mining the deep sea will be ruled by competition or probably by restricted joint ventures, environmental care ranges outside competition and falls within the interest of all parties involved. Environmental studies, unlike technologies for the same function, do not primarily need duplication. International cooperation in PMO monitoring would equally well support all mining companies or consortia, it would minimize the efforts for all engaged in this challenging venture of deep-sea mining and it would maximize the precautionary discussion on and the care for the deep-sea environment.

Jan 1, 1994

By B. A. Kutlin, S. A. Ropeyko, N. A. Yurlova

"The aim of NPO RIVS research and practice activities is to minimize impact of the mineral processing plants (MPP) on environment by using new concentration methods, high-technology equipment, implementation of engineering solutions directed to reduce emission of polluting substances (PS) into atmosphere, application of low-waste technologies, decrease of water withdrawal from a surface water or groundwater source for process needs. In our studies environmental safety of mineral flotation is provided through technologies using highly selective chemicals, that leads not only to reducing reagent consumption, and production of saleable products of high content of extracted minerals, but also to reducing pollutant emissions, decreasing supply of surfactants (SAA) in natural geosystems, primarily, in ground and surface waters. Decrease of water withdrawal from a surface water or groundwater sources for process needs can be achieved by using closed circuits and waste water treatment for further use in process operations, recycled water conditioning to obtain optimum quality parameters for process operations of concentration. Concentration in water (wet processing), tailings dewatering and semidry and dry (filtration cake) stockpiling in tailing ponds, efficient dust-collecting systems contribute to pollutant emission reduction. Use of mineral wastes – concentration tailings as a source of valued components, facilitates efficient use of natural resources and reduces wastes and its impact on natural ecosystems due to smaller areas of damaged lands during waste products disposal. Process and engineering solutions of NPO RIVS that allow diminishing impact of MPP on natural environment (NE) have been implemented in mining and processing complexes of Russia, Kazakhstan, Ukraine, Kirghizia and Mongolia. Compliance with environmental safety requirements contributes to enhancement of mineral processing and sustainable mineral development.INTRODUCTION Mining and processing complexes have a significant impact on environment as a result of extraction and recovery of mineral resources, landscape changes, waste disposal and, as a consequence, pollution of soils, surface and underground water sources. Therefore, the aim of the operation of the mineral processing enterprises in its research and practical activities is to reduce impact on environment due to new beneficiation technologies, high-technology equipment, implementation of engineering solutions directed to reduce emissions of polluting substances (PS) into atmosphere, use of low-waste technologies, decrease of water withdrawal from a surface water or groundwater source for process needs. Compliance with the requirements of environmental safety encourages advancement of mineral processing technologies and sustainable mineral development. Concentration in water, tailings dewatering and semidry and dry (filtration cake) stockpiling in tailing ponds, efficient dust-collecting systems contribute to pollutant emission reduction. Use of mineral wastes – concentration tailings as a source of valued components, facilitates efficient use of natural resources and minimizes waste formation and its impact on natural ecosystems due to reduction of damaged land areas during waste disposal."

Jan 1, 2018

By A. K. Stagg

Toxic substances in On solutions can retard biological leaching of copper sulfide dump ores. On solutions were analyzed for metals, organics, and chloride, and showed inhibitory concentrations of aluminum, manganese, and chloride. Inhibition of bacterial activity by the solid fraction of On solution, with and without the organic constituents, was evaluated. Toxicity to bacterial species was evaluated by monitoring bacterial numbers, pH, Eh, and rates of iron oxidation. The On solution solids were toxic at 50 -60% of their field concentration. Most of the toxicity of the On solution was due to the organic fraction. Different SX reagents show varying degrees of inhibition of T. ferrooxidans. Bacterial inhibitory effects of carriers and lixiviants used in the SX plant should be determined so that entrained SX reagents do not retard biological dump leach systems. The reagents used should be the most cost effective and the least toxic.

Jan 1, 1994

By Thomas Buenger

The Hamburg smelter of Norddeutsche Affinerie AG is situated near the city of Hamburg’s downtown and is therefore particularly subjected to fulfill environmental requirements according to the German legal regulations. Thus, investments related to increasing concentrate throughput are always linked to packages to enhance the emission status of the smelter. This connection between environmental protection and productivity enhancement should be explained by the example of the Peirce-Smith converter plant of the Hamburg smelter. Such outstanding investments can be demonstrated by the transition from scrap charging via boat from the front side to a fully automatic and completely sucked scrap charging system.

Jan 1, 2009

By M. T. Ernett

Significant amounts of arsenic are often present in effluents arising from the mining of sulfide ores for the extraction of metals such as copper, gold, lead and zinc. The arsenic is usually removed from the process effluent by co-precipitation with iron because of its common occurence in the mined ore bodies and the excellent adsorptive property of the precipitated hydrous ferric oxide compound. There has been controversy, however, over the long-term stability of the arsenic-bearing ferrihydrite which is produced. This paper presents the results of laboratory studies which indicate that the cations of calcium, magnesium, zinc, cadmium and lead, increase the pH range of effective arsenic adsorption in the Fe-As precipitate from 4-7 to 4-9. The increase in the pH range is similar for all of the added cations investigated. Sulphate ions are shown to have a minimal effect on the residual dissolved arsenate concentration. Silicate ions reduce the adsorptive capacity of ferrihydrite if they are present before the arsenic is adsorbed.

Jan 1, 1994

By Carol E. Jones

Outline ? Reclamation is a primary mitigation. ? Understand baseline environment and land use. ? Determine reclamation goals. ? Selecting reclamation technology. ? Determine technical risk. Reclamation ? Primary Mitigation ? Through land and water disturbance, mining can have significant local and regional environmental impacts. ? Impacts can also result from associated land use changes. ? Reclamation is a primary tool that the mining industry uses to manage its environmental impacts.

May 1, 2008

By Ulrich Von Stackelber

Deep sea mining of manganese nodules actually will have an environmental impact to the seafloor and to the water column. However, we are far from being able to predict the possible consequences. Therefore, in 1992 environmental studies were conducted with the R/V Sonne in a manganese nodule field of the Peru Basin. The bathymetry of the seafloor was mapped using the hydrosweep system and the distribution and type of sediments were investigated by the parasound system and by collecting surface samples and sediment cores. Deep towing of a side-scan sonar system revealed a Mn encrustation of sediments and a nodule coverage of variable density. Along the tracks of a photo sledge a great variability of bottom fauna and of bioturbation was observed. Bottom-mechanical investigations of surface-near sediments were completed on board. Additionally water samples were collected near the sea floor to determine character and amount of dissolved and suspended particles. Manganese nodules and crusts were collected at 80 locations. In many aspects the nodules differ from those of the Clarion-Clipperton Zone: Big cauliflower-shaped nodules with growth rates up to 160 mm/ Ma may reach a maximum size of 24 cm in diameter, maximum abundance may be 44 kg/m2, the mean size of buried nodules is greater than that of surface nodules. The reason for that difference is due to the relatively high bioproductivity in surface waters and to a Mn redox boundary in the sediment column 10 cm below the seafloor. Histograms of nodules showing the distribution of size and growth type clearly indicate that the growth history is different for basins, slopes and tops of seamounts and ridges. Nodules with diameters >7 cm show mainly diagenetic and to a minor degree hydrogenetic growth. Smaller nodules of the same assemblage are composed mainly of hydrogenetically grown Mn oxide. The optimum diagenetic growth occurs within the sediment immediately above the Mn redox boundary, a level which is not reached by the small nodules.

Jan 1, 1994

By N. B. Aughenbaugh

Compacted, fine-grained soils, often referred to collectively as clays, are used as permeability barriers in many mineral engineering projects such as heap leaching, containment ponds, tailings disposal and earth dams. Source materials for these liners include a variety of sand, silt and clay admixtures. These exhibit dramatically different engineering properties when densified. Therefore, it is imperative to adequately assess and characterize any soils being considered for compacted liners. The permeability and plastic properties of fine-grained soils are reviewed with respect to the state of compaction as the water content varies. Because they are weak in tension, compacted clays are susceptible to cracking when subjected to differential flexural movements. Designs of compacted clay liners also must include an evaluation of their flexibility. That is the ability of a fine-grain soil to bend plastically without cracking. This paper will also discuss the importance of flexibility with respect to soil types, compaction effort, failure mechanism and testing evaluation to the performance of clay liners in preventing seepage of pollutants from a containment site.

Jan 1, 1991

By N. B. Aughenbaugh

Compacted clays are used as permeability barriers in many mineral engineering projects such as heap leaching, containment ponds, tailings disposal and earth dams. Source materials used for clay liners include a wide variety of sand, silt and clay admixtures that exhibit dramatically different engineering properties when densified. The permeability and plastic properties of fine-grained soils are reviewed with respect to the state of compaction as the water content varies. Be-cause they are weak in tension, compacted clays are susceptible to cracking when subjected to differential flexural movements. Designs of compacted clay liners must include an evaluation of their flexibility which is the ability of a fine-grain soil to bend plastically without cracking. This paper will also discuss the importance of flexibility with respect to soil types, compaction effort, failure mechanism and testing evaluation to the performance of clay liners in preventing seepage of pollutants from a containment site.

Jan 1, 1990

By D. Sotiropoulos

In the recent years, the mining sector is looking for specific indices, taking into account economic, environmental and social criteria, in order to meet the sustainable development requirements. In the present study traditional and environmental sustainable indices used in the Agios Dimitrios Power Plant, Northern Greece, are compared to those of ESKOM Company, South Africa, taken as reference. These indices are referred to, a) the solid fuels consumption, such as lignite, and, b) the emissions to the atmosphere, such as SO2, NO2 and dust. Last five years data show a remarkable improvement of all indices in the Agios Dimitrios Power Plant. Although the lignite used in this Power Plant is by far of poorer quality than that used by ESKOM - net calorific value 1272 and 4638 kcal/kg, respectively - dust emissions in both Power Plants are similar (52 and 31 g/kWh, respectively). The SO2 and NO2 emissions are very low in Agios Dimitrios compared to those of South Africa, respectively 1.92 and 7.91, and 1.74 and 3.61 g/kWh. This is mainly due to natural desulfurization (by the lignite?s calcium content) and the low NOx burners.

Jan 1, 2003

By Avi Nanda, Robert Brandt, Alex Piatkiewicz, David M. Jones

In 2010 the United States Environmental Protection Agency (UESPA) revised the National Ambient Air Quality Standards (NAAQS) by lowering the permissible value to a 1-hour average SO2 concentration of 75 ppb. In 2012, the USEPA designated the Miami area as non-attaining for the new SO2 NAAQS. A number of options were studied to assist in bringing the Miami smelter into attainment with the new standard. The chosen solution included: Installation of a large tertiary hooding system over the converter aisle; Hooding of the anode vessels and treatment of the anode gas in a baghouse; Installation of a large 2,325,212 Nm3/hr caustic scrubber to treat the captured converter fugitives and anode off-gases; Installation of a secondary ESP for the tapping fugitive off-gas treatment system; and the continuous scrubbing of all acid plant tail stack gases. The modifications have reduced smelter SO2 emissions by 85%, achieving a world class SO2 stack emissions rate of 0.45 kg of SO2/tonne Cu. INTRODUCTION The Freeport McMoRan Miami smelter has been previously described in literature (Steinborn, Pasca, Sallee, Binegar, Bhappu). For the sake of brevity a brief description is given here. The Miami smelter is located 129 km east of Phoenix, Arizona near the town of Miami, Arizona. The smelter was established in 1915 and has undergone a number of process upgrades and modernizations over the years. The present smelter consists of an Isasmelt furnace, an electric settling furnace, four Hoboken converters, two anode refining vessels & one casting wheel; and one double contact sulfuric acid plant. Concentrates are railed & trucked to Miami from four Freeport McMoRan mines located in Arizona & New Mexico. The wet concentrates, typically containing 10% H2O with a Cu/S ratio of 0.85, are smelted in an Isasmelt furnace to a matte grade of 58%. The entire output from the Isasmelt is laundered into an Elkem electric furnace (originally installed in 1972 as the primary smelting furnace) for separation into matte and slag. Slag containing 0.85% Cu is skimmed from the electric furnace and discarded. Molten matte, containing 60% Cu, is tapped from the electric furnace and processed in one of four Hoboken converters to produce blister copper. Two anode refining vessels further refine the blister copper before the final product is cast on a single, 30 mold, casting wheel. All of the anodes produced at Miami are shipped to the Freeport McMoRan electrolytic refinery in El Paso Texas for refining into cathode copper. Smelter off-gases from the Isasmelt, electric furnace and Hoboken converters are combined and treated in a double contact acid plant to produce sulfuric acid. Acid produced at Miami is internally consumed at Freeport McMoRan mines in the region.

Jan 1, 2019

By Robert L. Virta

An asbestos substitute is any material that replaces asbestos in a commercial product. There are many asbestos substitutes, each with its own unique physical and chemical properties. Substitutes can be inorganic or organic, fibrous or nonfibrous, and natural or synthetic. They also can be used as a direct substitute for asbestos or as a replacement product. Probably in no other field is the diversity of substitute materials so great. The concept of asbestos substitutes is not new. The first major effort to develop asbestos substitutes was undertaken by the federal government. The United States has always been dependent on foreign sources for strategic-grade asbestos, and during World War II, the government was concerned that these supplies would be cut off. Strategic-grade asbestos was critical in many electrical and thermal insulation applications (electrical insulation, battery plate separators, flame-proof boards, insulation for rocket components, etc.). A reliable supply of nonstrategic-grade asbestos also was required for general civilian and military applications, such as in brakes, clutches, and construction materials. The government not only initiated a major search for deposits containing strategic-grade asbestos, it also funded research on synthesizing asbestos in the laboratory and developing products that did not contain strategic- grade asbestos. These efforts, as well as those conducted by the private sector, generally were unsuccessful. In the late 1960s and early 1970s, a second major effort to develop asbestos substitutes began because the general public was concerned about the health threat posed by the release of asbestos fibers during the manufacture, use, repair, and disposal of asbestos-containing products. Strict regulations covering the mining and manufacturing sector already had been enacted because of the issue of occupational exposure. The issue then became environmental exposures. Environmental regulations were enacted, and through time they became more strict. The combination of increasingly strict environmental regulation, maturing of some asbestos markets, and liability issues prompted many manufacturers to discontinue asbestos product lines or search for asbestos substitutes. As a result, asbestos usage dramatically declined from the 1970s to the present (Table 1).

Jan 1, 1994

By Karan S. Keith, Haydn H. Murray

The sorptive and impervious nature of clay materials was recognized long before modem technology allowed us to understand the physiochemistry of clays. In Cyprus, around 5000 BC, sorbent clays were used for fulling woolen cloth. One of the earliest recorded uses of clays as an impervious liner was more than 3200 years ago in the construction of a bitumen-sand-gravel-clay liner built along the embankment of the Tigris River at Assur. Today one of the most common applications for clay minerals in the environmental industry is for use as impermeable barriers to fluid transport. Clay minerals are fine in particle size and thus have large surface areas, which, as a result of intermolecular forces and ionic substitutions, make them excellent materials for both ion exchange and ion sorption. Therefore it was logical to consider certain clay materials for applications in the environmental industry, where they can act as physical and chemical traps for potential contaminants. Certain bentonites have historically been used as sealants for fluids (Grim, 1962), and other clays have been used as sorbents for both water and oil (Haden, Jr., 1972). Prior to the 1980s, disposal of the nation's municipal, commercial, chemical, and nuclear wastes was largely indiscriminate and poorly regulated. This created environmental pollution problems, especially with respect to groundwater contamination. Promulgation of federal regulations like the Resource Conservation and Recovery Act (RCRA) and the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA - commonly known as Superfund) have forced a more careful and costly approach to waste disposal. The US Environmental Protection Agency (EPA) is the government body charged with enforcing and ensuring compliance with federal regulations governing toxic waste production, storage, and disposal. Widespread application of geotechnology to the design and construction of waste containment systems and to pollution remediation has become necessary due to such laws and because of increasing use of the subsurface environment for the disposal of hazardous wastes. In the United States nearly 1.8 kg of trash is disposed of per person per day, which amounts to nearly 181 Mt per year. This amount is more than double the waste produced in 1960, and these numbers are expected to continue to increase. Canada produces approximately 1.68 kg of waste per person per day. The EPA estimates that in the United States 64% of our garbage is landfilled, 18% recycled, and 18% incinerated. Even with continued increases in recycling and incineration efforts, the EPA projects that the United States will still need 82% of today's landfill capacity in the year 2000. Data on the exact number of landfills in the United States and Canada is conflicting in part because of changing definitions of what constitutes a landfill and because of inadequate record- keeping by some states and provinces. An estimate of the number of municipal solid waste (MSW) landfills in the United States in 1990 to 1991 ranged from 4 462 to 10 467 with an average estimate of 6 600. In Canada the number of MSW landfills reported varied from 5 493 in a 1982 survey to 1 766 reported in a 1991 National Solid Wastes Management Association (NSWMA) survey (Repa and Sheets, 1992b). A properly operated MSW landfill on average requires 1 hectare of land per year per 25 000 people (Coates, 198 1). In addition to MSW facilities, there are also waste disposal facilities needed for hazardous waste and low level and high level radioactive waste. In 1983, approximately 266 Mt of hazardous waste was generated in the United States, almost 50% of this by industrial production. About 68% of the hazardous waste generated in the United States and Canada and almost 50% generated in Europe are still landfilled (Egger, 1987). In 1985, approximately 51 000 m3 of commercially produced low level radioactive waste was disposed of in radioactive waste disposal sites across the United States (Jungling and Greeves, 1989). By 1987, the US defense program had produced approximately 10 000 t of high level nuclear waste. In addition, there were approximately 14 000 t of spent fuel assemblies from commercial nuclear power plants in temporary storage; the amount is expected to nearly triple by the year 2000. Presently most commercial spent fuel assemblies are stored in water-filled pools at nuclear power plants. Defense waste is stored on federal reservations in surface and underground steel tanks (Anon., 1987). Under federal law nearly all waste disposal and containment sites are required to have a liner or barrier and a cover system design that meets federal- or state-approved hydraulic conductivity requirements for the type of waste that the site will receive. When approved materials, necessary for constructing the waste containment structure, are not available on site, one of the most economical ways to meet these requirements is through the use of clay, soil/clay, or clay/geotextile materials. In a 1991 survey by NSWMA of its members and other select private sector facilities, 81% of the surveyed landfills had some type of liner system. About 75% of these liners were clay materials (either recompacted or natural). The remaining 30% were using flexible membrane liners as part of a liner system. Clay liner materials are most commonly used in the South, Midwest, West-central, and South-central regions of the United States. About 93% of the landfill facilities had closure plans, and of these 91 % were using clay materials in some way for the final cover material (Repa and Sheets, 1992a). Waste barriers and containment structures take several basic forms, and they are used in a variety of different applications: 1) cutoff walls, 2) soil or soil/clay-admix liners, 3) geosynthetic bentonite-clay/geotextile membranes, 4) radioactive waste containment barriers, and 5) synthetic geomembranes. This chapter will discuss the first four of these categories. The field of synthetic geomembranes, although a related topic, is beyond the scope of

Jan 1, 1994

By Robert C. Freas

Over the past twenty years people throughout the world, but particularly in the United States, have been taking an increasing interest in the environment, sources and causes of pollution, and pollution abatement. Air quality in the United States has been and continues to be an area of primary emphasis. In 1970, the US Congress passed the Clean Air Act and subsequently revised and strengthened it in 1977 with the issuance of the New Source Performance Standards. The Act has been further strengthened with the passage of the 1990 Amendments. By far the largest single source of sulfur dioxide (SO,) pollutants are coal fued electric generating power stations. Hence, a substantial portion of the flue gas desulfurization (FGD) research and equipment installation has been geared to the utility industry. Several competing FGD technologies were touted during the period 1970 to 1990 with varying degrees of success. Subsequently, the more successful technologies have been accepted, revised, and improved to the point that by 1991 third and fourth generation technology is available. A second area of emphasis for FGD has been coal fired industrial boilers. While individually they are much smaller than any electric utility generating station, they do represent a significant source of sulfur pollution. However, due to the size of industrial boilers and their location within industrial and educational complexes, the wet scrubber technology being employed by the utilities is not appropriate for these applications. Hence, fluidized bed combustion (FBC) technology has been developed for the industrial boilers. Since the installation of the first full scale test unit at Georgetown University, several equipment vendors have come forward with an increasing array of more sophisticated FBC units. Currently, FBC technology has matured to the point that the Tennessee Valley Authority (TVA), in cooperation with the Electric Power Research Institute (EPRI), has installed an FBC system on a 250 MW test unit at the Shawnee Power Station in Kentucky.

Jan 1, 1994