Click for next page ( 214


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 213
Appendix C Glossary ABANDONED IMPOUNDMENT An impoundment that is not in operation and is closed. It has been filled to capacity and reclaimed. ACTIVE IMPOUNDMENT An impoundment that is in operation and . . receiving s urry. AQUITARD A low permeability geologic horizon that restricts the migration of water under ordinary hydraulic gradients. ASH The inorganic residue after burning, esp. of coal. The term is also used informally to refer to the non-coal mineral matter associated with coal that will become ash after combustion at the power plant. Coal with more ash has less heating value. AUGER Mining equipment used to extract coal by boring horizontal holes into the coal seam. Auger mining is conducted from the outcrop most typically in conjunction with contour surface mining. BARRIER PILLAR Block of coal left in place in an underground mine for safety and stability purposes and to prevent water influx. BASIN (as used in this report) Area of existing contours within an impoundment that excludes the embankment; the area covered by slurry and water; both the floor and the walls of the pool behind the embank- ment. BEACH (as used in this report) The subaerial accumulation of the coarser fraction deposited Tom slurry. BED SEPARATION The parting of strata along upper and/or lower contacts due to subsidence. BLACK WATER Water mixed with fine coal refuse. BLIND FLUSHING Injection into an underground mine whose access has been obstructed. BLOW-IN Opposite of blow-out; catastrophic failure resulting from water pressure building up on the surface of an outcrop coal barrier; the material "blows in" to the underground workings from the surface. 213

OCR for page 213
214 COAL WASTEIMPOUNDMENTS BLOW-OUT Opposite of blow-in; catastrophic failure resulting Tom build- up of underground water pressure against an outcrop coal barrier. Material "blows out" from underground workings to the surface. BONY COAL Coal high in mineral content, usually clay shale particles. BREAKTHROUGH Catastrophic failure/opening of mine working along a fracture, joint, bedding plane, or other zone of weakness. BTU (BRITISH THERMAL I5NIT) Heating value for a unit weight of coal. The heat needed to raise one pound of water one degree Fahrenheit. BULKHEAD A seal constructed to prevent water from entering or exiting an area of the mine. Barrier design and construction is based upon the amount of water pressure (water head, expressed in feet) that will be exerted against the bulkhead. CLOSED-LOOP SURVEY Method of establishing He accuracy of a mine survey by conducting a loop traverse to the point of beginning. The accuracy is measured in terms of a ratio of feet of error to feet of traverse, e.g., 1:5000 indicates an error of 1 foot over a 5000-foot traverse. COMPRESSIVE STRESS Stress that pushes together material on opposite sides of a real or imaginary plane. CONTROLLED PLACEMENT (as used in this report) Injection of coal waste slurry into an underground mine that has been mapped and inspected, whose volume is known, and in which bulkheads may be built to control the direction and extent of flow. DAM An artificial barrier or wall constructed across a watercourse to confine flowing water for a variety of purposes, such as creating a pond or lake for storage of water; creating a hydraulic head that can used to generate power; controlling floods; or retention of debris. DEPTH-TO-MINED-HEIGHT RATIO Ratio of the depth of the coal seam to the mined-height, or "effective thickness," of the mined seam. DOWNSTREAM CONSTRUCTION EMBANKMENT A method of staged embankment construction where the embankment centerline is moved downstream with subsequent embankment raises. EMBANKMENT has used in this report) A linear engineered structure extending above the natural ground surface that retains fine coal slurry waste material; it is built with earthen materials or coarse coal refuse (waste material). EXTENSOMETER An instrument for measuring changes caused by stress in a linear dimension of a body. FACTOR OF SAFETY A quantitative measure of the ratio of available strength to applied force. For slope stability, factor of safety is the ratio of forces resisting slope movement to forces causing slope movement.

OCR for page 213
APPENDIX C 215 FINES An informal term referring to fine particles, either product or waste, resulting from processing and preparation; usually less than 100 mesh (150 micrometers) and greater than 325 mesh (45 micrometers). FOOTPRINT OF THE EMBANKMENT The area of natural ground to be covered by the embankment. FREEBOARD The difference in elevation between the embankment crest or spillway invert (bottom) and the water pool elevation in an impound- ment. FRENCH DRAIN Small underground channel filled with permeable materials used to convey water passively. GRANDFATHERED/PRE-LAW IMPOUNDMENT An impoundment that has not been in operation since promulgation of the 1977 Surface Mining Control and Reclamation Act (SMCRA) regulation. These impoundments are reclaimed under the Abandoned Mine Lands Program. HYDRAULIC HEAD The height of the free surface of a body of water above a given subsurface point; or, pressure against the dam from the weight of the slurry (as used in this reports. IMPOUNDMENT (as used ire this report) The entire structure used for coal slurry waste disposal, including the embankment, basin, beach, pool, and slurry. INACTIVE IMPOUNDMENT An impoundment that is not in operation or receiving slurry. Inactive impoundments may receive slurry in the future, becoming active again, and therefore have not been closed permanently. JOENT A fracture or parting in rock along which no displacement has occurred. LIQUEFACTION The transformation of a solid material, such as loosely packed sediment or cohesionless soil, into a fluid mass due to increased pore pressure and reduced effective stress. LOADING Mass and other vertical stresses applied to structure. MOISTURE CONTENT (as used in this report) The percentage of water in a waste slurry. Calculated as the weight of water divided by the weight of the dried solids multiplied by 100. MONITORING Observing, regulating, and evaluating a system to ensure that it is operating properly. NORTH AMERICAN DATUM 27 (NAD27) Mapping coordinate standards established in 1927, measured in feet. NORTH AMERICAN DATUM 83 (NAD83) Mapping coordinate standards established in 1983, measured in meters. OUTCROP The intersection between a geologic formation (e.g., coal seam) and the Earth's surface. =

OCR for page 213
216 COAL WASTEIMPOUNDMENTS OUTCROP BARRIER (Boundary/Perimeter Pillar) Distance between the coal outcrop and the furthest extent of underground mine workings in the direction of the outcrop. PACKERS Plugs that are used to isolate fluid under pressure in a specific segment of pipe in a hole. PARTINGS Thin sedimentary layers that follow a surface of separation between thicker units of rock. PERMEABILITY The capacity of a porous medium to permit flow of a given fluid. PHREATIC SURFACE The groundwater interface or a zone of saturation where the water pressure is equal to atmospheric pressure. PIPING Seepage through embankments, which can lead to failure by internal erosion. POOL Area of free-standing water separated from the slurry discharge point by the beach; it may contain a low percentage of fines and ultra-f~nes, and suspended and unconsolidated solids. PROBABLE MAXIMUM PRECIPITATION The theoretical, greatest depth of precipitation for given duration that is possible over a particular drainage basin. P-WAVE Compressional seismic waves; sound waves; they travel faster than other seismic waves. QUADRANGLE MAP, 7/2-MINUTE GEOLOGICAL Topographic and geologic maps produced by the U.S. Geological Survey. The maps depict an area of 7/ minutes of latitude and longitude. RAISE (as used in this reports The construction of an embankment in a staged manner so that the embankment crest is higher in elevation than the previous stage. REFUSE (OR GOB) PILE Area where coarse waste material (larger than 28 mesh, 800 micrometers) is disposed. RUN-OF-M[NE Raw mined material, unaltered from what is transported out of the mine. SIDE SLOPE Natural embankment. SLIMES Material in the waste stream smaller than 325 mesh (45 micro- meters) and composed mainly of clay or clay-like particles; have high moisture content or the ability to retain water. SLURRY A mixture of water and solids (less than 28 mesh, 800 micrometer, particle size) prepared for handling as a liquid for processing and disposal. SOLIDS CONTENT (as used in this reports The percentage of solids in a waste slurry. SPAD A flat spike, hammered into a wooden plug, anchored in a hole drilled into the mine ceiling from which is threaded a plumbline. The sped is an

OCR for page 213
APPENDIX C 217 underground survey station similar to the use of stakes in marking survey points on the surface. A brass tag permanently attached to the mine roof. STACKING Disposing of dewatered coal waste in "stacks" or layers (from 4-6 inches to 1-3 feet in thickness) piled on top of each other without an embankment. STARTER DAM The initial embankment constructed as the first stage of a staged embankment construction system. STRATA Multiple layers of sedimentary rock. SURFACE WAVES Seismic waves that travel only near the surface of the earth; they travel about 90 percent as fast as S-waves. S-WAVE A wave reflecting shear motion, with oscillation perpendicular to the direction of propagation. TAILINGS Fine particle waste streams from either coal preparation or other mineral processing plants. TAILINGS DAM (as used in this report) A structure constructed to contain fine particle waste streams from other mineral processing plants. TENSILE STRESS A normal stress causing separation across the plane on which it acts. TOE DRAIN A zone of permeable materials constructed at the downstream toe of an embankment to collect and convey water from the downstream region of the embankment. ULTRA-FINES Fine particles, either product or waste, resulting from the processing or preparation of any mineral; particles are smaller than 325 mesh (45 micrometers). UPSTREAM CONSTRUCTION DAM A method of staged embankment construction where the embankment centerline is moved upstream with subsequent embankment raises. =

OCR for page 213