NPDP Dam Dictionary

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Term AKA Definition
Slope protection The protection of an embankment slope against wave action or erosion.
Slough Movement of a soil mass downward along a slope because of a slope angle too great to support the soil, wetness reducing internal friction among particles, or seismic activity. It is also called a slope failure, usually a rather shallow failure. A wet place of deep mud or mire, or a temporary or permanent lake; ordinarily found on or at the edge of the flood plain or a river. Also refers to a creek or sluggish body of water in a bottomland.
Slug Large initial amount.
Sluiceway An opening in a diversion dam used to discharge heavy floating debris safely past the dam.
Sluicing A method of compacting soil where the soil is washed into placed with a high velocity stream of water.
Slurry Watery mixture of insoluble matter which is pumped beneath a dam to form an impervious barrier.
Slurry trench A narrow excavation whose sides are supported by a mud slurry filling the excavation. Sometimes used incorrectly to describe the cutoff itself.
Smolts Adolescent salmon 3 to 7 inches long.
Social value Psychological value Concept that the existence of wilderness provides a condition that could allow an individual to achieve control over stressful conditions, thus contributing to the psychological health of many off-site users.
Soil Sediments or other unconsolidated accumulations of solid particles produced by the physical and chemical disintegration of rocks, and which may or may not contain organic matter. Soil components may consist of clay, silt, sand, or gravel.
Soil cement A mixture of water, cement, and natural soil, usually processed in a tumble and mixed to a specific consistency, then placed in lifts and rolled to compact to provide slope protection
Soil classification Systematic arrangement of soils into classes of one or more categories or levels of classification for a specific objective. Broad groupings are made on the basis of general characteristics and subdivisions are made on the basis of more detailed differences in specific properties.
Soil-cement bedding A mixture of soil, portland cement, and water placed for pipe bedding.
Solid head buttress dam A buttress dam in which the upstream end of each buttress is enlarged to span the gap between buttresses. The terms round head diamond head tee head" refer to the shape of the upstream enlargement. See massive head buttress dam."
Spacing In blasting, the distance between holes in a row. Apparent spacing is the spacing as outlined by the delay pattern.
Spalling The loss of surface concrete usually caused by impact, abrasion, or compression.
Spawn To lay eggs, refers mostly to fish.
Spawning beds Underwater places where eggs lodge or are placed during or after fertilization.
Special features Area containing ecological, geological, or other features of scientific, educational, scenic, or historical value.
Species Basic category of biological classification intended to designate a single kind of animal or plant. See candidate species, endangered species, exotic species, extirpated species, obligate riparian species, sensitive species, and threatened species.
Specific weight The weight per unit volume.
Spectrum intensity The integral of the pseudo-velocity response spectrum taken over the range of significant structural vibration periods of the structure being analyzed.
Spillway A structure that passes normal and/or flood flows in a manner that protects the structural integrity of the dam. Overflow channel of a dam or impoundment structure. See auxiliary spillway, emergency spillway, and service spillway.
Spinning reserves Available capacity of generating facilities synchronized to the interconnected electric system where it can be called upon for immediate use in response to system problems or sudden load changes.
Splitter wall A wall or pier parallel to the direction of flow in a channel that separates flows released from different sources as a means of energy dissipation.
Spoil Dirt or rock which has been removed from its original location.
Springline An imaginary horizontal reference line located at midheight, or halfway point, of a circular conduit, pipe, or tunnel. Also the maximum horizontal dimension or diameter of a circular conduit, pipe, or tunnel.
Stability Tendency of systems, especially ecosystems, to persist, relatively unchanged, through time; also, persistence of a component of a system.
Staff gauge A graduated scale on a plank or metal plate used to indicate the height of the water in a canal.
Standby reserves Unused capacity in an electric system in machines that are not in operation but that are available for immediate use if required.