NPDP Dam Dictionary

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Term AKA Definition
Standpipe Pipe or tank connected to a closed conduit and extending to or above the hydraulic grade line of the conduit to afford relief from surges of pressure in pipelines. A tank used for storage of water in distribution systems.
State The state in which the dam is located.
State ID State or agency unique dam identification number.
Static head The difference in elevation between the pumping source and the point of delivery.
Station use Energy used in a generating plant as necessary in production of electricity. Includes energy consumed for plant light, power, and auxiliaries regardless of whether such energy is produced at plant or comes from another source.
Steady flow Flow in an open channel is said to be steady if the depth of flow does not change over a given time interval. No change occurs with repect to time.
Stemming Crushed stone, soil, sand, or drill cuttings used to plug the unloaded portion of a drill hole.
Stilling basin Concrete portion downstream from conduit, tunnel, or control structure. A pool, usually lined with reinforced concrete, located below a spillway, gate, or valve into which the discharge dissipates energy to avoid downstream channel degradation. See terminal structure.
Stilling pool A pool located below a spillway, gate, or valve into which the discharge dissipates energy to avoid downstream channel degradation.
Stockpile A storage pile of materials.
Stone A concretion of earthy or mineral matter; rock.
Stoplogs Large logs, planks, cut timbers, steel or concrete beams placed on top of each other with their ends held in guides between walls or piers to close an opening in a dam, conduit, spillway, etc., to the passage of water; the logs are usually handled one at a time.
Stratification Thermal layering of water in lakes and streams. Lakes usually have three zones of varying temperature, the epilimnion, the metalimnion, and the hypolimnion.
Stratified reservoir A reservoir with several thermal layers of water.
Stratigraphy Geology that deals with the origin, composition, distribution, and succession of strata (layers of rock).
Stream Natural water course containing water at least part of the year. See ephemeral stream, gaining stream, incised stream, intermittent stream, losing stream, or perennial stream.
Stream capacity Total volume of water that a stream can carry within the normal high water channel.
Stream line An imaginary line within the flow which is everywhere tangent to the velocity vector.
Streambed at the dam axis The elevation of the lowest point in the streambed at the axis or centerline crest of the dam prior to construction. This elevation defines the hydraulic height.
Strike The direction taken by a bedding or fault plane as it intersects the horizontal. To be aligned or to trend in a direction at right angles to the direction of the dip.
Stripping Removal of a surface layer or deposit for the purpose of excavating other material beneath it.
Structural Height Distance between the lowest point in the excavated foundation (excluding narrow fault zones) and the top of dam. The structural height of a concrete dam is the vertical distance between the top of the dam and lowest point of the excavated foundation area, excluding narrow fault zones. The structural height of an embankment dam is the vertical distance between the top of the embankment and the lowest point in the excavated foundation area, including the main cutoff trench, if any, but excluding small trenches or narrow backfilled areas. The top elevation does not include the camber, crown, or roadway surfacing. See hydraulic height.
Subdrilling Overdrilling or drilling below final grade. Sometimes necessary to assure that final grade is obtained when blasting.
Subgrade Soil prepared and compacted to support a structure or pavement system.
Substation capacity The substation capacities are given in kVA (kilovolt-amperes). To determine the load in kilowatts, which could be served from the transformers, the kilovolt-ampere rating should be multiplied by the load power factor
Substrate Surface on which a plant or animal grows or is attached. The base on which an organism lives; a substance acted upon.
Subsurface irrigation system Irrigation by means of underground porous tile or its equivalent.
Succession Directional, orderly process of community change in which the community modifies the physical environment to eventually establish an ecosystem which is as stable as possible at the site in question.
Sulfate attack Damage to concrete caused by the effects of a chemical reaction between sulfates in soils or groundwater and hydrated lime and hydrated calcium aluminate in cement paste. The attack results in considerable expansion and disruption of paste.
Sump A pit or pool for draining, collecting, or storing water.