NPDP Dam Dictionary

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Term AKA Definition
Channel Natural or artificial watercourse of perceptible extent, with a definite bed and banks to confine and conduct continuously or periodically flowing water.
Check dam A small dam designed to retard the flow of water and sediment in a channel, used especially to control soil erosion.
Check structure A structure used to regulate the upstream water surface and control the downstream flow in a canal.
Check valve Any device which will allow fluid or air to pass through it in only one direction.
Chute Portion of spillway between the gate or crest structure and the terminal structure, where open- channel flow conditions will exist. A conduit for conveying free-flowing materials at high velocity to lower elevations.
Cipolletti weir A contracted weir of trapezoidal shape in which the sides of the notch are given a slope of 1 horizontal to 4 vertical
Clay The fine-grained portion of soil that can be made to exhibit plasticity (putty-like properties) within a range of water contents and that exhibits considerable strength when air-dry. Plastic soil which passes a No. 200 United States Standard sieve.
Climatic year Continuous 12- month period during which a complete climactic cycle occurs
Coarse gravel protection Gravel generally placed in a layer upon a finished surface to protect the finished surface from deterioration or erosion.
Coating The protective material applied to the outer surface of metalwork
Cobble Cobblestone A rock fragment, usually rounded or semirounded, with an average dimension between 3 to 12 inches; will pass a 12-inch screen, but not a 3-inch screen.
Cofferdam A temporary structure enclosing all or part of the construction area so that construction can proceed in the dry. A diversion cofferdam diverts a river into a pipe, channel or tunnel. See dam.
Cohesion The mutual attraction of soil particles due to molecular and capillary forces in the presence of water. Cohesion is high in clay (especially dry) but of little significance in silt or sand.
Cohesionless materials Cohesionless soil Soil materials that when unconfined have little or no strength when air-dried and that have little or no cohesion when submerged. Soil that has little tendency to stick together whether wet or dry, such as sands and gravels.
Cohesive soil Predominantly clay and silt soil, fine- grained particles, that sticks together whether wet or dry. A soil that when unconfined has considerable strength when air-dried, and that has significant cohesion when submerged.
Cold joint An unplanned joint resulting when a concrete surface hardens before the next batch is placed against it. Fresh concrete placed on harden concrete.
Collar The open end of a drill hole.
Collaring Starting a drill hole. When the hole is deep enough to hold the bit from slipping out of it, it is said to be collared.
Common material All earth materials which do not fall under the definition of rock.
Compacted backfill Backfill which has been reduced to bulk by rolling, tamping, or soaking.
Compacted embankment Embankment which has been reduced in bulk by rolling, tapping, or soaking.
Compaction To make soil dense by mechanical manipulation. See dumped, dynamic compaction, jetting, ponding, puddling, rolling, saturation, sluicing, surface vibration, and tamping.
Compaction curve Proctor curve; Moisture-density curve The curve showing the relationship between the dry density and the water content of a soil for a given compactive effort.
Compressibility Property of a soil describing its susceptibility to decrease in volume when subjected to load.
Concrete dam See arch dam, buttress dam, or gravity dam. See also masonry dam.
Concrete lift In concrete work, the vertical distance between successive horizontal construction joints.
Conduit Covered portion of spillway between the gate or crest structure and the terminal structure, where open channel flow and/or pressure flow conditions may exist. Portion of an outlet works between the intake structure and gate chamber and/or the control structure. Conduits are located beneath embankment dams and within concrete dams. Conduits are concrete lined or concrete/steel lined. A pipe, box, or horseshoe structure, or natural channel that is constructed by means of cut and cover". A conduit can convey water or house other conduits or pipes. "
Consequence Type Type of the consequence that might have resulted from a dam incident. Examples include fatalities, injuries, property damages, etc.
Consolidation grouting Strengthening an area of ground by injecting grout.
Constant angle arch dam An arch dam in which the angle subtended by any horizontal section is constant throughout the whole height of the dam.