Technical Manual: Conduits through Embankment Dams (FEMA 484)

GlossaryImpervious: Not permeable; not allowing liquid to pass through.Incident (ICOLD, 1974): Either a failure or accident, requiring major repair.Inclinometer (ASCE, 2000): An instrument for measuring the angle of deflectionbetween a reference axis and casing axis.Infiltration: The flow of water through a soil surface or the flow of water into aconduit through a joint or defect.Inspection: The review and assessment of the operation, maintenance, andcondition of a structure.Inspector: The designated on-site representative responsible for inspection andacceptance, approval, or rejection of work performed as set forth in the contractspecifications. The authorized person charged with the task of performing a physicalexamination and preparing documentation for inspection of the embankment damand appurtenant structures.Instrumentation (FEMA, 2004): An arrangement of devices installed into or nearembankment dams that provide for measurements that can be used to evaluate thestructural behavior and performance parameters of the structure.Intake structure (FEMA, 2004): Placed at the beginning of an outlet workswaterway (power conduit, water supply conduit), the intake establishes the ultimatedrawdown level of the reservoir by the position and size of its opening(s) to theoutlet works. The intake may be vertical or inclined towers, drop inlets, orsubmerged, box-shaped structures. Intake elevations are determined by the headneeded for discharge capacity, storage reservation to allow for siltation, the requiredamount and rate of withdrawal, and the desired extreme drawdown level.Internal erosion: A general term used to describe all of the various erosionalprocesses where water moves internally through or adjacent to the soil zones ofembankment dams and foundation, except for the specific process referred to as“backward erosion piping.” The term “internal erosion” is used in this document inplace of a variety of terms that have been used to describe various erosionalprocesses, such as scour, suffosion, concentrated leak piping, and others.Inundation map (FEMA, 2004): A map showing areas that would be affected byflooding from releases from a dam’s reservoir. The flooding may be from eithercontrolled or uncontrolled releases or as a result of a dam failure. A series of mapsfor a dam could show the incremental areas flooded by larger flood releases.405