Technical Manual: Conduits through Embankment Dams (FEMA 484)

GlossaryThe terms defined in this glossary use industry-accepted definitions wheneverpossible. The source of the definition is indicated in parentheses.Abandonment: Discontinuation of the use of a structure without intent to resume.Abrasion (ASTM D 653, 2002): A rubbing and wearing away.Abutment (FEMA, 2004): That part of the valley side against which anembankment dam is constructed. The left and right abutments of embankmentdams are defined with the observer viewing the dam looking in the downstreamdirection, unless otherwise indicated.Accident (ICOLD, 1974): A significant problem with an embankment dam thathas been prevented from becoming a failure by remedial measures.Acidity: A measure of how acid water or soil may be. Water or soil with a pH ofless than 7.0 is considered acidic.Acre-foot (FEMA, 2004): A unit of volumetric measure that would cover 1 acre toa depth of 1 foot. An acre-foot is equal to 43,560 ft 3 .Admixture (ASTM C 822, 2002): A material other than water, aggregates, cement,and reinforcement used as an ingredient of concrete and added to the batchimmediately before or during its mixture.Aggregate (ACI, 2000): Granular material, such as sand, gravel, crushed stone, andiron blast furnace slag, used with a cementing medium to form a hydraulic cement,concrete, or mortar.Aging: The process of changing properties over time.Air vent: A system used to permit air to enter the conduit to prevent collapse or toprevent the formation of low pressures within flowing water that could lead tocavitation and its possible attendant damage.Alkali-aggregate reaction (ACI, 2000): Chemical reaction in concrete or mortarbetween alkalies (sodium and potassium) from Portland cement or other sources andcertain constituents of some aggregates; under certain conditions, deleteriousexpansion of the concrete or mortar may result.Alternate design method: See Working stress design method.389