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<br />002411 <br /> <br />Maximum credible earthquake (MCE): The severest earthquake that is believed to be <br />possible at the site on the basis of geologic and seismological evidence. It is determined <br />by regional and local studies that include a complete review of all historic earthquake <br />data of events sufficiently nearby to influence the project, all faults in the area, and <br />attenuations from causati ve faults to the site. <br /> <br />Moderate frequency flood: See "flood, moderate frequency." <br /> <br />MDA: Acronym for modification decision analysis. <br /> <br />Multipurpose project: A project designed for irrigation, power, flood control, municipal <br />and industrial, recreation, and fish and wildlife benefits, in any combinations of two or <br />more. Contrasted to single-purpose projects serving only one need. <br /> <br />o <br /> <br />O&M: Acronym for operation and maintenance. <br /> <br />Ogee crest: The shape of the concrete spillway crest that represents the lower profile of <br />the undernappe of a jet of water flowing over a sharp-crested weir at a design depth. <br /> <br />Operating log: See "logbook." <br /> <br />, ---./ <br /> <br />Outflow: The amount of water passing a given point downstream of a structure, <br />expressed in acre-feet per day or cubic feet per second. <br /> <br />Outlet works: A series of components located in a dam through which normal releases <br />from the reservoir are made. <br /> <br />Piezometer: An instrument which measures pressure head or hydraulic pressures in a <br />conduit or hydraulic pressures within the fill of an earth dam or the abutment; at the <br />foundation because of seepage or soil compression; or on a flow surface of a spillway, <br />gate, or valve. <br /> <br />Pattern cracking: Fine cracks in the form of a pattern on a concrete surface. <br /> <br />Penstock: A pipeline or conduit designed to withstand pressure surges leading from a <br />forebay or reservoir to power-producing turbines, or pump units. <br /> <br />Pipe: A circular conduit constructed of anyone of a number of materials that conveys <br />water by gravity or under pressure. <br /> <br />Piping: The action of water passing through or under an embankment dam and carrying <br />with it to the surface at the downstream face some of the finer material. <br /> <br />, <br />...._.1 <br /> <br />I <br />'::J <br /> <br />-, <br />1 <br /> <br />o <br /> <br />, --, <br />I <br /> <br />.' I <br /> <br />, I <br /> <br />--, <br />, I <br /> <br />'I <br />I <br /> <br />I <br /> <br />.-=.-=. <br /> <br />'I <br /> <br />:', . <br />