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Intentional release of water is confined to water releases through outlet works and <br /> spillways. A dam typically has a principal or mechanical spillway and a drawdown facility. <br /> Additionally, some dams are equipped with auxiliary spillways to manage extreme floods. <br /> Spillways ensure that the reservoir does not overtop the dam. Outlet works may be provided <br /> so that water can be drawn continuously,or as needed,from the reservoir. Outlets also <br /> provide a way to draw down the reservoir.for repair or safety concerns.Water withdrawn <br /> may be discharged into the river below the dam,run through generators to provide <br /> hydroelectric power,or used for irrigation. Dam outlets usually consist of pipes,box <br /> culverts or tunnels with intake inverts near minimum reservoir level. Such outlets are <br /> provided with gates or valves to regulate the flow rate. <br /> Dam Classifications <br /> Dams are classified in one of three categories: <br /> Dam Hazard Classification <br /> Hazard Description of Quantitative <br /> Classi�cation Potential Dama e Guidelines <br /> Low Interruption of road service, low volume Less than 25 vehicles/day <br /> roads; <br /> Economic Damage <$30,000 <br /> Intermediate Damage to highways,interruption of 25 to less than 250 <br /> service vehicles/da <br /> Economic dama e $30,000 to<$200,000 <br /> High Loss of human life (due to breached Probable loss of 1 or more <br /> roadwa or brid e on or below the dam) human lives <br /> Economic dama e >$200,000 <br /> Damage to highways,breached 250 vehicles/day at 1000 <br /> roadway or bridge feet visibility <br /> 100 vehicles/day at 500 feet <br /> visibility <br /> 25 vehicles/day at 200 feet <br /> visibility <br /> Source:Dam Safety Program,NC Division of Land Resources. <br /> Note:Cost of dam repair and loss of services should be included in economic loss estimate if the dam is a publicly <br /> owned utility,such as a municipal water supply dam. <br /> National Dam Safety Program <br /> The National Dam Safety Program Act,enacted in 1996, was established to improve dam <br /> safety by: <br /> l.providing assistance grants to state dam safety agencies to improve regulatory programs; <br /> 2. funding research to enhance technical expertise as dams are built and rehabilitated; <br /> 3. establishing training programs for dam safety inspectors; and <br /> 4. creating a National Inventory of Dams. <br /> 19 <br />